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Genome

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The entirety of an organisms heredity information encoded either in DNA or for many viruses in RNA.

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Gregor Mendel

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In mid 1800's, he discovered parents pass traits to their offspring in predictable ways.

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The Human Genome Project

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Plan to map out the entire sequence of the human genome.

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Gene

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Codes for a particular heritable trait or protein, example: blood type, hair color, eye color, etc.

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Chromosomes

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Referred to as homologous as they contain genes that control the same trait, humans have 46 total, 23 from Mother, 23 from Father, and composed of DNA.

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Chromatin

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Combination of DNA and proteins that make up the contents of the nucleus of a cell.

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Chromatid

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One copy of a duplicated chromosome.

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Genetics

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The study of inheritable and variability, the term "genetics" is derived from the word "gene".

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Allele

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Each version of a gene is referred to as a allele. One or more different forms of a gene for the same trait at a specific gene site on homologous chromosomes. There may be multiple alleles for one trait.

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Heterozygous

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Bb

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Homozygous Dominant

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BB

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Homozygous Recessive

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bb

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Genotype

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The genetics; are the genes dominant, recessive, homozygous, or heterozygous.

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Phenotype

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The appearance; how the gene presents itself in a physical manner; brown eyes or blue eyes.

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Dominant

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Takes 1st place.

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Recessive

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Takes 2nd place.

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Penetrance

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Phenotype presentation; whether or not the allele is seen in phenotype; types: complete and incomplete.

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Complete Penetrance

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All who have allele have trait.

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Incomplete Penetrance

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Only some with allele show trait.

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Expressivity

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How much the phenotype is expressed; sometimes variable intensity is seen in different people; ex: some people with polydactyly have 1 extra digit, others have 4 digits.

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Pleiotrophy

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When a single genotype affects many phenotypes due to protein having many locations and functions.

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Genetic Heterogeneity

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When more than one genotype causes the same phenotype; ex: many different clotting disorders are known but they all have the same symptoms.

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Polygenic Traits

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Determined by more than one gene; height, skin color, eye color.

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Multifactorial Traits

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Determined by more than one gene and environment; height is multifactorial because it is polygenic plus nutrition plays a role.

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Diploid

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Fused together, in humans, each somatic or body cell is diploid which means the cell contains 46 chromosomes.

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Haploid

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Half the cells, in humans their sex cells carry 23 chromosomes.

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Crossing Over

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Due to the closeness of the 2 homologous chromosomes, they can intertwine to the point they cross over during meiosis; when this occurs you form a new variation that may be passed onto offspring.

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Independent Assortment

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The chromatids of each parent line up randomly at the metaphase plate; it is not that the parental chromatids line up on one side and the maternal ones on the other side, they mix up and this is one reason for genetic variation.

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Autosomal Dominant

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Affect parent = +, HD; unaffected parent = +, +; example: Huntington's disease.

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Autosomal Recessive

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Both parents are heterozygous or carriers; they have 1 normal + and 1 mutant cf allele genotype = +, cf; ex: Cystic Fibrosis.

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Incomplete Dominance

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Sickle cell anemia or disease in which one of the 4 amino acid chains in hemoglobin is incorrect causing sickling of erythrocytes; the heterozygous or carrier parents express a moderate form of the disease called sickle cell anemia.

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Codominant

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Results when both alleles are expressed; example: AB blood.

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Monosomy

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Missing a chromosome; usually a fatal defect however if it is a sex chromosome survival ay be possible; 23 egg and 22 sperm; example: Turner Syndrome- female has one X.

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Polysomy

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One or more extra chromosomes in an infant; often results in severe disabilities; Polysomy 17 frequently seen in breast cancer.

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Polyploidy

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Cells and organisms are those containing more than two paired homologous sets of chromosomes.

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Significance in DNA:

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DNA holds the code for every protein that makes us and allows us to function.

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Mutation

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An error in DNA; if mutation occurs the end product will be altered or absent.

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Examples of mutations:

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1. The protein may not be made at all; example: Tay-Sachs and PKU. 2. The protein may have altered function; example: seen in fibrosis and sickle cell anemia. 3. The protein may be produced in excess; example: seen in epilepsy, where excess GABA leads to excess norepinephrine.

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Sex Chromosomes determine:

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They determine the sex of the individual; female = XX; male = XY; happens in gametogenesis or sex cell formation meiosis.

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In Females

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The ova or gametes contain 22 autosomes and the X sex chromosome.

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In Males

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The sperm contain 22 autosome, but half the sperm carry X and half carry Y.

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During fertilization the chance of having a female or male is:

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50/50 or 50% male and 50% female.

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Karyotype

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Is the number and appearance of chromosomes in the nucleus, term also used for complete set of chromosomes in a species or an individual organism.

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Punnett Squares

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A method used to visually predict the outcome when two genotypes are crossed.

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IA Blood

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Type A blood.

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IB Blood

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Type B blood.

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IA IB Blood

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Type AB blood.

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ii Blood

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Type O blood.

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Possible outcomes of chromosomal disorders:

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1. Make zygote growth impossible. 2. Cause a miscarriage. 3. Cause abnormality that results in live birth but prevents length of life. 4. Not affect length of life.

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List the four categories in genetic abnormalities:

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1. Chromosomal Abnormalities. 2. Mendelian Single Gene Disorders. 3. Non-Mendelian Single Gene Disorders 4. Polygenic Disorders

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Chromosomal Abnormalities

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Caused by errors in crossover, meiosis or mitosis; results in the wrong number of chromosomes or defective chromosomes. Aneuploidy, Anaphase Lag, and Polyploidy.

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Aneuploidy

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Abnormal # of Chromosomes; The usual causes for this are Nondisfunction.

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Nondisfunction

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Result of Aneuploidy; paired homologous chromosomes fail to separate during meiosis; 24 egg + 23 sperm; Downs - trisomy 21, Patau's - trisomy 13, Edwards - trisomy 18, and Klinefelter's Syndrome - XXY

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Down Syndrome

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Aneuploidy; most common autosomal aneuploidy event; causes: short stature, strait - sparse hair, protruding tongue and thick lips, reflexes/muscle tone poor, development slow, warm and loving personalities. Intelligence varies; many physical problems like: kidney and heart defects, digestive blockage, and are 15 times more likely to get cancer.

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Anaphase Lag

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One chromosome lags behind and is left out of the cell. Includes: Monosomy, Polysom, and Polyploidy

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Monosomy

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Anaphase Lag; missing a chromosome; usually a fatal defect however if it is a sex chromosome survival may be possible; Example: Turner Syndrome.

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Polysomy

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Anaphase Lag; One or more extra chromosomes in an infant; often results in severe disabilities in the infant; polysomy 17 frequently seen in breast cancer; additional sex chromosome abnormalities: Multiple X - XXX, XXXX called super-females, and Multiple Y - XYY called super-males

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Polyploidy

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Anaphase Lag; a complete extra set of chromosomes; triploid = three sets of chromosomes or 69 instead of 46; results in death as embryo or fetus.

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Abnormal Chromosome Structure or Defective Chromosomes

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Will have the correct number of chromosomes but have errors within the chromosome; occurs in crossing over during meiosis; Translocation, Inversion, Deletion, and Duplication.

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Translocation

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Crossing over happens between nonhomologous chromosomes

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Inversion

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Reversal or Rearrangement of the order of genes on a chromosome.

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Deletion

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Loss of part of a chromosome.

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Duplication

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Part of the chromosome is duplicated.

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Mendelian Single Gene Disorders

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These disorders result from alteration of mutations of single genes which then code for abnormal enzymes, structural proteins, or regulatory proteins; classified by: location, whether its dominant or recessive, and their origin: Types Autosomal Dominant and Autosomal Recessive.

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Autosomal Dominant Disorders

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One copy of the bad allele is needed to have the disease; examples: Marfan's Syndrome, Huntingtons Disease, Polycystic Kidney Disease, Osteogenesis Imperfecta.

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Marfan's Syndrome

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Autosomal dominant disorder; connective tissue disorder; it is thought Abraham Lincoln had this.

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Huntington's Disease

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Autosomal dominant disorder; nervous system disorder resulting in uncontrolled movements and emotional disturbances.

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Polycystic Kidney Disease

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Autosomal dominant disorder; multiple cysts on kidneys eventually cause kidneys to shut down.

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Osteogenesis Imperfecta

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Autosomal dominant disorder; bone disorder where bones fracture easily.

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Autosomal Recessive Disorder

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Need two copies of the bad allele in order to have the disease; examples: albinism, phenylketonuria or PKU, cystic fibrosis, and sickle cell anemia.

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Albinism

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Autosomal recessive disorder; lack of pigment in skin, hair, and eyes.

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Phenylketonuria or PKU

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Autosomal recessive disorder; Unable to metabolize the amino acid phenylalanine.

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Cystic Fibrosis

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Autosomal recessive disorder; excessive mucus in lungs and pancreas.

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Sickle Cell Anemia

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Autosomal recessive disorder; abnormal hemoglobin.

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Non-Mendelian Single Gene Disorders

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These disorders do not follow classic mendelian principles of random and independent assortment; examples: long triple mutations, fragile X syndrome, mitochondrial gene mutations, and genomic imprinting.

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Long Triple Repeat Mutations

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Non-Mendelian; have many repeating triplets of bases in the DNA.

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Fragile X Syndrome

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Non-Mendelian; One of the most common causes of mental retardation; more severe in men.

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Mitochondrial Gene Mutations

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Non-Medelian; very rare.

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Genomic Imprinting

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Non-Medelian; chromosome source affects the phenotype.

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Polygenic Disorders

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Two or more mutant genes act together to cause the disorder; can be influenced by environment factors; examples: hypertension, cancer, diabetes, cleft lip, and severe kinds of congenital heart defects; cancer needs 6 to 10 bad genes.

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Sex-Limited Traits

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Only tend to affect certain sex; reason that a women doesn't grow a thick beard but her sons can.

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Sex-Influenced Traits

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They are dominant in one sex but recessive in the other; due to hormonal differences; reason that more men are bald than women.

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Methods used for genetic testing:

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Amniocentesis, chronic villi sampling or CVS, and fetal cell sorting.

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Amniocentesis

answer

Performed after 14th week gestation; needle is inserted into amnionic sac and 5mL of fluid containing fetal cells is extracted; cells are analyzed by karyotyping; indicated in women over the age of 35, who have already given birth to a child with chromosomal abnormality. whose family history shows any sign of genetic disease; 0.5% chance of a miscarriage.

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Chorionic Villi Sampling or CVS

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Performed as early as 8 weeks gestation, 1-2% spontaneous abortion rate.

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Fetal Cell Sorting

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Involves obtaining and analyzing rare fetal cells in maternal circulation; these cells may be responsible for autoimmune disorders including scleroderma.

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Genes are carried on chromosomes which are composed of:

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DNA or deoxyribonucleic acid.

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There are _____ pairs of chromosomes in humans.

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46 chromosomes.

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When does crossing over take place?

answer

During prophase I.

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Order or sequence of fertilization:

answer

Zygote, morula, blastocyst, embryo, and then fetus.

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Zygote

answer

Day 1; fertilized egg.

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Morula

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Day 4; solid sphere of cells.

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Blastocyst

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Day 5; hollow ball of cells.

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Embryo

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1st 8 weeks or 2 months; embryo is most vulnerable to damage/birth defects during this period.

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Fetus

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Months 3-9; all organs present.

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______ is a series of functional changes that prepares the oocyte so that it can join with the sperm.

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Capacitation

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Fertilization normally occurs within the:

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Fallopian tube.

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Gene Therapy

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Gene therapy corrects the genetic defect disease symptoms; two type: heritable gene therapy and nonheritable gene therapy.

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Heritable Gene Therapy

answer

Alters all genes of the individual; must be performed on a fertilized egg or zygote; not being performed in humans,but has shown some success in animal models.

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Nonheritable Gene Therapy

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Targets affected cells of the afflicted individual; bone marrow transplants may be used to add an absent enzyme to particular blood cells, ex: ADA deficiency; Aerosols may be used to treat cystic fibrosis patients by introducing a functional CFTR gene; injection of certain proteins directly to tumors.

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The Oocyte is viable for:

answer

12-24 hours after ovulation.

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Sperm is viable for:

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48 hours.

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Fertilization can occur from:

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2 days before ovulation to 1 day after.

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Capacitation happens with in the:

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Female.

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Events of capacitation:

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1. Sperm's flagellum beats faster. 2. Sperm's cell membrane changes to fuse with the oocyte.

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The sperm has to penetrate through 2 layers called:

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The corona radiate and zona pellucida.

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Corona Radiata

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Is the 1st layer the sperm needs to penetrate; it is composed of granulosa cells that surround the secondary oocyte.

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Zona Pellucida

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Clear glycoprotein layer located between the corona radiate and the oocyte's plasma membrane; is 2nd layer penetrated; the sperm penetrated this layer by using enzymes from sperm's acrosome.

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Polyspermy

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Blockage from the first sperm that fertilizes the egg; no other sperms can fertilize.

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Once the sperm has entered the secondary oocyte:

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The oocyte finishes meiosis II by dividing into an ovum and 2nd polar body, the sperms tail is shed; and the pronuclei fuse.

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Nuclei of sperm and ovum each change into a:

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Pronucleus; these two pronuclei then fuse to form one nucleus.

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The fertilized egg is called:

answer

A zygote and life begins.

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Monozygotic Identical

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Identical twins; developing cells split 1-8 days after fertilization and form two genetically identical embryos, same sex.

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Monozygotic Identical conjoined

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Conjoined twins or siamese twins; an incomplete split; frequently happens after 8 days.

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Dizygotic Fraternal

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Two sperm fertilize two eggs; basically two siblings born at the same time can be the same or different sex.

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cleavage

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Is the division of cells early on in development; the fertilized egg divides to two cells, then four cells, eight cells. etc.

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The first division begins about:

answer

24 hours after fertilization and takes 6 hours to complete.

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By 96 hours the zygote:

answer

Is a solid ball of cells which is referred to as a morula.

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Morula

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Is the term for the solid sphere of cells by day four; reaches the uterus on day 4 or 5 after fertilization.

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Blastocyst

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Hollow ball of cells surrounding a central cavity by day 5.

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Inner Cell Mass

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Develops into the embryo body.

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Trophoblast

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Outer covering of cells just beneath the zona becomes part of the fetal portion of the placenta.

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Blastocoel

answer

is the internal fluid filled cavity.

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Implantation

answer

6-7 days after fertilization.

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Ectopic Pregnancies

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Development of embryo/fetus outside of the uterus; most commonly occurs in the fallopian tube; can rupture and kill mother.

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hCG or Human Chorionic Gonadotropin

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Helps maintain the corpus luteum so that it can continue to secrete progesterone and estrogen; It helps to maintain the pregnancy until the placenta is fully developed and secreting estrogen and progesterone on its own.

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Development of bilaminar embryonic disc

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Embryoblast cells differentiate to form two layers which form a small cavity that eventually enlarges to form the amniotic cavity.

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Amnion

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Thin protective membrane that surround the embryo; produces amniotic fluid which cushions the embryo and eventually the fetus and regulates temperature.

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Amniocentesis

answer

Removal of some amniotic fluid which is analyzed for genetic abnormalities.

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Yolk Sac

answer

Early site of blood formation supplies early nutrients to the embryo; early source of blood cell; produces primitive cells for oogonia and spermatogonia; forms part of the gut; and aids in shock absorption.

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Chorion

answer

Surrounds the amnion and becomes fetal part of the placenta also produces hCG which helps sustain an early pregnancy.

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Chorionic Villi Sampling

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Some tissue from the chorion is removed and analyzed for genetic abnormalities.

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Allantois

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Early site of blood and blood vessel formation, also helps develop bladder.

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Primary Germ Layer Formation

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By day 14 differentiation has produced three distinct layers of the cell: ectoderm, mesoderm, and endoderm; damage to cells of these layers now can cause predictable damage to the embryo.

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Ectoderm

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Outer cell layer; becomes nervous system and epidermis of the skin.

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Mesoderm

answer

Middle cell layer; becomes muscle and bone.

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Endoderm

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Inner layer; becomes the GI and respiratory tracts.

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Development of the cardiovascular system:

answer

By the end of 3rd week; heart forms and begins to beat.

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Chorionic Villi

answer

Finger-like projections of the chorion projecting into the endometrium.

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Umbilical Cord

answer

Blood vessels in the chorionic villi connect the embryonic heart through body stalk or umbilical cord; maternal and fetal blood does not mix; exchange is by diffusion only.

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Protection

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Most microorganisms cannot pass thro the placenta; some viruses, drugs, and alcohol can cross the placenta and cause various problems in the fetus.

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All major organs develop:

answer

Weeks 5-8; very rapid brain development

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Organogenesis

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Formation of body organs and systems.

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Second and Third Trimester

answer

Tissues and organs developed earlier grow and differentiate; very few new structures appear; fetus is less vulnerable to damaging effects caused by drugs, radiation, and microbes, however damage can still occur; weight gain and final maturation of the fetus.

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Human Chorionic Somatomammotropin or hCS or Human Placental Lactogen or hPL

answer

Produced by the chorion; helps prepare mammary glands for lactation; regulates certain aspects of fetal and maternal metabolism.

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Relaxin

answer

Produced by the corpus luteum and placenta serves to increase flexibility of the pubic syphysis and helps dilate the cervix during labor.

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Cortiocotrophin-releasing Hormone or CRH

answer

Produced by placenta; In non-pregnant people secrete only by the hypothalamus; thought to be part of the "clock" establishing timing of birth; Increases secretion of cortisol needed for maturation of fetal lungs and production of surfactant.

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Physiological changes in pregnancy:

answer

Weight gain; increased storage of proteins, triglycerides and minerals breast enlargement; lower back pain.

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Changes in cardiovascular system in pregnancy:

answer

Due to increase maternal blood flow to the placenta and increased metabolism; blood volume increases by 30-50%; hear rate increases 10-15%.

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Changes in respiratory system during pregnancy:

answer

Altered to meet the added oxygen demands of the fetus; tidal volume is increased by 30-40%; Expiratory reserve is reduced by up to 40%.

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Digestive system changes in pregnancy:

answer

Increased appetite; decrease in GI tract motility which can cause constipation; delayed gastric emptying which can cause nausea, vomiting, and heartburn.

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Urinary system changes during pregnancy:

answer

Increased pressure on the urinary system; increasing size of the uterus and pressure it exerts on the bladder; increased blood volume means increased glomerular filtration.

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Changes in pregnancy:

answer

Physiological, cardiovascular, respiratory, digestive, urinary, and changes in the skin.

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Labor or Parturition

answer

Process by which the fetus is expelled from the uterus through the vagina; onset is determined by interactions between several placental and fetal hormones; control of labor is through positive feedback loop.

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Involution

answer

Uterus begins to decrease in size to a pre-pregnant state.

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Adjustments of the infant at birth include:

answer

Respiratory and cardiovascular.

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Respiratory adjustments of infant at birth:

answer

The supply of oxygen from the mother ceases and an amniotic fluid with in the lungs is absorbed by the body; rising CO2 caused the respiratory center within the medulla oblongata to be stimulated and the baby takes his/her first breath.

question

Cardiovascular adjustments of infant at birth:

answer

Baby's first breath stimulates cardiovascular changes; foramen ovale closes and becomes the fossa ovalis; ductus arteriosus constricts due to the contraction of muscles within its wall and becomes the ligamentum arteriosum; umbilical arteries and umbilical vein become ligaments.

question

Physiology of Lactation:

answer

Secretion and ejection of milk from mammary glands; prolactin hormone is secreted by anterior pituitary; oxytocin causes the release of milk into the mammary glands.

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Birth defects are classified as:

answer

Congenital, hereditary, intrauterine, and some defects may be genetic and environmental.

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Congenital Birth Defects

answer

Any defect present at birth.

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Hereditary Birth Defects

answer

Genetic defect that can be passed on or inherited; gene/chromosome defect that can be passed on to offspring.

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Intrauterine Birth Defects

answer

These are caused by some agent or event while developing in the uterus; maternal health can influence these defects by nutrition, physical drama, and mental state; drugs and chemicals can be passed through the placenta to the fetus: infections agents like viruses and bacteria; radiation.

question

Common birth defects:

answer

Heart defects, spina bifida, genital/urinary tract defects, metabolic disorders, and fetal alcohol syndrome.

question

Teratogen

answer

Any agent that causes developmental defects in the embryo.

question

Periods of fetal vulnerability:

answer

1-2 weeks minimal damage, 3-9 weeks organs start developing and are very susceptible to damage, 3-9 months damage frequently results in slowed growth or organ damage.

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