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multiplication rule

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- used to determine the probability of two or more independent events occuring together; multiple prob of each event together

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gene

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- the genetic material on a chromosome that contains the instructions for creating a particular trait; codes for a trait, i.e genes that code for flower colour

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allele

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- one of the several varieties of a gene; i.e the allele that codes for purple or white flowers

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locus

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- the location of a chromosome where a gene is located.

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homologous chromosome

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- pair of chromosomes that contain the same genetic information - at a locus, two genes on a pair of homologous chromosomes may represent 2 alleles

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dominant allele

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trait encoded is the actual trait expressed; i..e the purple flower allele

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homozygous dominant

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inheritance of two dominant allelles ( PP); dominant trait is expressed

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homozygous recessive

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- inheritence of two recessive alleles ( pp_; recessive trait is expressed

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heterozygous

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- two inherited alleles are differnt ( Pp); dominant trait is expressed

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phenotype

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- actual expression of a gene; i..e blue eyes are green eyes

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genotype

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- actual elleles; i.e. PP = homozygous dominant; genotype pP would express the phenotype of purple flowers.

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law of segregation

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- on member of each chromosome pair migrates to an opposite pole so that each gamete contains only one copy of each chromosome ( and each allele)

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law of independent assortment

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- independent assortment of alleles; the migration of homologues within one pair of homologous chromosomes to opposite poles does not influence the migration of homologues of other homologous pairs

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What are the four principles of inheritence?

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- genes exist in alternative forms ( alleles) - an organisms has two alleles for each inherited trait, one from each parent - two alleles segretate during meiosis, resulting in gametes that carry only one allele for any given trait after meiosis - expressed = dominant, silent = recessive

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'crossed'

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- means 'mated'

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hybrids

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- offspring of different things

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P generation

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parents

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F1 generation

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- offspring from crossing the parents

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F2 generation

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- offspring produced from crosses among the F1

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monohybrid cross

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- experiment in which only one trait is investigated - i.e cross b/t purple and white flower pea, only investigating the genes for the the flower colour trait

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dihybrid cross

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- cross where two traits are involved - i.e. investigating traits of flower colour and plant height, or seed colour and texture

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complete dominance

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- traits are expressed as if one allele is dominant to a second allele - PP and Pp, dominant is expressed, pp is recessive is expressed

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true-breeding

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- self crossed; produce progeny only with the parental phenotype

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F in F generation means

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- flial

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incomplete dominance

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- the phenotype of the heterozygote is an intermediate of the phenotypes of the homozygotes - i.e. red + white snapdragon flowers = pink flower ( Rr in F1 generation)

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codominance

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- when multiple alleles exist for a given gene and more thanone of them is dominant - when two dominant alleles are present the phenotype is the result of the expression of both dominant alleles simultaneously

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example of codominance

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- inheritance of ABO blood groups - heterozygous I^AI^B have a AB blood type and have characteristics of both A and B blood groups

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autosomes

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- pairs of homologues

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sex chromosomes

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- determines sex - females = homologous X chromosomes - males = heterozygous chromosomes X and Y

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humans have ____ pairs of autosomes

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22

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gender is the gamete is determined by:

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- the genetic contribution of the male gamete - if sperm carries a Y chromosome, zygote is male, if sperm carries an X chromosome, zygote is female - 50% chance b/t fertilization is an independent event

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sex-linked

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- genes that are located on the X or Y chromosome - most are found on the X chromosome, but some are Y-linked like hair on the outer ears

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sex-linked recessive gene

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- found on X chromosome - some males do not have have a dominant allele to mask it, recessive phenotype is more frequently found in males

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Examples of sex-linked recessives

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- hemophilia - colour blindness

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How are sex-linked recessive genes passed on ?

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- cannot pass from father to son, because father passes X chromosome to all his daughters - daughter becomes a normal carrier, in which half her sons will receive the recessive trait; therefore, can pass from father to grandson! skips a generation!

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Drosophilia Malangaster

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- fruit fly - reproduces often and in large numbers - chromosed are large and easily recognizable in size and shape - chromosomes are few ( 4 pairs, 2N = 8) - mutations occur frequently

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T or F: Environment can effect the expression of a gene

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- True - fruit flights develop crooked wings at low temp, and straight wings at high temp - temp effects colour of himilayan hair; cool = black, warm = white

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nondisjunction

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- failure of homologous chromosomes to seperate properly during meiosis I - failure of sister chromatids to seperate properly during meiosis II -in mitosis, failure of two chromatids of a single chromosome to seperate and segregate produces daughter cells with extra or mjissing chromo

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How many chromosomes will result in the zygote after nondisjunction?

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- PLOIDY: resulting zygote may have 3 copies of that chromosome ( trisomy - 2N + 1 chromosomes) or a single copy ( monosomy - SN - 1 chormosomes) - MOSAICISM: a fraction of the body cells, have extra or missing chromosomes

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Down syndrome

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- caused by a trisomy of chromosome 21

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chromosomal breakage

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- chromosome that loses a fragment is said to have a deficiency - occur spont. or induced by environmental factors like mutagentic agents and x-rays

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mutations

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- changes in the genetic information of a cell, coded in the DNA - can be added, deleted, or substituted - permanent change in the DNA sequence of a gene that may or may not alter the AA sequence of the corresponding protein

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mutations in somatic cells lead to

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tumors

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mutations in sex cells lead to

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transmission to the offspring

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silent mutations

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- mutations that occur in region of DNA that do not code for proteins - not expressed in the phenotype

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mutagenic agents

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- induce mutations - carcinogenic - i.e. cosmic rays, x-rays, UV rays, radioactivity

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colchicine

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- mutagenic agent - inhibits spindle formation and causes ploidy

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mustard gas

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- mutagenic agent

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phenylketonuria (PKU)

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- molecular disease caused by the inability to produce the proper enzyme for the metabolism of phenylalanine - degradation product ( phenylpyrivic acid) accumulates and causes physiological problems

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sickle-cell anemia

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- disease in which RBCs become cresent shaped b/c they contain a defective hemoglobin - RBC carries less Oxygen

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What causes sickle-cell anemia?

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- cause by substituton of valine ( GUA or GUG) for glutemic acid * GAA or GAG) b/c of a single base pair substitution in the gene coding for hemoglobin - as a result, RBC becomes sickle shaped ( pleiotropy!)

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DNA

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- deoxyribonucleic acid - contains genetic information coded in the sequence of it's base pairs - provide cell with a blueprint for protein synthesis - can self replicate - is mutable and can be altered that can be passed from generation to generation

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DNA is the basis of ________.

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- heredity

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nucleotide

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- subunit of DNA - composed of deoxyribose ( a sugar) bonded to a phosphate group and a nitrogenous base

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Purines

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- Adenine and guanine

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pyrimidines

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- cytosine and thymine

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cytosine and guanine make ___ double bonds. adenine and thymine make ___ double bonds

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- 3 - 2

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double standed helix

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- sugar-phosphate chains on outside with bases on the inside ( or the 'rungs' of the ladder)

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watson-crick DNA model

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- base-pairing formed link the two polynucleotide chains together

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Higher G/C content means...

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- more tightly bound the strands and MP

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helicase + gyrase

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- unwinds the DNA double helix

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antigen

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- foreign substances in the body

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antibody

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- attack antigens

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agglutination

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- clumping of blood that may be caused by tranfusion of blood from an unlike phenotype

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Which blood type can accept any blood type?

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- AB because both A and B carbohydrates are recognized as self

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Which blood type can donate to anyone?

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- O blood type - because has neither A nor B carbohydrates to be recognized as an antigen - universal donor!

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epistasis

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- occurs when one gene affects the phenotypic expression of a second gene - i.e expression fo pigmentation; one gene could turn on or off the production of pigment, while the second controls the amount or colour

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pleiotropy

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- occurs when a single gene has more than one phenotypic expression - i.e the gene in pea plants that expresses the round or wrinkled texture of seeds also influences the phenotypic expressions of starch metabolism and water absorption - round seeds = more conversion of glucose to starch, wrinkled seed = more unconverted glucose, increase osmotic gradient and higher water which dehydrates upon maturation

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polygenic inheritence

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- the interaciton of many genes to shape a single phenotype - the opposite of pleiotrophy

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continuous variation

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when a triat is express as a range of varieties

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What is the opposite of polygenic inheritence?

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- pleiotrophy!!!! is when one gene influencing many phenotypes - meanwhile, polygenic inheritence is many genes shaping one phenotype

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linked genes

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- genes that reside on the same chromosome and thus cannot segregate independently b'c are physically connected - are a 'linkage' - are inherited together

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X-inactivation

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- during embrionic development in female mmamal, one of the 2 x chromosomes in each cell does not uncoil into a chromatin ( is a compacted body called a barr body) - random and independent event - call female mammal cells wil not be functionally identical

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barr body

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- inactive x chromosomes - most genes are not expressed nor interact with alleles on the corresponding x chromosome that is expressed

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Calico cats are an example of

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- X-activation - have white, yellow and black patches - activation of black allele causes yellow patches, inactivation causes black allele on active X to be expressed

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point mutations

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- when a single nucleotide in the DNA of a gene is incorrect - i.e. sickle cell disease

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aneuploidy

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- genome with extra or missing chromosomes - most often caused by nondisjunction - most are sterile, but survive and lead to genetic defects - i.e. downs syndrom, and turner syndrome

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turner syndrome

answer

- results from non-disjunction of sex chromosomes - sperm will have both XY or none ( O), eggs either XX or O. - turner's syndrome zygote XO is a female who has only one x and no second chromo ( from nondijunction in an egg or sperm)

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chromosomal aberrations

answer

- caused when chromosomes segments are changed

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duplications

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- chromosomal aberration - chromosome segment is repeated on the same chromosome

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inversion

answer

- when chromosome segments are rearranged in reverse orientation on the same chromosome

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translocation

answer

- when a segment of a chromosome is moved to another chromosome - down syndrome ca also result from tranlocation of chromo segment from chormo 12 to 14

DAT Biology – Genetics – Flashcards

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