Genetics

genetics
the study of heredity
heredity
heredity
the passing of traits from one generation to the next
trait
a specific characteristic that varies from one individual to another
gene
gene
sequence of DNA that codes for a protein and thus determines a trait
genome
genome
the entire “library” of genetic instructions in DNA that an organism inherits
Gregor Mendel
Gregor Mendel
father of genetics
allele
allele
alternative form of a gene (one member of a pair) located at a specific position on a specific chromosome (a letter)
dominant allele
dominant allele
an allele that produces the same phenotype whether its paired allele is identical or different (capital letter)
recessive allele
recessive allele
an allele that produces its characteristic phenotype only when its paired allele is identical (lowercase letter)
genotype
genotype
the combination of alleles located on homologous chromosomes that determines a specific characteristic or trait (the allelic combination such as Bb)
phenotype
phenotype
the observable physical or biochemical characteristics of an organism, as determined by the genotype (the expressed trait such as brown eyes)
homozygous
homozygous
term used to refer to an organism that has two identical alleles for the same trait (ex. BB or bb)
heterozygous
heterozygous
term used to refer to an organism that has two different alleles for the same trait (ex. Bb)
Punnett square
Punnett square
diagram showing the gene combinations that might result from a genetic cross
gamete (sex cell)
gamete (sex cell)
specialized cell involved in sexual reproduction (sperm or egg)
probability
probability
the possibility of different outcomes (percentage or ratio)
monohybrid cross
monohybrid cross
a one-trait cross (ex. color)
dihybrid cross
dihybrid cross
a two-trait cross (ex. color & shape)
P generation
P generation
parental generation is the first generation involving two individuals that are mated to predict or analyze the genotypes of their offspring
F1 generation
F1 generation
first filial generation is the generation resulting immediately from a cross of the first set of parents (P generation)
F2 generation
F2 generation
second filial generation is the generation resulting from a cross between two F1 individuals
purebred
purebred
offspring that are the result of mating between genetically similar kinds of parents; opposite of hybrid; same as true breeding
hybrid
hybrid
offspring that are the result of mating between two genetically different kinds of parents; opposite of purebred
Principle of Dominance
Principle of Dominance
when individuals with contrasting traits are crossed, the offspring will express only the dominant trait
Law of Segregation
Law of Segregation
states that allele pairs separate, or segregate, during gamete formation
Law of Independent Assortment
Law of Independent Assortment
states that genes for different traits can segregate independently during the formation of gametes
non-Mendelian inheritance
non-Mendelian inheritance
refers to any pattern of inheritance in which traits do not segregate in accordance with Mendel’s laws (ex. incomplete dominance, codominance, multiple alleles, polygenic traits, sex-linked traits)
incomplete dominance
incomplete dominance
when one allele is not completely dominant over the other, or blending occurs (ex. Red + White = Pink)
codominance
codominance
occurs when BOTH alleles of a gene are expressed in an individual (ex. Black + White = Black & White Speckled)
multiple allele traits
multiple allele traits
traits that are controlled by more than two alleles (ex. ABO blood typing = A allele, B allele, & O allele)
polygenic traits
polygenic traits
a trait controlled by two or more genes; produce a wide range of phenotypes
sex-linked traits
sex-linked traits
a trait genetically determined by an allele located on the sex chromosome
pedigree chart
pedigree chart
a diagram that shows the occurrence and appearance or phenotypes of a particular gene or organism and its ancestors from one generation to the next
chromatin
chromatin
unraveled and long DNA (during interphase)
chromosome
chromosome
condensed, coiled, and shorted DNA (this occurs during mitosis and meiosis)
chromatids
chromatids
the two identical halves of a single replicated eukaryotic chromosome and joined at the centromere
homologous chromosomes
homologous chromosomes
chromosome pairs of approximately the same length, centromere position, and staining pattern, with genes for the same characteristics at corresponding places (one homologous chromosome is inherited from the mother; the other from the father)
daughter cells
daughter cells
new cells
mitosis
mitosis
a type of cell division that results in two genetically identical daughter cells each with the same number of chromosomes of the parent cell
meiosis
meiosis
a type of cell division that results in four genetically different daughter cells each with half the number of chromosomes of the parent cell (also known as reduction division)
sexual reproduction
sexual reproduction
process by which two cells from different parent unite to produce the first cell of a new organism
asexual reproduction
asexual reproduction
process by which a single parent reproduces by itself
crossing over
crossing over
process in which homologous chromosomes exchange portions of their chromatids during meiosis (also called gene shuffling)
genetic variation
genetic variation
genetic differences within a species
fertilization
fertilization
a process in sexual reproduction in which a sperm unites with an egg to make the first cell of a new organism, or zygote
zygote
zygote
fertilized egg
somatic cell
somatic cell
body cell (non-sex cell)
haploid (N)
haploid (N)
term used to refer to a cell that contains only a single set of chromosomes and therefore only a single set of genes (Humans N = 23)
diploid (2N)
diploid (2N)
term used to refer to a cell that contains both sets of homolgous chromosomes (Humans 2N = 46)
chromosomal mutation
chromosomal mutation
mutation that affects the number or structure of whole chromosomes
deletion chromosomal mutation
deletion chromosomal mutation
a mutation that involves the loss of all or part of a chromosome
duplication chromosomal mutation
duplication chromosomal mutation
a mutation that produces extra copies of parts of a chromosome
inversion chromosomal mutation
inversion chromosomal mutation
a mutation that reverses the direction of parts of a chromosome
translocation chromosomal mutation
translocation chromosomal mutation
a mutation that occurs when part of one chromosome breaks off and attaches to a different chromosome
nondisjunction
nondisjunction
the most common error in meiosis and occurs when homologous chromosomes fail to separate
trisomy
trisomy
a condition in which an extra copy of a chromosome is present in the cell nuclei, causing developmental abnormalities
polyploidy
polyploidy
condition in which an organism has extra sets of chromosomes because a complete set of chromosomes failed to separate during meiosis (ex. 3N or 4N)
DNA fingerprinting
DNA fingerprinting
an individual’s unique sequence of DNA base pairs, determined by exposing a sample of the person’s DNA to molecular probes
genetic engineering
genetic engineering
the process of making changes in the DNA code of living organisms
genetically modified organism (GMO)
genetically modified organism (GMO)
one that has artificially acquired one or more genes from the same or different species
plasmid
plasmid
circular DNA found in bacteria
recombinant DNA
recombinant DNA
DNA produced by combining DNA from different organisms (DNA is cut out of one organism and recombined with another organism’s DNA)
enzyme
enzyme
protein that speeds up chemical reactions in organisms
restriction enzyme
restriction enzyme
DNA-cutting enzymes found in bacteria
biotechnology
biotechnology
the use of living organisms or other biological systems in the manufacture of drugs or other products or for environmental management, as in waste recycling
karyotype
karyotype
a picture of an organism’s genome and can be used for chromosomal anlysis
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