Flashcards in Ch. 3 Deck (52):
Basic unit of inheritance
turn genes on and off
long strands of DNA plus associated proteins.
pairs of chromosomes
denotes the site of a particular gene on a chromosomes
alternate forms of these genes
more than twp possible alleles at a locus. ex. coat color in dogs
if both genes at a given locus are functionally the same
If the genes at a given locus are functionally different
Gregor Mendel (1822-1884)
Father of Modern Genetics. Performed genetic experiments on peas. Called genes "factors"
Law of segregation*
During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.
Law of Independent Assortment*
Genes for different traits can segregate independently during the formation of gametes.
Law of Dominance *
Some alleles are dominant while others are recessive; an organism w/at least one dominant allele will display the effect of the dominant allele.
the process of germ cell formation
During metaphase, chromosomes line up in Pairs, but they line up randomly
the occurrence of two or more loci of interest on the same chromosome
A reciprocal exchange of chromosome segments between homologs. Occurs during prophase 1 prior to the time homologous chromosomes are separated to form gametes. Exchanges genetic info which increases genetic variability
The formation of a new combination of genes on a chromosome as a result of crossing over
the result of the fusion starting embryonic development
A device for determining genotypes of possible zygots obtainable from a mating
Rule #1 of Probability w/Punnet Squares
The Probability of two independent events occuring together is the product of the probabilities of their individual occurrences (chance of getting homozygous)
Rule #2 of Probability w/Punnet Squares
The probability of one of the other of two mutually exclusive events occuring is equal to the sum of the probabilities of their individual occurences (chance of getting heterozygous)
Before Mendel, scientists thought blending of fluids determined genetic make-up (% blood)
Medelian Inheritance allows for
extreme genetic variability and thus randomness
Medelian Sampling *
The random sampling of parental genes caused by segregation and independent assortment of genes during germ cell formation and by random selection of gametes in the embryo. Reduces the ability of animal breeders to control outcomes of matings
Animal Breeding goal:
Shift the bell curve
An interaction between genes at a single locus such that in heterozygotes one allele has more effect than the other. Usually uppercase
4 different forms of Dominance
Complete, partial, codominance, overdomincance
The expression of the heterozygote is identical to the expression of the homozygous dominant genotype.
Often letha, semilethal, and deleterious conditions in animals
Exs. of Deleterious Recessives in livestock
Arthrogyposis Multiplex in cattle (curly calf)
Spider syndrome in sheep
Lethal White syndrome in Horses
Porcine stress syndrome
A form of dominance in which the expression of the heterozygote is intermediate to the expressions of the homozygous genotypes, but more resembles the expression of the homozygous dominant genotype.
Ex. of partial dominance
Hyperkalemic Periodic Paralysis
a form of dominance in which the expression of the heterozygote is exactly midway between the expressions of the homozygous genotypes. aka no dominance
ex. of codominance
A form of dominance in which the exression of the heterozygote is outside the range defined by the expressions of the homozygous genotypes, but most closely resembles the expression of the homozygous dominant genotype.
Ex, of overdominance
Warfarin-resistant wild rates: Homo r dies; Homo d is Vit. K deficience and hetero is normal
An interaction among genes at different loci such that the expression of genes at one locus depends on the alleles present at one or more loci.
2 types of epistasis
Masking and modifying
A phenotype for a simply-inherited trait is said to breed true if two parents w/that phenotype produce offspring of that same phenotype exclusively.
Chromosomal Sex leads to Gonadal Sexy . Gonadal Sex leads to Phenotypic Sex. Each step is dependent on the previous one
Which sex determines sex?
XY one Y will always cause testis formation, no matter how many Xs
XX One of the two X chromosomes in each cell inactivates by supercoiling into a structure known as a BARR BODY. This irreversible process is known as Lyonization
Having only one gene of a pair. Males are this because genes appear on the X
the pattern of inheritance for genes located on sex chromosomes
SRY gene encodes Testis Determining Factor
the males duct systems
The female duct systems
Ex. of sex-linked inheritance
Calico cats, color blindness in humans, barred and black plumage in poultry, hemophilia, and AIS
A pattern of inheritance in which the phenotypic expression is limited to one sex. However, other gender still has alleles for trait ex. BOOBS
A pattern of inheritance in which modes of gene expression differ between makes and females. Allele may be dominant in one gender, but recessive in the other gender