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Flashcards in Ch. 3 Deck (52):
1

Genes*

Basic unit of inheritance

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Transcription facotrs

turn genes on and off

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Chromosomes*

long strands of DNA plus associated proteins.

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Homologs*

pairs of chromosomes

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Locus*

denotes the site of a particular gene on a chromosomes

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Alleles*

alternate forms of these genes

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multiple alleles*`

more than twp possible alleles at a locus. ex. coat color in dogs

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homozygous*

if both genes at a given locus are functionally the same

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Heterozygous*

If the genes at a given locus are functionally different

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Gregor Mendel (1822-1884)

Father of Modern Genetics. Performed genetic experiments on peas. Called genes "factors"

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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.

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Law of Independent Assortment*

Genes for different traits can segregate independently during the formation of gametes.

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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.

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meiosis*

the process of germ cell formation

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Independent Assortment

During metaphase, chromosomes line up in Pairs, but they line up randomly

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Linkage*

the occurrence of two or more loci of interest on the same chromosome

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Crossing over*

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

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Genetic recombination*

The formation of a new combination of genes on a chromosome as a result of crossing over

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Zygote*

the result of the fusion starting embryonic development

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Punnett Square

A device for determining genotypes of possible zygots obtainable from a mating

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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)

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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)

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Blending Theory

Before Mendel, scientists thought blending of fluids determined genetic make-up (% blood)

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Medelian Inheritance allows for

extreme genetic variability and thus randomness

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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

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Animal Breeding goal:

Shift the bell curve

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Dominance*

An interaction between genes at a single locus such that in heterozygotes one allele has more effect than the other. Usually uppercase

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4 different forms of Dominance

Complete, partial, codominance, overdomincance

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Complete dominance*

The expression of the heterozygote is identical to the expression of the homozygous dominant genotype.
Often letha, semilethal, and deleterious conditions in animals

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Exs. of Deleterious Recessives in livestock

Arthrogyposis Multiplex in cattle (curly calf)
Spider syndrome in sheep
Lethal White syndrome in Horses
Porcine stress syndrome

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Partial Dominance*

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.

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Ex. of partial dominance

Hyperkalemic Periodic Paralysis

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Codominance*

a form of dominance in which the expression of the heterozygote is exactly midway between the expressions of the homozygous genotypes. aka no dominance

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ex. of codominance

shorthorn catte

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Overdominance

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.

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Ex, of overdominance

Warfarin-resistant wild rates: Homo r dies; Homo d is Vit. K deficience and hetero is normal

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Epistasis

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.

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2 types of epistasis

Masking and modifying

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Breed true

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.

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Jost Paradign

Chromosomal Sex leads to Gonadal Sexy . Gonadal Sex leads to Phenotypic Sex. Each step is dependent on the previous one

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Which sex determines sex?

male

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Male

XY one Y will always cause testis formation, no matter how many Xs

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Female

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

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Hemizygous*

Having only one gene of a pair. Males are this because genes appear on the X

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Sex-linked inheritance*

the pattern of inheritance for genes located on sex chromosomes

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Y-Chromosomes

SRY gene encodes Testis Determining Factor

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Wolffian

the males duct systems

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Mullerian

The female duct systems

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Ex. of sex-linked inheritance

Calico cats, color blindness in humans, barred and black plumage in poultry, hemophilia, and AIS

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Sex-Limited Inheritance*

A pattern of inheritance in which the phenotypic expression is limited to one sex. However, other gender still has alleles for trait ex. BOOBS

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Sex-influenced inheritance*

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

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Exs. of sex-influenced

Horns in sheep, male pattern baldness, Scurs in cattle