Genetics Flashcards
what is a gene?
a gene is a sequence of DNA that directs protein synthesis in a specific manner. these proteins influence how traits are developed
what is mRNA?
messenger RNA, is a template which directs assembly of amino acids into proteins
what is a genotype?
the numer and type of genes an animal possesses (gentic composition)
what is a phenotype?
it is the characterisic of an animal that can be seen or measured (outward appearance)
what is genomics?
involves estimating genetic composition of animals and the function of the genes
what is a chromosome?
it is a collection of genes, typically large, rod-like structures in the cell nucleus. somatic cells have paired chromosomes (diploid) while gametes (sperm, egg) have one copy of the chromosome (haploid)
how is gender determined in mammala?
one chromosome pair determines gender. XX is female (eggs always gets an X chromosome) while XY is male (sperm carry X or Y). the sire determines the gender of the offsrpings.
what is a locus?
a locus (loci) is the location of a gene on a chromosome
what is an allele?
an allele is the gene(s) that occupies the same locus on homologous chromosomes. Homolgous refers to the matching chromosomes (pairs) in somatic cells.
what does it mean for gene pairs to be homozygous?
both alleles are the same on the corresponding chromosomes
what does it mean for gene pairs to be heterozygous?
means the alleles are different
what is simple dominance?
in simple dominance, when an animal is heterozygous, one gene is expressed (dominant alles) and coat color is not (recessive allele)
how does simple dominance apply to beef cattle coat color?
black color is dominant (B) and red color is recessive (b). the possible genotypes are BB (homozygous dominant, black), Bb (heterozygous, black but carries red gene), and bb(homozygous recessive, red)
if you breed a BB bull and a Bb cow, what are the possible genotypes and phenotypes of the offspring?
BB (50%), Bb(50%) possible phenotype: blackl
if you brred a BB bull and a bb cow, what are the possible genotypes and phenotypes of the offsprings?
Possible: Bb (100%) possible phenotypes: black
if you breed a Bb bull and a Bb cow, what are the possible genotypes and phenotypes of the offspring?
possible phenotypes: BB (25%), Bb (25%), bb (25%). possible phenotypes: black (75%), red 25%)
Are most traits expressed by simple dominance?
no. Sometimes with heterozygous pairings, both alleles are shown to some extent, and many times there is more than one gene involved.
how does the horse example illustrate traits beyond simple dominance?
a chestnut (red) color (homozygous recessive at one locus) with one dilution allele ( at another locus) shows up as a palomino horse. with 2 dilution alleles, it results in a cremello color.
are all traits influenced equally by genetics?
no. environment influence is not passed on, and breeding animals are selected based on genetics.
what is the relationship between genotype, environment and phenotype?
genotype+environment= phenotype (what you see)
what is heritability?
the proportion of phenotypic differences among animals that is due to differences in genotype
give examples of traits that are 100% heritable.
eye color and coat color. however, sometimes the uterine environment can influence coat color patterns, such as holstein cattle.
if the environment does not influence a trait, what is the equation for phenotype?
genotype= phenotype
do most traits involve both genetic and environment component?
yes. the higher the heritability number, the greater the influence of genetics
what is “selection differential”?
the superiority of selected animals compared to the average of herd or group of animals
how do you calculate selection differential?
by subtracting the herd average from the individual’s measurement.
example: bull calf has 235 lb weaning weight, herd calves average 540 lb weaning weight, so the selection differential is 535-450= 85 lbs.
what is crossbreeding?
mating of animals from two breeds to reproduce offspring with complementary traits that will enhance the offspring’s economic value
how can maternal ancestry be traced?
using DNA found in mitochondria
how can paternal ancestry be traced?
through Y chromosomes
how can total DNA analysis be traced through the Y chromosome?
total DNA analyzes the entire genome- all 23 pairs of chromosomes- as opposed to only looking at the y chromosome of mitochondrial DNA. autosomal chromosomes carry genetic information from both parents that’s passed down through the generations
what is epigenetics?
the study of heritable changes in gene function that occur without a change in the sequence of the DNA. “Tags” on DNA can turn genes on or off
can epigenetic effects be passes on to the next generation?
yes, they can without altering the genetic codes in the DNA
what is embryo tranfer in catter?
Steps: 1. superovulate the donor cow with FSH hormone. Breed her AI. collect the embryos one week later. transfer embryos into recipient cows at the same stage of the cycle. the recipient cows carry the fetuses to term. embryos can be frozen for later use.
