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Animal Science Chapters 12-14


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What are the functional units of inheritance?
From which process are more body cells produced?
Which livestock animals have the most pairs of chromosomes?
Which livestock animals have the least pairs of chromosomes?
In which process are sex cells produced?
What are the male and female gametes?
What is the cell division in which gametes are formed?
Where does meiosis occur?
in the primordial germ cells
What occurs to a cell before it is called a primary spermatocyte or oocyte?
chromosome replication and synapsis
How many sperm are produced from each primary spermatocyte?
How many chromosomes are present in the primordial germ cell?
4 (2 pairs)
How many chromosomes are present in each sperm?
2 (1 pair)
What does the first maturation division of oogenesis produce?
a secondary oocyte and the first polar body
What does the second maturation division of oogenesis?
an egg and the second polar body
How many chromosomes are present in each egg?
2 (1 pair)
What is the fertilized egg called?
a zygote
Is the zygote haploid or diploid?
Are gametes haploid or diploid?
What process in gametogenesis re-establishes the diploid number?
What are homologous chromosomes?
chromosomes that have the same size and shape and carry genes that affect the same hereditary characteristics
What is the purpose of genes?
to direct enzyme and protein production
What is the structural configuration of DNA?
a double helix
What is the locus?
the location of a gene on a chromosome
Which three products make up DNA?
deoxyribose sugar, phospate, and four nitrogenous bases
What is the nucleotide made up of?
deoxyribose, phosphate, and a nitrogenous base
What are the four nitrogenous bases of DNA?
adenine, thymine, guanine, and cytosine
How are nitrogenous bases coupled in DNA?
What are the three types of RNA?
transfer, messenger, and ribosomal
What is the first step in protein synthesis?
What is a codon?
the triplet sequence that codes for one amino acid in mRNA
Where does protein synthesis take place?
in the ribosome
What is the second step of protein synthesis?
the union of amino acids with their respective tRNA molecules
What binds with the mRNA codon?
the anticodon in the tRNA
Which chromosomes determine the sex of offspring?
the X and Y chromosomes
What are homozygous chromosomes?
chromosomes in which the genes located at corresponding loci correspond with each other in the way they control a trait
What are heterozygous chromosomes?
chromosomes in which the genes located at corresponding loci contrast with each other in the way they control a trait
What are alleles?
genes that occupy corresponding loci in homologous chromosomes but that affect the same trait in a different way
What are identical alleles?
genes that are alike and affect the character in the same way
What are the 6 mating possibilities with homozygous-dominant, heterozygous, and homozygous-recessive parents?
1) BBxBB
2) BBxBb
3) BBxbb
4) BbxBb
5) Bbxbb
6) bbbxbb
What is the ratio of offspring produced by the BbPpxBbPp combination?
9 black polled
3 black horned
3 red polled
1 red horned
What is linear interaction?
the interaction of a gene with other genes in the same chromosome
What is allelic interaction?
the interaction of a gene with its corresponding gene in a homologous chromosome
What is epistatic interaction?
the interaction of a gene with genes in nonhomologous chromosomes
What is an internal environmental factor that interacts with genes?
What are three external environmental factors that interact with genes?
nutrition, temperature, and amount of light
What occurs in complete dominance?
unlike genes occupy corresponding loci and only the effect of the dominant gene is expressed
When does lack of dominance occur?
when a phenotype is shown that is intermediate between the two homozygous phenotypes
What do the more vigorous crossbred offspring possess?
What is partial dominance?
when the heterozygote expresses a phenotype that is intermediate to either homozygote but more closely resembles the homozygous dominant pairing
What is an example of partial dominance?
the presence of hyperkalemic paralysis in horses
What is the most important external environmental factor on genes?
feed supply
What is biotechnology?
the use of living organisms to improve, modify, or produce industrially important products or processes
What are quantitative traits?
those that can be objectively measured and are controlled by many gene pairs
What are qualitative traits?
those that are visible to the eye and are controlled by few gene pairs
What is the phenotype?
the observation or measurement of each trait
What two sources cause phenotypic variation?
genotype and environment
What is breeding value?
the portion of the genotype that can be transferred from parent to offspring
the total of all the independent genetic effects in an animal on a given trait
What is nonadditive value?
the portion of genotype that is attributed to the gene combinations unique to a particular animal
What are known environmental effects?
those that have an average effect on indivuals in a specific category
What are unknown environmental effects?
those that are random and are specific to an individual phenotype
Can unknown or known effects be quantified?
What is selection?
preventing some animals from reproducing while allowing other animals to breed commonly
What are the three factors that affect the rate of genetic improvementfrom selection?
selection differential, heretability, and generation interval
What is selection differential also called?
What is selection differential?
the superiority of selected animals compared to the herd average
What is heritability?
the percent of total phenotypic that is due to breeding value
the portion of the selection differential that is passed from parent to offspring
What is realized heritability?
the portion of heritability actually obtained compared to what was attempted in selection
Which traits are considered highly heritabile?
those that have heritability estimates of 40% and higher
Which traits are considered mediumly heritable?
those that have heritability estimates between 20 and 39%
Which traits are considered to have low heritability?
those that have heritability estimates lower than 20%
average age of the parents when the offspring are born
generation interval
species in which artificial insemination is used more than any other species
dairy cattle
three methods of selection for genetic change
tandem, independent culling level, and selection index
What is the tandem method?
selection for one trait at a time
What is the independent culling level selection method?
establishing minimum culling levels for each trait
the most prevalent selection method
independent culling level
What is the selection index selection method?
establishing a culling level for multiple traits
the most effective selection method
selection index
the basis for modern selection
expected progeny differences
are most commercial slaughter livestock purebred or crossbred?
the mating of closely related animals whose ancestors have been inbred for several generations
intensive inbreeding
mild inbreeding where a high genetic relationship is maintained with an ancestor or line of ancestors
four types of outbreeding
species cross, crossbreeding, outcrossing, grading up
crossing of animals of different species
species cross
mating of animals of different breeds
mating of unrelated animals within the same breed
mating of purebred sires to commercial-grade females and their offspring for several generations
grading up
is heterosis highest for low-heritability or high-heritability traits?
low-heritability traits
the most widely used breeding system

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