genetics

Question 1

single nucleotide polymorphism (SNP)

Answer 1

diff in DNA sequence at the same site of genome btwn 2 diff people

Question 2

double muscle cattle

Answer 2

myostatin stops muscle hypertrophy after birth

• single point mutation GCGA ➔ GTGA disrupts myostatin
• no control on muscle hypertrophy ➔ double muscled cattle

Question 3

selective breeding traits

Answer 3

• growth rate
• food efficiency
• muscle
• marbling ability
• coat color
• disease resistance

Question 4

genetic probability

Answer 4

actual and expected ratios of genotypes may not match in small populations, but in very large populations, actual ratio may come close to the expected

Question 5

pedigree

Answer 5

genetic representation of a family tree that shows inheritance of a trait or disease across several generations

• shows relationships between herd members & indicates which individuals have or carry the trait/disease

Question 6

allele frequencys

Answer 6

proportion of a particular allele present in a population, for a specific locus

• # of copies of an allele divided by the # of copies of all possible alleles at that particular locus in a population

Question 7

genotype frequency

Answer 7

proportion of a particular genotype in a population, at a specified number of loci

Question 8

Hardy-Weinberg equation

Answer 8

gives expected genotype frequency

• p² + 2pq + q² = 1
• genotypic value is the sum of the effects of each allele for that genotype
• additive gene action: each allele present in an animal contributes to the phenotype in an additive manner

Question 9

partial dominance

Answer 9

expression of the heterozygote is intermediate to the expressions of homozygous genotypes and more closely resembles the expression of the homozygous dominant genotype.

Question 10

no dominance (incomplete dominance)

Answer 10

intermediate phenotype (blend)

• exactly midway

Question 11

overdominance

Answer 11

phenotype is more pronounced in a heterozygote than homozygote, but most closely resembles the expression of the homozygous dominant phenotype

Question 12

epistasis

Answer 12

multiple genes interact to determine phenotype

• ex: albino color in mice, where two recessive alleles at one locus affect expression all other coat color loci

Question 13

law of segregation

Answer 13

two copies of a gene (1 maternal + 1 paternal) separate so that each gamete receives only one copy

• mendel’s 1st law
• Each gamete will have one allele at any given locus

Question 14

law of independent assortment

Answer 14

alleles of different genes assort independently of one another during gamete formation

• genetic recombination (crossing-over)
• mendel’s 2nd law
• allele pairs segregate independently of one another

Question 15

quantitative traits

Answer 15

• phenotypes show a continuous, numerical expression
• bell curve
• affected by combination of diff genes
• phenotypes cannot be divided into a number of discrete classes only continuous range of measurements
• determined by a large number of genes, each with a small effect
• influenced by environmental factors
• ex: height, weight, intelligence

Question 16

additive gene action

Answer 16

each allele present in an animal contributes to the phenotype in an additive manner