Breeding and Genetics Exam 1

What are genes?

All the information needed to create a functioning organism

What is the central dogma of biology?

DNA leads to RNA which leads to a protein

What is a genotype?

The genetic makeup of an individual (or DNA)

What is a trait?

An observed or measurable characteristic of an individual

What is a phenotype?

An observed category or a measured level of performance for a specific trait

How are traits and phenotypes different?

Traits are a characteristic while phenotype is the level of performance of that trait

What are interactions?

A dependent relationship among components of a system where the effect of any component depends on the others present

Explain P = G X E

Phenotype is equal to genotype by environment. Dependent relationship

What is a system?

A group of interdependent component parts

What would count as parts of a system?

Animals, physical environment, resources, economics

What are alleles?

An alternative form of a gene

What is the randomness of inheritance?

Genetic variability in populations. Random selection of parental genes and random selection of gametes

What are chromosomes?

A long strand of DNA and associated proteins present in the nucleus of every cell

What is the law of independent assortment?

Assuming normal conditions, genes assort independently during meiosis and all possible gametes form in equal proportions

What is the law of segregation?

The single copy of the gene the gamete receives from its parent cell is random

What is linkage?

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

What is crossing over?

Occurs during DNA replication between non-sister chromatids where a small part is transferred to the other

What is recombination?

The formation of a new combination of genes on a chromosome due to crossing over

What is the difference between a gamete and a zygote?

The zygote is the sperm plus the egg. A gamete is each individual piece

What is a haploid cell?

One copy of each gene (1n)

What is a diploid cell?

Two copies of each gene (2n)

How do we determine the number of gametes?

2ⁿ

Equation for the number of unique zygotes.

3ⁿ x 2^m. n is number of loci BOTH parents are heterozygous, m is the number of loci ONLY ONE parent is heterozygous

Why do we choose superior genetic stock during selection?

More likely to produce improved or high-performing offspring (randomness affects this)

What is complete dominance?

The expression of the heterozygote is identical to the expression of the homozygous dominant genotype

What is partial dominance?

In heterozygotes, expression of genotypes is indeterminant or resembles homozygous dominant genotype

What is co-dominance?

Both genes are dominant and expressed in a 1:1 ratio

What is epistasis?

Genes at different loci can interact

What does it mean when inheritance is sex linked?

Expression of genes differ between males and females

What is a simply inherited trait?

Traits affected by only one or a few genes

Are simply inherited traits affected by environment?

Almost never

What is a polygenic trait?

Traits affected by many genes

Are polygenic traits affected by the environment?

Yes

How do we tell simply inherited traits apart from polygenic traits?

Simply inherited traits are qualitative while polygenic traits are quantitative

What is a threshold trait?

Polygenic traits that look like simply inherited traits

Why are polygenic traits important for livestock?

The influence growth rate, fertility, egg production, and milk production

What is a test mating?

A mating designed to reveal the genotype of an individual for few loci

What is the most useful genotype to have in a test mating?

A homozygous recessive dam

Why are test matings not always practical?

Need labor, care for the animals, home for the calf. Costs a lot of money

What are the differences between artificial and natural selection?

Natural selection is independent of human control. Artificial selection is with human control

Is artificial or natural selection faster?

Artificial selection

What are breeding values?

The most value as genetic parents (best set of genes)

What is phenotypic selection?

Individuals with certain observable traits (phenotypes) have higher survival and reproduction rates. This drives evolution

What is performance testing?

The systematic measurement of performance (phenotype) in a population

What is progeny data?

Information on the genotype or performance of descendants of an individual

What is pedigree data?

Information on the genotype or performance of ancestors and (or) relatives of an individual

How are pedigree and progeny data different?

One focuses on the individual’s past while the other focuses on the future

What is gene frequency?

The relative frequency of a particular allele in a population

What is genotypic frequency?

The frequency of a particular genotype in a population

What do q and p stand for?

p = frequency of the dominant allele

q = frequency of the recessive allele

What do P, H, and Q stand for?

P = homozygous dominant

H = heterozygous

Q = homozygous recessive

What does it mean when an allele is fixed?

Only one allele is present in a population

What is a recessive lethal allele?

A recessive allele that leads to death at birth. Leads to a reduction in heterozygotes

What is P equal to in HWE?

p²

What is H equal to in HWE?

2pq

What is Q equal to in HWE?

q²

What is Hardy Weinberg Equilibrium?

In a population with no changes, gene frequencies will remain the same

What needs to occur for a population be in HWE?

No mutation, disease, migration, or random drift