Genetics Flashcards by Ann Sargen

Define genetics

Study of heredity

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When and who started modern genetics? (Quantitative genetic testing)

Gregor Mendel 1800s

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Define phenotype

Physical appearance of animal
Physical expression of genes

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Define genotype

Genetic makeup

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Define genome

Entire genetic material of an animal

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Define genes

Functional units of inheritance

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Polymer of DNA and its 3 parts

Nucleotide
1. 5 carbon sugar (ribose vs. deoxyribose)
2. Phosphate
3. Nitrogenous base

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5 main nitrogenous bases

Pyrimidines: cytosine and thymine (uracil)
Purines: Adenine and Guanine

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Significance of base pairing

Easy to exactly replicate (duplicate) accurately

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Define mutation

When replication is not exact due to chemical change in DNA
(This word is overused)

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Define migration

Bringing new genotypes through breeding stock into a population

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Define selection

Using some animals more than others as parents
Natural: by nature
Artificial: by management

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What are the products of genes?

Protein molecules via synthesis of amino acids

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Triplet codes vs. codon

Triplet code: DNA
Codon: RNA
- 64 possibilities for 20-21 amino acids

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Define autosomes

Chromosomes in somatic cells

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How many chromosome pairs do humans, horses, cattle, wheat, and fruit flies have?

Humans- 23
Horses- 32
Cattle- 30
Wheat- 21
Fruit fly- 4

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Define transcription

Synthesis of mRNA strand by “copying” a DNA segment

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Define translation

Production of amino acids from RNA codon sequences

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Protein synthesis pathway

DNA (transcription in nucleus) mRNA (translation in ribosomes) proteins folding

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3 types of RNA

Messenger (mRNA)- contains information to directs protein synthesis
Ribosomal (rRNA)- structure and function of ribosomes
Transfer (tRNA)- identifies codons in mRNA and brings correct amino acid

Define locus

Location of a particular gene on a chromosome (address)

Define homologous chromosomes

Same loci and structure

Define alleles

Different forms of the same gene

Define homozygous

Genes are alike for a particular trait (same alleles)

Define heterozygous

Genes are not alike for a particular trait (different alleles)

Define dominant

An allele that overpowers and prevents the expression of another allele

Define recessive

An allele that is expressed only when animal is homozygous for non-dominant allele

Where does random (independent) assortment occur?

Meiosis

3 gene actions

Qualitative inheritance (simple traits) Sex-linked inheritance Quantitative inheritance (polygenic traits)

Describe qualitative inheritance

Controlled by a single gene Phenotype is discontinuous (Ex. Cow coat color)

Define codominance

When two alleles are both expressed in heterozygote Ex. Checkered chickens

Define incomplete dominance

Get 3 distinct phenotypes instead of 2 Hetero is dilute or medium (Ex. Pink flower)

Sex-linked inheritance in mammals vs. birds/ reptiles

Mammal F- XX M- XY Reptiles/ Birds F- ZW M- ZZ Genes uncontested on sex chromosome is expressed no matter what.

Describe quantitative inheritance

Many genes involved (additive effects) Phenotypes described by measurements Continuous distribution of phenotypes

Define heterosis

Other names: overdominance + hybrid vigor Heterozygote shows better results than either homozygote Often in crossbreeding

Most common equation in genetics

Phenotype= genotype + environment (Means we must standardize environment for studies)

Formula for genetic progress

Genetic gain/year= (heritability x selection differential (intensity))/generation interval in years

What is heritability?

(h^2) Percent of trait dictated by genetics Estimates variation in phenotypes Ranges from 0-1 .4-.5 for weight .1 for health, fitness, reproduction

How to calculate selection differential?

Compare average of selected male/female with population average and divide by two. Then Add to pop. Avg.

What is the generation interval?

The average age of parents when offspring born.

Evidence of genetic change

Meat to bone ratio in turkey Lean pigs

3 selection methods

Tandem- one trait at a time Independent culling levels- minimal acceptable levels assigned to traits Selection index- traits evaluated and expressed as a single score (can include economics and correlation)

Define registered

Recorded in some breed association and meets criteria outlined by org.

Define “grade”

Not registers Could be about same genetically as registered

3 effects of inbreeding

Increases homozygosity Decrease reproductive performance and growth More susceptible to stress and disease

Define line breeding

Milder form of inbreeding Emphasizes one outstanding ancestor

3 types of outbreeding

Species cross: ex. Mule or beefalo Crossbreeding: same species by different breed (max. Heterosis and breed complementation) Outcrossing: mating unrelated animals within a breed

How fast can inbreeding effects be eliminated?

In one generation

Positive vs. negative correlations

Positive= both increase together Negative= one goes up and the other decreases Close to 1 or -1 is stronger