Stutts - ANSC 4395 Breeding & Genetics - Test 3 QUESTIONS
AND ANSWERS 100% CORRECT
Simply-Inherited Traits Correct Answer: traits affected by only a few genes
qualitative or categorical
affected little by environment
Quantitative Correct Answer: measured with numbers
Polygenic Traits Correct Answer: Affected by many genes with no gene having an overriding
influence.
- EX: Growth rate, milk production, ribeye area
Typically quantitative or continuous in expression.
- Phenotypes are usually described by numbers
Greatly influenced by environment
Examples of Simply-Inherited Traits Correct Answer: Coat color, horns
Examples of Polygenic Traits Correct Answer: Weaning weights, milk yield, REA... CANT DO
TEST MATINGS FOR THIS TYPE OF TRAIT
Threshold Traits Correct Answer: Polygenic traits that have categorical phenotypes
- Pregnancy, dystocia, gait
- Influenced by many genes but have an either/or result
Which traits are more important? Correct Answer: Polygenic traits, traits that determine
profitability and productivity
EX) Growth rate, fertility, milk production
Niche markets Correct Answer: markets more sensitive to simply-inherited traits
Simply Inherited Correct Answer: Genetic Defects
Common characteristics of Polygenic and Simply Inherited Correct Answer: 1. Both are subject
to the same Mendelian Mechanisms: Law of Segregation and Independent Assortment
2. Affected by dominance and epistasis
3. Principles of selection and mating apply to both
- Attempt to increase frequency of desirable alleles
(More difficult to do with polygenic traits)
Function of the Number of genes involved Correct Answer: - The more genes involved, the
more DIFFICULT it is to observe the effects of individual genes, and therefore the less specific
info we have about those genes
- When a few or one gene affects a trait, the effects of those genes are well understood (Exact
genotype may not be known, but a probable genotype may be identified.)
, Test Matings Correct Answer: Matings designed to reveal the genotype of an individual for a
small number of loci.
- used on simply inherited traits
- Have to characterize the net effect (breeding values, expected progeny differences)
Why test matings cannot be done on polygenic traits Correct Answer: Polygenic traits have so
many different genes affecting them
- Cannot observe the effects of specific genes
An individual that is Aa will produce gametes Correct Answer: - Half will contain A, other half
will contain a
- When populations are small, there may not be exactly half of each
Three types of test matings to determine if an individual is heterozygous Correct Answer: 1.
Mating to recessive
2. Mating to heterozygous
3. Mating sire to daughters (last resort)
Method with the highest probability of detection Correct Answer: Mating to recessive
- Probability of siring a recessive offspring is 1/2
If the condition is deleterious Correct Answer: - May be hard to find homozygous recessive
- Use known heterozygotes
- Probability of a recessive offspring is 1/4 or the probability of the offspring showing the
dominant phenotype is 3/4
If heterozygous females are hard to find, then mate sire to daughters Correct Answer: - Assume
the daughter's dams do not carry the recessive gene
- Probability that a daughter carries the recessive gene is 1/2 if sire is heterozygous
The probability of offspring showing the recessive phenotype is 1/8 Correct Answer: - 1/4 is
probability of homozygous recessive from mating heterozygotes
- 1/2 comes from half of the daughters of a heterozygous male are expected to carry the recessive
gene
- Probability of dominant phenotype from this mating is 7/8
The probability of a heterozygous male having all normal offspring ______ rapidly as the
number of matings _______ Correct Answer: diminishes ; increases
- When many normal offspring result from these matings, it is said that male is not a carrier of
gene
Most economically important traits are Correct Answer: quantitative
Quantitative Traits Correct Answer: - Measured on a numerical scale
- Under the influence of many genes and environment
- Express a continuous distribution from one extreme to another
AND ANSWERS 100% CORRECT
Simply-Inherited Traits Correct Answer: traits affected by only a few genes
qualitative or categorical
affected little by environment
Quantitative Correct Answer: measured with numbers
Polygenic Traits Correct Answer: Affected by many genes with no gene having an overriding
influence.
- EX: Growth rate, milk production, ribeye area
Typically quantitative or continuous in expression.
- Phenotypes are usually described by numbers
Greatly influenced by environment
Examples of Simply-Inherited Traits Correct Answer: Coat color, horns
Examples of Polygenic Traits Correct Answer: Weaning weights, milk yield, REA... CANT DO
TEST MATINGS FOR THIS TYPE OF TRAIT
Threshold Traits Correct Answer: Polygenic traits that have categorical phenotypes
- Pregnancy, dystocia, gait
- Influenced by many genes but have an either/or result
Which traits are more important? Correct Answer: Polygenic traits, traits that determine
profitability and productivity
EX) Growth rate, fertility, milk production
Niche markets Correct Answer: markets more sensitive to simply-inherited traits
Simply Inherited Correct Answer: Genetic Defects
Common characteristics of Polygenic and Simply Inherited Correct Answer: 1. Both are subject
to the same Mendelian Mechanisms: Law of Segregation and Independent Assortment
2. Affected by dominance and epistasis
3. Principles of selection and mating apply to both
- Attempt to increase frequency of desirable alleles
(More difficult to do with polygenic traits)
Function of the Number of genes involved Correct Answer: - The more genes involved, the
more DIFFICULT it is to observe the effects of individual genes, and therefore the less specific
info we have about those genes
- When a few or one gene affects a trait, the effects of those genes are well understood (Exact
genotype may not be known, but a probable genotype may be identified.)
, Test Matings Correct Answer: Matings designed to reveal the genotype of an individual for a
small number of loci.
- used on simply inherited traits
- Have to characterize the net effect (breeding values, expected progeny differences)
Why test matings cannot be done on polygenic traits Correct Answer: Polygenic traits have so
many different genes affecting them
- Cannot observe the effects of specific genes
An individual that is Aa will produce gametes Correct Answer: - Half will contain A, other half
will contain a
- When populations are small, there may not be exactly half of each
Three types of test matings to determine if an individual is heterozygous Correct Answer: 1.
Mating to recessive
2. Mating to heterozygous
3. Mating sire to daughters (last resort)
Method with the highest probability of detection Correct Answer: Mating to recessive
- Probability of siring a recessive offspring is 1/2
If the condition is deleterious Correct Answer: - May be hard to find homozygous recessive
- Use known heterozygotes
- Probability of a recessive offspring is 1/4 or the probability of the offspring showing the
dominant phenotype is 3/4
If heterozygous females are hard to find, then mate sire to daughters Correct Answer: - Assume
the daughter's dams do not carry the recessive gene
- Probability that a daughter carries the recessive gene is 1/2 if sire is heterozygous
The probability of offspring showing the recessive phenotype is 1/8 Correct Answer: - 1/4 is
probability of homozygous recessive from mating heterozygotes
- 1/2 comes from half of the daughters of a heterozygous male are expected to carry the recessive
gene
- Probability of dominant phenotype from this mating is 7/8
The probability of a heterozygous male having all normal offspring ______ rapidly as the
number of matings _______ Correct Answer: diminishes ; increases
- When many normal offspring result from these matings, it is said that male is not a carrier of
gene
Most economically important traits are Correct Answer: quantitative
Quantitative Traits Correct Answer: - Measured on a numerical scale
- Under the influence of many genes and environment
- Express a continuous distribution from one extreme to another
