Exam 4 Flashcards
What is inbreeding?
Mating of relatives more closely related than the average of the population
What are some effects of inbreeding?
Increase homozygosity
Prepotency in inbreds
Expression of deleterious recessive alleles
Inbreeding depression
What increases homozygosity?
Number of common ancestors
What is a common ancestor?
An ancestor common to more than one individual
What is prepotency in inbreds?
Ability of an individual to produce progeny whose performance is the same as its own or is uniform
What does prepotency cause?
Fewer heterozygous loci
Cannot produce as many different gametes
Does inbreeding create genetic defects?
No, they must already be in the population
What does inbreeding do for deleterious recessive alleles?
Increases the likelihood of them becoming homozygous and expressing themselves
What is inbreeding depression?
Reverse hybrid vigor
What does inbreeding depression mean for gene combination value?
It’s poor
What is poor gene combination value a direct result of?
Increased homozygosity
What is homozygosity and heterozygosity like with increased inbreeding?
Increased homozygosity, decreased heterozygosity
What traits does hybrid vigor work on first?
Fitness
What is GCV and BV like with low heritability?
More GCV and less BV
What is GCV and BV like with high heritability?
Less GCV and more BV
What is the inbreeding coefficient?
Measure of the level of inbreeding in an individual
What does it mean if an individual is 25% inbred?
It means that at a given locus in the individual, the probability that the two genes at the locus are identical by descent is 25%
Know the formula for inbreeding coefficient and Wright’s coefficient of relationship
Know the formula for inbreeding coefficient and Wright’s coefficient of relationship
What are the 6 steps for calculating inbreeding and relationship coefficient using path method?
- Convert the pedigree to an arrow diagram in which each individual appears only once
- Locate common ancestors
- Locate inbred common ancestors and calculate the inbreeding
- Fill in the table
- Sum the last column
- Divide the sum
What is line breeding?
Mating of individuals within a particular line
What are 2 reasons to inbreed?
Increase uniformity
Create an opportunity for hybrid vigor–inbred line crossed with inbred line
What is outbreeding/outcrossing?
Mating of unrelated individuals
What does outbreeding do for homozygosity and heterozygosity?
Increase heterozygosity, decrease homozygosity
What are 3 effects of outbreeding?
Masking deleterious alleles
Hybrid vigor or heterosis
Breed complementarity
What does hybrid vigor increase?
GCV
Fitness traits
What is heterosis/hybrid vigor?
An increase in the performance if hybrids over that of purebreds, most noticeably in traits like fertility and survivability
How do you measure hybrid vigor?
The difference between the average performance of crossbreds and the average performance of their parent lines of breeds
What is F1 hybrid vigor?
The amount of hybrid vigor attainable in first cross individuals
Maximum hybrid vigor
Know equations 3, 4, 5, and 6 in notes
Know at equations 3, 4, 5, and 6 in notes
What are some hybrid vigor estimates?
Individual (direct component)
Maternal
Paternal
What is measuring heterosis levels doing?
Matching of unlike genes
What is retained hybrid vigor?
Hybrid vigor remaining in later generations of hybrids
What are general rules for retained hybrid vigor? (3)
Retained hybrid vigor is commonly expressed as a proportion of F1 vigor
Hybrid vigor displayed by two-breed F1 crosses is halved in the corresponding F2s
Mating of F2s to produce F3s will not diminish hybrid vigor–Hardy-Weinberg equilibrium
What are the 7 criteria for evaluating different crossbreeding systems?
Merit of component breeds Hybrid vigor Breed complementarity Consistency of performance Replacement considerations Simplicity Accuracy of genetic prediction
What is the amount of hybrid vigor in progeny in a two-breed terminal crossbreeding system?
100%
What is the amount of hybrid vigor in females in a three-breed terminal crossbreeding system?
100%
What is the amount of hybrid vigor in progeny in a three-breed terminal crossbreeding system?
100%
Look at the terminal crossbreeding chart
Look at the terminal crossbreeding chart
What is the amount of hybrid vigor in progeny in a two-breed rotational crossbreeding system after 7 generations?
67%
In a two-breed rotational crossbreeding system, what are the progeny females made of?
67% breed of sire
33% breed of maternal grandsire
What is the amount of hybrid vigor in progeny in a three-breed rotational crossbreeding system after 7 generations?
86%
In a three-breed rotational crossbreeding system, what are the progeny females made of?
57% breed of sire
29% breed of maternal grandsire
14% remaining breed
Look at 2-breed and 3-breed rotational crosses
Look at 2-breed and 3-breed rotational crosses
What is the amount of hybrid vigor in progeny in a two-breed rotational and terminal crossbreeding system after 7 generations?
67% in rotation
100% in terminal
What is the amount of hybrid vigor in progeny in a three-breed rotational and terminal crossbreeding system after 7 generations?
86% in rotation
100% in terminal
Look at 2-breed and 3-breed rotational and terminal crosses
Look at 2-breed and 3-breed rotational and terminal crosses
What is the amount of hybrid vigor in progeny in a four-breed rotational crossbreeding system?
93%
What is a sire rotation?
Rotate sire every 4th year
How was selection done in the past?
Selection based on phenotypes
Selection based on genetic predictions
What are 4 examples of technology used in animal breeding?
MOET
Cloning
Sexed semen
Split embryos
What is MOET?
Multiple ovulation and embryo transfer
What can MOET be used to do?
Increase numbers of offspring per female
What happens in cloning?
Somatic tissue is taken from a female and cells are grown, then transferred to recipients to get the exact copies of the cloned individual
What is accomplished with sexed semen?
Sex control
How is sex control done?
X sperm produces female, Y sperm produces males
How do split embryos work?
If there is a 16 cell embryo, 8 cells are put into one recipient and the other 8 are put into another
What is some DNA technology now available to producers? (3)
Fingerprinting
Genetic markers
Gene transfer
What is fingerprinting?
The occurrence of a fragment indicates it was received from one or both parents
What are genetic markers?
Positions on a chromosome that can be identified
How is selecting at the DNA level done? (3)
DNA fingerprinting
Identification of genetic defects
Marker-assisted selection
What does marker assisted selection use?
Genetic markers to select animals for quantitative traits
What should genetic markers be used in association with?
Measures of genetic merit to make the most genetic change
Why do genetic markers not change very much in performance?
There are associated with one gene
What is fingerprinting useful for?
Parental identification in multi-sire herds
What should marker assisted selection be used with?
Quantitative measures
