Final Exam Flashcards
Contrast the terms dominance and epistasis.
Both deal with alleles and loci
Dominance is alleles at one loci
Epistasis is the interaction of between alleles at multiple alleles
Define chromosome.
Mammal genome split in strands that holds genetic material and is diploid
Define Locus
Chromosome location
Define Gene
sequences in the genome that encode molecules and help the cells function
Define Allele
The different variants at a polymorphic loci
Define Mendel’s two laws.
Law of Segregation- animals ability to only pass on one set of chromosomes
Law of Independent Assortment- all loci and the alleles at the loci act independently of each other
Explain the differences between sex linked, sex influences and sex limited inheritance
Sex linked- XX and XY
Sex Influenced- Phenotype is affected by sex and genotype
Sex Limited- Milk for females or Semen for males
Names the four bases and if they are purine or pyrimidene.
Adnine and Guenine-Purines
Cytosine and Thymine- Pyrimidene
Is the double strand of a DNA helix bound in a parallel or antiparallel direction?
Antiparallel
What is the difference between an exon and an intron?
Both are transcribed
Introns are never translated into proteins
Exons are translated into proteins
What are the 3 steps during RNA processing before translation
1) Add 5’ Guanosine triphasphate cap
2) Add a 3’ poly A tail
3) Splice out introns and rebond exons
What is the function of the transcription factor?
Increase expression of a gene
Why are transcription factors necessary in cells?
Determine which genes will be expressed in each cell
What are the five forces that can change genotype frequencies in a population? Which cannot also change allele frequencies?
Mutation, Migration, Selection, Random Drift, Non Random Breeding
Explain why it is possible to completely eliminate a dominant allele from a population through selection but almost impossible to completely eliminate a recessive allele through selection?
1) You can’t differentiate between non carriers and recessive carriers
2) When the frequency of the recessive gets really low in a herd, most recessives are found in heterosous animals
Provide an example of how each of the five forces that can change genotype frequencies works in a population.
1) Mutation-Mistake in DNA replication
2) Migration-Purchase or sale of animals
3) Selection-choose animal for a trait
4) Random Drift-Small Random changes in allele frequencies
5) Non Random Breeding-crossbreeding or inbreeding
What is measured by a standard deviation?
The spread of the data but in units easier to interpet
Compare and contrast correlation of coefficients +0.89, +0.02 and -0.91.
1) Direction of correlation-positive or negative, +0.89 and +0.02 are positive, -0.91 is negative
2) Magnatude- Correlation is stronger closer to 1 and -1.
0. 02 is weak and -0.91 and 0.89 is strong
What is fitness?
Average number of offspring produced by a genotype
List a Polygenic Quantitative.
Ribeye Area
List a Qualitative Simply Inherited Trait.
Coat Color
List a Qualitative Polygenic.
Fertility
Why is selection for a simply inherited trait often easier than selection for a polygenic trait?
1) SI traits are only affected by several genes
2) Polygenic traits are more affected by the environment than SI traits
How is it possible for the true breeding value of an offspring to be greater than the average of the true breeding values of its parents?
Medallion Sampling.
Provide an example of a repeated trait. Why is it a repeated trait?
Litter size- It can be recorded more than once
What is the mathematical relationship between an animals BV and PD or TA?
PD=1/2 x BV
Write a definition of heritability.
Regression of BV on Phenotype
Why is heritability important?
Higher heritability makes genetic change faster
Name three ways you can increase trait heritability. Why would you want to increase it?
1) Treat all animals uniformly
2) Increase number of records
3) Be precise when measuring traits
Why?- Our phenotype becomes a more accurate selection tool for BV
What is contemporary grouping?
A group of animals of the same gender, age and managed the same.
What are three ways you can manage for or against a simply inherited trait?
1) Crossbred
2) DNA test and cull carriers
3) DNA test and only breed to noncarriers
What are the factors that affect rate of genetic gain in a herd. Define these factors.
1) Selection accuracy-Correlation between true and estimated BV
2) Selection Intensity-How picky you are for a trait
3) Genetic variance- standard deviation of the BV
4) Generational Interval- average age parents in the herd
Why do we calculate EPDs?
Allows us to increase selection accuracy
What does it mean when we say that EBV is an “unbiased” estimate of the true BV?
As we add more info on an animal we have an EQUAL likelihood that the EBV will increase or decrease
What does accuracy of an EBV measure? How should we use accuracies when making selection decisions?
Use accuracy as a measure of selection risk
Is an EPD=0 always the mean EPD in a breed? Why or why not?
No, because 0 is not the mean, its the genetic base
Describe tandam selection.
Focus in on one trait at a time
Describe selection by independent culling levels
Looking at all the traits and set thresholds
Describe selection using an economic selection index.
Choosing by the index that accounts for all economically valuable traits
How can we avoid inbreeding or reduce the frequency of inbreeding in a herd?
Crossbreeding
Outbreeding
Will crossbred offspring always perform better than both purebred parents? Why or why not?
No, because crossbred doesn’t always outperform the highest performing parent. Hybrid vigor accounts for the amount over the average of the parents
What is the difference between random mating and random selection?
Mating-Selected quality animals but don’t choose exactly who individually breeds who
Selection-No selection in the genetics at all
Does inbreeding increase homozygosity or heterozygosity?
Homozygosity
Define inbreeding depression.
A decrease of performance that results from an increase in inbreeding
Does heterosis increase homozygosity or heterozygosity?
Heterozygosity
Inbreeding depression and hybrid vigor are due to opposite but similar genetic causes. Explain
Both affect the GCV
Depression-Makes GCV worse
Vigor-Makes GCV better
What is the difference between identity by state and identity by descent?
State- Alleles at a loci are the same but not from the same common ancestor
Descent- Alleles at a loci are the same and come from the same common ancestor
Why is maternal hybrid vigor more important than individual vigor?
1) Fertility traits are important to capture in your females
2) Heterosis has the most effect on survival and fertility traits
What percent of a population would within one standard deviation of the mean?
68%
What term is used for a breed that is made up of two or more other component breeds?
Composite
Between a well designed terminal and rotational crossbreeding system, which one makes the best use of breed complementarity? Why?
Terminal- Breed complimentarily is antagonistic to uniformity of the offspring in a rotational system
What are 3 considerations to think about into account when designing and evaluating crossbreeding systems?
1) Breeds
2) Uniformity
3) Complexity
True or False-Crossbred offspring are more variable than purebred offspring.
False
What is a composite?
A breed that is made up of two or more composite breeds. Like a Bhrangus
What is the chief advantage of rotations in time over rotations in space?
Can use in a smaller herd
Explain why DNA testing will never completely replace the need for performance testing in livestock species.
Genetics are constantly changing and the DNA tests are developed by using performance records
Why should producers be skeptical about DNA tests polygenic traits based on a single genes?
It doesn’t explain all the genetic variation for a trait
What is one benefit of using a DNA test for polygenic traits in livestock?
Increase accuracy of selection at a younger age
What is one limitation of using a DNA test for polygenic traits in livestock?
They only explain a fraction of the genetic variation
Which parts of the key equation for calculating rate of genetic change does DNA testing affect?
Accuracy and Generational Interval
What is breed complementarity?
Mixing two breeds to capture the benefits of both breeds
What is heterosis and hybrid vigor?
Average performance of crossbreeding offspring compared to the performance of the purebred parents
What are at least two reasons why a producer would want to parentage test their progeny?
1) Find out how many offspring each sire has sired
2) Avoid Inbreeding
3) Which sire carry genetic abnormalities
What is the difference between a transgenic animal and a cloned animal?
Transgenic-Genetic modification of the genetic sequence
Clone-Replicate the entire genome
What are two arguments for and against transgenic animals?
For:
- Improve animal health- disease resistant
- Improve animal welfare-Polled
Against:
- Creating this animal may cause unintended consequences
- Could create an unfavorable image for the species
Is it more beneficial to a producer to test proven bulls or young bulls?
Young bulls
Define Complete dominance.
When one allele is completely dominant and is always shown
Define Partial dominance.
Phenotype falls between the average and the homozygous
Define No Dominance.
Average of the two homozygous
Define Overdominance
Rare, when the phenotype is outside the range
Explain how DNA is transcribed into RNA. Include RNA polymerase II.
1) RNA polymerase II binds to the promoter region and unwinds the helix
2) Synthesizes a new strand and creates an RNA molecule by base pairing
3) RHA Polymerase II falls off
ANGUS BEEF Q: How should the individual performance values be used when selecting these bulls?
Don’t use them, Use the EPD’s
ANGUS BEEF Q: What is the difference between $EN, $W, and $B. What traits are in each and when do you use them?
$EN-Milk and Mature Cow Size-Use when there are feed concerns
$W-BW, WW, Milk, Mature Size-Use when selling at weaning
$B-WW, YW, REA, Cauracuss, Fat Thickness, Marbling- Selling on Grid
Explain how DNA is replicated. Include in your answer the roles played by the helicase, single-stranded binding proteins, DNA polymerase I, DNA Polymerase II, RNA primase, DNA ligase.
1) Unwind with helicase
2) single stranded binding proteins bind single strands of protein
3) RNA primase- lays down RNA primer
4) DNA polymerase II enters bubble and bonds to 3’ ends and replicates DNA
5) DNA polymerase I bind to RNA primers and throw them out
6) DNA ligase take the two strands and ligate them
Explain how mRNA is translated into protein. Include in your answer the roles played Aminoacyl site, Peptidyl site, and tRNA.
1) Small Ribosomal Unit binds to 5’ end and runs into AUG
2) Large ribosomal comes along attaches and makes one ribosome in the aminoacyl site
3) tRNA enters the ribosome in the aminoacyl site
4) AA on tRNA enters ribosome
5) Everything shifts three nucleotides into Peptidyl
6) Repeat
