Genetics Flashcards
For a long time, genetics was a very ____ field.
Stagnant.
Explain the sequence of genetics.
Gene (Genotype), mRNA, microRNA, protein, measurable trait or change within an animal. (Phenotype)
Define a gene
Sequence of DNA that direct protein synthesis in a very specific manner. These proteins then influence how traits develop.
What is mRNA?
Messenger RNA. Template which directs assembly of amino acids into proteins.
What is MicroRNA?
RNA template that can block or disrupt protein production.
Genotype?
The number and types of genes an animal possess (Genetic composition)
What is phenotype?
The characteristics of an animal that can be seen or measured (Outward appearance or behavior trait)
What is genomics?
Study of the genetic composition of animals.
What is epidenetics?
Heritable changes in gene expression that do not involve changes in DNA.
What is proteomics?
Study of Proteins that are produced by a specific genome (Or set of genes)
There are two animals. One can tolerate high ambient temperatures, one cant. Describe the phenotype differnce.
Heat tolerance.
In a phenotypic difference, what can be the four possible causes?
Genomic
Epigenetic
Proteonomic
Combination of all of the above.
If a phenotype difference is caused by a genomic difference, what does that mean? Look like?
Different genes cause the different phenotype!
Could be different forms of the same gene (allele difference)
Could be a different association among several genes.
If a phenotype difference is caused by a epidenetic difference, what does this look like? Mean?
Same genes, but certain ones are turned off or on.
DNA methylation patterns turn off a gene. The structure is exactly the same.
If a phenotype difference is caused by a Proteonomic differences, what does this mean? Look like?
The genes are the same, the same genes are turned on and off in each other, but the amount of protein produced is different!!
These are translational differences!! The genetics are exactly the same, but how much the gene is expressed depends on the proteins produced.
If a phenotype difference is caused by an all of the above?
The animals may have different alleles, an epigenetic change turning a gene off, and a protein difference changing the expression.
Things get complicated!
What is something intresting aboout sperm that can make reproductive difficulties hard to figure out?
If you look at sperm under a microscope, it may look completly functional but still not work.
Often this is from the seminal vessels not properly producing protein.
To understand an animals phenotype, we need to understand that:
Both the genetics and the environment of the animal contribute.
What is the basic equation of genetics?
Genotype + environment = phenotype.
What is Heritablity?
The proportion of variation or phenotypic differences among animals that is due to differences or variation in genotype.
What is heritability simplier?
A mathematical ratio! How much do genes contribute to a phenotype versus enviroment.
What does it mean if a trait is 100% heritable? Examples?
Environment has no effect on phenotype?
Ex: Eye color, coat color.
What is complete dominance?
The dominant gene completely masks the recessive.
There are only two phenotypes, and homozygous dominant (BB) is the same as heterozygous (Bb)
In complete dominace, what do the genes look like?
One loci, two forms of the gene (Alleles)
In complete dominace, is the dominate gene always the goal?
NO! sometimes recessive is more healthy. In this case, we select against dominant.
Describe partial dominance.
One loci, two difference forms of the gene.
Now there is a middle ground between dominant and recessive!
Give an example of partial dominance.
-Hyperkalemic periodic paralysis (HYPP) in horses
HY – muscle spasms or tremors
hy – normal physiology
- HYHY = severe spasms (can be fatal)
- HYhy = mild to moderate spasms
- hyhy = normal physiology
What is overdominance?
One loci, two different forms of gene.
Phenotype of heterozygote exceeds that of homozygous dominate.
Give an example of overdominance.
- WW = resistant to poison, but when consume it have vitamin K deficiency
- Ww = resistant to poison and healthy if they consume poison
- ww = die when eat poison
Remember, in these examples, we are talking about what?
Traits that are 100% inheritable.
Give a quick wrap up of the three kinds of genetic dominance.
Complete dominance: The heterozygous and homozygous dominant are the same phenotype.
Partial dominance: The heterozygous phenotype is somewhere between the homozygous dominant and recessive.
Overdominance: The heterozygous phenotype exceeds the phenotype of the homozygous dominant.
What is Epistasis?
Interaction among genes at different loci.
Two loci each with two different forms of gene.
Like 4 possiblities.
Give an example of epistasis!
Lab coat color!
Black color= BbEe
Yellow = BBee
Chocolate= bbEE
Some say that neo-natal survival is what? Who disagrees and why?
A trait based soley on the enviroment.
Dr. Flowers disagrees, he thinks birth weight helps!
The vast majority of traits involve both _____ and a ____ component.
Genetic and Enviromental. Remember, heritablity measures this!!
What is selection differential?
Superiority of selected animals compared to the average of a herd or group of animals.
What is an old term for selection differential?
Reach.
How do we find genetic chnage?
Selection difference times heritability.
If a bull has a 535 lb weaning weight and the herd has a 450 lb weaning weight, what is selectional differential?
535- 450 = 85 lbs
Just desired trait minus the average!
Why is it sometimes confusing to figure out genetic change?
Sometimes we want the trait to increase. Ex: weaning weight.
Sometimes we want it to decrease. Ex: Back fat
Once you have the selection differential number, what do you do?
Multiply by the heritablity by the decimal form.
Then, divide by 2!!! Babies only get half of their genetics from their parents.
What is the genetic change then calculated?
The mother plus the father numbers. That creates the genetic chnage in next generation.
How do you predict the phenotype for the next generation?
Add the genetic change to the old herd average.
Just look at this example!
Data - Weaning Weight (cattle)
Superior Bulls - 535 lbs
Superior Heifers - 480 lbs
Herd average bulls - 450 lbs
Herd average heifers - 450
Heritability - .30
Bulls
535 - 450 = 85 lbs
85 lbs x .3 = 25.5 lbs
25.5 lbs/2 = 12.75 lbs from bulls
Heifers
480 - 450 = 30 lbs
30 lbs x .3 = 9 lbs
9 lbs/2 = 4.5 lbs from heifers
- Genetic change in next generation
12.75 + 4.5 = 17.25 lbs - Predicted phenotype of next generation
450 lbs + 17.25 lbs = 467.25 lbs
What is the next generation?
When superior animals have completely replaced their parents.
If you were asked to do this process for two generations, what do you need to do??
Replace the herd average with the new normal! Then repeat process.
What are inbreeding Coefficients good for?
People who work in purebred industries (dogs, horses, beef cattle, ect) and for people that work with captive breeding of endangered species.
Why can inbreeding be beneficial?
It can concentrate or increase the frequency of advantageous traits.
Why can inbreeding be harmful?
It can have negative consequences in terms of development and or behavioral complications by increase undesirable traits.
What are negative consequences when inbreeding called?
Inbreeding depression.
This is similar to decreased genetic diversity.
Imbreeding is more common in what animal?
Dogs more than cats generally.
What is reduced variation?
Deleterious alleles become homozygous.
Similar to inbreeding depression.
Happens when close relatives mate
What are the consequences of reduced variation?
Fewer less viable offspring
Lower survivorship
Increased chance of exinction.
In a pedigree, who is always on top?
MALE! female is always on the bottom.
When looking for a common ancestor, how can you verify that it is the same animal?
Checking the parents of the common ancestor.
How do you find the number of paths?
Start at the parent of the singular individual animal that you are doing this for.
This is where the animal gets its genetics from!!
What kind of shape counts as one path? A
A side ways segment, one upward or downward segment and then one more sideways segment all counts as one!
What do you do after you have found the number of paths of mother and father?
Add them!
In the inbreeding coefficient formula, what does the exponent n mean?
Is the number of paths connecting the dam and sire through the common ancestor.
What is the weird E symbol in the inbreeding coefficent formula?
A symbol that requests that the information from all the common ancestors be added or summed together.
So, lets say that we have one common ancestor with 2 paths and another with 3 paths. What do we do??
One of them will be 0.5 to the power of 2
Another will be 0.5 to the power of three.
So we end up with 0.25 and 0.125. Now what?
We add them up! Thats that the weird E means.
Okay, now we have 0.375! Now what?
The last step of the formula! Just multiply by 0.5 and you get your answer!
=0.1875
Then make it a percentage. 18.75% is the inbreeding coefficent.
What is the correct definition for heritability?
Variation in phenotype due to the variation in genotypes
OR
Difference in phenotype due to the difference in genotypes
List one similarity and one difference between complete dominance and overdominance.
Both involve a single gene with two different forms or alleles. Both are also 100% heritable. In complete
dominance, the phenotype of the heterozygote is similar to the phenotype of the homozygous dominant whereas
in overdominance the phenotype of the heterozygote surpasses that of the homozygous dominant. Technically, it
isn’t correct to say one is more desirable or lethal since there are situation with overdominance where this isn’t
the case
