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Lecture 4
Gene interaction & regulation
46
Veterinary Medicine
Not Applicable
01/20/2017

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Term
What is incomplete dominance?
Definition
blending of parental traits produces a third phenotype

e.g. cross a red flower with a white flower, and produce a pink flower
Term
Roaning in horses and cows is an example of....
Definition
co-dominant gene expression
Term
What is epistasis?
Definition
When more than one gene contributes to phenotype, in a way which is not merely additive.
Term
Is epistasis reflected in the phenotype or genotype?
Definition
phenotype
Term
What allele produces black pigment in horses? Red?
Definition
E = black
e = red
Term
What are mimic genes?
Definition
Mutations in different genes (and therefore different loci) which produce the same phenotype
Term
If one gene affects multiple tissues, this is an example of...
Definition
pleiotropic effect
Term
True or False

Lavender foal syndrome in horses, and deafness associated with merle colouring in Australian shepherds, are examples of the mimicking effects of genes
Definition
false

pleiotropy

Both of these diseases are an example of a single mutation/gene which affects multiple different tissues
Term
Is threshold level of a trait a parameter of the population or the individual?
Definition
population
Term
Is liability a parameter of the population or the individual?
Definition
individual
Term
What is threshold?
Definition
the level of liability of a trait, above which all animals in the population will show the trait
Term
What is expressivity?
Definition
individual variability in the degree to which a phenotype is expressed.

e.g. polydactyly in cats is controlled by one gene. It will always cause cats with this gene to have extra toes. But some cats will have more toes than others.
Term
What is incomplete penetrance
Definition
If less than 100% of the individuals with the genotype, express the corresponding phenotype.

e.g. If a gene is known to cause a disease in only 70% of the population who has that gene, then it only has 70% penetrance
Term
What are phenocopies?
Definition
A result of interaction between genotype and environment. In some instances, environment can compensate for poor genotype, or vice-versa.
Term
What is heritability?
Definition
The degree of correlation between genotype and phenotype.

H^2 = Vg / (Vg + Ve)

Variance of genotype divided by variance of phenotype
Term
In horses, E produces ____ pigment while e produces ____ pigment
Definition
black
red
Term
Define pleiotropy
Definition
when a single gene affects multiple tissues
Term
Pleiotropy is often due to _____ and associated with neural signs
Definition
neural crest cell migration
Term
True or False

Polygenic traits are often controlled by multiple genes
Definition
false

one
Term
Define incomplete penetrance
Definition
<100% of the genotype expresses the phenotype
Term
KNOW THE FLOWCHART FOR THE 5 LEVELS OF GENE CONTROL!!!
Definition
-transcription
-RNA processing
-RNA transport
-translation
-post translational modification
Term
What is mRNA?
Definition
a blueprint copy of a strand of DNA, with Uracil replacing Thymine
Term
How does translation work?
Definition
-mRNA + ribosomal subunits form a complex
-tRNA has anticodons which match mRNA codons
-tRNA transports AA's, associates with ribosome complex, AA's form peptide bond with mRNA
-protein chain forms 1 pair at a time, moving to the right
-ribosome unit moves one step along, repeat!
Term
After transcription, nuclear RNA is spliced. During this process, (introns/exons) are removed while (introns/exons_ form messenger RNA.
Definition
introns removed

exons form messenger RNA
Term
What is the universal 'start' codon in mRNA? What does it code for?
Definition
AUG

methionine
Term
What are the primary stop codons in mRNA?
Definition
UAA
UAG
UGA
Term
What defines a genetic mutation?
Definition
uncorrected mistakes in DNA (NOT RNA) which alter the DNA sequence
Term
What is the difference between somatic vs germ-line mutations?
Definition
somatic mutations affect on individual (not a population), and may be advantageous or disadvantageous

germ-line mutations are associated with meiosis, and therefore hereditary. They will affect a larger population
Term
What point mutations
Definition
affect a single base pair

e.g. insertions/deletions/substitutions
Term
What are splice mutations?
Definition
when mutations result in introns being left in the mRNA
Term
A point mutation in which A is exchanged for G, or T for C
Definition
transition (A & G are purines, T & C are pyrimidines)
Term
What nucleic acids are purines?
Definition
A & G
Term
What nucleic acids are pyrimidines?
Definition
C & T
Term
A point mutation in which A is exchanged for C, or G for T
Definition
transversion
Term
What are the possible outcomes of a point mutation?
Definition
Mis-sense (protein with a new AA sequence)

Nonsense (premature stop codon, or the protein isn't even coded for at all)

Silent (redundant codon copy, so it codes for the same AA and the same protein is produced)
Term
Lavender foal syndrome is a result of what type of mutation?
Definition
frameshift (change in the reading frame) mutation in MYO5A
Term
What are SNPs?
Definition
variations at a single position in a DNA sequence among individuals, resulting in 'alleles' if the SNP occurs in gene regions of DNA
Term
When would it be particularly advantageous to have a lot of SNP's within a gene region?
Definition
immune-related proteins (will result in a more robust population/immune system)
Term
What effect does methylation of DNA have?
Definition
-nucleosomes pack tightly together so TF's can't bind to the DNA and the genes are not expressed
Term
What role does acetylation have on epigenetic control?
Definition
When an acetyl group is added to a histone tail, the nucleosomes become more loosely packed. transcription factors can then bind and the genes are expressed
Term
What is x-inactivation?
Definition
Happens in individuals with 2 x chromosomes (females, or kleinfelter males)

-in embryo, one of the X chromosomes in each cell is randomly inactivated
-usually 50% will express the mother's X chromosome, 50% will express the father's X
Term
What is imprinting?
Definition
-only one allele is expressed, and the other one (imprinted one) is silenced
-the gene that comes from the father will act differently than the one that comes from the mother
Term
What is a mule?
Definition
male donkey X female horse
Term
What is a hinny?
Definition
female donkey X male horse
Term
True or False

All oocytes have the same number of mitochondria
Definition
false
Term
In the case of mitochondrial diseases, if an individual carries the gene, did it come from the mother or the father?
Definition
mother (it's always the mom that supplies mitochondria via her oocytes)
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