Genetics Lecture 9 Flashcards
Do all genes follow mendelian ratios? Does this imply the laws of segregation and the principles of independent assortment are also always followed?
No, not all genes follow mendelian ratios, but they always follow the law/principle. Only the ratios are different.
Do mendelian ratios assume genes are linked or unlinked?
Unlinked
Define the formula for the number of genotypes.
n(n+1)/2
n = number of alleles
Define the formula for the number of heterozygote types.
n(n-1)/2
n = number of homozygotes
Define incomplete dominance. What would the phenotype be like?
When an allele is not completely dominant to the other allele of the same gene.
Phenotype would be an intermediate of the homozygote and heterozygote phenotypes.
ie. Red dominant, white recessive, pink incomplete
With an incomplete dominance phenotype, can the heterozygote be distinguished from the dominant homozygote?
Yes, it will be distinct.
With incomplete dominance, what are the phenotypic ratios like compared to the genotypic ratios?
They are equal.
Define codominance.
Alleles are equally dominant, and so both are expressed.
ie. AB blood type
If two allelic pairs affect the same phenotype, do they follow mendelian ratios?
Yes.
Define epistasis.
One gene pair of alleles masks the expression of another gene pair of alleles.
Can recessive genes be epistatic?
Yes.
What number of alleles are needed for epistasis in recessive vs dominant?
Recessive would need 2, dominant needs just 1.
In a dihybrid cross, both with epistatic recessive allele pairs, what would the resulting ratios be modified to? What about if they were dominant epistatic alleles?
9:3:3:1 becomes modified to 9:3:4 with recessive epistatic genes.
Dominant epistatic alleles would modify to 12:3:1.
Define duplicate genes.
Genes that produce identical phenotypes.
Typically on different loci
What ratio will a duplicate recessive epistatic allele pair result in?
9:7
