Genetics

Question 1

Single Gene Traits

Complete Dominance

Answer 1

• dominant allele fully expressed
• recessive allele not fully expressed
• all of Mendel’s pea plants traits showed complete dominance

Question 2

Single Gene Traits

Codominance

Answer 2

• both alleles express themselves fully and simultaneously
• codominant alleles: I^A and I^B
• recessive allele: i

Question 3

Single Gene Traits

Pleiotropy

Answer 3

• 1 gene controls 2+ traits

- ie sickle cell anemia causes blood clumping, and poor physical development

Question 4

Multi-Gene Traits

Incomplete Dominance

Answer 4

• heterozygote phenotype is intermediate to dominant and recessive phenotypes
• RR x rr –> Rr –> 25% RR (red), 50% Rr (pink), 25% rr (white)

Question 5

Multi-Gene Traits

Epistasis

Answer 5

• 1 gene controls the expression of another gene
• ex: labrador fur color: B = black pigment, b = brown pigment, E = pigment deposited, e = pigment not deposited
• pigment deposition gene is epistatic to pigment color gene

Question 6

Multi-Gene Traits

Quantitative Characters

Answer 6

-multiple alleles control 1 character
-“continuous variation”
-normal distributions
-polygenic inheritance
AABBCCDDEE = tallest, aabbccddee = shortedst
-dominant alleles lead to traits on one end of a spectrum, and recessive alleles lead to traits on the other end

Question 7

Multi-Gene Traits

Multifactorial Characters

Answer 7

• “Genetic Determinism” = are all traits genetically determined?
• physical attributes, disease, behavior, intelligence… ?
• effect of environment on phenotype? (nature vs nurture)