Genetics: Problem types

Question 1

What are the 5 steps in solving genetics problems?

Answer 1

1: Write down given traits
2: Express traits as genotypes
3: Segregate genes into possible gametes
4: Put gametes into a Punnett square and complete the square
5: Determine genotype and phenotype ratios of the offspring

Question 2

What are monohybrid crosses?

Answer 2

Crosses considering only one trait. (Eg; Tt x TT)

Question 3

What is a test cross?

Answer 3

Cross used to determine whether an individual showing dominant traits is homozygous or heterozygous. Unknown genotype is crossed with a recessive genotype. If offspring all show dominant traits, than unknown genotype is homozygous. If any offspring show recessive traits, than the unknown genotype is heterozygous.

Question 4

What is the principle of independent assortment?

Answer 4

Principle Mendel proposed stating the inheritance of one set of alleles does not affect the inheritance of other allele sets. Basis of dihybrid crosses. (Eg; Tt x Rr)

Question 5

What are dihybrid crosses?

Answer 5

Crosses looking at two traits simultaneously. In true dihybrid crosses, both individuals are hybrid for both traits. PR is 9:3:3:1

Question 6

What are other inheritance patterns?

Answer 6

1: Incomplete Dominance
2: Codominance
3: Multiple alleles
4: Multiple genes/Polygenic inheritance

Question 7

What is incomplete dominance?

Answer 7

Hybrid genotype shows a blend of the two alleles. No dominant or recessive, so all letters are capitalized (Eg; snapdragon flowers being red, white, or pink)

Question 8

What is codominance?

Answer 8

Both alleles are expressed separately expressed in the phenotype of a hybrid organism. (Eg; Roan coat (RW), Barred plumage (BW), and AB blood (AB))

Question 9

What are multiple alleles?

Answer 9

More than two alleles are possible for a given trait, making many genotype and phenotype combos possible (Eg; Human blood types A, B, and O alleles)

Question 10

What are all the blood type combinations?

Answer 10

AA - Type A
AO - Type A
BB - Type B
BO - Type B
AB - Type AB
OO - Type O

A and B are dominant to O
A and B are codominant

Question 11

What is Polygenic inheritance?

Answer 11

Traits are controlled by 2 or more pairs of genes, showing much variation (Eg; Human height, skin colour and eye colour)