C20 Patterns of Inheritance and Variation

Question 1

(Variation and Inheritance)
Gene causes:

Answer 1

-Gene mutations
-Chromosome mutations
-Meiosis/ sexual reproduction
-Inherited combination of alleles

Question 2

(Variation and Inheritance)
Environmental causes:

Answer 2

-Interaction of environmental and genetic factors (e.g chlorosis and etiolation).

Question 3

Discontinuous variation

Answer 3

Each characteristic falls into one of a few discrete categories (e.g ABO blood types, Rhesus +/- blood).

Question 4

Continuous Variation:

Answer 4

There are no definite categories, the characteristics exist along a range of possible values between 2 extremes (e.g height, body mass).

Question 5

Genetic Explanation for Discontinuous Variation:

Answer 5

-Often due to monogenic inheritance
-Single gene locus, multiple alleles
-Pattern of dominance, recessiveness, codominance or incomplete dominance.

-Multiple genes acting epistatically

Question 6

Genetic Explanations for Continuous Variation:

Answer 6

-Polygenic inheritance
-Multiple gene loci influencing a particular characteristic
-Multiple genes with multiple alleles
-Tend to show normal distribution

Question 7

Monohybrid Inheritance (Mendel’s Pea Plants):

“Pure Breeding” parents:

Answer 7

Both homozygous and opposites
GG (homozygous dominant), gg (homozygous recessive), Gg (heterozygous).