2.4 - Variation and inheritance

Question 1

Discrete / single gene variation

Answer 1

Discontinuous, where the values do not occur in a range and fall into distinct groups (usually descriptions e.g. colour)

Question 2

Continuous / polygenic variation

Answer 2

Where there is a range of values on a scale e.g. height

Question 3

Polygenic characteristics

Answer 3

Caused by many genes working together. They show continuous variation and very common in phenotypes.

Question 4

Gene

Answer 4

A section of DNA which codes for a protein (characteristic)

Question 5

Alleles

Answer 5

Different forms of a gene which control one characteristic

Question 6

Phenotype

Answer 6

The visible physical characteristic you see as a result of a gene

Question 7

Genotype

Answer 7

The pair of alleles a person has which control one characteristic, e.g. AA, aa or Aa

Question 8

Dominant

Answer 8

An allele which is always seen in the phenotype if it is present (in the genotype)

Question 9

Recessive

Answer 9

An allele which is only seen in the phenotype if there is no dominant allele present

Question 10

Homozygous

Answer 10

When a genotype has two alleles exactly the same, e.g. AA or aa

Question 11

Heterozygous

Answer 11

When a genotype has alleles which are different from each other e.g. Aa

Question 12

P1

F1

F2

Answer 12

The genotypes of the parents in a cross

The genotypes of the offspring from a cross

The genotypes of the offspring resulting if two of the original F1 offspring were crossed

Question 13

Predicted ratios are not always achieved

Answer 13

Because fertilisation is a random process