Genetic Inheritance

Question 1

What is Dihybrid Inheritance?

Answer 1

Dihybrid inheritance:
“The inheritance of two genes controlling two different features”

For example:

Height and seed colour

• Tall stem, yellow seeds (TtYy)
• Short stem, green seeds (tt,yy)

Question 2

What is homozygous?

Answer 2

Both alleles in the genotype are the same (AA or aa)

Question 3

What is heterozygous?

Answer 3

Both alleles are different (Aa)

Question 4

What is complete dominance?

Answer 4

When the dominant allele (A) is always expressed in the phenotype when that allele is present in the genotype

The presence of the dominant allele masks the presence of the recessive allele

Question 5

What is incomplete dominance?

Answer 5

• Either allele dominates the other
• Both alleles are present in the heterozygous genotype - they both contribute to a phenotype that is an intermediate or blend of the two
• For example, red (dominant) x white (recessive) = pink offspring

Question 6

What is co-dominance?

Answer 6

• Both alleles are equally dominant
• Both alleles are present in the heterozygous genotype they are both expressed in the phenotype
• For example, black (dominant) x white (recessive) = mixture of black and white hairs of coat

Question 7

What are multiple alleles?

Answer 7

Genes that have more than two different alleles

For example, blood types: iA, iB, i

Question 8

What are linked genes?

Answer 8

Linked genes occur on the same chromosome and

are inherited together

Question 9

Why do linked genes reduce genetic variation?

Answer 9

Linked genes reduce genetic variation in a population because they are on the same chromosome and more likely to stay together and end up in the same gamete / pass on same parental allele combination / offspring will display phenotypes similar to that of the parents

Question 10

What happens when the linked genes are close together on a chromosome?

Answer 10

When linked genes are closed together on the chromosome crossing over with recombination does not occur meaning that the homozygous genotypes are favoured.

Question 11

What happens when the linked genes are far apart on a chromosome?

Answer 11

When linked genes are further apart on a chromosome crossing over with recombination does occur meaning that there will be more heterozygous genotypes i.e 9:3:3:1