S11 Genotype, Phenotype And Inheritance

Question 1

What is the genotype?

Answer 1

Genes on a chromosome in the nucleus

Question 2

What is the phenotype?

Answer 2

Proteins in the cytoplasm

Question 3

What does hemizygous mean?

Answer 3

Only one allele of a gene on the x-chromosome (males only)

Question 4

What is homozygous?

Answer 4

Two alleles of a gene are the same

Question 5

What is heterozygous?

Answer 5

Two alleles of a gene are different

Question 6

What does autosomal recessive mean? Give an example of a disease.

Answer 6

• heterozygotes are unaffected
• heterozygotes who produce an affected offspring are carriers
• males and females are equally affected
• disease can skip generations
• 25% change of two heterozygotes having an affected offspring
• two homozygotes produce only affected offspring

Cystic fibrosis

Question 7

What does autosomal dominant mean? Give an example of a disease.

Answer 7

• heterozygotes are affected
• every affected individual will have at least one affected parent
• males and female are equally affected
• disease can’t skip a generation
• every heterozygous individual has a 50% chance of having affected offspring, if two heterozygotes, 75% chance of affected offspring
• disease is rarely found in homozygous state - life is less viable with homozygous

Huntington’s disease

Question 8

What does x-linked recessive mean?

Answer 8

• hemizygous males and homozygous females affected
• affected males can only give trait to daughters
• males and females equally affected
• affected heterozygous females have a 50% chance of having affected offspring, if heterozygotes female and hemizygous male 75% chance

Question 9

What does y-linked mean?

Answer 9

• only males affected
• can’t be a carrier
• if father has the disease, all sons will have the disease
• not common as the y-chromosome contains very few genes

Question 10

What is mitochondrial DNA inheritance?

Answer 10

All individuals inherit mitochondrial DNA from their mother

Question 11

What does polygenic mean? Give an example of a disease.

Answer 11

• more than one gene can be involved in producing a phenotype
• genes on the same chromosome are linked
• genes on different chromosomes are not linked

Albinism

Question 12

Is albinism recessive or dominant?

Answer 12

Recessive

Question 13

How many genes are involved in albinism?

Answer 13

Two

Question 14

Do linked genes show independent assortment in meiosis?

Answer 14

No

Question 15

What does the recombination frequency between linked genes depend on?

Answer 15

The distance between the genes.

The closer the genes, means less likely to recombine, the further apart the genes, they act as unlinked genes.

Question 16

What is genetic recombination?

Answer 16

The exchange of genetic information between organisms which leads to the production of offspring with a different combination of traits to with parent.