B1 - Alleles

Question 0

What does it mean to be heterozygous for a gene?

Answer 0

Having two alleles that are different, the dominant one is the one expressed.

Question 1

What is an alleles and why do we have 2?

Answer 1

Alleles are different versions of the same gene. One is inherited from each parent.

Question 2

What do we call it when we have 2 copies of the same alleles?

Answer 2

Homozygous

Question 3

What is a dominant allele?

Answer 3

The dominant alleles is alway expressed if it is heterozygous - recessive cannot be expressed. Huntingtons disorder is caused by a dominant allele. There is a 50% chance that a child will inherit the disorder if one parent is a carrier

Question 4

What is a recessive allele? Give an example.

Answer 4

Recessive alleles are expressed in offspring only when inherited from both parents. Cystic fibrosis is a recessive disorder and people with only one allele will not have the disorder - instead they would be a carrier. Both parents have to be carriers or sufferers for the child to inherit the disorder

Question 5

What are the male and female sex chromosomes?

Answer 5

Female - XX

Male - XY

Question 6

What happens if you have a Y chromosome?

Answer 6

You are genetically male

Question 7

What happens if you do not have a Y chromosome?

Answer 7

You are genetically female

Question 8

What does genotype refer to?

Answer 8

the genetic constitution (make up)of an individual organism

Question 9

What does phenotype mean?

Answer 9

The set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.