Chapter 15.2.1 (Exam 4)

Question 1

Describe one example of loss of enzyme function that causes PKU.

Answer 1

Phenylketonuria (PKU) is caused by an abnormal phenylalanine hydroxylase (PAH)

Question 2

What happens when there is an abnormal phenylalanine hydroxylase enzyme?

Answer 2

Phenylalanine and phenylpyruvic acid accumulate

Question 3

Describe the mutations that cause PKU.

Answer 3

The mutant alleles are recessive

> 400 different mutations in PAH can cause PKU

Question 4

Describe one example of loss of enzyme function that causes sickle-cell disease.

Answer 4

One amino acid in the β-globin polypeptide is abnormal

Question 5

What is the result of an abnormal β-globin polypeptide?

Answer 5

The abnormal protein results in sickle-shaped cells that block capillaries and impair the ability to carry oxygen

Question 6

Describe the mutations in the β-globin polypeptide that cause sickle-cell disease.

Answer 6

Hundreds of amino acid substitutions in β-globin have been reported, but only 3 specific mutations actually lead to sickle-cells

Many don’t alter the function of hemoglobin but some result in diseases – different diseases

Question 7

What are large deletions?

Answer 7

Deletions in a chromosome

In some cases, only part of the gene is missing, leading to a partly functional protein

Question 8

What is Duchenne muscular dystrophy caused by?

Answer 8

Deletions in the X chromosome that include the gene for the muscle protein dystrophin result in Duchenne muscular dystrophy

Question 9

Mutations in somatic cells can lead to cancer. More than two mutations are usually needed. What are the mutations leading to colon cancer?

Answer 9

Three tumor suppressor genes and one oncogene must be mutated in the sequence