Ch. 17 Quiz

Question 1

Why might a defective gene not have an effect on an organisms phenotype?

Answer 1

Because the organism is diploid and the other copy compensated for the defective copy

Question 2

Which of the following is the first molecular disease to be identified?

Answer 2

Sickle cell anemia

Question 3

What causes Down syndrome?

Answer 3

An extra copy of chromosome 21

Question 4

What are dominant negative mutations?

Answer 4

A mutant protein that loses its own function and also interferes with the function of another, non-mutated, protein

Question 5

What are dynamic mutations?

Answer 5

Tandem repeats of bases within the coding regions of DNA that increase in number each generation

Question 6

When does imprinting occur?

Answer 6

Methylation patterns in gametes survive and affect gene expression in the new organism

Question 7

Why are mitochondrial defects surprisingly prevalent?

Answer 7

All of the above

• damage to DNA due to reactive oxygen species is much higher
• mitochondrial DNA is not protected by histones
• mitochondria contain few repair systems
• mitochondrial DNA has much higher mutation rate than nuclear DNA

Question 8

How are mitochondrial disorders inherited?

Answer 8

Maternally

Question 9

In what way can the presence of a genetic defect on a segment of DNA be screened after positional cloning?

Answer 9

All of the above

• sequencing of the DNA
• hybridization of mRNA extracted from the tissues most affected by the disease to suspect DNA
• by the presence of open reading frames
• identification of CpG islands

Question 10

Which ion channel is defective in people with cystic fibrosis?

Answer 10

Chloride transporter

Question 11

What advantage does a delta(F508) heterozygote have over a patient with cystic fibrosis (i.e. homozygous for delta(F508))?

Answer 11

They are more resistant to the effects of enteric diseases, such as typhoid and cholera

Question 12

Which statement about CRISPR is false?

Answer 12

CRISPR is exactly the same as RNAi.

Question 13

Of the following nucleases, which is currently in clinical trials for gene editing?

Answer 13

Zinc-finger

Question 14

Which of the following has been approved for age-related macular degeneration?

Answer 14

Aptamers

Question 15

Why is mating between close relatives not a good idea, genetically?

Answer 15

Recessive genes within the family have a chance to come together and cause disease

Question 16

What is a specific case in which genetic screening has saved and improved the quality of life for an individual through diet modification?

Answer 16

Phenylketonuria

Question 17

True about CRISPR

Answer 17

• CRISPR is a bacterial system that combats foreign DNA
• CRISPR uses guide RNAs derived from foreign genetic material
• Cas nuclease destroys foreign genetic material
• short sequences of foreign DNA are stored within the hosts own genome