lecture 24 - human genome & disease

Question 1

What is the name for mutations that have been inherited and can therefore be passed on to offspring?

Answer 1

Germline mutations

Question 2

What are somatic mutations?

Answer 2

Mutations to DNA in somatic cells, meaning they cannot be inherited

Question 3

What is the name for a mutation that causes a gene to function poorly?

Answer 3

Loss of function mutation

Question 4

Are loss of function mutations typically recessive or dominant, and why?

Answer 4

Recessive - if a normal copy of the gene exists on the homologous chromosome pair, then it can perform the genes intended function instead, meaning the mutation has no effect.

Question 5

What is the name for a mutation that causes a gene to work ‘too well’?

Answer 5

Gain of function mutation

Question 6

Are gain of function mutations typically dominant or recessive, and why?

Answer 6

Dominant - an allele that works too well will exceed the smaller effects of the normal allele.

Question 7

What are monogenic diseases?

Answer 7

Disease caused by genetic mutations in single genes, that can be passed down generations

Question 8

What is haemophilia?

Answer 8

A disorder of blood clotting

Question 9

Are males or females more commonly affected by haemophilia?

Answer 9

Males

Question 10

What mode of inheritance does Haemophilia display?

Answer 10

X linked recessive

Question 11

What is the chance of a male inheriting Haemophilia (X linked recessive) if their mother is a carrier?

Answer 11

50%

Question 12

Are males or females carriers of Haemophilia, an X linked recessive disorder?

Answer 12

Females - mutation on X chromosome so all males with mutation will be affected, not just carriers

Question 13

What mode of inheritance is displayed by Huntington disease?

Answer 13

Autosomal dominant

Question 14

Where is the mutated Huntingtin gene, that causes Huntington’s disease, found?

Answer 14

Chromosome 4

Question 15

What is the mutation to the Huntingtin gene that causes Huntington’s disease?

Answer 15

Too many copies of the CAG triplet in the gene.

Question 16

What is the mode of inheritance of cystic fibrosis?

Answer 16

Autosomal recessive

Question 17

What are polygenic disorders?

Answer 17

Disorders that appear to have a genetic basis but do not follow clear inheritance patterns - cannot be linked to a specific gene and are instead caused by a combination of mutations of different genes

Question 18

Are the majority of genes probabilistic or deterministic?

Answer 18

Probabilistic

Question 19

If a disorder is observed in every generation, is it considered dominant or recessive?

Answer 19

Dominant

Question 20

If a disorder is not observed in every generation, is it considered dominant or recessive?

Answer 20

Recessive

Question 21

If a dominant condition affects males and females equally, what is the mode of inheritance?

Answer 21

Autosomal dominant

Question 22

If a dominant condition affects males and females at different rates, what is the mode of inheritance?

Answer 22

X-linked dominant trait.

Question 23

What is the predicted sex ratio of an autosomal dominant condition?

Answer 23

1:1

Question 24

In an X-linked dominant condition, why are more females affected than males?

Answer 24

Affected males produce 100% affected daughters but no affected sons while affected mothers have a 50% chance of passing on the gene to their offspring, for both males and females.

Question 25

What is the chance that an individual affected by an autosomal dominant condition will pass on their condition to their offspring?

Answer 25

50%, regardless of gender, assuming they are heterozygous.

Question 26

If a recessive condition affects males and females equally, what is the mode of inheritance?

Answer 26

Autosomal recessive

Question 27

If a recessive condition affects more males than females, what is the mode of inheritance?

Answer 27

X-linked recessive

Question 28

If a recessive condition affects only males, what is the mode of inheritance?

Answer 28

Y-linked

Question 29

What is the probability that an affected individual with a Y-linked condition will pass on the condition to their offspring?

Answer 29

100% chance of passing to male, 0% chance of passing to female.

Question 30

Are males of females carriers in X-linked recessive conditions, and why?

Answer 30

Heterozygous females are always carriers, males will always express the gene if they have it.

Question 31

What is the genotype of a female affected by an X-linked recessive condition?

Answer 31

homozygous recessive

Question 32

What is the predicted sex ratio of affected individuals with an X-linked recessive condition?

Answer 32

More males than females

Question 33

What is the predicted sex ratio of an X-linked dominant condition?

Answer 33

More females than males