lecture 24 - human genome & disease Flashcards
What is the name for mutations that have been inherited and can therefore be passed on to offspring?
Germline mutations
What are somatic mutations?
Mutations to DNA in somatic cells, meaning they cannot be inherited
What is the name for a mutation that causes a gene to function poorly?
Loss of function mutation
Are loss of function mutations typically recessive or dominant, and why?
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.
What is the name for a mutation that causes a gene to work ‘too well’?
Gain of function mutation
Are gain of function mutations typically dominant or recessive, and why?
Dominant - an allele that works too well will exceed the smaller effects of the normal allele.
What are monogenic diseases?
Disease caused by genetic mutations in single genes, that can be passed down generations
What is haemophilia?
A disorder of blood clotting
Are males or females more commonly affected by haemophilia?
Males
What mode of inheritance does Haemophilia display?
X linked recessive
What is the chance of a male inheriting Haemophilia (X linked recessive) if their mother is a carrier?
50%
Are males or females carriers of Haemophilia, an X linked recessive disorder?
Females - mutation on X chromosome so all males with mutation will be affected, not just carriers
What mode of inheritance is displayed by Huntington disease?
Autosomal dominant
Where is the mutated Huntingtin gene, that causes Huntington’s disease, found?
Chromosome 4
What is the mutation to the Huntingtin gene that causes Huntington’s disease?
Too many copies of the CAG triplet in the gene.
What is the mode of inheritance of cystic fibrosis?
Autosomal recessive
What are polygenic disorders?
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
Are the majority of genes probabilistic or deterministic?
Probabilistic
If a disorder is observed in every generation, is it considered dominant or recessive?
Dominant
If a disorder is not observed in every generation, is it considered dominant or recessive?
Recessive
If a dominant condition affects males and females equally, what is the mode of inheritance?
Autosomal dominant
If a dominant condition affects males and females at different rates, what is the mode of inheritance?
X-linked dominant trait.
What is the predicted sex ratio of an autosomal dominant condition?
1:1
In an X-linked dominant condition, why are more females affected than males?
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.
What is the chance that an individual affected by an autosomal dominant condition will pass on their condition to their offspring?
50%, regardless of gender, assuming they are heterozygous.
If a recessive condition affects males and females equally, what is the mode of inheritance?
Autosomal recessive
If a recessive condition affects more males than females, what is the mode of inheritance?
X-linked recessive
If a recessive condition affects only males, what is the mode of inheritance?
Y-linked
What is the probability that an affected individual with a Y-linked condition will pass on the condition to their offspring?
100% chance of passing to male, 0% chance of passing to female.
Are males of females carriers in X-linked recessive conditions, and why?
Heterozygous females are always carriers, males will always express the gene if they have it.
What is the genotype of a female affected by an X-linked recessive condition?
homozygous recessive
What is the predicted sex ratio of affected individuals with an X-linked recessive condition?
More males than females
What is the predicted sex ratio of an X-linked dominant condition?
More females than males
