Transmission of genetic disease

Question 1

What are the two types of inheritable disease?

Answer 1

Monogenetic: Clear inheritance, not environmentally effected

Complex disorders: no clear inheritance, effected by environment and common

Question 2

What are alleles?

Answer 2

Different forms of a gene at the same locus

Question 3

What are homologous chromosomes?

Answer 3

Matching pair of chromosomes inherited from each parent

Question 4

What is a polymorphism?

Answer 4

Mutation present in >1% of population

Question 5

What are the types of mutation?

Answer 5

Point mutation

Insertion/deletion - leading to frameshift

Question 6

What are the two types of point mutation?

Answer 6

Missense: Incorrect amino acid coded
Nonsense: Stop codon coded

Question 7

What is the risk of an affected child with an Autosomal Dominant condition?

Answer 7

50-75%

Question 8

What increases the risk of Autosomal recessive gene expression?

Answer 8

Consanguinity:

closely related individuals who reproduce can increase likelihood of recessive conditions in children

Question 9

Give an example of an Autosomal dominant disease

Answer 9

Huntington’s

Question 10

Give an example of an Autosomal Recessive disease:

Answer 10

Cystic Fibrosis: chronic, life-limiting condition leading to excess mucus production in lungs and pancreas, causing breathing difficulties and stunted growth (CFTR gene mutation leads to mutated form of chloride ion channel in epithelial cells) - 1500 mutations identified and CF testing included in UK newborn screening programme

Question 11

Give an example of an X-linked recessive disease:

Answer 11

Haemophilia

Question 12

What is Genetic Heterogeneity?

Answer 12

Same gene with different mutations causing different symptoms.
Same disease, different genes/inheritance patterns

Question 13

Give an example of Genetic heterogeneity:

Answer 13

Congenital absence of vas deferens also caused by CFTR mutation

Question 14

What is it called when symptoms are not always present in an individual w/disease-causing mutation?

Answer 14

Incomplete penetrance

Question 15

What is Variable expressivity?

Answer 15

Severity of disease differs between people w/same disease-causing mutation

Question 16

What is it called when two people have the same disease but with a different underlying cause?

Answer 16

Phenocopy

Question 17

What is Epistasis?

Answer 17

Interactions between disease gene mutations and other modifier
genes can affect the phenotype.

Question 18

What are the molecular mechanisms of disease for each type of inheritance?

Answer 18

Dominant: Toxic protein production, masking normal copies

Recessive: Absence of functional proteins