GENO- patterns of inheritance

Question 1

define autosomal dominant and give an example

Answer 1

not a sex chromosome - altered gene refers to pathogenic variant

example 
mum = normal 
dad = 1 copy of bad gene
mum = no condition
dad = has condition
children = 50% chance they will have the condition

Question 2

give an example of autosomal recessive inheritance

Answer 2

example - mum is a carrier
dad is a carrier
neither have the condition
children - 25% chance of child having the condition 75% not having the condition 2/3 chance of being a carrier

Question 3

define x linked and give an example

Answer 3

mother is a carrier of the condition

example
mother = carrier
dad = no condition
daughters wouldn’t be affected but have 50% chance of being a carrier
if boy = 50% chance they would have the condition

if dad has the condition but not mum (due to it being x linked) all the daughters would be carriers - all sons unaffected

Question 4

what is meant by the term multifactorial when referring to genetics

Answer 4

diseases can be caused by more than just a single variant, so no consistent disease incidence in a family

genomic factors + environmental factors = multifactorial

Question 5

what is unique about mitochondrial inheritance

Answer 5

maternally passed on

unable to give an exact chance of the child be affected due to the bottle neck effect

Question 6

list factors that influence inheritance patterns

Answer 6

de novo - variant arises spontaneously in embryogenesis

variable expressivity - not all individuals who have the variant will develop the condition

anticipation - disease severity increased and generally age of onset decreases in each generation

skewed X inactivation - turning off of one x chromosome happens more often that the other one - 10% of women

mosaicism

Question 7

define polygenic causes of disease

Answer 7

combination of many genomic variants

Question 8

what is the Hardy-Weinberg principle

Answer 8

P^2 +2pq + q^2 = 1

P^2 – unaffected frequency
2Pq= carrier frequency
q^2 = affected individuals

Question 9

if the disease incidence of spinal muscular atrophy (SMA) is approx. 1 / 10,000 what is the carrier frequency

Answer 9

q^2 = 1, 10,000
q = 1/ 100
as p + q = 1
q = 99 / 100

therefore

carrier frequency = 2 x 1/100 x 99/100 = 1/50

Question 10

define carrier risk

Answer 10

(chance parent 1 is a carrier x chance of passing it on)

x

(chance parent 2 is a carrier x chance of passing it on)

= chance child is born with the condition

Question 11

describe the relationship between disease incidence and carrier frequency

Answer 11

as disease incidence increases, so does carrier frequency