Genetic disorders

Question 1

Why study genetic disorders?

Answer 1

Clinal practise

Theory

Question 2

Phenylketonuria

Answer 2

Adheres to Mendellian laws
Dysfunction in pathway producing the amino acid tyrosine
Autosomal recessive
Two carriers = 3:1

Question 3

Huntingdon’s Corea

Answer 3

Adheres to Mendellian laws
Due to progessive damage to basal ganglia and cortex
Autosomal dominant on chromosome 4
Affected x unaffected = 2:2

Question 4

What are the two types of sporadic mutation?

Answer 4

Abnormalities in chromosome numbers

Deletions of single or multiple genes

Question 5

Down’s syndrome

Answer 5

Doesn’t adhere to Mendellian laws
Abnormality in chromosome number
Caused by errors in segregaatio when gametes are produced
- Usually trisomy of chromosome 21
Prevalence increases as parents age
Great variability in cognitive profile but usually IQ=55

Question 6

William’s syndrome

Answer 6

Doesn’t adhere to Mendellian laws
Microdeletion on chromosome 7
- Due to errors in replication of DNA during gamete formation
Uneven cognitive profile

Question 7

What are the 3 types of X-linked disorder?

Answer 7

Changes in the number of X chromosomes
Gene dysfunctions for single genes on X chromosome
Complex traits

Question 8

Turner’s syndrome

Answer 8

Doesn’t adhere to Mendellian laws
Changes in number of X chromosomes
X0 foetus
Infertile, normal verbal IQ, lower performance IQ

Question 9

Klinefelter syndrome

Answer 9

Doesn’t adhere to Mendellian laws
Changes in number of X chromosomes
X+XY
Lower than average IQ, speech and language difficulties
Breast development, poor beard growth, wide hips etc. (hormone imbalance is treatable)

Question 10

Fragile X syndrome

Answer 10

Doesn’t adhere to Mendellian laws
Gene dysfunction for single genes on X chromosome
Complex profile of relative cognitive strengths