Modes Of Inheritance

Question 1

What is dominant

Answer 1

Dominant if manifests in heterozygote
Gain of function usually

Question 2

Why are brown eyes dominant over blue eyes

Answer 2

gene responsible of eye color OCA-2 controls melanin production in melanocytes

Question 3

Dominant autosomal disorders

Answer 3

A single gene/allele that is passed to offspring with multiple generations affected
Affected person usually has 1 affected parent
Each child has a 50% chance of being affected

Question 4

Dominant autosomal pedigree

Answer 4

Vertical pedigree

Question 5

Gain of functional

Answer 5

Gene makes a protein with a new function
Huntingtons disease-symptoms start at age from 30-50 causing difficulty concentrating,depression,stumbling,involuntary jerking,problems swallowing
CAG repeat causes protein aggregation

Question 6

Dominant negative effect

Answer 6

Mutated form interfere with activity of protein which reduces activity
Normal happens in dimers and multimers

Question 7

HaploInsufficient

Answer 7

Mutant in gene causes 50% the amount of a protein that isn’t enough for normal function

Question 8

Autosomal recessive carriers

Answer 8

Carriers have lost a single copy of gene but normal one is sufficient to maintain normal function

Question 9

Recessive disorder

Answer 9

2 copies of gene must be present in order for disease to develop
Loss of function

Question 10

Pedigree of autosomal recessive

Answer 10

Parents and Children are carriers
25% chance of infection
Horizontal pedigree

Question 11

Risk factor of autosomal recessive diseases

Answer 11

Consanguineous marriages elevate risk

Question 12

Cystic fibrosis

Answer 12

Defective chloride ion channels result in mucus build up and impaired airway defense
Mutations on gene encoding chloride ion channels(CFTR gene on chr7)
Single copy is enough to prevent mucus build up
Loss of function mutwtion

Question 13

X linked recessive disorder

Answer 13

Affects mainly makes
Inherited from unaffected carrier Mum
Females are carriers

Question 14

X and Y chromosomes protein

Answer 14

X has 1000-1300 genes (850 protein coding)
Y chrom has 150 genes (50-70 protein coding)

Question 15

Why do females carriers show sign of disease eg fabrys disease

Answer 15

Although females have 2 X chromosomes, during development one of them is randomly silenced so you could have mutant gene expressed in some cells

Question 16

X linked dominant disorder

Answer 16

All daughters and no sons of an affected father are affected
Milder in females due to random gene inactivation
Increase in function

Question 17

X linked hypophosphatemia

Answer 17

PHEX gene mutation
Overproduction of FGF21
This inhibits kidney phosphate reabsorption
Results in vitamin D results in rickets
Causes overproduction of gene

Question 18

Y linked disorders

Answer 18

Only affects makes
Vertical pedigree pattern

e.g. retinitis pigmentosa → mutation in RPY gene → defective protein produced in retina

Question 19

How does mDNA replicate

Answer 19

Binary fission

Question 20

How does mitochondrial disease affect people

Answer 20

All mitochondria inherited from mum
All children may be affected
Vertical pedigree pattern

Question 21

Heteroplasmy

Answer 21

Mitochondria have multiple copies of their genome some normal and some mutant

Question 22

What causes mitochondrial disease variability

Answer 22

They can lose/gain mutated genes
Depends on number of affected mitochondria
Develops with age due to accumulation of mutant mitochondria