Genes

Question 1

Modern genetics is based on experiments made by who

Answer 1

Gregor mendel
thomas morgan

Question 2

How do genes interact by

Answer 2

By encoded peoteins

Question 3

What is morbid risk
What do you need to know to calculate it

Answer 3

It is the risk one person to have genetic disease

Need to know inheritance (autosomal linkage, sex linked etc)
And know probability of risk

Question 4

What does it mean by gain of function

Answer 4

mutant protein by mutant gene is more active than normal

Question 5

Is Achondroplasia dominant or recessive

Why

Answer 5

Dominant

AA- lethal, baby ribcage so small cant breathe so die
Aa- dwarf
aa- normal

• gene encodes for FGFR3 which limits ossification of cartilage
• Mutant allele codes for more active FGFR3- gain of function (makes mutant protein causing early ossification)
• 2 copies of this mutant alleles AA causes death

Question 6

What id dominant negative mutations and give example

Answer 6

Wherby even if person heterozygous, having 1 copy of the mutant allele causes loss of function

Epidermolysis simplex- Extremely sensitive skin

• gene encodes a keratin,mutant codes defective keratin
• Even if there is normal keratin in cells Aa, the utant keratin molecules mix with the normal ones and dont allow formation of functional filaments

Question 7

What is loss of function and example

Answer 7

Most of these mutations are recessive
Gene loses its original function

Albinism
* Tyrosinase catalyses first step in synthesis of melanin
*Mutation in this enzyme, inhibits catalytic activity-loss of fucntion
* aa to be albino Aa may hv normal pigemnt unless incomplete domiance
*

Question 8

what is codominance and example

Answer 8

2 alleles of the same gene expressed together/ shown in phenotype

Blood groups- heterozygotes with A and B allele= AB blood

Question 9

What is multiple allelism

Answer 9

more than 2 alleles for same gene

eg ABO blood groups has A,B and O

Question 10

What is penetrance

Answer 10

The probabiltiy for a dominant gene to be expressed- the chance for expression of 1 gene carried in our genotype

Eg if penetrance 60%, then if particular gene exists in our genotype, then chance for it to be expressed in 60% (so not alwyas 100%)

Sometimes dominant genes never expressed= incomplete penetrance
* Osteogenesis imperfecta, defective collagen fibrils and is a dominant mutation but some are just carriers and never hv symptoms

Question 11

What is expressivity

Answer 11

Degree at which the phenotype is expressed

Variable expressivity is when ypu have the same genotype but you express it in different powers

• polydactly, some extra 2 fingers or soe have only extra1

Question 12

Morbid risk equation

Answer 12

MR= probability x penetrance