Question

Genetic

QUESTIONS FOR RESEARCH AND DISCUSSION

• 1. Discuss how incomplete penetrance, variable expressivity, pleiotropy, and genetic heterogeneity can affect the severity of a disease in a family.
• 2. A person can lower risk of preventable types of cardiovascular disease by exercising regularly and following a diet low in saturated fats and simple carbohydrates and high in fruits and vegetables. Why are these approaches ineffective against long QT syndrome?
• 3. Explain how the molecular bases of the various forms of long QT syndrome make genetic heterogeneity very likely.

3-4 pages ( I don't want hand written)

thank you

Answer 1

Penetrance refers to the probability of trait being expressed .

INCOMPLETE PENETRANCE

If the genetic trait is expressed by a part of population that is not all people express the gene trait although all of them carry the mutant gene.

VARIABLE EXPRESSIVITY

Refers to the range of signs and symptoms that occur in different people with same genetic condition .It results from the lifestyle ,enviroment ,genetic changes in peopleRet

This makes the researchers difficult to study the genetic conditions which may pass to the future generations as genes as alleles have variable expression .

It occurs in both incomplete penetrance and variable expressivity.

EXAMPLE -Channelopathies( inherited arrhythmogenic disease ) is a main cause of suuden cardiac deaths in people because previous generation have not expressed that gene like same manner.

Sudden death generally occur in people with no previous symptoms of disease or they occur within 24hr or 1 hr before death.This is genetic variability or incomplete penetrance .

OTHER EXAMPLE

Retinoblastoma(retina cancer ) caused by mutation of Rb gene in which not all family members show symptoms of disease although all are carriers.

PLEIOTROPY

Genetic variant or gene has biological influence on more than one phenotype trait that is mutation at one gene loci showing different phenotype trait .

Two people in family may carry gene but one has disease and other carry or might show other signs.

EXAMPLE

Phenylketouria(PKU) occur because of in activation of enzyme Parahydroxylase which converts Phenylalanine to Tyrosine and form homozygous mutant individuals because of excess phenylalanine and deficiency of Tyrosine

Results -skin and hair pigmentation and mental retardation .

It include disorder where multiple traits occur because of of 1 gene mutant

In pleiotropy one individual in pedigree can have cardiac problem and other with same mutant gene may have deafness .

GENETIC HETEROGENEITY

Mutation at 2 or more genetic loci showing same or similar phenotype .

EXAMPLE

Different people in family experience different level of disease

Ehlers-Danlos syndrome -disease of connective tissue by mutation at multiple gene inherited as x-linked chromosome ,autosomal recessive,autosomal dominant pattern of inheritance .

Ans 2Lqts is caused by typical elongation of QT interval on ECG and by cardiac arrest .

QT INTERVAL are de polarization and re polarization phases of cardiac area

This syndrome is best example of genotype phenotype correlation

It is mainly transmitted in autosomal dominant and also in autosomal recessive pattern .

These people should not participate in competetive sports as it may deteriorate the case .

Here genetic variation leads to loss of potassium gene function and gain in sodium and calcium gene function .

Sports and physical stress worsen the syndrome and dietary modification can help to control it with medication as wrong diet may further lead to more complications but without medication and treatment they will not control it as it more genetic specific syndrome .