Question

Briefly explain the difference between microsatellite markers and SNPs, and why they’re both useful for linkage mapping

Describe genetic linkage

After genotyping chip results indicate patient is heterozygote for one of the known CF causing mutations, how do we know whether a genetic variant does cause this disease? due to false positive

Answer 1

microsatellite marker is a segment of repeatitive DNA where certain nucleotide sequences are repeated, typically 5- 50 times. This occurs at thousand of location within a DNA with highest and fastest mutation rate.

-SNPs are single nucleotide polymorphism, is the most common type of genetic variation and is also pronounced as SNIPS. it is the substitution of a single nucleotide at a specific position within the genome and it varies from one person to another person by 0.5% in a population.

-microsatellite markers are very much different from the SNPs on the basis of two reasons.

1. microsatellites are more polymorphic than SNPs, thus gives more information about an individual.

2. the density of SNP map is more as compared to microsatellites which will be problematic for analysis method.

microsatellites and SNPs both are useful for linkage mapping because it helps in analysing and locating the gene or a mutation which is responsible for a given trait or disease. these are also used to find out the relationship between sub- species, groups and individuals.

ques- GENETIC LINKAGE-

Genetic linkage is a phenomenon which tells us how the two genes are linked together and are inherited together at the time of gamete formation during sexual reproduction.

-It means if the two genes are very closely linked or placed, then their chances of getting separated at the time of crossing over during gamete formation, is also very less.

-Morgan did experiment on Drosophila melanogaster in 1919 to define linkage. The ratio of this cross slightly deviates from Mendel's 9:3:3:1 ratio.

-In linkge, he found two combinations i.e., parental combination and non- parental combination. He found that the proportion of parental combination is much more higher (98.7%) than the non- parental combination(1.3%).

Ques- After genotyping chip results indicate patient is heterozygote for one of the known CF causing mutations, how do we know whether a genetic variant does cause this disease? due to false positive.

ans- Cystic fibrosis is caused by the mutation in chromosome number 7 or a child inherit from their parents. because of the mutation, the patient is not able to make a protein called as cystic fibrosis transmembrane regulator (CFTR). this protein is responsible for balancing the concentration of salt and water on the various surfaces of our body. because of mutation, CFTR is not synthesised and as a result of it, the salt is trapped inside the cells and causes abnormality in the functioning of the cell.