Question

Looking at Figure 20.15, what does it mean for a SNP to be “linked” to a disease-associated allele? How does this allow the SNP to be used as a genetic marker?(See Concept 15.3.)

Short answer

Single nucleotide polymorphism is the marker to depict an allele that is polymorphic by a single nucleotide in a genome. Recombination is a variation occurring due to the crossing over between two loci. As the distance between these loci increases, the chances of crossing over increase.

If an SNP is associated with a disease-related allele, crossing over will not occur between the allele and SNP, so SNP is used as a genetic marker to recognize the presence of a disease-associated allele.

Step-by-step solution

Linkage

Linkage is found between two genes on the chromosomes that are found in closed association. They are more likely to inherit together to the children from their parents. Also, they have fewer chances to be recombinant. There are many genetic tools that are used to find this linkage.

Step 2: Genetic Marker

A genetic marker is the marker sequence of DNA in the chromosome for which the location is known. It can be helpful in linking a genetic disease to the gene that produces it. It is used to track the inheritance of a linked gene of a known location.

Step 3: SNP as Genetic Marker

Recombination is the process of creating variations in the genome that involves crossing over that is a random event. The possibility of crossing over between two loci in a chromosome is proportional to the distance between them.

The genes are called linked when they are in a closed association. Thus when variation in a single nucleotide occurs in a closed link with the disease-associated allele, chances of crossing over between SNP and this allele are very minimized. Thus for finding the presence of an allele, SNP can be used as a genetic marker.