Question

Consider the following allele frequencies for three SNPs

	SNP1	SNP2	SNP3
Africa	A:20%,T:80%	G:70%,T:30%	C:20%,A:80%
Asia	A:50%,T:50%	G:20%,T:80%	C:20%,A:80%
South America	A:60%,T:40%	G:80%,T:20%	C:70%,A:30%

Write down all possible 27 genotypes for these three SNPs.

Can someone please help me? Showing all the steps. I don't know what to do. Thank you! This is all that is provided

Answer 1

• SNP is a single nucleotide polymorphism.
• Genes are made up of long stretches of DNA which are in turn made up of many nucleotides such as adenine A, guanine G, thymine T and cytosine C.
• These nucleotides are arranged like beads on a chain and in different orders to form a functional sequence. But Sometimes there is more than one type of nucleotide observed at a locus in the sequence, in other words, there is a possibility of different nucleotides in the same location and this common variation is termed as single nucleotide polymorphism.
• SNPs are common in a genome and occur one in every 1000-2000 nucleotides. These serve as markers in identifying the possibility of a disease.
• In the current scenario, each SNP is represented by a nucleotide and a genotype for an SNP can be written as two nucleotides, for example, SNP1 AA/AT/ TT.
• In any organism, the genotype is written with all the alleles representing the genes on two homologous chromosomes. In this case, the SNP in a gene alters it and with a single change, it is a different allele.
• There are 3 SNPs and each should be represented by two nucleotides and the possible combination with 3 SNPs would be drawn as a three-hybrid cross.