A small population of individuals was genotyped for a single nucleotide polymorp
ID: 85343 • Letter: A
Question
A small population of individuals was genotyped for a single nucleotide polymorphism (SNP) marker, with the two alleles for this SNP being designated as A and B. The observed genotypes within this population were: AA = 208; AB = 178; BB = 78
a) What are the observed allele and genotype frequencies?
b) Is this population in Hardy-Weinberg equilibrium? c) Is allele B of the SNP recessive? Justify.
d) Variation is a common and important evolutionary feature of living organisms. The most common variant found in the genome are SNP. Discuss what they are and their importance in modern genetic research
*I want a geneticist or someone who really knows what they are talking about to answer this please*
Explanation / Answer
A] To obtain the genotypic frequencies, one first has to find the total number of all the observed genotypes..
Total = 208+178+78= 464.
Frequency of a particular genotype = observed number of that genotype/ total number of observed genotypes
Frequency of genotype AA = 208/464 = 0.45
Frequency of genotype AB = 178/464 = 0.38
Frequency of genotype BB = 78/464 = 0.17
Allele Frequency can be defined as the number of times an allele is observed in a population divided by the total number of alleles in that population.
Number of times Allele A occurs is 208x2 times in AA genotype individuals and178 times in AB genotype individuals, which is 416+178 = 594.
Number of times Allele B occurs is 178 times in AB genotype individuals and 78x2 times in BB genotype individuals, which is 178+156 = 334.
Total number of alleles in the population = 594+334 = 928.
Therefore, Allele frequency for allele A = 594/928 = 0.64
And, Allele frequency for allele B = 334/928 = 0.36.
B] For a population to be in Hardy-Weinberg equilibrium, the addition of the genotype frequencies should be 1.
In this case the addition of all the genotypic frequencies is 0.45+0.38+0.17 = 1. Thus the population is in Hardy-Weinberg equilibrium.
C] One cannot state whether the allele B is recessive or not, since only the genotypes are given. This does not show whether the allele is dominant or recessive and which can be known only through phenotype numbers and comparison of it with genotypes.
D] A single-nucleotide polymorphism as the name suggests is the difference observed at a single nucleotide, resuting in different morphs for a DNA strand. For example, one DNA strand may have the sequence AACCTGC and another DNA strand from another individual may have a sequence AAGCTGC. Comparing the two, one observes that there is difference of a single nucleotide at the third position of the sequence, thus called the single-nucleotide polymorphism. SNPs are used to study the different response of individuals to chemicals, diseases, vaccines and other agents and how this variation can determine whether an individual develops a disease or not. They are used for comparing individuals who have a disease with ones who don't have a disease and to use this information to personalize medicines.
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