Q1. Number of SNP in human genome.
Ans:
The normal frequency of SNPs = 1 in 1000bp.
Human genome = 3x10^9 bp, hence the number of SNPs in human genome = 3x10^6.
Q2.
Ans:
SNP may have a variable number of effect.
When present in Exons, the SNP might change the amino acid sequence and thus the protein that can be either more active or ineffective or inactive. It might not change the amino acid sequence, and just be a change in the nucleotide sequence. It might change the amino acid sequence such that a truncated protein is produced or it may change the nucleotide such that the null gene or pseudogene is formed.
When present in intron and intragenic regions, SNP may affect gene regulation, DNA replication, rate of transcription, etc. The SNP might cause local topographical changes, DNA affecting its properties.
Q3.
DNA microarray:
In this technique, an array of unique nucleotides in multiple copies is arranged in a defined way on a solid matrix such a glass surface. The sequence of these spots is defined and is saved in a computer. The genome of any organism is fragmented, labelled and then the fragments are allowed to pair with the array. The complementary sequences get paired with their corresponding spot and the change in fluorescence is measured. Form the computer database of that array the sequence of bound DNA at that spot is identified. Hence we can know about different sequences present in the genome as well as their relative amounts (concentrations) based on the fluorescence change, that is in-turn based on how many DNA fragments have bound to a particular spot. DNA microarray of two individuals can tell about their differences in the Genome sequence, such as SNPs, mutations, deletions, etc. If performed only with the cDNAs isolated from any individuals, microarray can also tell about the relative abundance/expression of transcripts

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