6 - MOLECULAR MARKERS Flashcards
why are genetic crosses for mapping not possible for humans and what is a better method?
controlled cross not possible
mating couples make small amount of offspring
experiments would take many years to conduct
better approach is to map a gene using molecular markers
what are molecular markers and their characteristics
small DNA sequence differences (polymorphisms) within a specie that are present at specific chromosomal location
present throughout the genome
most don’t have biological functions, no phenotype
molecular markers are seen as bands on a gel
can be used to map a gene by determining the linkage between the gene of interest and a molecular marker
what are simple sequence length polymorphisms and characteristics
human genomes have a lot of repetitive DNA, including multiple repeats of short simple DNA sequences called SSLPs at specific locations in the genome
unrelated people likely have a different number of those repeats
humans have one set of paternal and one set of maternal SSLPs
length can be determined by PCR amplification using primers
what are single nucleotide polymorphisms (SNPs)
genome sequence of two unrelated individuals is 99.9% identical
most of the 0.1% differences are single nucleotide variants
to be an SNP, variant must be found in at least 1% of any population among common people
if not, it’s a mutation of an individual
some SNPs are more common in a specific population/ethnicity
could be in the intergenic region, within a gene or in a regulatory region
most SNPs have no effect on health or development
some (especially if found within a gene or a regulatory region near a gene) can play a role in susceptibility of a disease or sensitivity to an external factor
how can you map disease genes with molecular markers
example of environmental influence in gene variance
spanish colonists established in the andes mountains
experienced chronic mountain sickness
couldn’t get enough oxygen
tested it with tibetans are chinese, who are closely related
tibetans have more of the EPAS1 SNP than the chinese
EPAS1 regulates the number of blood cells that our bodies produce in response to the level of oxygen in our tissues
