Genome variation Flashcards
What is the Genome?
The number of chromosomes and its gross structure (23 pairs of chromosomes)
what is the exome?
The genome (2%) that codes for proteins
How do humans differ at the lvl of their DNA?
Due to variation in DNA as a result of coding variants that effect traits e.h hair colour. As well as major macro-lvl differences and micro/molecular-lvl pathogenic difference.
variation is caused by major macro-lvl differences and micro/molecular-lvl pathogenic difference. Describe their differences
1) Major= generally associated with disease (aneuploidy, translocations, ec)they are very rare
2)micro= sometimes associated with disease (point mutations and SCA, 3bp deletion inCFTR). you can have people carrying recessive disorders as a result of this
Define Polymorphic position
Any position in the genome that varies between individuals is considered polymorphic= a variant
what is the reference/ consensus sequence?
The consensus sequence is what summarises what the vast majority of people have at a particular position, so what sequence we expect at a particular position
what is a genetic variant?
when the sequence is different to what is expected (the consensus sequence)
Define Homozygous, Heterozygous, major allele, minor allele and reference allele
Homozygous= identical alleles
Hetrozygous= different alleles
Major allele= most common e.g T
minor allele= not common
reference allele= what is expected/ most common
what is minor allele frequency?
Any pathogenic site or a variant
how can we know what is a normal sequence and what is a variant?
by comparing to the human genome mapping project
what are the 3 types of variants found in the human genome?
1) SNV
2)Microsatellites
3) Copy number variation
What is a single nucleotide variant/ polymorphism?
A change in a single base pair
How are snv/snp generated?
They are generated through mismatch repair, during DNA replication, which goes wrong.
Explain the mechanism of generation of SNV/P
1) During DNA replication the 2 strands will separate and will be used as templates to synthesise complementary strands
2) If that goes well u should end up with 2 identical copies
3)However, when synthesising this strand, instead of incorporating an A (which would be complimentary to the T in the template strand) a G is incorporated
4) The mismatch repair mechanism will identify this mistake and correct it so that it is a standard Watson-crick base pair: rather than converting the G to a A they replace the T in the template to a C
5) If this change occurs in the gametes and isn’t deleetrious then it will be passed on to the next gen
what are SNPs generally?
Biallelic- 2 allelic variants are segregating in the population
