Intro to genetic Variation Flashcards
DNA polymorphisms
DNA differs between human by 0.1%
Usually considered to be neutral variations in DNA sequence in the DNA sequence, common in the general population
Dominantly inherited variants are rare
Recessive mutations more common
What are the type polymorphisms
SNP
TRP
Structural
Describe SNPs
Single base substitutions can occurs across the genome- even in axons- with limited detrimental effect
Some are associated with phenotypic difference while others are not
Generally bi allelic
Closely located SNPs are not independent- if you have one SNP in one location, you are likely to have another SNP at another location
- > SNPs in the same genetic region may be correlated
ie. knowing the allele at SNP1 gives you information about SNP2
Haplotype
A series of SNP alleles along a single chromosome
Genotype
two alleles that are present at the single SNP
Describe Tandem Repeat Polymorphisms
Much of the DNA non coding region is repetitive- consists of DNA sequences that occur over and over
The number of base pairs in a repeat can be from 2bp +
Used in forensic investigation for identity matching
eg. Hunningtons diseases
CAG triplet repeat- if 40+ repeats lead s to disease
Structural Variation
Segment of the DNA that can be absent in some chromosomes or present in multiple tandem copies
Known as CNV/CNP—> duplication/deletion/ chromosomal inversion
eg 16p11.2
duplication of large section of chromosome 16
dominant pattern of inheritance
Leads to delayed development, behavioural problems, autism, schizophrenia
What requirements are needed for the frequency of alleles and genotypes will remain stable across generations
Large pop
No migration
No new mutation
No selection
Random mating
Hardy Weinberg Equation
A balanced reactionship between allelic frequencies and genotype frequencies therefore the knowledge of allelic frequencies allow prediction of genotype frequency
P + q =1
p^2 + q^2 + 2pq = 1
How can allelic frequency be changed
Selection
Migration
Mutation
Genetic drift
random change in the allelic frequency- all genetic frequency change
Selection-
acts on top of genetic drift-
usually leads to much faster changes in allele frequency over time
Leads to increase in frequency of one allele in population due to higher fitness of some genotypes
Fitness measures the ability of genotypes to reproduce
eg. Lactase gene- ability to drink milk due to advantageous C/T polymorphisms of lactase gene on Chromosome 2
Allowed the expression of lactase gene to persist into adulthood
Migration
Leads to diversity of genetic variants across the globe
Different allele frequencies between ethnic groups
eg. ABO blood group
Mututions
genome is constantly changing
Most new mutations have no biological effect-
some may be lost after one generation
some may be incompatible in life
others remain in the gene pool
