Introduction to Genetic Variation Flashcards
Definition of DNA polymorphism
Differences in base sequences between humans by 0.1%
Definition of biallelic
Have 2 alleles, 2 copies
Definition of haplotypes
Series of SNP alleles along a single chromosome
Definition of genotypes
2 alleles, present at a SNP in an individual
Definition of alleles
Single copy, allele A, G, C, T
Definition of linkage disequilibrium
Non random association of alleles at 2 or more loci in a general population. Haplotypes do not occur at the expected frequencies
Definition of SNP
Single nucleotide polymorphism, single base substitutions that occur throughout genome
Definition of tandem repeat polymorphisms
Repetitive sequences of DNA, individuals carry different non of repeats
Definition of structural variation
Segment of DNA that can be absent in same chromosomes or present in multiple tandem copies
Definition of Hardy Weinburg equilibrium
Explains stability of allele and genotype frequencies within a population
Definition of genetic drift
Random changes in genetic variants
Definition of selection
A change that favors 1 allele in a population due to higher fitness of some genotypes
Definition of fitness
Measures the ability of genotypes to reproduce
Measured on a scale between 0-1
Definition of heritability
Proportion of phenotypic variation due to genetic differences among individuals
What are DNA polymorphisms considered
Neutral variations in DNA sequence
Common in general population (freq>1%)
Contrast DNA polymorphisms with mutations that cause Mendelian diseases
Dominantly inherited variants v rare
Recessive mutations more common
Forms of genetic variation
Single nucleotide polymorphisms (SNP)
Tandem repeat polymorphisms
Structural variation
What is a SNP
Single base substitutions occur throughout genome, most common
Can occur in exons without detrimental effects
Roughly 10mn in 1 genome
Some associated with phenotypic differences
Generally are biallelic
The relationship between 2 closely located SNPs
SNPs in same genetic region may be correlated
In linkage disequilibrium
Knowing the allele at SNP1 gives information on allele at SNP2
What is a tandem repeat polymorphism
Non coding DNA mainly consists of repetitive sequences
Individuals carry different non of repeats
No of base pairs in a repeat can be from 2 and more base pairs
Microsatellite markers
Used in forensic investigations
What is structural variation
Segment of DNA that can be absent in some chromosomes or present in multiple tandem copies
Known as copy no variant (CNV)/polymorphism (CNP)
Segments contain 100s of genes, have impact on health, increase risk of disease
Assumptions in Hardy Weinburg equilibriums
Large populations No migration No new mutations No selection Random mating
What is the Hardy Weinburg equilbrium
Frequency of alleles and genotypes will remain stable across generations
Hardy Weinburg equations
p+q=1 allele frequency
p^2 + 2pq + q^2=1 genotypes frequency
