Introduction to Genetic Variation

What is the primary definition of a polymorphism?

What type of polymorphism occurs once in every 1-2kb throughout the genome?

What is the term for the process of generating sequence changes?

What type of polymorphism includes triplet repeats?

What is the term for a change in a DNA sequence?

How often do Single Nucleotide Polymorphisms (SNPs) occur in the human genome?

What is the characteristic of almost all alleles?

What is the frequency of the A allele in the example given?

What is the term for the phenomenon where knowing the allele at one SNP gives information about the allele at another SNP?

What type of polymorphism is characterized by repeat elements within non-coding DNA?

What is the genotype frequency of the AA genotype in the example given?

What is the term for a specific combination of alleles at multiple loci?

What is the number of alleles in the example given for SNP rs9416742?

What is the characteristic of SNPs that are close together?

Genetic Variation

Genetic variation refers to the differences in DNA sequences between individuals or populations.
There are several types of genetic variation, including:
- Base pair variations
- Tandem repeats
- Structural variations

DNA Polymorphisms

Polymorphism is the presence of two or more variations in a DNA sequence.
Types of polymorphisms include:
- Single Nucleotide Polymorphism (SNP)
- Insertion-deletion polymorphism (Indel)
- Tandem repeats
- Structural variation and copy number variation (CNV)

Single Nucleotide Polymorphism (SNPs)

SNPs are single base substitutions that occur throughout the genome.
They are the most abundant type of polymorphism in the human genome.
SNPs occur once in every 1-2 kilobase (kb) of DNA.
Some SNPs are associated with phenotypic differences, but most are not.
Almost all SNPs have only two alleles (bi-allelic).

Potential Functional Effect of SNPs

SNPs can have a direct functional effect on the genome.

Genotypes and Allele Frequency

Genotypes are the measured expression of a gene.
Allele frequency is the calculated proportion of different alleles in a population.
Example: The genotype of SNP rs9416742 has alleles G or A.
- Genotypes in Europeans (n=503): GG = 339, GA = 155, AA = 9
- Allele frequency: G allele = 83%, A allele = 17%

Linkage Disequilibrium

Close SNPs are not independent and may be correlated.
Allele A at SNP1 may be associated with allele G at SNP2.
Knowing the allele at SNP 1 gives information on the allele at SNP2.

Haplotypes and Phase

Haplotypes are a set of SNPs that are inherited together.
Phase refers to the specific combination of alleles at multiple SNPs.
Determining the phase of a set of SNPs is important for understanding genetic variation.

Tandem Repeat Polymorphisms

Tandem repeat polymorphisms occur when repeat elements are present within non-coding DNA.
These repeats can vary in length and are often found in non-coding regions of the genome.

This quiz covers the basics of genetic variation, including variant types, genotypes, and haplotypes, as well as factors that affect allele frequencies. Learn about the frequency of polymorphisms in the population and more.