Genetic Variation

Genetic Variation

• Genetic variation can be classified into four types: base pair, tandem repeats, structural variations, and others.

DNA Polymorphisms

• Polymorphism is defined as the presence of two or more variations in a DNA sequence.
• Types of polymorphisms include:
  • Single Nucleotide Polymorphism (SNP): a change in a single nucleotide, e.g., A to G or C to G.
  • Insertion-deletion polymorphism (Indel): a change in the number of nucleotides, e.g., AAAAT or AAT.
  • Tandem repeats: a sequence of nucleotides repeated in a row, either short or long.
  • Structural variation and copy number variation (CNV): a change in the number of copies of a DNA sequence, typically larger than 1kb.

Single Nucleotide Polymorphism (SNPs)

• SNPs are the most abundant type of polymorphism in the human genome.
• They occur approximately every 1-2 kilobase pairs.
• Some SNPs are associated with phenotypic differences, but most are not.
• Almost all SNPs have only two alleles (bi-allelic).

Genotypes and Allele Frequency

• Genotypes are the measured genetic makeup of an individual, while allele frequency is the percentage of individuals with a particular allele.
• Example: SNP rs9416742 has alleles G and A, with a frequency of G allele = 0.828 and A allele = 0.172 in Europeans.

Linkage Disequilibrium

• Close SNPs are not independent, and may be correlated with each other.
• Linkage disequilibrium occurs when the presence of one allele at one SNP is correlated with the presence of another allele at a nearby SNP.

Haplotypes and Phase

• Haplotypes are a set of alleles at multiple SNPs that are inherited together.
• Phase refers to the specific sequence of alleles in a haplotype.

Tandem Repeat Polymorphisms

• Tandem repeat polymorphisms occur when a sequence of nucleotides is repeated in a row, either short or long.
• They are often found in non-coding DNA.

This quiz covers the fundamentals of genetic variation, including variant types, genotypes, haplotypes, and linkage disequilibrium, as well as factors affecting allele frequencies. Learn about the different types of genetic variations and their frequencies in the population.