Genetic Variation Flashcards
Explain mutation, purifying selection, and and positive selection.
Mutations alter DNA sequences and accumulate over time, many have no adverse affects on phenotype, however those that adversely affect gene function are typically removed form the population (IF affected individual have lower fitness) by purifying selection. So why do some persist at high frequencies? A mutation which is beneficial in effect may increase in frequencies if individuals have high fitness (positive selection).
Define large and small scale changes.
Large; results from errors in chromosome segregation and recombination.
Small; result from unrepaired errors in DNA replication, etc…
Define DNA variants and Polymorphism.
Variants; are different forms of DNA sequences. If there is more than one variant in a population which is a relatively common (>1%), its a POLYMORPHISM.
What is the most common type of genetic variation? Define SNPs and SNVs.
Most common type of genetic variation is a single nucleotide variation. This can be a result of single nucleotide substitutions, deletions, or insertions so that a base present in one variant is not in a different variant.
SNV; if frequency of minor allele is <0.01
SNP; when 2+ or more variants have frequency of >0.01
How do SNV and SNPs occur?
The pattern of single nucleotide substitutions is not random, for example, C -> T substations are in excess.
Another reason is evolutionary ancestry.
Define structural variants(SV), indels, and copy number variations(CNV). (How do you detect them?)
structural variants(SV); involves more than one BP.
indels; may affect a SNV, but if more bases involved the SV.
copy number variations(CNV); is a change in copy number of sequences resulting in larger deletion and insertions.
Define variable number tandem repeats(VNTR), and list the types of VNTRs.
VNTR; a location in DNA where a short nucleotide sequence has a series of tandem repeats with variations in length between individuals.
Minisat; a short segment of DNA (15-100bp) that repeat in tandem.
Microsat; a short segment of DNA (5-15bp) that repeat in tandem.
DNA fingerprinting; uses a multi-locus DNA probe to identify individuals.
How to detect VNTRs, Indels, SNPs, etc…?
View image in notion!
Where within the genome are DNA sequence variants located?
Variants may be located within coding or outside coding sequences.
Coding;
Syn. Subs; codon replaced by another that still specifies the same amino acid.
Non-syn. Subs; codon replaced by another specifying a different amino acid (missense) to by a stop codon (nonsense).
Missense; can be pathogenic if alternative amino acid different from original
Nonsense; results in non-functional proteins
Frameshift; insertions or deletions that causes a frameshift, usually results in a nonfunctional protein.
Non-coding:
Most introns start with GT, end with AG. Mutations that change this will disrupt splicing.
Define exon skipping and intron retention.
Exon skipping; mutation inactivates splice acceptor site, next exon used instead.
Intron retention; splicing of intron 1 abandoned and sequence included as part of a new exon.
Define chromosome variation and list general types of chromosome variations.
Large scale mutations visible via microscope.
Numerical & structural
Sex and autosomal
List/outline 3 numerical and structural chromosomal abnormalities.
Polyploidy; possession of more than two haploid sets of chromosomes
Aneuploidy;his a diploid chromosomes set with one or more chromosomes extra or missing
Trisomy; three copies instead of 2 (e.g. DS)
Ring; occurs as a result of a chronometer break in two places, which the fuse in a ring shape (e.g. 46XY)
Duplication; one or more segments of DNA is produced (e.g. 46XX)
Translocation; a section of a chromosomes is added to another chromosomes that is not its homologous partner (e.g. 46XX)
Define haplotypes.
A set of DNA variants alone a single chromosome that tend to be inherited together. (Research)
