Genetic variations Flashcards
(31 cards)
What is a polymorphism?
A DNA variant with a frequency of more than 1% in the population (has to have 2 or more alleles)
What is the most common type of polymorphism?
SNP - single nucleotide polymorphism
How are SNPs distributed in the DNA and how are they inherited?
Distributed evenly, approximately every 100 bp. They are inherited in haplotype blocks or linkage groups - because of the limited opportunity of crossing over in meiosis.
Name the 4 types of extragenic DNA sequences
- Unique DNA (single copy)
- Low copy repetitive DNA
- Moderatley repetitive DNA
- Highly repetitive DNA
Which type of extragenic DNA sequence is highly conserved through evolution?
Unique DNA - often has a function in gene regulation.
Where are low copy repetitive DNA sequences found?
Close to centrosomes
What are highly repitive DNA sequences derived from?
Mobile DNA elements
Name a type of highly repetitive DNA in humans, what are they?
Transposons - DNA sequences that can move in the genome.
Retrotransposons - type of transposon. Sequence is copied by reverse transcriptase and inserted back into the DNA
Transposons - sequence of DNA that moves using cut and paste
What is the importance of transposons?
Creates novel genes, allows exon shuffling.
What is penetrance?
The proportion of a population with a genotype that shows the associated phenotype
What is expressivity?
Qualitative or quantitative variations in the phenotypes among individuals with a specific genotype.
What effects can DNA mutations have on gene expression?
Effects the regulatory region - change the expressivity of the gene
What effect can DNA mutations have on protein function?
Loss of function, gain of function, dominant-negative (interacts with wild type gene and loses function)
Complex diseases are all polygenic. They can be additive or non-additive, what does this mean?
Additive - equal contribution of all gene loci.
Non-additive - unequal contribution of all gene loci
Is there a familial tendency in complex diseases?
Yes with close relations but still a lot lower than expected.
What causes numerical abnormalities?
Non-dysjunction during meiosis or mitosis.
What is aneuploidy?
Loss or gain of 1 or more chromosomes.
Monosomy - loss of 1
Triploidy - gain 1
What is polyploidy?
Gain of 1 or more complete chromosome sets
Why are chromosomal abnormalities not common in the population?
Often cause embryonic fatality
What can cause structural changes?
Chromosomal breakage and abnormal reunion or unequal crossing over during recombination.
What is translation and what are the different types?
Transfer from 1 chromosome to another. Caused by chromosomal breakage and abnormal reunion.
Reciprocal - 2 chromosomes exchange segments.
Robertsonian- breakpoint is near the centromere of an acocentric chromosome.
What is inversion and what are the different types?
Chromosome segment is reversed.
Pericentric - involves the centromere
Paracentric - only involves 1 arm
What is insertion and deletion?
Caused by unequal crossing over during recombination. part of chromosome is inserted into another or lost.
What is a ring chromosome?
Broken chromosome forms a ring
