Variation Flashcards
What is C-DNA
The amount of DNA in a haploid genome
What do we mean when there is a genetic mutation?
An inherited change in genetic information
How is variation created in DNA?
Mutation is the only means by which new genetic variation is created.
All other genetic/evolutionary processes reshuffle variation that is already present.
What are genetic mutations caused by?
*copying errors
*exposure to radiation or chemicals (mutagens)
*viruses or virus-like sequences
What are somatic mutations?
Somatic mutations can not be evolutionary as they occur anywhere that is not reproductive germ line cells (egg and sperm)
What are the three main classes that mutations fall into?
*POINT MUTATIONS= Change in a single nucleotide
*CHROMOSOMAL MUTATIONS=Eliminate, duplicate, or rearrange segments .
*WHOLE GENOME EVENTS=duplication of entire genomes (e.g. ploidy changes)
What is substitution?
One base is simply substituted for another
transitions: The bases still make up the same amino acid
transversions: The base substitution codes for a different amino acid.
What are the types of substitutions?
- Neutral mutation
e.g. microsatellite …ATATATATAT mutates to …ATATATATATAT - Synonymous/Silent (=same-sense) mutation
e.g. AAA (lysine) changes to AAG (lysine) - Non-synonymous/Coding (=mis-sense) mutation
e.g. AAA (lysine) changes to CAA (glutamine)
4.Non-sense mutation
e.g. TAC (tyrosine) changes to TAA (stop codon)
What is the most likely base substitution that will cause a silent mutation?
3rd base
What is an example of a non-synonymous point mutation
Sickle cell anaemia is the result of valine being produced instead of glutamic acid.
What are Deletions and Insertions also referred to as?
Indels
What is insertion and deletion?
Deletions: one or more nucleotide(s) are deleted from the DNA sequence
Insertions: one or more nucleotide(s) are inserted into the DNA sequence
Both of these are frameshift mutations except when there are 3 nucleotides (codon) inserted then there is an additional amino acid and no frame shift
What are the mutational hotspots in DNA molecules
UNEQUAL CROSSING OVER common among repetitive sequences (which are very common in the genome).
What are slippage mutational events?
During meiosis 1 crossing over the chromosomes don’t realign properly and therefore one is left with a deletion and the other an insertion so they both have a unique number of repeats.
What are some of the larger scale mutations
*Gene duplications
*Chromosomal rearrangements
*Aneuploidy= A change in the number of individual chromosomes (e.g. monosomy, trisomy, tetrasomy)
* Polyploidy= One of more complete sets of chromosomes is added, either from the same species (autopolyploids) or as a result of hybridisation between two difference species (allopolyploids).
What can cause gene duplications to occur?
Can be brought about by copying errors or transposable elements.
duplicate gene(s) can bring about pseudogenes (used to be coding but now just drifting and passed down generations that are non-functional but not detrimental or (multi)gene families(a group of genes that have descended from a common ancestral gene and therefore have similar functions which can be refined and are similar DNA sequences).
What are the processes that shape the size, complexity and organization of genomes?
- Exon shuffling=Creating genes that are mosaics of the original ‘donor’ genes
- Chromosomal rearrangements =Leading to e.g. gene duplications and new variants
- Whole genome duplication (ploidy)
- Transposable elements= These are often the drivers of e.g. exon shuffling/creation and chromosomal mutations, so these mechanisms are not mutually exclusive.
- Horizontal gene transfer= DNA is transferred between species. Especially common in bacteria but increasingly thought to possibly also be an important source of genome evolutionary change in eukaryotes too.
6.Potentially also artificially through GM technology.
What is an extreme regions that evolved very quickly in humans? (coding regions too)
Human Accelerated Region (HAR1F)
This gene was conserved highly in evolutionary time but in humans its evolution accelerated.
What are microsatellites in the genome?
Short repetitive segments of DNA scattered throughout the genome in noncoding regions between genes or within genes
Why is it important to know the molecular clock?
If we know the rate of change of particular DNA sequences through time we can estimate the time of divergence of taxa…
