Variation

Question 1

What is C-DNA

Answer 1

The amount of DNA in a haploid genome

Question 2

What do we mean when there is a genetic mutation?

Answer 2

An inherited change in genetic information ​

Question 3

How is variation created in DNA?

Answer 3

Mutation is the only means by which new genetic variation is created.​
All other genetic/evolutionary processes reshuffle variation that is already present.​

Question 4

What are genetic mutations caused by?

Answer 4

*copying errors ​
*exposure to radiation or chemicals (mutagens)​
*viruses or virus-like sequences​

Question 5

What are somatic mutations?

Answer 5

Somatic mutations can not be evolutionary as they occur anywhere that is not reproductive germ line cells (egg and sperm)

Question 6

What are the three main classes that mutations fall into?

Answer 6

*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)

Question 7

What is substitution?

Answer 7

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.

Question 8

What are the types of substitutions?

Answer 8

1. Neutral mutation​
   e.g. microsatellite …ATATATATAT mutates to …ATATATATATAT​
2. Synonymous/Silent (=same-sense) mutation​
   e.g. AAA (lysine) changes to AAG (lysine)​
3. 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)​

Question 9

What is the most likely base substitution that will cause a silent mutation?

Answer 9

3rd base

Question 10

What is an example of a non-synonymous point mutation

Answer 10

Sickle cell anaemia is the result of valine being produced instead of glutamic acid.

Question 11

What are Deletions and Insertions also referred to as?

Answer 11

Indels

Question 12

What is insertion and deletion?

Answer 12

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

Question 13

What are the mutational hotspots in DNA molecules

Answer 13

UNEQUAL CROSSING OVER common among repetitive sequences (which are very common in the genome).

Question 14

What are slippage mutational events?

Answer 14

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.

Question 15

What are some of the larger scale mutations​

Answer 15

*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).​

Question 16

What can cause gene duplications to occur?

Answer 16

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).

Question 17

What are the processes that shape the size, complexity and organization of genomes?​

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Answer 17

1. Exon shuffling​=Creating genes that are mosaics of the original ‘donor’ genes​
2. Chromosomal rearrangements ​=Leading to e.g. gene duplications and new variants​
3. Whole genome duplication (ploidy)​
4. Transposable elements​= These are often the drivers of e.g. exon shuffling/creation and chromosomal mutations, so these mechanisms are not mutually exclusive.
5. 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.​

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Question 18

What is an extreme regions that evolved very quickly in humans? (coding regions too)

Answer 18

Human Accelerated Region (HAR1F)​

This gene was conserved highly in evolutionary time but in humans its evolution accelerated.

Question 19

What are microsatellites in the genome?

Answer 19

Short repetitive segments of DNA scattered throughout the genome in noncoding regions between genes or within genes

Question 20

Why is it important to know the molecular clock?

Answer 20

If we know the rate of change of particular DNA sequences through time we can estimate the time of divergence of taxa…​