14 - Lifecycle of a Gene Flashcards
1
Q
Where do new genes come from?
A
- HGT
- Duplication of an existing gene
- De novo (new) gene from non-coding DNA
2
Q
What is an example of HGT in eukaryotes?
A
chloroplasts and mitochondria transferring their DNA into the nucleus
3
Q
How can whole genome duplication happen?
A
- autopolyploidisation -> increase in ploidy
- gametes have same number of chromosomes as somatic cells, forms a zygote
- Allopolyploidisation -> genome of different species combines
- meiotic error - hybrid formed by one gamete that is x2 and one haploid - hybrid
- combines with another haploid gamete to form a zygote
4
Q
How can whole chromosome duplication happen?
A
Aneuploidy
- non-disjuction happens in meiosis I or meiosis II
5
Q
How can DNA segment duplication happen?
A
- replication errors – DNA loop forms on nascent strand
- unequal cross overs - repeats cause incorrect alignment in recombination
- reterotransposition
- De novo - non-coding DNA - open reading frame is made
6
Q
What are 4 ways genes are lost?
A
- deletion - replicative error with repeats
- genetic drift
- selection against
- loss of function my mutation - start codon mutated ect
7
Q
How can genes be preserved?
A
- compensation - 1 gene silences or TFs split
- neofunctionalisation - one gene gains a new function
- subfunctionalisation - function of gene is split between the two
- no selection agains - amylase start breakdown in humans
8
Q
What are the two classes of transposable elements?
A
- retrotransposon - copy + pasta
- DNA transposon - cut and paste
9
Q
What will happen to a gene that is transcribed at the same time as a retrotransposon?
A
- it will go to mRNA with the introns removed
- when put back into the gene it will have no introns
10
Q
Explain the effect of duplications on tellomeres
A
can help lengthen them
11
Q
What is pseudogenisation?
A
functional gene becomes non-functional
