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Modern Theories of Evolution > Lecture 5 - Gene Duplication > Flashcards

Lecture 5 - Gene Duplication Flashcards

1
Q

What is subfunctionalisation?

A

Where the role of a gene is split over two or more copies, and the protein made is made at two independent loci.

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2
Q

What is gene conversion?

A

Where multiple copies of a gene are advantageous when the cell needs a lot of something quickly.

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3
Q

What is nonfunctionalisation?

A

The original function of a gene is conserved within one copy, and mutations occur in the other copy and it loses function.

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4
Q

What is neofunctionalisation?

A

When one copy maintains its original function, and another is mutated to generate a new function.

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5
Q

Give six mechanisms of generating new genes.

A
  • Duplication
  • Exon shuffling
  • Retroposition
  • Mobile genetic element insertion
  • Gene fusion/fission
  • De novo origination
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6
Q

When does unequal crossing over occur?

A

In prophase 1 of meiosis

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7
Q

Where does unequal crossing over occur?

A

At non-homologous parts of the chromosomes

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8
Q

At what kind of gene is unequal crossing over likely to occur?

A

Where there is a repetitive sequence.

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9
Q

What does unequal crossing over result in?

A

Duplication of a part of a gene/complete gene.

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10
Q

What is the rate at which genes duplicate and increase to high frequency in populations?

A

0.01 per gene per million years.

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11
Q

What can happen to the second copy when a gene is duplicated?

A

The second copy may be free of selective pressure, and can accumulate mutations without consequences to the host.

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12
Q

What are two other terms for degeneration?

A
  • Gene loss

- Pseudogenisation

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13
Q

What is degeneration?

A

One copy of a gene may accumulate mutations leading to loss of its function and potential loss of the gene.

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14
Q

When can we lose the ability to recognise a gene duplication?

A

When degeneration occurs

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15
Q

What is adaptive conflict?

A

When a single copy of a gene performs more than one function, cannot optimise one function without detrimentally affecting the other.

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16
Q

When is a gene said to have ‘escaped adaptive conflict’?

A

If gene duplication allows each gene copy to specialise to a function/each takes on a different function.

17
Q

Give an example of escape from adaptive conflict.

A
  • Antifreeze proteins in Antarctic Eelpout
  • Type 3 AFP homologous to SAS (sialic acid synthase).
  • AFP3s secrete d plasma proteins, bind to invading ice crystals, arrest ice growth.
  • Ancestral gene fulfilled two functions, but Sas-B duplicated and moved to different chromosome.
18
Q

Name the chromosomes each human globin is found on.

A
  • Alpha: 16
  • Beta: 11
  • Myoglobin: 22
19
Q

What are globin genes descended from?

A

All from a single ancestral gene.

Initial split gave rise two two lineages: myoglobin and haemoglobin.

20
Q

What is exon shuffling?

A

The creating of new combinations of eons via intronic recombination.

21
Q

What is an exon?

A

Part of a gene coding for proteins.

22
Q

What is illegitimate recombination?

A

Recombination between short or non-homologous sequences.

23
Q

How can exon shuffling create new combinations of exons?

A

By illegitimate recombination, sometimes offering new variants that give a selective advantage.

24
Q

What happens in retroposition?

A

Processed mRNA is reverse-transcribed to form a double-stranded DNA segment. If integrated into a chromosome, the genome acquires a duplicated copy to the original gene.

25
Q

What are mobile genetic elements often associated with?

A

Cancer

26
Q

Describe how mobile genetic elements work.

A
  • Inserts itself into an intron

- New splice sites evolve with the transposable element, and the element becomes a new exon.

27
Q

How long is a mobile genetic element?

A

Approx 100 nucleotides

28
Q

What is gene fusion?

A

When two adjacent genes fuse into a single gene by deletion or mutation of a stop codon.

29
Q

What is gene fission?

A

The insertion of a stop codon followed by the insertion of a promoter region into the gene, resulting in two separate genes.

30
Q

What are orphan genes?

A

Genes with no sequence similarity to genes in other organisms; don’t know about their ancestry.

31
Q

What are orphan genes the result of?

A
  • Fast evolutionary change relative to ancestors - no longer detect similarity.
  • De novo orientation.
32
Q

What is de novo gene orientation?

A

New coding regions emerge anew from non-coding genomic sequences.

33
Q

How are de novo genes detected?

A

By a stretch of coding DNA encoding protein in one genome but not in the genome of a close relative.

Modern Theories of Evolution (9 decks)

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