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Genes Evo & Dev Y1 > Genes Evo & Dev L6 Notes > Flashcards

Genes Evo & Dev L6 Notes Flashcards

1
Q

How many base pairs are there?

A

3 billion

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2
Q

What proportion of base pairs code for proteins?

A

At most 3%

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3
Q

What proportion of base pairs are regulatory?

A

10%

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4
Q

What proportion of base pairs are repetitive?

A

45%

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5
Q

What proportion of base pairs are non-functional/junk?

A

85%

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6
Q

What are transposons?

A 
	Mobile genetic elements 
	Sequences DNA -> move in genome 
	Simplest ->transposons -> transposase
Enables removal & insertion of sequences from genome
	Do not require reverse transcriptase
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7
Q

What are the functions of retrotransposons?

A

• Retrotransposons
 Produce RNA
Require reverse transcriptase -> reverse transcribe RNA
-> DNA. -> insert into target site

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8
Q

Describe how movement of transposons is thought to have occur

A

• Movement of transposons -> mutations
Tool -> Drosophila
Possibly involved -> cancers
Characters -> Prevention of transposition -> favoured
->Conflict -> host & transposition
2% -> new insertion -> L1 element -> occurred in gametes/zygote
 Can be prevented by small interfering RNAs.

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9
Q

Outline how new genes are formed

A 
1.	Duplicate 
Non-coding sequence
Long strings -> 3 amino acids
2.	Change -> nucleotide bases
Tagged as secretory 
3.	Translocation
Moves sequence near promoter region
Activates/ functionalised gene
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10
Q

Give an example illustrating formation of a new gene

A

 Fish -> polar seas -> ‘Anti-freeze’ glycoproteins
Northern gaddids -> Arctic cod -> different glycoproteins to those -> Antarctic fish.
Adaptation
Protein doesn’t become functional -> last step -> gene assembly
Doesn’t require designer ->arising -> natural processes.
All parts incl. proteins -> synthesised -> translocation & duplication alone,
- Series of steps -> neutral/ slightly advantageous

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11
Q

Give an example of a structure thought to have arisen as a result of transposition?

A

 Mammalian placenta -> requires syncitins
>Genes -> once encoded -> envelope -> retrovirus
Repeatedly coopted -> mammals
>Evolution of placenta
>Control gene expression -> pregnancy
Evolution -> placenta -> viviparous Mabuya lizards

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12
Q

Why is it thought the new structures can be formed as a result as a result of transposition.

A

Eg. Gravid Mabuya ->Gives birth -> Studied placental transcriptome
> Extract RNA -> tissue of interest
> Find genes expressed -> particular tissue / developmental stage
> Functional genes identified

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13
Q

What does information does a transcriptome provide?

A

Function of a genome in time (eg. developmental stage) & place (eg. organs)

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14
Q

What are LINE elements?

A

Long Interspersed Elements

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15
Q

What is horizontal gene transfer?

A

The transfer of genetic material between organisms other than parent & offspring.

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16
Q

What does horizontal gene transfer involve?

A 
•	Horizontal gene transfer
-	Widespread -> prokaryotes 
-	Minor source -> genetic variation
mitochondrial DNA genes -> integrated -> nuclear DNA
-	Multicellular organisms 
Involves parasite/symbiote
-	Possibly leads -> adaptations
17
Q

Give an example if evidence of horizontal gene transfer.

A

Eg. – Aprrox. 25% cow genome -> composed -> BovB elements -> reptiles
- Long interspersed element -> 3.2 kb -> repetitive piece DNA
- Inert element -> Comparison of animal genomes
BovB closely related to element -> sheep
>Closely related -> elements -> snakes
&raquo_space;Closer to snakes than marsupials
- 25% cows’ genomes -> from snakes.
- Explanation -> ticks.
 Transfer gene from snakes -> cows -> horizontal gene transfer

18
Q

Give examples of horizontal gene transfer.

A

Spodoptera moth -> immune barrier -> acquired through virus -> lives in parasitoid wasp.
Carotenoids -> red colouration
–> Acquired -> animals -> food.
Pea aphids -> normally green -> red form in some clones
–>Linked -> predation avoidance=
Genes -> carotenoid biosynthesis
–>Acquired -> fungus.

19
Q

What did reconstruction of extinct genomes enable?

A
  • By comparison -> genomes -> many diff taxa
    ->possible identification ->25 groups genes -> required to be an animal.
    New genes -> appeared -> animal origin
    >Homeobox developmental genes, signalling
    pathways, cell adhesion molecules, receptors, etc.
20
Q

How is it thought insects are crustaceans

A

 DNA analysis -> 62 genes
 Hexapods -> within Pancrustacea
 Remipedes & Cephalocarids -> crustaceans -> sister group -> insects.
 Most purposes; crustacea -> (not incl. insects) still valid.

21
Q

Describe the spread of the Cabbage White butterfly.

A

• Spread of Cabbage White -> butterfly
- Rough but unclear idea of spread through history
- Asked world -> catch & send butterflies
3000 insects -> 293 localities
- Nuclear & mitochondrial DNA genotyping
European & Asian diverge -> 1200yrs
->Carried along silk road -> Coinciding -> widespread adoption -> brassica Crops
- Last 160 yrs -> trade -> dispersed butterfly

22
Q

Outline the argument on the number of giraffe species.

A
  • Traditionally -> several sub-species -> pattern morphology
  • 7 nuclear genes & mitochondrial DNA sequenced
    4 groups -> diverge 1-2million years ago
    Argued -> 4 species -> no gene flow
    ->No evidence isolated
    Cannot conclude species based on DNA only. -> no minimal
    change in base pairs
  • Populations geographically isolated -> can’t use “biological species definition”
    Members of different species, when present in same area, do not mate with each other, or do mate but cannot produce fertile offspring.
    Found can hybridize in zoos -> but still can’t apply
    ->Other isolating barriers in nature -> different breeding times/genetically
    based aversion -> could keep separated anyway.
  • Therefore must use genetic divergence -> as don’t encounter
    Genetic divergence -> measures amount of sequence difference -> DNA
23
Q

What are the 4 species of giraffe that are thought to exist?

A

i) Southern giraffe (Giaffa giraffa)
ii) Masai giraffe (G. tippelskirchi)
iii) Reticulated giraffe (G. reticulata)
iv) Northern giraffe (G. Camelopardalis) -> incl. Nubian giraffe (G. c. camelopardis) as distinct related species.

24
Q

Describe eDNA

A

• eDNA -> Environmental DNA
Extraction DNA sequences -> no organism
>Soil, water, air
Non-invasive -> conservation & ecology
Molecules behave differently -> different situations
Requires careful amplification & bioinformatic identification
Effective -> aquatic systems.
Eg. Loch Ness Monster

25
Q

Describe differences in human genomes

A
  • Avrg. Difference -> 0.1% -> eachother
  • Human genetic variation -> severely underestimated -> Only European DNA in reference
  • 910 African descent -> compared
    10% more DNA -> reference genome
    Some variants -> protein-encoding genes
    Functional significance unclear
26
Q

Give genetic evidence of natural selection in humans

A
  1. -50 Tibetans -> 4000m -> 40% less oxygen -> 2750 yrs
    -40 Han Chinese
    EPAS1 gene -> controls production -> red blood cells
    ->87% -> Tibetans
    ->9% -> Han
  2. Bajau people -> SE Asia -> Diving ability -> long periods
    Selection on -> PDE10A gene -> larger spleens -> reservoir blood cells
    ->BDKRB2 gene -> diving reflex
27
Q

Describe variation in skin colour

A

• Skin colour
 Darker skin -> protects -> UV
 Light skin -> enables biosynthesis -> Vitamin D -> sun is weaker.
 Skin colouration -> 15 genes
 Substantial variation in Africa
Indigenous peoples -> South Africa
>Large colour variation
>Large variation -> Underlying genes -> incl. genes coding -> lighter skin
 Complex underlying local evolutionary pressures
 Doesn’t correlate with any other trait

Genes Evo & Dev Y1 (23 decks)

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