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Evolution > Exam 4 - Ch. 15 > Flashcards

Exam 4 - Ch. 15 Flashcards

1
Q

What is the C-value?

A

the total amount of DNA found in a cell

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2
Q

What are the two types of Prokaryotes?

A

bacteria and archaea

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3
Q

What is the C-value paradox?

A

In eukaryotes, where there is little correlation between DNA quantity and an organism’s perceived morphological complexity

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4
Q

What are the two phenomena that explain the C-value paradox?

A
  1. whole-genome duplications resulting in polyploidy (genome is doubled)
  2. the existence of large portions of an organism’s genome that are largely functionless from the cell’s viewpoint
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5
Q

What does Satellite DNA do?

A

the tandemly repeating sequences of DNA that are commonly used for DNA profiling

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6
Q

What do telomeres do?

A

they are the regions of repetitve DNA at the end of the chromosome, that protect against chromosomal deterioration

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7
Q

What do introns do?

A

they are the non-coding sequences within genes that are removed by RNA splicing

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8
Q

What do Non-coding RNA genes do?

A

they are the codes for RNA molecules that are not translated into proteins

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9
Q

What are gene regulatory sequences?

A

sequences involved in the process of transcription (ex: promoters, enhancers, and silencers)

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10
Q

Larger genomes have:

A

more DNA that codes for proteins

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11
Q

The size of a plant or animal’s genome is unrelated to its body size or phylogenetic position. True or false?

A

True

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12
Q

In complex organisms, RNA molecules transcribed from __________ regions of the genome have roles in regulating gene expression, so in other words, they do not code for _________.

A

noncoding regions, proteins

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13
Q

What do mobile genetics elements do, and how do they do that?

A

replicate and insert themselves into an organism’s genome regardless to the consequences to the organism, by hijacking the same cellular machinery that replicates and transcribes protein-coding DNA

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14
Q

What are mobile genetic elements sometimes called and why?

A

selfish genetic elements, because they are more focused on making copies of themselves

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15
Q

Mobile genetics elements can:

A
  1. can cause gene duplication elements
  2. can cause mutations in protein-coding regions, which alters the protein functions
  3. can rearrange genes in the host genome
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16
Q

Mobile genetic elements can disrupt the function of? What does this result in?

A

protein-coding genes, results in obvious changes to an organism’s phenotype

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17
Q

How much of the DNA sequence is derived from mobile genetic elements?

A

45%

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18
Q

Do unicellular organisms have mobile genetic elements in their genomes?

A

they often do not

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19
Q

Intergenic regions

A

space between coding genes in the eukaryotic genome

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20
Q

What makes up the intergenic regions?

A

mobile genetic elements and their remnants

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21
Q

What is the most predominant noncoding DNA found in eukaryotic genomes?

A

introns

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22
Q

Where do introns occur?

A

within the coding regions of genes

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23
Q

What are introns transcribed into?

A

mRNA

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24
Q

Unicellular eukaryotes typically have _ to _ introns per genome.

A

1 to 2

25
Q

What is the average amount of introns in vertebrates?

A

5-8

26
Q

Do prokaryotes have introns?

A

no

27
Q

Is there any implied importance to the positions of introns?

A

yes

28
Q

Just because MGEs could be considered parasitic, does this mean they are good or bad?

A

neither

29
Q

Could mobile genetic elements be considered parasitic?

A

yes

30
Q

Transposons

A

mobile genetic elements that can change their position within a genome

31
Q

Retrotransposons

A

mobile genetic elements that leave a copy of themselves behind when they move

32
Q

How do retrotransposons leave copies of themselves behind?

A

by converting RNA into DNA through reverse transcription

33
Q

What happens if transposition occurs in the germ line?

A

it will be passed on to the host’s offspring

34
Q

Do host genomes have mechanisms to counter mobile genetic elements?

A

yes

35
Q

What are the mechanisms used to defend against mobile genetic elements?

A

DNA methylation and RNA silencing

36
Q

Methylation

A

attachment of methyl groups to nucleotides, which prevents the transcription of DNA into RNA, thus preventing retrotransposons

37
Q

RNA interference/RNA silencing

A

short sequences of RNA that match a particular mobile genetic element, and silences the expression of it

38
Q

Polyploidization

A

whole-genome duplication

39
Q

Segmental duplication

A

duplication that affects smaller sections of the genome, can copy a single complete gene, a piece of a gene, or several genes

40
Q

What are the molecular mechanisms that cause segmental duplication?

A

unequal cross-over between chromosomes during meiosis, and mobile genetic elements

41
Q

Duplication events are often selectively _______. Why?

A

neutral, because it does not affect the phenotype

42
Q

Does fixation typically occur by chance alone? What does this mean for duplications in the long run?

A
  • No, neutral alleles rarely drift to fixation
  • most duplications are soon lost from a population
43
Q

What are the steps taken to preserve duplicated genes?

A
  1. a duplicated allele must rise to fixation in a population
  2. one of those duplicates acquires a mutation that changes its function from A to B
  3. one of the gene copies acquires a mutation that changes its function
  4. the new allele contains one copy that performs the new function, and then a second copy that performs a new function
44
Q

What is the reason for the preservation of a duplicated gene?

A

can be attributed to selection, the new function increases fitness

45
Q

Neofunctionalization

A

the gene copy that mutates from the original acquires an entirely new function that by chance benefits the organism

46
Q

What happens to each copy of a gene in neofunctionalization?

A

one copy continues to perform the ancestral function, while the other acquires mutations that give it a new function

47
Q

What is the widely accepted mechanism for the preservation of duplicate genes?

A

neofunctionalization

48
Q

Subfunctionalization

A

the ancestral gene has two different functions, meaning that after the ancestral two-function gene is duplicated, one copy performs the ancestral function A, while acquiring a mutation that inhibits the other ancestral function

49
Q

What eventually happens to a gene in subfunctionalization?

A

The other copy acquires another mutation that inhibits the ancestral function B

50
Q

Gene families

A

groups of anywhere from two to hundreds of genes that are all descendants of a single ancestor gene

51
Q

What are gene families a result of?

A

repeated duplication events

52
Q

All genes in a gene family typically have similar structures and functions, but they do not:

A

perform identical function

53
Q

What was adaptive genetic variation generated by?

A

mutational processes

54
Q

Adaptation from new mutation

A

if the alleles that encode a novel adaptive phenotype appear after a new selective challenge arises (selection causes a new mutation)

55
Q

Adaptation from standing genetic variation

A

alleles favored by the new selective challenge are present at low frequency in the population before the challenge arose (mutation was neutral until selected for)

56
Q

What is the neurotoxin that garter snakes possess?

A

tetrodotoxin, which block the movement of sodium ions across cell membranes, and result in paralysis

57
Q

What is theory behind garter snakes being resistant to neurotoxin tetrodotoxin?

A

it is possible that the alleles conferring with the resistance were passed down from the common ancestor

58
Q

How did the resistance for TTX arise in each species?

A

independently

59
Q

What is the adaptive resistance to TTX in garter snakes an example of?

A

adaptation from new mutation

Evolution (3 decks)

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