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Chapter 18 Flashcards

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1
Q

Why are mutations important?

A
  • sustains life and causes challenges
  • genetic variation
  • raw material for evolution
  • creates diseases and disorders
  • to help understand the fundamental biological processes
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2
Q

Adaptive mutation

A

Genetic variation occurs —> environment determines what is the best fit
Stressful conditions, adaptation necessary to survive through mutation, induced in bacteria

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3
Q

What causes mutations?

A
  • spontaneous replication errors
  • spontaneous chemical changes
  • chemically induced mutations
  • radiation
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4
Q

What are the two major types of mutations?

A

Somatic mutations
Germ-line mutations

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5
Q

Somatic mutations

A

Within body cells (i.e. non reproductive cells)
Not passed on to the next generation of offspring
Passed on through mitosis

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6
Q

Germ-line mutations

A

Cells that make the gametes
Can be passed onto your progeny

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7
Q

Genome shock hypothesis

A
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8
Q

Types of gene mutations based on their molecular nature

A

base substitutions
Insertion and deletions
Expanding nucleotide repeats

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9
Q

Base substitution

A

Transition (purine to purine, pyrimidine to pyrimidine)
Transversion (purine to pyrimidine or vise versa) —> distorts the shape of the helix, therefore the function
Changes a single codon

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10
Q

Insertions and deletions

A

Frameshift mutations
In-frame mutations
Change protein created for that gene
How different alleles are produced
Can affect STOP codons

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11
Q

Expanding nucleotide repeats

A

Increase in the number of copies of a set of nucleotides
Fragile X-chromosomes, a characteristic constriction on the long site —> lose that section

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12
Q

Nucleotides

A
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13
Q

Phenotypic effects of mutations

A

Forward mutation
Reverse mutation
Missense mutation
Nonsense mutation
Silent mutation
Neutral mutation

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14
Q

Forward mutation

A

Changes wild type to mutant

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15
Q

Reverse mutation

A

Change mutation to wild type

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16
Q

Missense mutation

A

Amino acid to different amino acid

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17
Q

Nonsense mutation

A

Sense codon (coding for an amino acid) —> stop codon

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18
Q

Neutral mutations

A

No change in functio

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19
Q

Silent mutations

A

Codon —> synonymous codon

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20
Q

Synonymous mutation

A

Change the base but don’t change the amino acid

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21
Q

Phenotypic effects of mutations

A

Loss-of-function mutation
Gain of function mutation
Lethal mutation

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22
Q

Loss-of-function mutation

A

Functional protein, mutate sequence, protein no longer works

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23
Q

Gain of function mutation

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A

Rarer
On evolutionary scale, produces more advantageous phenotypes

24
Q

Lethal mutation

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A

Kills off the organism

25
Start codons
Methionine, m formal NOT AMINIO ACIDS Attract release factors
26
Stop codons
27
Central Dogma
DNA —> mRNA —> protein
28
Suppressor mutation
Hides or suppresses the effect of another mutation Interagency Intergenic
29
Intragenic
Within the same gene containing the mutation that’s suppressed
30
Intergenic
THINK: international Across different genes Mutation in the second gene that hides the mutation in the first gene
31
What factors affect mutation rates?
Frequency that changes take place in DNA Probability that if a change occurs, it will be repaired Probability that the mutation will be detected
32
Wobble base pairing
- Prokaryotes cannot correct this, eukaryotes can - Leads to replicated error - Gets passed on if not corrected, how alleles are formed, through mutations - Base substitutions in general, not paired perfectly, physically wobble around because the base pairs are mismatched - does NOT occur after the first replication - ANOTHER EXAMPLE: tRNA does not match mRNA
33
Strand slippage
- when a bunch of repeats occur, strand slips - if it slips on a newly synthesized strand, additional bases occur and bubble out - in the next replication, there will be an increased number of As andTs - in the template replication, there will be reduced number on the newly formed strand
34
Unequal crossing over impact?
Insertions and deletions
35
What happens if DNA is introduced to chemicals?
DNA bases could be modified/altered look, i.e. radiation
36
What are the impacts of RADIATION?
- increased mutation rates - thymine dimer: two thymine bases dimerized and block replication - SOS system in bacteria: SOS system allows bacterial cells to bypass the replication to block with a mutation prone pathway
37
Thymine dimer
Two thymines back to back, if radiation occurs, covalent bonds between the two thymine bases, forming the thymine dimer (a bulge) DNA polymerase can’t tell what base it is
38
What were the impacts of Hiroshima?
- radiation caused mutations, even after bombs were dropped
39
How do you repair changes in DNA?
Mismatch repair Direct repair Base-exicision repair Nucleotide-excision repair
40
Mismatch repair
- mismatched bases and DNA lesions corrected by this - enzymes cut out a section of the newly synthesized strand of DNA, replacing it with new nucleotides - Methylation determines which strand is new - sealed with DNA ligase
41
Direct repair
Restores the correct structures of altered nucleotides, is exactly how it sounds
42
Methylation
43
Base-excision repair (JUST THE BASE NOT THE WHOLE NUCLEOTIDE)
– Glycosylase enzymes recognize and remove specific types of modified bases FIRST STEP – The entire nucleotide is then removed, and a section of the polynucleotide strand is replaced SECOND STEP
44
AP site
Nucleotide without its base
45
Nucleotide excision repair
– Removes and replaces many types of damaged DNA that distort the DNA structure. – The two strands of DNA are separated, held apart by SSBP (single stranded binding proteins), a section of the DNA containing the distortion is removed, DNA polymerase fills in the gap, and DNA ligase seals the filled-in gap.
46
What repairs changes in DNA?
- can only happen after S phase - G1 stage mutation —> cell will bring together chromosomes Homologous directed Nonhomologous directed Translesion DNA polymerases
47
Homologous directed
48
Nonhomologous directed repair
49
Tranlesion DNA polymerases
50
Types of TEs
- retrotransposons CLASS 1 - DNA transposon CLASS 2
51
Chromatin
Supercoiled DNA
52
Acetylation
Uncoiling of the chromatin structure, allowing it to be accessed by the transcriptional machinery for the expression of genes
53
Deacetylation
condensed or closed structure of the chromatin, less transcription occurs
54
Heterochromatin
Hibernating Densely packed, transcriptionally INACTIVE DNA
55
Euchromatin
Less dense, transcriptionally ACTIVE DNA
56
Carsinogenesis
DEVELOPment of cancer
57

Genetics (10 decks)

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