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Genetics > Chapter 18 > Flashcards

Chapter 18 Flashcards

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Biology 101 flashcards
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

A

Rarer
On evolutionary scale, produces more advantageous phenotypes

24
Q

Lethal mutation

A

Kills off the organism

25
Q

Start codons

A

Methionine, m formal
NOT AMINIO ACIDS
Attract release factors

26
Q

Stop codons

A
27
Q

Central Dogma

A

DNA —> mRNA —> protein

28
Q

Suppressor mutation

A

Hides or suppresses the effect of another mutation
Interagency
Intergenic

29
Q

Intragenic

A

Within the same gene containing the mutation that’s suppressed

30
Q

Intergenic

A

THINK: international
Across different genes
Mutation in the second gene that hides the mutation in the first gene

31
Q

What factors affect mutation rates?

A

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
Q

Wobble base pairing

A
  • 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
Q

Strand slippage

A
  • 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
Q

Unequal crossing over impact?

A

Insertions and deletions

35
Q

What happens if DNA is introduced to chemicals?

A

DNA bases could be modified/altered look, i.e. radiation

36
Q

What are the impacts of RADIATION?

A
  • 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
Q

Thymine dimer

A

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
Q

What were the impacts of Hiroshima?

A
  • radiation caused mutations, even after bombs were dropped
39
Q

How do you repair changes in DNA?

A

Mismatch repair
Direct repair
Base-exicision repair
Nucleotide-excision repair

40
Q

Mismatch repair

A
  • 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
Q

Direct repair

A

Restores the correct structures of altered nucleotides, is exactly how it sounds

42
Q

Methylation

A
43
Q

Base-excision repair (JUST THE BASE NOT THE WHOLE NUCLEOTIDE)

A

– 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
Q

AP site

A

Nucleotide without its base

45
Q

Nucleotide excision repair

A

– 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
Q

What repairs changes in DNA?

A
  • can only happen after S phase
  • G1 stage mutation —> cell will bring together chromosomes
    Homologous directed
    Nonhomologous directed
    Translesion DNA polymerases
47
Q

Homologous directed

A
48
Q

Nonhomologous directed repair

A
49
Q

Tranlesion DNA polymerases

A
50
Q

Types of TEs

A
  • retrotransposons CLASS 1
  • DNA transposon CLASS 2
51
Q

Chromatin

A

Supercoiled DNA

52
Q

Acetylation

A

Uncoiling of the chromatin structure, allowing it to be accessed by the transcriptional machinery for the expression of genes

53
Q

Deacetylation

A

condensed or closed structure of the chromatin, less transcription occurs

54
Q

Heterochromatin

A

Hibernating
Densely packed, transcriptionally INACTIVE DNA

55
Q

Euchromatin

A

Less dense, transcriptionally ACTIVE DNA

56
Q

Carsinogenesis

A

DEVELOPment of cancer

57
Q
A

Genetics (10 decks)

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