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MBG*2040 > MBG Part Two: Lecture 12 > Flashcards

MBG Part Two: Lecture 12 Flashcards

1
Q

How often do spontaneous mutations occur?

A

Very infrequently

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2
Q

How Many mutations are in bacteria cells?

A

1 in 100 per every 10 billion cells

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3
Q

How many mutations are in Eukaryotic cells?

A

1 - 10 mutations per every million gametes

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4
Q

What happens within genes?

A

Some are known to be more “hotspots” for mutations

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5
Q

What does the APC gene account for?

A

Account for greater than 80% of colon cancer - the MCR region in the gene is where most of the mutations occur.

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6
Q

What happens to DNA that is in nucleosomes?

A

Due to it being wrapped around histones, it may have more reduced exposure to mutagens.

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7
Q

What is the overall rate of a base substitution in humans?

A

1 x 10^-8 per base per generation

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8
Q

What does research suggest about each person and a loss of function gremlin mutation?

A

That each person carries about 100 loss of function germline mutations.

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9
Q

What are factors that affect mutation rate?

A

Frequency
Probability
Detection

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10
Q

What can cause DNA damage?

A
  • UV light exposure
  • Cellular Metabolism
  • Ionizing Radiation
  • Chemical Exposure
  • Replication Error
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11
Q

What are “spontaneous mutations”?

A

When mutations occur under normal circumstances as a result of internal factors

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12
Q

What are “induced mutations”?

A

As a result of an exposure to external factors (i.e, chemicals)

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13
Q

What are spontaneous replication errors?

A
  • Tautomeric Shifts
  • Mispairing due to other structures
  • Incorporated errors and replicated errors
  • Insertions and Deletions
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14
Q

What are some spontaneous chemical changes?

A
  • Depurination
  • Deamination
  • Methylated Cytosine
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15
Q

What are some chemical induced mutations?

A
  • Base Analogs
  • Alkylating Agents
  • Deaminating Chemicals
  • Hydrooxylamine
  • Oxidative Radicals
  • Intercalating Agents
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16
Q

What is radiation?

A

Energy released in the form of electromagnetic waves

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17
Q

In tautomeric shifts, what bases pair together?

A

A - C pairing (two hydrogen bonds)

T - G pairing (three hydrogen bonds)

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18
Q

What happens during mispairing of other structures?

A

It can arise through wobble, which can allow for flexibility in the DNA structure and any shifts in the helix can allow for different bases to bond

Can also arise by the protonated forms of the bases

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19
Q

What is incorporated errors?

A

Occur when a base substitution causes a mispaired base to incorporate into a newly synthesized strand

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20
Q

What does an incorporated mutation lead to?

A

A replication error that causes a permanent mutation

21
Q

How can insertions and deletions happen?

A

From strand slipping or unequal crossing over during meiosis

22
Q

What is strand slipping?

A

Strand slipping is when the template loops out which results in the omission of one new nucleotide

23
Q

What is the unequal crossing over during meiosis?

A

The homologous chromosomes misalign and one crossover has an insertion and the other has a deletion.

24
Q

What is depurination?

A

The loss of a purine base (G,A) from a nucleotide

25
Q

What does depurination cause?

A

The breakage of the covalently bond between the purine base and the 1’ carbon atom of the deoxyribose sugar.

26
Q

What does depurination lead to?

A

An apurinic site

27
Q

What happens do to the apurinic site?

A

No complement base (it doesn’t know what the previous base was) so a random nt is incorporated (usually an A) which leads to a mutant

28
Q

What is Deamination?

A

Loss of an amino group (typically from cytosine)

29
Q

What does the demaintion of cytosine lead to?

A

Uracil which will pair with Adenine during replication. And in the next cycle A will pair with T, resulting in a C to T transition

30
Q

What is a methylated cytosine?

A

Leads to the conversion of cytosine to thymine transition

31
Q

What are base analogs?

A

Molecules with similar structures to the normal standard 4 nucleotides

32
Q

What is 5BU?

A

An analog of Thymine, which pairs with Adenine but can also pair with Guanine

33
Q

What is 2AP?

A

A base analog of Adenine, can mis pair with Cytosine (T to C transition)

34
Q

What are Alkylating Agents?

A

Mutagens that can react with DNA bases and add methyl or ethyl to them

35
Q

What are examples of Alkylating Agents?

A

Ethylmethylsulfonate (EMS) and Mustard Gas

36
Q

What happens when the alkylating agents add an ethyl to guanine?

A

It can base pair with thymine

G to A transition

37
Q

What happens when the alkylating agents add an ethyl to thymine?

A

It can base pair with guanine

T to C transition

38
Q

What are examples of Deaminating Chemicals?

A

Nitrous Acid

39
Q

What can Nitrous Acid change?

A

Cytosine to Thymine

Adenine to Hypothoxanthine, which can base pair with cytosine

Change guanine to Xanthine, which can base pair with Thymine

40
Q

What is hydrooxylamine?

A
  • Adds a hydroxyl to cytosine (increases rate of pairing with adenine)

C to T transition

41
Q

What are oxidative Radicals?

A

Reactive forms of oxygen

42
Q

What can Oxidative Radicals Cause?

A

G to T transversion

43
Q

What are examples of Intercalating Agents?

A

Ethidium Bromide, Acridine Orange, Dioxin, Proflavin

44
Q

What do intercalating agents do?

A

Sandwich themselves between base pairs which distorts the DNA helix

45
Q

What do intercalating agents lead to?

A

Insertions and Deletions which cause frameshift mutations

46
Q

What does radiation cause?

A

Causes a stable atom top turn into a free radical reaction ion and breaks phosphodiester bonds leading to double stranded breaks

47
Q

What bases absorb UV light?

A

Pyrimidine bases

48
Q

What does the absorbance of UV light cause?

A

Induces chemical bonds between two adjacent pyrimidine molecules

49
Q

What dimers are most frequent with the induced chemical bonds?

A

Thymidine Dimers

MBG*2040 (26 decks)

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