Spontaneous Mutations

Reactive oxygen species comes around G:C.. what happens?

|G:C| → |8-oxoG:C| →|8-oxoG:A| →|G:C| |T:A| This is a transversion mutation.

What is a transition mutation?

pyrimidine to pyrimidine or purine to purine

You start with |Tk:A| and a tautomeric shift happens.. describe?

|Tk:A| → |Te:G| → |Tk:A| |G:C|

Why won't the change of 5-methylcytosine be caught? This creates what?

5-methylcytosine changing to thymine wo't be caught because Thymine is actually a part of the DNA. This creates a hot spot for DNA mutations!

Once cytosine goes through a tautomeric shift, what does it pair with?

After the tautomeric shift, it will pair with adenine.

Once Thymine goes through a tautomeric shift, what does it pair with?

After the tautomeric shift, it will pair with guanine.

What is a hot spot?

Certain regions of DNA that are more likely to mutate than other regions.

Deamination occurs with what two bases?

Cytosine and 5-methylcytosine

Why is it that in deamination of Cytosine we only talk about the change to AT instead of including UA?

Hypothesis: Because Uracil does not belong in DNA it can be repaired, so UA will change to TA anyhow?

When we talk about a mutation, where is it located?

In DNA.

When 5-methylcytosine becomes deamination, what happens?

It becomes Thymine. It will become TA.

What is a transversion mutation?

It is pyrimidine to purine and vice versa.

What is a transition mutation again?

It is pyrimidine to pyrimidine or purine to purine.

If we don't have 5'→3'ε proofreading, what do we have to catch spontaneous mutations?

Methyl Directed Mismatch Repair

What are conditional mutations?

Mutations that happen under certain conditions. (e.g. Temperature Mutations)

In a frameshift mutation, how many bases do you add? After a frameshift mutation, the protein is what?

One or two. Afterwards, the protein is then nonfunctional.

What is depurination? When this occurs, what is the space left called?

Removing a purine; It is called an apurinic site.

AUG is what in DNA?

TAC

You start out with CG, but deamination occurs! What happens?

1. |CG| → |UG| : Cytosine is deaminated and changes to Uracil. 2. |UG| → |UA| |CG| 3. |UA| → |UA| |AT|

What is a Missense mutation?

A base pair change resulting in a different amino acid.

What is a Nonsense mutation?

A base pair change resulting in a stop codon.

What is a Silent mutations?

A base pair change resulting in the same amino acid as before.

What is a trinucleotide repeat disorder?

A repeated sequence of three nucleotides can readily increase in number from one generation to the next.

What is a tautomeric shift?

A temporary change in base structure.

What are the purines?

Adenine and guanine

What do Reactive oxygen species do? Example? What type of substitution mutation is this?

They give oxidative stress. G → 8-oxoG

Deamination of 5-methylcytosine makes what?

Thymine

DNA substitution mutations types?

Types are transitions and transversions.

Deamination of Cytosine makes what?

Uracil

What is Amino Imino Tautomerism? What bases go through a tautomeric shift?

When adenine or cytosine change from their common, stable form of amino to the unstable imino form.

What is Keto Enol Tautomerism? What bases go through a keto enol tautomeric shift?

When guanine or thymine changes from it's common, stable form of keto to an unstable form of enol.

What is replication slippage? What does mutation formation depend on?

When there are a string of repeated sequences, which may lead to insertions or deletions. Mutations from this depend on where in the sequence and the gene it's in.

****What does it mean for a protein to be leaky?

You could possibly reverse and go back or maybe get an amino acid here and there.

What are tautomers?

Bases that exist in keto and enol or amino and imino form.

Where is 5-methylcytosine found?

CpG islands and compaction of DNA around histones.

What are the pyrimidines?

Cytosine and Thymine

What are the types of spontaneous mutations? (That we learned about)

Frameshift, Deamination, Depurination,

What is a spontaneous mutation?

Just happened to occur.

Are frameshift mutations leaky? why or why not?

No, because it is such a large change. The only way it would have little effect is if it were at the end.

What is a Frameshift mutation?

Nucleotide addition that alters the reading frame.

Method of replication?

Semiconservative

Types of mutations?

Spontaneous (Just happened to happen) and Induced (Mutagen or carcinogen)