MBG Part Two: Lecture 11

Question 1

What are examples of Base Substitutions?

Answer 1

Transition and Transversion

Question 2

What is a transition mutation?

Answer 2

Replaces a pyrimidine with another pyrimidine or a purine with another purine

Question 3

What is a Transversion mutation?

Answer 3

Replaces a pyrimidine with a purine or a purine with a pyrimidine

Question 4

What are Insertions and Deletions mutations?

Answer 4

Frameshift Mutations and In-frame insertions and deletions

Question 5

What happens in an Insertion and Deletion mutation?

Answer 5

A base-pair gets added or deleted which alters the reading frame of the gene, cause the protein sequence to drastically change

Question 6

What are Tautomeric Shift?

Answer 6

A reversible change in the location of a hydrogen atom that alters it from one to another isomer (or the movement of H+ atoms from one position in a purine or pyrimidine base to another)

Question 7

What can a Tautomeric Shift generate?

Answer 7

Rare A:C and G:T base pairs during DNA replication

Question 8

What are Expanding Nucleotide Repeats?

Answer 8

Increase in the number of copies of a set of nucleotides (known as a “dynamic mutation” because the nucleotide repeat copy number can expand or contract dramatically in each cell or over generations)

Question 9

What is the Cause of Numerous Human Diseases?

Answer 9

Expansion of Triplet Repeats

Question 10

What does the mechanism of expansion involve?

Answer 10

DNA replication

Question 11

Why is an expanding nucleotide repeat called a dynamic mutation?

Answer 11

Because the repeat copy number is in flux with each round of replication.

Question 12

What is an example of Mutations being inside the coding sequence?

Answer 12

Huntington’s Disease is an expansion of the CAG codon creating extra glutamines

Question 13

What is an example of Mutations being outside of the coding region that affects its expression?

Answer 13

In the 5’ UTR region for example (such as in Amyotrophic Lateral Sclerosis; Fragile-X Syndrome)

Question 14

How many CGG repeats in a normal person with no Fragile X Syndrome?

Answer 14

<55

Question 15

How many CGG repeats in a pre-mutation for Fragile X Sydrome?

Answer 15

55 - 200

Question 16

What does a pre-mutation of Fragile X syndrome lead to?

Answer 16

Fewer protein production or non-functional production that leads to different types of diseases

Question 17

How does a pre-mutation occur?

Answer 17

Gets a certain amount of methylation

Question 18

How does a full-mutation occur?

Answer 18

Has an increase in methylation

Question 19

How many CGG repeats for a person who has Fragile X Syndrome?

Answer 19

> 200

Question 20

What does a full mutation of Fragile X syndrome Lead To?

Answer 20

No protein production

Question 21

What is a forward mutation?

Answer 21

Wildtype to Mutant Type

Question 22

What is a Reverse Mutation?

Answer 22

Mutant Type to Wildtype

Question 23

What is a Missense Mutation?

Answer 23

Amino Acid to Different Amino Acid

Question 24

What is a Non-Sense Mutation?

Answer 24

Sense Codon to Nonsense Codon - a base substitution that changes a sense codon to one of the three nonsense (stop) codons (UAG, UGA, UAA)

Question 25

What is a sense codon?

Answer 25

A coding going on to translate into amino acid

Question 26

What is a Nonsense Codon?

Answer 26

A stop codon (not translating into amino acid)

Question 27

What is a Silent Mutation?

Answer 27

Codon to Synonymous Codon - a base substitution that changes the codon to one still specifying the same amino acid.

Question 28

What is a key note about the functional effects of mutations?

Answer 28

They are not unique and can be overlapping. A forward mutation could be nonsense mutation. A missense mutation could be neutral

Question 29

What is a Neutral Mutation?

Answer 29

A missense mutation in which the amino acid is changed to one of a similar chemical type (i.e, glycine to alanine, therefore no observable effect)

Question 30

What is a Loss of Function Mutation?

Answer 30

The result of mutations that cause complete or partial loss of normal protein function (i.e, cystic fibrosis results from a loss of function mutation in the CF gene)

Question 31

What is a Gain of Function mutation?

Answer 31

The result of a mutation that causes the cell to produce a protein or gene product whose function is not normally present (think cancerous cells)

Question 32

What is an Example of a Gain of Function Mutation in Fruit Flies?

Answer 32

A transcription factor that is normally restricted to the stem cells in the larvae that gives rise to the legs is inadvertently expressed in the stem cells in the larva that gives rise to the antenna (antennapedia gene)

Question 33

What is a conditional Mutation?

Answer 33

Expressed only under certain conditions (i.e, a temperature sensitive mutation only observed at extreme temps)

Question 34

What is a Temperature Sensitive Allele?

Answer 34

An allele whose functional product is conditional on the temperature

Question 35

What is an example of a temperature sensitive allele in fruit flies?

Answer 35

A fruit fly has a mutation in a wing Developmentent gene. At low temperatures, the protein is nom-functional (no wing) and functional at warm temperatures, therefore known as a cold-sensitive allele

Question 36

A lethal mutation?

Answer 36

Causes premature cell death.

Question 37

What is a Suppressor mutation is a second site mutation?

Answer 37

That hides or suppresses the effect of the first mutation.

Question 38

What is an Intragenic suppressor?

Answer 38

Suppressor Mutations can be within the same gene

Question 39

What is an Intergenic Suppressor?

Answer 39

Suppressor Mutations can be present within a different gene.

Question 40

What are Harlequin Norway Maple Trees a result of?

Answer 40

A result of a mutation in Chlorophyll production. They are partly albino.

Question 41

What happens when you see green leaves in a Harlequin Norway Maple Tree?

Answer 41

This is a revertant and a secondary mutation that masks the effect ts of the first mutation to give the wild-type phenotype.

Question 42

What happens in a Dwarf Alberta Spruce Trees?

Answer 42

There is one section of rigorous growth - unlike the slow growing dwarf species

These reversions have to be pruned back to prevent the tree from taking the new form. May also be conditional mutation since it seems to be dependant on environmental conditions.