Lec 5-1

Question 1

Mutations are

Answer 1

Changes in DNA sequence

Inheritable by cells or organisms

Question 2

Importance of mutations

Answer 2

Necessary for evolution (source of genetic evolution)

Cause of many diseases and disorders

Cannot have one without the other

Question 3

Two basic classes of mutations

Answer 3

Somatic

Germ-line (most common)

Question 4

Gene mutations

Answer 4

Mutations that affect a single gene

Base substitutions

Insertions and deletions expanding nucleotide repeats

Question 5

Types of base substitutions

Answer 5

Transition (common-changing a purine to another purine or a pyrimidine to another pyrimidine)

Transversion (more possibilities- switches a purine into a pyrimidine or vise versa)

Question 6

Causes of base substitutions

Answer 6

Spontaneous replication errors

Spontaneous chemical changes

Mutagens

Question 7

Base substitutions may

Answer 7

Alter one codon

Question 8

Tautomers

Answer 8

Distinct forms each base can have depending on position of hydrogen (proton)

Question 9

Tautomeric shift

Answer 9

When hydrogen (proton) shifts to another position creating a new tautomer form

Question 10

Base substitutions

Spontaneous chemical changes

Answer 10

Depurination-Loss of a purine

Deamination-Loss of amino group

Usually result in incorrect base substitutions

Question 11

Depurination

Answer 11

Covalent bond between purine and sugar backbone is broken

Question 12

Loss of a purine creates

Answer 12

An apurinic site (a wrong base is added to replace the purine)

Question 13

Deamination

Answer 13

Loss of an amino group (NH2) from a base

Converts the base pair into a uracil

Replication treats it like a thymine and binds it to an adenine

Question 14

Insertions and deletions

Answer 14

Addition or removal of one or more nucleotide pairs

Question 15

Insertion and deletion causes

Answer 15

Strand slippage

Unequal crossing over

Question 16

Insertion and deletion

Strand slippage

Answer 16

Occurs when one DNA strand forms a small loop

Results in the additions of one nucleotide on the new strand

Question 17

Expanding nucleotide repeats

Answer 17

Set of nucleotides that increase in copy number

Causes numerous diseases such as ALS

Question 18

Expanding nucleotide repeats

Number of copies correlates with

Answer 18

Severity of disease

Age of onset

Instability

Question 19

Cause of expanding nucleotide repeats

Answer 19

Repeats lead to a hairpin being synthesized

New extensive strand serves as a template

Question 20

Base substitutions can cause

Answer 20

Missense (makes a different amino acid)

Nonsense (creates a stop codon as the triplet does not code for any amino acid)

Silent mutations (caused by altering the last base of a triplet. Does not change the protein sequence)

Question 21

Insertions or deletions can cause

Answer 21

Frameshift mutations

In-frame mutations

Question 22

Types of effects on protein function and phenotypes

Answer 22

Loss of function mutation

Gain of function mutation

Conditional mutation

Lethal mutation

Question 23

Loss of function mutations

Answer 23

Partial or complete absence of gene product function

Usually recessive- requires two copies to see a phenotype

Question 24

Gain of function mutation

Answer 24

Gene product has a new function

Usually dominant- one copy produces a phenotype

Question 25

Conditional mutation

Answer 25

Phenotype seen under certain conditions (eg. elevated temp)

Question 26

Lethal mutation

Answer 26

Causes premature death

Question 27

Forward mutation

Answer 27

Original mutation changing phenotype away from wild type

Question 28

Reverse mutation

Answer 28

A second mutation that reverses the original mutation site back and returns phenotype back to wild-type

Question 29

Suppressor mutation

Answer 29

A second mutation that reverses the phenotype back to wild-type, but through mutating a different site in the DNA

Question 30

Suppressor mutation types

Answer 30

Intragenic

Intergenic

Question 31

Intragenic mutation

Answer 31

In the same gene as original mutation being supressed

Question 32

Intergenic mutation

Answer 32

In a different gene as the original mutation

Can also occur through interactions of two genes functioning in the same protein complex