DNA Repair and How Mutations Occur

Question 1

Which type of mutation does not result in a change in the amino acid sequence?

nonsense
deletion
missense
silent

Answer 1

silent

Question 2

What are single gene disorders?

Answer 2

caused by mutation in one particular gene

Question 3

What are chromosome disorders?

Answer 3

broad group
-anomalies in chromosome number may not be actual mutations, just difference in numbers of genes expressed
-rearrangements
-insertions
-deletions

Question 4

What are multifactorial or complex disorders?

Answer 4

multiple gene variants, gene variant with environment interactions
-caused by a combined effect of numerous common, low impact variants that individually would not cause disease

Question 5

What is expressivity of a disorder ?

Answer 5

the fact that there can be different expressions in individuals that have this disorder

Question 6

What is penetrance of a disorder?

Answer 6

the amount of people in a family that have it

Question 7

What does variant mean?

Answer 7

gives no indication of disease state, just a different form
-still arisen by the mutation process

Question 8

What does SNV mean?

Answer 8

single nucleotide variant

Question 9

What are the ways to describe the frequency of a variant?

Answer 9

novel, rare, or common

Question 10

What are the way to describe the impact of a variant?

Answer 10

low or high impact

Question 11

What are ways to describe pathogenicity of a variant?

Answer 11

benign, likely pathogenic, or pathogenic

Question 12

What are spontaneous mutations?

Answer 12

mutations that arise naturally during DNA replication

Question 13

What are induced mutations?

Answer 13

caused by radiation and chemicals

Question 14

Where can mutations occur in the DNA?

Answer 14

anywhere in the nuclear or mitochondrial DNA

Question 15

Where are mutations located that are most heavily studied?

Answer 15

mutations that affect the protein coding sequence of genes

Question 16

Can mutation in the introns cause disease?

Answer 16

yes

Question 17

What are some examples of non-coding DNA?

Answer 17

gene regulatory elements, introns, and repetitive elements

Question 18

What are silent mutations?

Answer 18

SNVs that do not change the Amino acid sequence

Question 19

What are nonsense mutations?

Answer 19

SNVs that cause premature stop codon

Question 20

What are missense mutation?

Answer 20

SNVs that cause a different amino acid to be brought in

Question 21

What are conservative mutations?

Answer 21

mutations that cause an incorrect amino acid to be brought in, but have a similar side chain so there is not that big of difference seen

Question 22

What are nonconservative mutations?

Answer 22

mutations that cause an incorrect amino acid to be brought in, but have a different sized side chain so there can be a significant difference in folding and function

Question 23

What are deletions?

Answer 23

deletion of a single or many nucleotides in a sequence

Question 24

What are insertions?

Answer 24

insertion of a single or many nucleotides in a sequence

Question 25

What are rearrangements?

Answer 25

When segments of DNA are moved around to place they are normally not at

Question 26

What are frameshift mutation?

Answer 26

often involve deletion of insertion of a nonfactor of 3 number of nucleotides -causes the reading frame to be shifted

Question 27

What is an allele?

Answer 27

one of the two copies of a gene

Question 28

What is homozygous?

Answer 28

if an individual has two copies of the same allele

Question 29

What is heterozygous?

Answer 29

when an individual has one of each copies of an allele

Question 30

What does it mean if something is dominant?

Answer 30

only need one copy to have a certain phenotype

Question 31

What does it mean if something is recessive?

Answer 31

need two copies of the same allele to have that phenotype

Question 32

What causes oxidative damage to DNA?

Answer 32

reactive oxygen species

Question 33

What are the most common hydrolytic attack regions?

Answer 33

deamination and depurination

Question 34

How much depurination occurs daily?

Answer 34

around 5000 purine bases are lost each day during depurination

Question 35

How much deamination occurs daily?

Answer 35

around 100 pyrimadines lost each day during deamination

Question 36

What are some things that can cause DNA damage?

Answer 36

-reactive metabolites -exposure to chemicals in the environment -UV radiation (can cause thymine dimers)

Question 37

What percentage of Cytosine nucleotides are methylated in the genome?

Answer 37

around 3%

Question 38

What do methylated cytosine do?

Answer 38

help to control gene expression

Question 39

What is formed if the methyl group is removed from a cytosine?

Answer 39

thymine *not removed by base excision repair

Question 40

What helps to remove large regions of damaged DNA?

Answer 40

nucleotide excision repair

Question 41

What removes a single nucleotide in a sequence of DNA?

Answer 41

base excision repair

Question 42

What is homologous recombination?

Answer 42

natural process that occurs during meiosis -base pairing between DNA strands and is used to facilitate genetic exchange between homologous chromosomes

Question 43

what is non-homologous recombination?

Answer 43

does not add any base pairs to damaged DNA, just sticks the strands back together with a ligase

Question 44

Is homologous recombination associated with single stranded or double stranded breaks?

Answer 44

both

Question 45

What happens if you do not have/have mutation in repair proteins?

Answer 45

generally lethal -or can lead to cancer

Question 46

what type of diseases are caused by the combined effect of numerous common, low impact variants that individually would not cause disease but in combination they have the potential to do so?

Answer 46

multigenic or multifactoral diseases

Question 47

what are the transitions mutations?

Answer 47

purine --> purine (A <--> G) or pyrimidine --> pyrimidine (C <--> T)

Question 48

what are transversions mutations?

Answer 48

purine --> pyrimidine (A/G --> C/T) or pyrimidine --> purine (C/T --> A/G)

Question 49

what kind of mutations causes Huntingtons and ALS?

Answer 49

repeat expression mutations

Question 50

can silent mutations cause disease?

Answer 50

yes- can cause issues with splicing region

Question 51

what type of mutation causes branchio-oto-renal (BOR) syndrome?

Answer 51

intronic variant impacting splicing

Question 52

SNP's are generally....

Answer 52

benign

Question 53

why can cancer be difficult to treat?

Answer 53

the associated hyper-mutability

Question 54

are mutations always bad?

Answer 54

no- a very low level of mutation accumulation is important for evolution

Question 55

what is an AP site?

Answer 55

a location in DNA that has neither a purine or pyrimidine base

Question 56

what does deamination cause?

Answer 56

DNA substitution (point mutation) *one strand remains unchanged

Question 57

what does depurination cause?

Answer 57

DNA deletion *one strand remains unchanged

Question 58

what happens when C is deaminated?

Answer 58

changed to U

Question 59

when are mutations inherited? in somatic tissue in DNA of gametes

Answer 59

in DNA of gametes