DNA Mutations and Repair

Question 1

Mutation

Answer 1

any heritable change in genetic material

Question 2

Heritable

Answer 2

mutations passed through cell division

Question 3

Somatic Cells

Answer 3

body cells. mutations that are somatic are passed only to the daughter cells in that area and are not transferred to future generations

Question 4

Germ Cells

Answer 4

reproductive cells.

Mutations passed to offspring

Question 5

Rates in mammals

Answer 5

Rate of mutation in somatic cells much higher than rate in germ cells

Question 6

Mutational hotspots

Answer 6

certain nucleotides are prone to mutations

Question 7

percent of human genome that encodes for proteins

Answer 7

Only 2.5%

So most mutations in noncoding DNA, so causes no changes (neutral)

Question 8

mutation per organismal generation

Answer 8

Most important for germline mutations
important to evolutionary processes because through transmission between generations they may become present in many individuals.

Question 9

mutation per cycle of DNA replication

Answer 9

Most important in somatic cells
A somatic mutation is not transmitted to future generations, but to progeny cells in mitotic divisions. Only the cells that descend from the
mutated cell are affected.

Question 10

Higher mutation rates

Answer 10

RNA viruses and retroviruses
Lots of breakage and repair in lifecycle
somatic cells

Question 11

Lower mutation rates

Answer 11

DNA molecules
multicellular organisms
Germline cells

Question 12

• Mutation per organismal generation

Answer 12

o Accumulating mutations over genome in your life time
o # germline mutations, genome size
o youre passing on about 30 mutation to you offspring
• mutations that occurred in you before you passed them on
• But you didn’t have these mutations

Question 13

• Mutation per cycle of DNA replication

Answer 13

o Linked to cancer
o Fidelity of replication process in any gene in your body
o (first one we looked at)
o Probability that mutation can occur at any nucleotide at any time
o There are certain types of “viruses” that have a very high mutation rate
• RNA viruses and retroviruses
o Multicellular organisms
• Much much much lower mutation rate
• Pretty good replication accuracy occurring

Question 14

Male v Female

Answer 14

o Sperm production: rapid replication, MUCH higher replication rate than female eggs
o By the time you’re 30, germ line cells have 400X greater mutation rate (sperm cells specificially)
• Older fathers→ higher probability of autistic children

Question 15

Multiple Mutation Model of Cancer Progression: Somatic Mutations

Answer 15

o Start with a colon cell
• Divides
• More dividing
• One cell line you get a mutation in APC
• Divides and passes on mutation to its “offspring”
• Cell line carring muated APC gene
• Eventually pick up a mutation in ras
• 2 mutation in cell line
• mucho much more dividing
• APC and ras mutation, give rise to more mutated cells
• Accumulate third mutation in TP53, go from benign to malignant.

Question 16

Mismatch repair

Answer 16

enzymes can fix errors missed by DNA polymerase
• Proofreading done by DNA polymerase
• Last base added is checked and if incorrect, removed and replace with right base

Question 17

Small Scale Mutations

Answer 17

• Synonymous (silent)
• Nonsynomouys (missense)
• Nonsense muatations

Question 18

Large Scale Mutations

Answer 18

• Insertion

* Deletion

Question 19

Point Mutations

Answer 19

o Incorrect base pair that isn’t caught
o Inccorect base pair then correctly paired with new partner, so not seen as an error anymore because base pairing is now correct
o Original copy still around

Question 20

Synonymous mutation

Answer 20

at amino acid level
When both original and mutated codon code for the same protein
Change at third position

Question 21

Silent Mutation

Answer 21

At genomic level
When both original and mutated codon code for the same protein
Change at third position

Question 22

Nonsynonymous mutation

Answer 22

amino acid level
• Most likely change at second position site in codon
• Changes what amino acid is coded for
o Will make different protein

Question 23

Missence Mutation

Answer 23

genomic level
• Most likely change at second position site in codon
• Changes what amino acid is coded for
o Will make different protein

Question 24

Nonsense mutations

Answer 24

•	Change in first position site
•	Incorporation of stop codon instead of protein coding
•	Shortened protein codon
•	Depends on where in protein it occurs
o	Can totally shut down synth of protein

Question 25

Sickle Cell Anemia

Answer 25

o Altered form of beta subunit of hemoglobin
o Don’t allow red blood cells to effectively carry oxygen
o Sickeled shape instead of round

Question 26

Deletions

Answer 26

o Delete one amino acid (1 codon)
• Cystic fibrosis
• Code for one less protein, missing entire codon that encodes for it
• Result: incorrectly folded protein
• Misfolded gotten rid of by cell
• Without it, cant regulate amount Cl passing in and out of cell and maintaining correct concs on same side of cell
• Abnormal secretions in lungs, liver, pancreas and other glands

Question 27

Frame Shift Mutation

Answer 27

o Insertion or deletion of one or two bases results in disruption/shifting of reading frame
o Change all amino acids encoded there
o Encode totatally different proteins

Question 28

Transposable Elements are…

Answer 28

DNA sequences that can move from one location to another in genome
• Can be inserted into protein coding gene, causes huge frameshift
o Can disrupt function of entire gene
• When removed, function of original gene can be restored
• Discovery: Barbara McClintock and corn
o Transposable element move into anthocyanin, change pigmentation

Question 29

Xeroderma Pigmentosum

Answer 29

o XP: rare autosomal recessive disease in humans: development of skin lesions
• Caused by mutations of one of several nucleotide excision repair systems.
• These mutations mean the cells of peple with XP cant repair DNA damaged by UV radiation (sun xposure)
Due to errors in repair mechanisms

Question 30

Nucleotide Exision repair

Answer 30

•	Can remove more than one damaged base
•	Mismatching of bases
•	Damaged bases
•	 Like damge to backbone
Removes a STRAND of DNA.

Question 31

Base Exision repair

Answer 31

• Uracil
• Uracil glyclosolase cleaves out U, leaves deoxyribose backbone
• Endonucleouse IDs where there is bulge where base was removed. Removes portion of backbone
• Sews back together
remove a SINGE BASE

Question 32

DNA ligase

Answer 32

seal breaks in backbone

Question 33

Mismatch repair

Answer 33

single mis-paired bases repaired by removing and replacing DNA segment
•	Incorrect pair 
•	Enzyme makes a break
•	Enzyme chews up strand
•	Enzyme to re make the strand

Question 34

How mutations arise

Answer 34

o Spontaneously

o Mutagens

Question 35

Mutagens

Answer 35

• E-rays: breaks in backbone
• UV light: thimine dimers make kinks in DNA
• Bleach or H2O2 causes loss of base, cap
• Smoking can add weird side groups=improper pairing

Question 36

Balitimore thing

Answer 36

all has to pass from whatever genetic material comes in through mRNA so it can make protein using the host cell
need positive mRNA strand

Question 37

Polio/Dengue

Answer 37

come in as + single strand RNA

make - stranded RNA, so we have double stranded RNA, can make proteins more easily

Question 38

Flu

Answer 38

single stranded RNA -
Make RNA + using RNA depended RNA pol
can then encode proteins

Question 39

another + RNA strand

Answer 39

copy using reverse transcriptase, make - DNA and + DNA, makes double stranded DNA, replicate, make mRNA

Question 40

Dideoxide

Answer 40

Hydrogen where it should have hydroxyl

strand cant grow, terminates

Question 41

Cystic Fibrosis

Answer 41

abnormal secretion in lungs, pancreas, liver
missing phenoalenine (missing entire codon and genome level)
Incorrectly folded protein
discarded
the AFCR gene regulates Cl ion levels
shorter life span

Question 42

Duplication and Divergence

Answer 42

Globin
Duplicate, diverge allows them to be retained in genome
ancestral copy–> 2 decendents
gene family that arose millions of years ago

Question 43

Inversion

Answer 43

Double strand break

during repair, inserted in opposite direction (inverted)

Question 44

Recipricoal Translocation

Answer 44

Large change
chromosome break in DNA
repair sews it together wrong
resulting chromosomes that are part of ancestor of each version (fusion)
join nonhomologus sections

Question 45

X-rays

Answer 45

breaks in sugar phosphate backbone

Question 46

UV Light

Answer 46

Thymine dimers

kinks in DNA

Question 47

Bleach, H2O2

Answer 47

gaps

deltion of bases

Question 48

Smoking

Answer 48

add weird side groups to bases

improper pairing