Exam 1 - Chp 4: Descent with Modification - Continuity and Variation in the Genome

Question 1

How many hydrogen bonds between adenine and thymine?

Answer 1

2

Question 2

How many hydrogen bonds between cytosine and guanine?

Answer 2

3

Question 3

What is semiconservative DNA replication?

Answer 3

DNA replication occurs to produce two double stranded DNA molecules consisting of a parent strand paired with a daughter strand

Question 4

What temperature is DNA heated to to cause it to anneal (separate)?

Answer 4

95C

Question 5

What do origin binding proteins do?

Answer 5

Recognize the origin of replication

Question 6

What does DNA helicase do?

Answer 6

Separates DNA strands for replication

Question 7

What do single strand binds proteins (SSBs) do?

Answer 7

Keep DNA strands apart long enough for DNA polymerase to bind during DNA replication

Question 8

What does primase do in DNA replication?

Answer 8

Initiates synthesis of each Okazaki fragment and the leading strand by creating an RNA primer so DNA polymerase can add to the primer because it has a 3’ OH group

Question 9

Why does DNA polymerase require RNA polymerase to begin DNA synthesis?

Answer 9

DNA polymerase can only add nucleotides to the 3’ OH group of another nucleotide which is not available when starting a new DNA strand, RNA polymerase does not require a 3’ OH group to being RNA synthesis

Question 10

What are Okazaki fragments?

Answer 10

Because the replication fork heads towards the 3’ end of the template lagging strand, DNA polymerase must synthesize the lagging strand in fragments as it because it is moving in the 3 → 5 direction of the new lagging strand

Question 11

Going towards the replication fork, which direction does the template leading strand go? The template lagging strand?

Answer 11

3’ → 5’
5’ →3’

Question 11

How many replication forks form at the origin of replication? where do they go?

Answer 11

Two; opposite directions along the DNA strand

Question 12

How is the fragmented lagging strand completed in DNA replication?

Answer 12

Okazaki fragments are sealed together by DNA ligase

Question 13

How is the RNA primer that initiated DNA synthesis handled without losing genetic information?

Answer 13

It is complementary to a repetitive telomere sequence known as TERC so the RNA primer can be degraded and only a TERC sequence is lost

Question 14

How do eukaryotes prevent loss of genetic information in offspring if telomeres and constantly decreasing in size?

Answer 14

Telomerase copies TERC and maintains its length in germlin cells

Question 15

How does prokaryotic DNA replication end?

Answer 15

When the two replication forks reach each other on the other side of the circular DNA molecule

Question 16

What is a clamp loader and sliding clamp involved in DNA replication?

Answer 16

The clamp loader loads the sliding clamp onto DNA which stabilizes DNA polymerase during replication

Question 17

What does topoisomerase do?

Answer 17

cuts double stranded DNA downstream of replication fork to relieve tension from supercoiling

Question 18

What are the five things needed to perform PCR

Answer 18

DNA
DNA polymerase
Primers in high concentration
dNTPS
Buffer and MgCL2

Question 19

What DNA polymerase is typically used in PCR?

Answer 19

Taq polymerase - found in thermos aquaticus that lives in deep sea vents so their proteins can withstand annealed temperature

Question 20

What are the four steps of PCR?

Answer 20

1) Anneal by heating up sample to 95 C
2) primers bind to target sequences
3) DNA polymerase adds dNTPs
4) Two double strands now produced, repeat process over and over

Question 21

What are tautomers?

Answer 21

isomers of nucleotide bases that nucleotides can easily switch to

Question 22

What are consequences of tautomers?

Answer 22

Mismatch pairing, unstable pairing, incorrect base pairing during replication

Question 23

Describe proofreading that occurs during replication

Answer 23

DNA polymerase reverses, uses exonuclease to excise base and polymerase replaces it

Question 24

During what stage of cell division do cells check their DNA for most mistakes?

Answer 24

G2 phase, after S-phase DNA replication

Question 25

What happens if a cell detects DNA damage during a checkpoint in cell division?

Answer 25

Cell division is halted and the damage is fixed

Question 26

What happens if cell damage cannot be fixed in a eukaryotic cell?

Answer 26

Apoptosis

Question 27

What is apoptosis?

Answer 27

Programmed cell death

Question 28

What response does a bacteria have to DNA damage?

Answer 28

SOS response; de-repress DNA repair genes and inhibit cell division. Repress SOS response once damage is fixed

Question 29

How is mismatch repair preformed?

Answer 29

Mismatch and surround bases are removed by exonuclease, replaced by DNA polymerase, and the DNA backbone is sealed by ligase

Question 30

How does the cell identify the original/correct strand in mismatch repair?

Answer 30

It is methylated, cell also methylates repair once done

Question 31

How is UV damage repaired?

Answer 31

Photolyase recognizes pyrimide dimers caused by UV rays and and breaks it apart using photo reactivation -energy from light

Question 32

How do humans repair UV damage?

Answer 32

Excision repair, do not have photoylase

Question 33

How is overmethylation of bases fixed?

Answer 33

Direct repair - breaking of bonds

Question 34

How is the breakage of between the sugar and base repaired?

Answer 34

Base excision repair via exonuclease, DNA polymerase, and ligase

Question 35

How are changes to multiple adjacent bases or extension damage fixed?

Answer 35

Nucleotide excision repair using exonuclease, DNA polymerase, and ligase

Question 36

How are double stranded breaks repaired?

Answer 36

Using ligase but can cause major issues if not attached correctly

Question 37

What happens if a mutation affects essential cell function?

Answer 37

Apoptosis

Question 38

What process does mutation need to affect to cause the cell to proliferate without normal growth?

Answer 38

Cell division

Question 39

If a mutation affects non-essential function, what happens to the cell?

Answer 39

Maintains relatively normal function, unharmful

Question 40

What do tumor suppressor genes do?

Answer 40

Regulate cell growth and prevent uncontrolled division

Question 41

What do proto-oncogenes do?

Answer 41

Promote normal cell growth and division

Question 42

What are oncogenes?

Answer 42

Proto-oncogenes that have been mutated causes rapid cell replication

Question 43

What does a mutation in a tumor suppressor gene do?

Answer 43

Allow unregulated cell growth and proliferation leading tumors

Question 44

What is p53?

Answer 44

A gene crucial for monitoring DNA integrity, can turn genes on and off, and activate repair processes or cell death

Question 45

What is retinoblastoma?

Answer 45

A common tumor suppressor gene that stops cells from dividing too rapidly

Question 46

What are the three major ways proto-oncogenes becomes oncogenes?

Answer 46

Mutation Chromosomal Translocation Regulation of protein product due to increased mRNA stability

Question 47

What is chromosomal translocation?

Answer 47

Gene broken down in the middle during crossover event or double stranded break and is reincorporated incorrectly

Question 48

What is a driver mutation?

Answer 48

Mutation responsible for transformation from normal growth to unregulated growth

Question 49

What is a passenger mutation?

Answer 49

Mutation that arises and accumulates more as the cell divides randomly after the driver mutation

Question 50

Is the passenger or driver mutation the cause of cancer?

Answer 50

Driver

Question 51

What are three possible fates of mutations?

Answer 51

Advantageous change Neutral change Deleterious change

Question 52

What are 4 places with DNA that advantageous or deleterious mutations occur at?

Answer 52

1st or 2nd base pair of codon Protein coding sequences Control regions Noncoding RNA that has a task

Question 53

What are 3 places within DNA that neutral changes occur at?

Answer 53

Noncoding DNA 3rd base pair in codon Pseudogene

Question 54

What kind of selection do deleterious changes in DNA result in?

Answer 54

purifying selection

Question 55

What is high number of neutral mutants within a population signify?

Answer 55

Purifying selection

Question 56

What kind of selection do advantageous changes in DNA result in?

Answer 56

Positive selection

Question 57

What can be used to map out genetic changes

Answer 57

Phylogenic trees

Question 58

What does monophyletic mean?

Answer 58

Branch of phylogenic tree that includes common ancestor and all of its descendants

Question 59

What does polyphyletic mean?

Answer 59

Groups on phylogenic tree derived from different common ancestors

Question 60

What does paraphyletic mean?

Answer 60

Group descended from a common ancestor but not including all descendants

Question 61

What is descent with modification?

Answer 61

Small changes between generations eventually lead to large changes within populations and species

Question 62

What is a transition mutation?

Answer 62

When a pyrimide is replaced with another pyrimide or a purine with another purine

Question 63

What is transversion mutation?

Answer 63

A pyrimide is paired with another pyrimide or purine with purine

Question 64

Is a transversion or transition more harmful? Which is easier to detect? Why?

Answer 64

A transversion mutation is more harmful and easier to detect because it distorts helix structure by changing distance between the two DNA strands