Chapter 15

Question 1

what is molecular biology

Answer 1

the study of heredity at the molecular level
- studies of bacteria and viruses

Question 2

phages

Answer 2

viruses that infect bacterial cells

Question 3

what were the phages labeled with in the Hershey Chase experiment

Answer 3

radioactive sulfur for proteins
radioactive phosphorus for DNA

Question 4

nucleotides

Answer 4

building blocks for nucleic acids

Question 5

what does the hydrogen bond hold together

Answer 5

complementary base pairs

Question 6

phosphodiester bonds

Answer 6

hold DNA and RNA together linking sugar and phosphate groups

Question 7

parental strand

Answer 7

serve as templates in the semi conservative model

Question 8

how are the daughter strands made in each DNA synthesis model

Answer 8

semiconservative model= has one old and one new strand

conservative model= one daughter has both old strands & the other has both new strands

dispersive replication= each daughter has old and new DNA interspersed

Question 9

semiconservative replication

Answer 9

parental strands separate & each is a template for new strand
- 2 DNA strands separate
- TRUE

Question 10

conservative replication

Answer 10

parental molecule serves as template for entirely new molecule

Question 11

dispersive replication

Answer 11

parent molecule cut into sections

Question 12

antiparallel stands

Answer 12

5’ to 3’ polarities run in opposite directions

Question 13

on which end are you always adding onto

Answer 13

3’ end

Question 14

what is the origin of replication

Answer 14

replication bubble forms at specific sequence

Question 15

replication bubble

Answer 15

forms when DNA is being synthesized
- grows in 2 directions

Question 16

what direction does the replication bubble follow

Answer 16

follows direction replication fork moves

Question 17

replication fork

Answer 17

region where DNA has been unwound and separated resulting in two branching prongs

Question 18

DNA helicase

Answer 18

breaks hydrogen bonds between the 2 DNA strands to separate them
- unzips DNA strand

Question 19

SSBPS

Answer 19

single strand DNA binding proteins
- holds strands apart
- prevent strands from closing
- come in and hold strands apart so it doesn’t close back in on itself

Question 20

DNA polymerase

Answer 20

• works only in 5’ to 3’ direction on single strand template
• adds dNTPs to primer 3’ end
• synthesizes leading strand in 5’ to 3’ direction

Question 21

what does DNA polymerase match

Answer 21

matches bases with high accuracy
- construction workers
- proofread: add nucleotide only if base pair is correct

Question 22

RNA polymerase

Answer 22

builds RNA & makes primers
- provide framework that DNA can be built off of

Question 23

DNA ligase

Answer 23

• joins Okazaki fragments
• attach fragments together
• links repaired strand to original undamaged DNA

Question 24

primase

Answer 24

synthesizes RNA primer
- signals where DNA needs to be built

Question 25

what build primers

Answer 25

enzyme primase

Question 26

what does primase do on the lagging strand

Answer 26

adds an RNA primer close to end of chromosome

Question 27

primer

Answer 27

act like flags to signal DNA polymerase where to build - DNA polymerase builds from where primer is

Question 28

topoisomerase

Answer 28

cuts and rejoins DNA to relieve then tension from the unwinding DNA helix - "stress reliever" - relives stress by cutting DNA in strategic points

Question 29

how is the leading strand synthesized

Answer 29

5' to 3' direction - toward the replication fork

Question 30

how is the lagging strand synthesized

Answer 30

- away from replication fork - short fragments called Okazaki fragments

Question 31

which is faster; lagging or leading strand

Answer 31

leading strand

Question 32

Okazaki fragments

Answer 32

- short, discontinues fragments that synthesize lagging strand -

Question 33

how is the okazaki fragments joined

Answer 33

DNA ligase

Question 34

what is the replisome

Answer 34

- enzyme machine - contains enzymes responsible for DNA synthesis around replication fork

Question 35

telomeres

Answer 35

ends of linear chromosomes - can be problematic - may add to aging process

Question 36

telomerase

Answer 36

- helps prevent or slow shortening process - adding this to cells will cause more cell division

Question 37

mismatch repair

Answer 37

occurs when mismatched bases are corrected after DNA synthesis is complete

Question 38

what is the purpose of mismatch repair enzymes

Answer 38

- recognize mismatched pair - remove section of new strand that has incorrect base - fill in correct bases

Question 39

nucleotide excision repair

Answer 39

recognizes types of damage - removes damaged single stranded DNA - uses intact strand as template for new DNA

Question 40

what could happen at the end of replication that would be a problem

Answer 40

- single stranded DNA is left at end of lagging strand and is eventually degraded - this would shorten the chromosome by 50-100 nucleotides each time replication occurs - chromosomes would vanish

Question 41

how can DNA be damaged

Answer 41

sunlight x-rays chemicals

Question 42

DNA damage repair systems

Answer 42

come in, cut out damaged section, & put in a new copy

Question 43

what did the Hershey-Chase experiment result in

Answer 43

only radioactive DNA was found inside the cells, therefore, genes must be composed of DNA - DNA was inside E. Coli, but proteins were not

Question 44

sulfur

Answer 44

proteins

Question 45

phosphorus

Answer 45

DNA