Z- Micro Exam 3 - Dna Replication

Front 1

DNA Replication

Back 1

Simple look: one strand acts as a template for the other;
ie. both individual strands act as templates to make copies of the other OP (Fig 8-2 or 3)

DNA -->DNA
(black & white DNA Replication)

Front 2

How do the two strands separate during DNA replication?

Back 2

separate like the halves of a zipper
the double helix unwinds
-involves unwinding & stabilizing enzymes

Front 3

How are free nucleotides polymerized in DNA replication?

Back 3

thru dehydration synthesis polymerized into place using one strand as template (like pop beads)

Front 4

What enzyme is involved with polymerizing free nucleotides

Back 4

DNA polymerase enzyme: OP (Fig 8.5)
DNA polymerase III
DNA ---------->more DNA + H2O
nucleotides + ?(energy)

Front 5

base pairing

Back 5

A–T (U in RNA)
G – C

Front 6

replication fork

Back 6

point at which the 2 strands separate & new strands are synthesized

Front 7

What is meant by semiconservative replication?

Back 7

each new double strand of DNA contains one old and one new strand (base pairing)

Front 8

Describe the 2 strands in DNA

Back 8

double helix are antiparallel (run in opposite directions)

a. like 2 cars going west and east on a two lane road

Front 9

Details of Replication... look at polarity in deoxyribose “sugar houses”

Back 9

(See Fig 8.4, 8.5, 8.6)
one strand runs 5’ to 3’ direction sugar phosphat & OP (Fig 8.4, 8.5, 8.6)
Know:
leading strand-
lagging strand
How they run...
one strand runs 5’ to 3’ direction sugar phosphate

other strand runs 3’ to 5’ direction sugar phosphate
(new strand called the lagging strand)

See DNA Replication (3-2) Page1

Front 10

How does the antiparallel structure of DNA affect the replication process?

Back 10

DNA polymerase can copy new DNA only in 5’ 3’ direction using the 3’ 5’ strand as template
a. adds nucleotides to free 3’ end

Front 11

What direction does DNA polymerase go?

Back 11

“DNA polymerase only has forward gear – no reverse”

Front 12

At the site of replication fork what two distinct product DNA strands that are synthesized?

Back 12

“leading strand” is synthesized continuously in 5’ 3’ toward replication fork as it opens (using 3’ 5’ template)
b. “lagging strand” is synthesized discontinuously in fragments of about 1000 nucleotides (long) which are later joined
i. growth heading away from replication fork (as it opens)
(analogy with blue print for house construction drawn on 20 separate pieces of paper, then cut & paste)

Front 13

Is replication fork is static? Explain.

Back 13

Replication fork is not static – it is moving along DNA
(very, very complicated, complex process requires many special enzymes & proteins.)

Front 14

List components required for DNA replication

Back 14

DNA template (blueprint)

b. deoxyribonucleotide triphosphates = energy (building blocks for new DNA)
OP (Fig 8.5)

c. bacterial enzymes

d. ribonucleotides (for primer)
e. stabilizing proteins (topoisomerase & s.s. binding protein)
f. energy

Front 15

Specific bacterial enzymes for DNA replication

Back 15

i. *DNA polymerase III synthesizes 5’ 3’ only
ii. * primase (RNA polymerase) makes 5-10 piece RNA primer
iii. *DNA polymerase I digests RNA primer & replaces with DNA
iv. *DNA ligase links pieces of DNA in lagging strand
v. helicase (unwinding enzymes)

Front 16

What happens In lagging strand of DNA replication

Back 16

a. RNA primase starts each new DNA fragment with a stretch of about 20 ribonucleotides called RNA primer.
b. Then DNA synthesis is continued by DNA polymerase
c. Another enzyme (DNA ligase) joins DNA framents
“Chance favors a prepared mind”
i. Okazaki pieces

Front 17

Comparison of leading/lagging strand synthesis OP (Fig 8.6)

Back 17

a. Synthesis of leading strand (no ligase required!)
i. priming 1 time (primase)
ii. continuous elongation (DNA pol III)
iii. replace RNA primer with DNA (DNA pol I)

b. Synthesis of lagging strand (for each “piece”)
i. priming for each Okazaki fragment (primase)
ii. elongation of each fragment (DNA pol III)
iii. replace RNA primer with DNA (DNApol I)
iv. joining of fragments (ligase)

Front 18

Replication steps (review)

Back 18

a. Unwind and stabilize DNA double helix (helicases + binding proteins)
b. Lay down RNA primer (primase)
c. Polymerize DNA strands (DNA pol III)
d. Remove RNA primer and replace with DNA nucleotides (DNA pol I)
e. Ligate (form phosphodiester bonds between) Okazaki fragments (ligase)

Front 19

Bacterial DNA replication

Back 19

a. begins at a special site on chromosome called the origin of replication (ORI)
b. in E. coli replication is bidirectional – 2 replication forks moving in opposite directions away from origin (ORI)
i. replication fork is not static, it is moving!

Front 20

Rate of DNA replication
in bacterial cell & human cell

Back 20

a. 500-1,000 nucleotides / second in bacteria! (such as E. coli)
b. 50 nucleotides / second in human cell

Front 21

Telomere

Back 21

special protective “cap” of noncoding DNA on the ends of linear chromosomes

Front 22

How do tolemeres function?

Back 22

by preventing chromosomes from losing base pair sequences at their ends.

Front 23

How do telomeres help out the chromosomes?

Back 23

They stop chromosomes from fusing to each other.

Front 24

What happens each time a cell divides?

Back 24

Some of the telomere is lost

Front 25

What two mechanisms control Telomere activity?

Back 25

erosion and addition

Front 26

Whar does telomerase do?

Back 26

adds material to the telomeres of chromosomes

Front 27

Where is telomerase located?

Back 27

found (& is active) in fetal tissues, adult sex cells, and also tumor cells.

Front 28

How might new information about telomerase help people?

Back 28

Research in the area of telomerase could uncover valuable information to combat aging, fight cancer, and even improve the quality of medical treatment in other areas such as skin grafts for burn victims bone marrow transplants, and heart disease.)