Chapter 13

Front 1

DNA is a polymer of ____

Back 1

Nucleotides

Front 2

What are the four nucleotides and how do they differ?

Back 2

The four nucleotides that make up DNA differ only in their nitrogenous bases.
There are two purines (adenine and guanine) and two pyrimidines (cytosine and thymine)

Front 3

Look at figure 11.3

Back 3

:)

Front 4

DNA has two polynucleotide chains running ____ to each other

Back 4

Antiparallel

Front 5

What are the four features that summarize the molecular architecture of DNA?

Back 5

The DNA molecule is a double-stranded helix.
The diameter of the DNA molecule is uniform.
The twist in DNA is right-handed.
The two strands run in different directions (they are antiparallel).

Front 6

____ between complementary bases hold the two strands together

Back 6

Hydrogen bonds

Front 7

__ always pairs with T (two hydrogen bonds)

Back 7

A

Front 8

__ always pairs with C (three hydrogen bonds)

Back 8

G

Front 9

What do the phosphate groups link?

Back 9

The phosphate groups link the 3' carbon of one deoxyribose molecule to the 5' carbon of the next

Front 10

A single strand of DNA has what group at the 5' and 3' end respectively?

Back 10

A single strand of DNA has a 5' phosphate group at one end (the 5' end) and a free 3' hydroxyl group at the other end (the 3' end)

Front 11

In a double helix, the 5' end of one polypeptide is ______-bonded to the 3' end of the other, and vice versa.

Back 11

Hydrogen

Front 12

Look at figure 13.9

Back 12

:)

Front 13

The genetic material performs what four important functions?

Back 13

It stores all of an organism’s genetic information.
It is susceptible to mutation.
It must be precisely replicated in the cell division cycle.
It is expressed as the phenotype

Front 14

Theoretically, DNA could serve as its own template in one of what three different ways?

Back 14

Semiconservative replication would use each parent strand as a template for a new strand (this is the correct one).
Conservative replication would build an entirely new double helix based on the template of the old double helix.
Dispersive replication would use fragments of the original DNA molecule as templates for assembling two molecules

Front 15

DNA replication takes place in what two steps?

Back 15

The hydrogen bonds between the two strands are broken, making each strand available for base pairing. Hydrogen bonds are weak bonds so they are easily broken
The new nucleotides are covalently bonded to each growing strand

Front 16

In DNA replication, nucleotides are added to which strand?

Back 16

The 3' end of the growing strand

Front 17

Where are the three phosphate groups of the deoxyribonucleoside triphosphate attached?

Back 17

The three phosphate groups of the deoxyribonucleoside triphosphate are attached to the 5¢ position of the sugar

Front 18

Where does energy for synthesis of nucleotides to the growing chain comes from?

Back 18

Energy for synthesis of nucleotides to the growing chain comes from breaking the bonds between these three phosphates

Front 19

Look at figure 13.12

Back 19

:)

Front 20

What are the Molecular Mechanisms of DNA Replication?

Back 20

A huge protein complex catalyzes DNA replication.
This replication complex recognizes an origin of replication on a chromosome.
DNA replicates in both directions from the origin, forming two replication forks.
In DNA replication, both strands of DNA act as templates. Replication occurs at many different sites simultaneously.

Front 21

Look at figure 13.19

Back 21

:)

Front 22

What is the main replication enzyme?

Back 22

DNA Polymerase

Front 23

Which strand does DNA polymerase bind to?

Back 23

DNA Polymerase binds to the template strand

Front 24

DNA polymerase can only add nucleotides to which strand?

Back 24

The 3 prime strand

Front 25

What is the use of a primer?

Back 25

DNA polymerases cannot build a strand without having an existing strand, called a primer, to start from. In DNA replication, the primer strand is a short strand of RNA complementary to the DNA template strand. RNA tells the cell where the primer was and checks where mistakes were done. An enzyme makes the primer strand.

Front 26

What is the use of a primer?

Back 26

DNA polymerases cannot build a strand without having an existing strand, called a primer, to start from. In DNA replication, the primer strand is a short strand of RNA complementary to the DNA template strand. RNA tells the cell where the primer was and checks where mistakes were done. An enzyme makes the primer strand

Front 27

Which strand will be in the correct orientation for addition of new nucleotides?

Back 27

The strands in the template DNA are antiparallel, however.
As a result, as the strands pass through the replication complex, one strand (the leading strand) will be in the correct orientation for addition of new nucleotides

Front 28

Which strand will go through the replication complex in the reverse orientation?

Back 28

The lagging strand

Front 29

Look at figure 13.16

Back 29

:)

Front 30

What are okazaki fragments?

Back 30

Because of its backward orientation, the lagging strand must grow in relatively small, discontinuous pieces, called Okazaki fragments.

Front 31

Which way does DNA polymerase synthesizes complementary DNA?

Back 31

DNA polymerase synthesizes complementary DNA starting from the 3' end of the new primer and working toward the previous Okazaki fragment

Front 32

Look at figure 13.15

Back 32

:)

Front 33

What happens when DNA polymerase reaches the previous Okazaki fragment?

Back 33

When DNA polymerase reaches the previous Okazaki fragment, it is released.
The RNA primer of the previous Okazaki fragment is then replaced with DNA.

Front 34

Look at figure 13.17

Back 34

:)

Front 35

The vast majority of DNA errors are __________________

Back 35

Neutral at best and fatal at worst

Front 36

To minimize the number of errors, our cells have what three DNA repair mechanisms?

Back 36

Proofreading
Mismatch repair
Excision repair

Front 37

When does proofreading happen in DNA?

Back 37

As they add new bases to a growing strand, DNA polymerases make a proofreading check.
When a DNA polymerase recognizes an error, it removes the wrong nucleotide and puts in correct one

Front 38

How does mismatch repair work in DNA?

Back 38

The mismatch repair mechanism scans new DNA for mismatched base pairs.
This mechanism can distinguish between the template strand and the new strand.
Thus, this mechanism can determine which base is correct (the base on the template strand) and which base needs to be replaced

Front 39

How does excision repair work in DNA?

Back 39

Excision repair proteins operate over the life of a cell.
DNA is subject to damage by chemicals, radiation, and random spontaneous chemical reactions.
Excision repair enzymes “inspect” the cell’s DNA for damage, then cut the damaged strand and remove it

Front 40

What is the polymerase chain reaction (PCR)?

Back 40

The polymerase chain reaction (PCR) technique is a simple method for making multiple copies of a DNA sequence

Front 41

PCR cycles through what three steps?

Back 41

Double-stranded fragments of DNA are heated to denature them into single strands.
A short primer is added, along with the four dNTPs.
DNA polymerase catalyzes the production of new DNA strands

Front 42

Look at figure 13.22

Back 42

:)