Chapter 12: DNA Structure, Replication and Organization

Question 1

Bacteriophages

Answer 1

A virus that parasitizes a bacterium by infecting it and reproducing inside it.

Question 2

Nucleotide

Answer 2

Composed of nitrogenous bases. Nucleotides form the basic structural unit of nucleic acids such as DNA.

Question 3

Deoxyribose sugar

Answer 3

The sugar component of DNA, phosphates that form the chains.

Question 4

Nitrogenous base

Answer 4

A nitrogen containing molecule that has the same chemical properties as a base. They are particularly important since they make up the building blocks of DNA and RNA: adenine, guanine, cytosine, thymine and uracil.

Question 5

Purine (adenine and guanine)

Answer 5

A substituted derivative of this, especially the bases adenine and guanine present in DNA and RNA.

Question 6

Pyrimidine (thymine and cytosine)

Answer 6

A substituted derivative of this, especially the bases thymine and cytosine present in DNA.

Question 7

Sugar-phosphate backbone

Answer 7

The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone.

Question 8

Phosphodiester bond

Answer 8

Links nucleotides together

Question 9

5’ end

Answer 9

attaches to a phosphate group

Question 10

3’ end

Answer 10

attaches to a hydroxyl group

Question 11

Double-helix model

Answer 11

Discovered by Watson and Crick. Anti-parallel DNA strands wind around each other, with purine and pyrimidine bases facing each other in the interior of the molecule.

Question 12

Why are the DNA strands Antiparallel?

Answer 12

The DNA strands are antiparallel to allow for complimentary base pairing.

Question 13

Complementary base pairing

Answer 13

Adenines pair with Thymines and Guanines pair with Cytosines.

Question 14

Semiconservative replication model

Answer 14

DNA replication produces DNA molecules with 1 parental strand and 1 newly made strand (Watson and Crick).

Question 15

Conservative replication model

Answer 15

DNA replication produces 1 double helix with both parental strands, and the other with 2 new daughter strands.

Question 16

Dispersive Replication Model

Answer 16

DNA replication produces DNA strands in which segmtns of new DNA are interspersed with the parental DNA.

Question 17

4 Deoxyribonucleoside triphosphates

Answer 17

dATP, dGTP, dCTP, dTTP (ps you guys should probe look up what these are but i just couldn’t find it in my notes)

Question 18

DNA helicase

Answer 18

Separates the two strands so the nucleotides are no longer base-paired.

Question 19

Replication fork

Answer 19

The DNA uncoils during replication creating a leading an a lagging strand.

Question 20

Single-stranded binding proteins

Answer 20

Proteins which bind to the single-stranded portions of the DNA molecule.

Question 21

Topoisomerase

Answer 21

protects the rest of the DNA molecule from being wound tighter.

Question 22

RNA primer

Answer 22

Connected ot the template strand by primase to initiate a new DNA strand. Once the RNA primer is in place then the DNA Polymerase can add DNA bases, copying the template strand.

Question 23

Primase

Answer 23

An enzyme which which connects a few complimentary RNA bases to the template strand – this is called an RNA Primer

Question 24

Leading strand

Answer 24

Strand of DNA being replicated continuously. In DNA replication, the strand that is made in the 5’ to 3’ direction by continuous polymerization at the 3’ growing tip.

Question 25

Lagging strand

Answer 25

The dna strand that is replicated discontinuously from the 5’ to the 3’ direction.

Question 26

Discontinuous replication

Answer 26

The synthesis of a new strand of a replicating DNA molecule as a series of short fragments that are subsequently joined together. Only one of the new strands, the so-called lagging strand, is synthesized in this way.

Question 27

Okazaki fragments

Answer 27

Relatively short fragment of DNA synthesized on the lagging strand during DNA replication.

Question 28

DNA ligase

Answer 28

A specific type of enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

Question 29

Replication origin

Answer 29

A particular sequence in a genome at which replication is initiated. This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses.

Question 30

Base-pair mismatch

Answer 30

The presence of an uncomplimentary base in double-stranded DNA caused by spontaneous deamination of cytosine or adenine, mismatching during homologous recombination, or errors in DNA replication.