DNA and DNA replication

Question 1

The amount of adenine…

Answer 1

equal amount of thymine

Question 2

The amount of guanine…

Answer 2

equals amount of cytosine

Question 3

Purines

Answer 3

*Double ring structure (A,G)

Question 4

Pyrimidines

Answer 4

*Single ring structure (C,U,T)

Question 5

How are nucleotides held together?

Answer 5

Hydrogen bonds

Question 6

Key features of DNA

Answer 6

1. Double-stranded helix, antiparallel strands
2. Sugar-phosphate backbone
3. Nucleotides pairing in the center

Question 7

Key function of DNA

Answer 7

Primary source of heritable information, genetic info stored and passed from one generation to the next through DNA.
EXCEPTION RNA primary source of heritable info in some viruses

Question 8

Eukaryotic Cells DNA

Answer 8

1. DNA found in nucleus
2. Linear chromosomes

Question 9

Prokaryotic Cells DNA

Answer 9

1. DNA in nucleoid region
2. Chromosomes are circular

Question 10

Plasmids

Answer 10

Small, circular DNA molecules that are separate from the chromosomes

Question 11

Plasmids importance

Answer 11

Contain genes that may be useful to the prokaryote when it is in a particular environment

Question 12

Plasmids and manipulation in laboratories

Answer 12

*Plasmids can be removed from bacteria, then a gene of interest can be inserted into the plasmid to form recombinant plasmid DNA
*When recombinant plasmid is inserted back into the bacteria the gene will be expressed

Question 13

RNA

Answer 13

-Ribonucleic acid
-Single stranded
-A=U C=G

Question 14

DNA

Answer 14

-Deoxyribonucleic acid
-Double stranded
-A=T C=G

Question 15

Models of DNA replication

Answer 15

1. Conservative
2. Semi-conservative
3. Dispersive

Question 16

Conservative model

Answer 16

The parental strands direct synthesis of: an entirely new double stranded molecule

Question 17

Semi-conservative model

Answer 17

*The two parental strands: Make a copy if itself
*After one round of replication, the two daughter molecules each have one parental and one new strand

Question 18

Dispersive model

Answer 18

*The material in the two parental strands is dispersed randomly between the two daughter molecules
*After one round of replication, the daughter molecules contain a random mix of parental and new DNA

Question 19

1st step in DNA replication

Answer 19

1. DNA replication begins at sites called origins of replication, various proteins attach to the origin of replication and open the DNA to form a replication fork

Question 20

2nd step in DNA replication

Answer 20

2. Helicase will unwind the DNA strands at the replication fork
   -To keep DNA from re-bonding to itself, single strand binding proteins bind to the DNA to keep it open
   -Topoisomerase will prevent strain ahead of the replication fork by relaxing supercoiling

Question 21

4th step in DNA replication

Answer 21

Antiparallel elongation
*DNA polymerase III: Attaches to each primer on the parental strand and moves in the 3’ to 5’ direction
-Adds nucleotides in the 5’ to 3’ direction
*DNAP III that follows helicase is known as the leading strand and it only requires one primer
-DNAP III on other parental strand, know as the lagging strand and requires many primers

Question 21

3rd step in DNA replication

Answer 21

3. The enzyme primase initiates replication by adding short segments of RNA, called primers to the parental DNA strand
   -The enzymes that synthesize DNA can only attach new DNA nucleotides to an existing strand of nucleotides
   -Primers serve as the foundation for DNA synthesis

Question 22

5th step in DNA replication

Answer 22

*The leading strand is synthesized in one continuous segment, but since the lagging strand moves away from the replication fork, it is synthesized in chunks
Okazaki fragments: Segments of the lagging strand

Question 23

6th step in DNA replication

Answer 23

*After DNAP III forms an Okazaki fragment, DNAP I replaces RNA nucleotides with DNA nucleotides
DNA ligase: Joins the okazaki fragments forming a continuous DNA strand

Question 24

Telomeres

Answer 24

Repeating units of short nucleotide sequences that do not code for genes
*Form a cap at the end of DNA to help postpone erosion
*The enzyme telomerase adds telomeres to DNA

Question 25

Proofreading and repair

Answer 25

-As DNA polymerase adds nucleotides to new DNA strand, proofreads bases added
-If errors still occur-Enzymes remove and replace incorrectly paired nucleotide
-If segments still damaged-Nuclease can remove segments of nucleotides and DNA polymerase and ligase can replace the segments