Ch16

Question 1

Describe the function of the enzyme Topoisomerase in DNA Replication & Repair

Answer 1

Relieves stress on twisted DNA helix when replication bubble forms

Question 2

Describe the function of the enzyme Helicase in DNA Replication & Repair

Answer 2

Unwinds DNA to form replication bubbles

Question 3

Describe the function of the enzyme DNA Ligase in DNA Replication & Repair

Answer 3

Mends loose ends of DNA caused by Okasaki fragments (lagging strand) & DNA excision & repair mechanisms

Question 4

Describe the function of the enzyme Nuclease in DNA Replication & Repair

Answer 4

Excises damaged DNA for repair such as Thymine dimers caused by UV damage

Question 5

Describe the function of the enzyme DNA Polymerase in DNA Replication & Repair

Answer 5

Polymerizes new DNA strands

Question 6

Describe the function of the enzyme RNA Primase in DNA Replication & Repair

Answer 6

adds RNA Primer to template strand for DNA Polymerase to bind & start replication

Question 7

What are nucleosides & how do they differ from nucleotides?

Answer 7

Each Nucleoside has 3 phosphates, 1deoxyribose sugar, & 1 nitrogenase base. DNA Polymerase uses nucleosides to form new DNA replicated strands, it removes two phosphates to bond nucleotides together.
Nucleotides has 1 phosphate, 1 deoxyribose, & 1 base. The 1 phosphate comes from the remaining phosphate left when the 2 phosphates are hydrolyzed off the nucleoside

Question 8

Name the purines and pyrimidines

Answer 8

Adenine & Guanine = 2 ring base purines
Thymine & cytosine = 1 ring pyrimidines
One purine hydrogen bonds to 1 pyrimidine

Question 9

What are histones & their function?

Answer 9

Histones are proteins that bind together to form nucleosomes for DNA to wind up on & loop out from as part of the condensing of the DNA. Without Histones, the DNA would not fit in the nucleus

Question 10

What is the difference between Heterochromatin & Euchromatin?

Answer 10

Heterochromatin is condensed DNA that is not transcribed into mRNA.
Euchromatin is loosely packed DNA that is transcripted into mRNA

Question 11

Briefly describe the importance of the Hershey -Chase Landmark Experiment

Answer 11

They were able to determine that DNA was genetic material & not proteins. They labeled DNA with radioactive Phosphorus & proteins with radioactive sulfur to distinguish the difference between DNA & protein in a Bacteriaphage T2

Question 12

What did Frederick Griffith discover during his landmark experiment?

Answer 12

When heat-killed S strain of Streptococcus pneumonia is injected into a mouse with a non-pathogenic R strain of Streptococus pneumonia, the R strain takes up some DNA from the S strain & becomes pathogenic killing the mouse. (heat killed bacteria are non-pathogenic)

Question 13

Briefly describe how Thymine Dimers from UV radiation are repaired by your skin cells

Answer 13

Nuclease removes the Thymine dimers, DNA polymerase repairs the DNA, & ligase glues it together

Question 14

What are telomeres?

Answer 14

Repeating sequences of TTAGGG about 100-1000 base pairs at the ends of our chromosomes that act as a buffer to prevent damage to the chromosome