Unit 7: Central Dogma

Question 1

Definition of DNA

Answer 1

is a double helix : 2 strands that twist around eachother
- each strand is made of nucleotides with a sugar-phosphate backbone

Question 2

What are the bases

Answer 2

Cytosine, guanine, adenine, and thymine (uracil)

• bases join the strands through hydrogen bonds

Question 3

Which bases are the purines?

Answer 3

Adenine and Guanine

Question 4

Which bases are the pyrimidines?

Answer 4

Thymine and Cytosine

Question 5

RNA vs DNA

Answer 5

RNA: ribose, single stranded, uracil

DNA: deoxyribose, double stranded, thymine

Question 6

Alfred Hershey and Martha Chase experiment.

Answer 6

found whether or not proteins or nucleic acids were responsible for inheritance, showed that DNA was the genetic material

• Sulphur labeled as protein
• Phosphorous labeled as DNA

1) Infection
2) Blending
3) Centrifugation

Question 7

Outline how the results of the Meselson-Stahl experiment supported semi-conservative DNA replication.

Answer 7

Meselson and Stahl treated DNA with a heavier nitrogen isotope (15N) and then replicated in the presence of a lighter nitrogen isotope (14N) so template DNA and newly synthesized DNA could be differentiated.

Question 8

What is helicase?

Answer 8

Breaks hydrogen bonds between complementary bases, unzips strands of DNA

Question 9

DNA Polymerase

Answer 9

the main architect of DNA replication. Constructs a new DNA strand by adding nucleotides in a direction that runs from 5’ to 3’. Requires a primer to add nucleotides.

Synthesizes a new strand of DNA. Nucleotides align opposite their partner and DNA Pol 3 joins them together.

Question 10

What is primase?

Answer 10

lays down RNA primers as helicase is moving away

Question 11

Lagging Strand Replication

Answer 11

DNA polymerase is compelled to work backwards, creating discontinuous Okazaki fragments

Question 12

SBB

Answer 12

Keeps strands separated, supercoiling needs to be controlled when replicating DNA

Question 13

anti-sense strand

Answer 13

the strand that is copied in translation

Is the strand that IS transcribed (this is complementary to the eventual RNA sequence)

Question 14

sense strand

Answer 14

strand that doesn’t get copied, and then the codon strand copies this strand

Is the strand that is NOT transcribed (this is identical to the RNA sequence, except U replace T)

Question 15

Linus Pauling

Answer 15

-Proposed a triple helix model for DNA. Although he was wrong, his research played a significant role in the exploration of molecular biology.

Question 16

Phoebus Levine

Answer 16

• Laid groundwork for understanding the structure and function of nucleic acids

Question 17

Erwin Chargaff

Answer 17

• Discovered that the percentage of adenine are equal to the amounts of thymine
  -Discovered that the percentage of cytosine is = to the amounts of guanine
  Suggested complimentary base pairings in DNA

Question 18

Rosaline Franklin

Answer 18

-Discovered the helical pattern of DNA and dimensions for helix.
- Her work was essential to the discovery of the double helix although she wasn’t recognized for a long time later

Question 19

Watson and Crick

Answer 19

Discovered the double helix structure of DNA which laid the foundation for understanding the mechanisms of heredity
- helped to understand genetics
- and molecular biology

Question 20

How is DNA rep. semi conservative?

Answer 20

When a new double stranded DNA molecule is formed:
- one strand is from the original template molecule (conserved)
- one strand is newly synthesized (non conservative)

Question 21

What is the purpose and process of PCR?

Answer 21

-Rapidly amplifies minute quantities of DNA
Involves a thermal cycler and 3 repeating steps;
1) Denaturation - DNA is heated to separate strands
2) Annealing - Primers are introduced to designate copying strands
3) Elongation - Taq polymerase synthesizes new strand

These steps double the amount of DNA, so a typical reaction of 30 cycles will produce over 1 billion copies of desire DNA sequence

Taq polymerase is heat resistant and so doesn’t denature during PCR

Question 22

Transcription

Answer 22

the process by which an RNA sequence is produced from a DNA template (a gene)

DNA –> mRNA

Question 23

Translation

Answer 23

is the process of protein synthesis, genetic information encoded by mRNA is translated into an amino acid sequence

mRNA –> protein

Question 24

What is the role RNA polymerase in transcription?

Answer 24

• Unwinds and separates the double stranded DNA and then synthesizes a new RNA strand based on the antisense template
  -the RNA strand is then released

Question 25

What is an anti-codon?

Answer 25

what tRNA carries, opposite pairing of the mRNA strand

Question 26

Main elements of translation

Answer 26

1) intiation
2) elongation
3) termination

Question 27

What is a common feature between mRNA and DNA?

Answer 27

• both have covalent bonds between adjacent nucleotides