Chapter 9: Molecular Structure of DNA and RNA

Question 1

What 4 criteria must genetic material meet?

Answer 1

1. Information
2. transmission
3. replication
4. variation

Question 2

What is information?

Answer 2

it must contain the information necessary to make an entire organism

Question 3

what is transmission?

Answer 3

it must be passed from parent to offspring (humans, bacteria, and viruses do this)

Question 4

what is replication?

Answer 4

it must be copied in order to be passed from parent to offspring

Question 5

Why is replication necessary for genetic material?

Answer 5

If the cells didn’t replicate, the donor cell would die.

Question 6

What is variation?

Answer 6

must be capable of changes to account for the known phenotypic variation in each species

Question 7

What scientist discovered/studied Transformation?

Answer 7

Frederick Griffith

Question 8

Describe Griffith’s Experiment with Streptococcus Pneumonia:

Answer 8

• He injected Type S and Type R strains into mice 4 ways and thats how he discovered transformation.
• Conclusion was that something from the dead type S bacteria was transforming type R bacteria into type S bacteria

Question 9

Contrast Type S and Type R S. pneumoniae

Answer 9

Type S - smooth and secretes a polysaccharide capsule that protects bacterium from the immune system of animals (immune buffer)
Type R - rough and unable to secrete a capsule and produces colonies with rough appearances

Question 10

What is transformation again?

Answer 10

the uptake of foreign DNA from the environment

Question 11

What did Avery, MacLeod, and McCarty experiment do?

Answer 11

• identify what the genetic material was through 3 types of enzymes.
• Discovered that if the DNA was destroyed, then no transformation occurred.

Question 12

What did the Hershey and Chase experiment do?

Answer 12

• Provided evidence that DNA is a genetic material of T2 phage
• used radioisotopes to distinguish DNA from proteins
• 32P (phosphorous) = DNA
  -32S (sulfur) = Protein
• radiolabelled phages were used to infect non-radioactive E.Coli cells and indicated that DNA is the genetic material

Question 13

What are nucleotides?

Answer 13

• form repeating unit of nucleic acids
• linked to form a linear strand of RNA or DNA

Question 14

What kind of strand is DNA?

Answer 14

double stranded that can interact to form a double helix

Question 15

What does the interaction of DNA with proteins produce?

Answer 15

chromosomes within living cells

Question 16

Put in order DNA from simple to complex

Answer 16

1. Nucleotides
2. Single strand
3. Double Helix with complimentary base pairs

Question 17

List the 3 groups/components of Nucleotides

Answer 17

1. Phosphate groups
2. Sugars ( Deoxyribose = DNA) (Ribose = RNA)
3. Adenine, Thymine, Uracil, Guanine, Cytosine

Question 18

List the purines (double rings)

Answer 18

1. Adenine
2. Guanine

Question 19

How do we tell Adenine and Guanine apart?

Answer 19

Adenine has NH2 while Guanine has an double oxygen bond

Question 20

List the pyrimidines (single rings)

Answer 20

1. Thymine (DNA)
2. Uracil (RNA)
3. Cytosine (both)

Question 21

How do we tell Thymine and Uracil apart?

Answer 21

Thymine has CH3 (methylation)

Question 22

Why is 3’ (3 prime) OH important?

Answer 22

allows for addition of new nucleotides

Question 23

What does nucleoside mean?

Answer 23

lacks a phosphate group

Question 24

How are nucleotides written?

Answer 24

5’ to 3’

Question 25

In 1953, who explained the double helical structure of DNA?

Answer 25

James Watson and Francis Crick

Question 26

Who helped Watson and Crick explain the double helical structure of DNA?

Answer 26

Erwin Chargaff (% of adenine = % of thymine) - Rosaline Franklin (looked straight down at the DNA)

Question 27

If an organism has 23% Thymine, how many cytosines does the organism have?

Answer 27

27% 23+23=46 100-46=54 54/2 = 27

Question 28

Explain the structure of the DNA double Helix

Answer 28

- two strands that are twisted together around a common axis - 10 base pairs and 3.4 nm per complete turn of the helix - the two strands are anti-parallel - helix is right handed

Question 29

List the structure of RNA

Answer 29

1. RNA uses Uracil as a base instead of T 2. Uses Ribose with 2 OH' instead of Deoxyribose 3. several hundred to several thousands nucleotides in length compared to DNA which is millions 4. Is a synthesis - only one of the 2 strands of DNA is used as a template

Question 30

Why and how do RNA double helices form?

Answer 30

1. RNA can form short double stranded regions so A to U and C to G. these short regions form a double helix 2. right handed, 11-12 base pairs how? strands fold on themselves which results in complementary base pairs