DNA Structure

Question 1

What was Meischer contribution?

Answer 1

First to isolate DNA

Question 2

What was Griffith contribution?

Answer 2

Transformation; genetic material can move

Question 3

What was Avery, MacLeod, McCarty contribution?

Answer 3

DNA is transforming principle

Question 4

What was Hershey and Chase contribution?

Answer 4

DNA is the genetic material in bacteriophages

Question 5

What was Yanofsky contribution?

Answer 5

colinearity between DNA and protein

Question 6

What was Franklin and Wilkins contribution?

Answer 6

X-ray crystallography

Question 7

What was Chargaff contribution?

Answer 7

base composition

Question 8

What was Watson and Crick contribution?

Answer 8

model of DNA structure

Question 9

What did Albrecht Kossel say?

Answer 9

DNA has 4 nitrogenous bases (adenine, guanine, cytosine, and thymine)

Question 10

What did Phoebus Levene say?

Answer 10

DNA is made of nucleotides

Question 11

What is a nucleotide?

Answer 11

Nucleotide: contains a sugar, base, and phosphate

Question 12

How many hydrogen bonds are between adenine and thymine?

Answer 12

2 hydrogen bonds

Question 13

How many hydrogen bonds are between guanine and cytosine?

Answer 13

3 hydrogen bonds

Question 14

What are hydrogen bonds?

Answer 14

Weak attractions between partial positive and partial negative charged molecules

Question 15

What is the main force that stabilizes the DNA double helix?

Answer 15

Hydrophobic interactions

Question 16

What does hydrogen bonding provide in the double helix?

Answer 16

It provides specificity (AT= 2 H-bonds and GC = 3 H-bonds)

Question 17

What is the Watson-Crick model of DNA?

Answer 17

B-DNA and right handed

Question 18

How do DNA fragments in gel electrophoresis migrate?

Answer 18

Fragments migrate from negative to positive. Smaller pieces move further than larger pieces.

Question 19

What results in higher Tm for DNA?

Answer 19

High GC content

Question 19

Describe hyperchromic effect

Answer 19

When there is an increase in UV absorption (40%) due to denaturation (exposed bases absorb more light)

Question 19

How is UV light used to measure the concentration of nucleic acids?

Answer 19

UV light is absorbed by the ring structures in bases. Relative maximum absorption at 260nm is used to quantify DNA

Question 20

What is euchromatin?

Answer 20

• chromatin that the cell is using
• lighter staining parts of the chromosome during interphase
• Actively transcribed genes into RNA
• condenses and relaxes

Question 21

What is heterochromatin?

Answer 21

• darker staining parts of chromosome
• usually condensed
• not involved in crossing over
• replicates late in the S phase