Second Half F24 II: Lecture Slides: 1 - 17

Question 1

What did Chargaff’s founding in all cellular DNAs?

Answer 1

That the Number of Guanine = The number of Cytosine and that the Number of Adenine = the Number of Thymine

Question 2

What is “Chargaff’s Rules”

Answer 2

A = T

C = G

Question 3

What did Rosalind Franklin and Maurice Walkins do?

Answer 3

They used X-ray crystallography to identify the secondary structure of DNA.

Question 4

What did Rosalind Frank obtain?

Answer 4

The first useful X-ray diffraction image of DNA: photo 51

Question 5

What did Photo 51 show?

Answer 5

DNA molecules are helical

This photo provided information about the shape.

Question 6

What is the primary/major pattern of the DNA?

Answer 6

3.4A

Question 7

What is the minor pattern of DNA?

Answer 7

34A

Question 8

What did Francis and Crick say the structure of DNA was?

Answer 8

Double Helical

Question 9

What do the two helical DNA chains wind around a single axis form?

Answer 9

A right handed double helix.

Question 10

Where does the hydrophilic sugar phosphate backbone remain?

Answer 10

On the outside of the helix facing the surrounding water.

Question 11

What are the nitrogenous bases considered to be?

Answer 11

Hydrophobic

Question 12

Where do the hydrophobic bases remain?

Answer 12

They are stacked inside the double helix perpendicular to the axis.

Question 13

What are the two strands of DNA?

Answer 13

They are antiparallel to each other: the 3’.5’ phosphodiester bond run in opposite directions.

Question 14

What is the distance between each base pair?

Answer 14

3.4A

Question 15

What is the distance between 10 base pairs?

Answer 15

34 A

Question 16

What is the diameter of the double helix?

Answer 16

20A (2nM)

Question 17

What does self - complementarity allow each pre-existing strand of a double helix to serve?

Answer 17

As a template to guide synthesis of new daughter strands.

Question 18

How many hydrogen bonds between Cytosine and Guanine?

Answer 18

Three

Question 19

How many hydrogen bonds between Adenine and Thymine?

Answer 19

Two

Question 20

What happens when you have a higher ratio of GC to AT

Answer 20

It will be more difficult to pull the strands apart as there are more hydrogen bonds.

Question 21

What can DNA undergo?

Answer 21

It can undergo super-coiling to give very impact structures.

Question 22

What are the glycosolic bonds between base pairs?

Answer 22

The glycosidic bonds are not collinear: they are at an angle.

Question 23

What is the short angle of the glycosilic bond?

Answer 23

Minor Groove

Question 24

What is the large angle of the glycosidic bond?

Answer 24

Major Groove

Question 25

What forces stabilize the double helix?

Answer 25

1.) The hydrophobic effect (hydrophobic bases are within the core)

2.) The Hydrogen bonds

3.) Van Der Waals stacking of bases

Question 26

What is the Central Dogma of Molecular Biology?

Answer 26

DNA —> RNA —> protein by transcription and translation.