Chapter 8 Definitions/Concepts Flashcards Preview

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Flashcards in Chapter 8 Definitions/Concepts Deck (42)
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1

Nucleotide

Nitrogenous Base
Pentose Sugar
Phosphate Group

2

Nucleoside

Nitrogenous Base
Pentose Sugar
NO Phosphate

3

Nitrogenous Bases

Purines
Pyrimidines

4

Purines

Adenine and Guanine

5

Pyrimidines

Cytosine, Thymine and Uracil.

6

Minor Nitrogenous Bases

Ribose, found in DNA subjected to oxidative damage.

7

Pentose Sugars

Found in beta Furanose form.

8

Ribose Conformation

Place C1' and C4' in the same plane with the nitrogen up. Up is endo, down is exo.

9

Phosphodiester Bond

Forms 3'-5' bond between nucleotides.

10

RNA Alkaline Hydrolysis

RNA is susceptible to non-enzymatic hydrolysis in alkaline conditions because of the 2'-hydroxyl group.

11

Nucleotide Base Properties (6)

1. Weakly basic.
2. Highly Conjugated/ Planar
3. Absorb UV light around 260nm.
4. Free bases are very hydrophobic and insoluble at physiological pH.
5. Bases stack antiparallel to minimized hydrophobic surfaces due to pi interactions.
6. Ring nitrogens, carbonyl groups, and exocyclic amino groups form hydrogen bonds with other bases.

12

Watson and Crick Basepairs

G-C has 3 hydrogen bonds
A-T has 2 hydrogen bonds

13

Miescher

First isolated DNA in 1868. He originally called it nuclein. It consisted of an acidic portion (DNA) and basic portion (protein).

14

Avery, McLeod and McCarthy

1944 extracted DNA from a virulent strain of strep pneumonia and transformed a non-virulent strain into a virulent strain.

15

Hershey and Chase

1952 radioactively labeled P viral DNA that enters a host cell and provides genetic information for viral replication whereas S viral protein doesn't enter the cell.

16

Erwin Chargaff

1940's established the base composition rules.
-varies across species
-constant across tissues
-constant through age
-shows amounts of A=T and C=G

17

Furberg

1951 first crystal structure of cytidine nucleoside. Used this info to start building structure because it gave bond angles.

18

Dekker, Michelson and Todd

Early 1950's established the 3'-5' phosphodiester linkage

19

Gulland

Electromagnetic titration found hydrogen bond linkage in 1947.

20

Astbury

Fiber x-ray diffraction hinted at base stacking in 1947.

21

Rosalind Franklin and Maurice Wilkins

Analyzed DNA fibers with x-ray diffraction and were able to interpret results in 1953.
-Franklin found 2 strands
-Phosphate groups on the outside
-2 forms of DNA
-3.4A and 34A

22

Watson and Crick

Put the pieces from Franklin and Wilkins together in 1953. They found base pairing with the correct tautomer, 2 anti-parallel strands, base paired and helical with 10 nucleotides per turn.

23

1962 Nobel Prize

Wilkins, Perutz, Crick, Steinbeck, Watson and Kendrew.

24

Characteristics Causing Conformational Variability

1. Ribose Conformation
2. Backbone Bond Rotations (5 bonds)
3. Glycosidic Bond Rotation (between sugar and anything else)

25

DNA Conformational Variability

A-Form
B-Form
Z-Form

26

A-Form

Function of binding protein
-right handed
-shorter and fatter turns
-high bp tilt
-C3' endo

27

B-Form

Most common
-right handed
-tall and thin turns
-low bp tilt
-C2' endo

28

Z-Form

-left handed
-smallest diameter
-C2' endo and C3' endo

29

Complementarity

T-A and C-G are found opposite each other on the helix.

30

Palindrome Sequence

Inverted repeat over both strands.