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Bio 2 (Let's go Chagnon) > DNA Structure > Flashcards

Flashcards in DNA Structure Deck (32):
1

Who discovered, in 1953, that DNA is a double helix?

Rosalind Franklin and Maurice Wilkins

2

Who discovered, in 1949, the base-pairing proportions and DNA varies between species?

Erwin Chargaff

3

In 1953, who discovered the organization of DNA + complimentary base-pairing?

James Watson and Francis Crick

4

In 1958, who discovered DNA replication?

Matthew Meselson & Franklin Stahl

5

Erwin Chargaff determined base pair proportions through what?

paper chromatography (he invented the technique)

6

Ratio of A equals that of ___

T (adenine = thymine)

7

Ratio of G equals that of ___

C (cytosine = guanine)

8

In humans, cytosine and guanine are less or more present in the composition than adenine and thymine?

LESS C-G
MORE A-T

9

DNA is a ___ acid.

nucleic

10

The building blocks of DNA are____.

nucleotides

11

What composes nucleotide?

5-carbon sugar (deoxyribose)
Phosphate group
Nitrogenous base

12

What are purines bases ?

Adenine and Guanine (A & G)

13

What are pyrimidines bases?

Cytosine, Thymine and Uracil (C & T & U)

14

What does 2nd position of carbon molecule mean?

If nucleotide is RNA of DNA

15

What happens in the 3rd position of carbon?

Incoming nucleotide binds during replication

16

DNA chains are ___

antiparallel (5'to 3' orientation)

17

How did Rosalind Franklin and Maurice Wilkins discover that DNA is helical?

X-ray chrystallography (3D structure of DNA)
[X-ray diffraction of DNA double helix]

18

Franklin had concluded that:
_____ and ____

However, organization of bases was unclear.

1. there were two antiparallel sugar-phosphate backbones
2. the nitrogenous bases paired in the molecule’s interior .

19

Who in 1953
deduced the structure of DNA using evidence from:
Chargaff
Franklin/Wilkins
others?

James Watson and Francis Crick

20

What did Watson and Crick show?

1. DNA composed of 2 chains of nucleotides, each in a helix
2. DNA chains run anti-parallel to each other
3. Purine-pyrimidine base pairs (keep distance between chain constant)

21

What happened when they tried to match purine and purine?

too wide

22

What happened when they tried to match pyrimidines and pyrimidines?

too narrow

23

What happened when they tried to match purine + pyrimidine?

width consistent with X-ray data

24

Two strands of DNA are _______.

Complementary

25

What did Watson and Crick deduce from replication?

Each strand acts as template for building a new strand in replication

Parent molecule unwinds and 2 daughter strands are built based on complemetary base-pairing rules

26

What are "daughter” DNA molecules?

each consisting of one parental strand and one new strand

27

What is the dispersive model?

Each strand is a mix of old and new

28

What is the semiconservative model?

Predicts each daughter molecule will have one old strand

29

What is the conservative model?

Two parent strands rejoin

30

Matthew Meselson & Franklin Stahl, 1958
Showed the process of DNA replication uses

semi-conservative replication

31

Used gradient centrifugation, E.coli, and nitrogen isotopes

Matthew Meselson and Franlinn Stahl

32

Meselson and Stahl concluded that the mechanism of DNA replication is the _____ model.

Semi-conservative model

OR
Each strand of DNA acts as a template for the synthesis of a new strand.