DNA Chapter 7.2

Question 1

the 2 types of nucleic acids

Answer 1

dna ( deoxyribonucleic acid)

Rna ( ribonucleic acid)

Question 2

Nucleotides

Answer 2

the building blocks of nucleic acid

Question 3

structure of a nucleotide

Answer 3

sugar ( deoxyribose or ribose)
a phosphate group
nitrogenous base
They always have the the same sugars and phosphate but have one of the different nitrogenous bases.

Question 4

DNA double helix resembles a twisted ladder or staircase

Answer 4

Railings —–( sugar phosphate backbone)
Alternating units of
deoxyribose and phosphate joined with covalent bonds.

The stairs——-A-T, G-C base pairs joined by hydrogen bonds.

Question 5

how are the Railings —–( sugar/ phosphate backbone)

Alternating units of deoxyribose and phosphate

Answer 5

with covalent bonds

Question 6

How are the The stairs——-A-T, G-C base pairs joined

Answer 6

with hydrogen bonds

Question 7

A-T and G-C arise from their chemical structure

Answer 7

A (adenine) and G (guanine) are purines
T ( thymine) and C ( cytosine) are pyrimidines

A———————–T

G———————-C

(PURINES) (PYRIMIDINES)

Question 8

Purines

Answer 8

bases with a double ring structure( Adenine

Question 9

pyrimidines

Answer 9

bases with a single ring structure

Question 10

A-T and G-C are the same width because

Answer 10

Each pair includes a purine and a pyrimidine

Question 11

Explain the pairings of the bases

Answer 11

A-T and G-C
Each pair has equal amounts of each base

The pairs have the same width because each contain a purine and a pyrimadine

Question 12

The two strands of DNA are COMPLEMENTARY because

Answer 12

The sequence of each strand defines the sequence of the other

( A on one strand means a T on the other)
( G on one strand means a C on the other)

Question 13

Why is complementary base important

Answer 13

It is the basis of gene function

Question 14

How are the two strand physically arranged

Answer 14

. They go in opposite directions

The two strands are parallel but tail to head ( anti parallel)

Question 15

The designation of the opposite end of the double helix

Answer 15

3 prime ( ending with a 3' carbon)
5 prime ( ending with a 5'carbon)

Question 16

What are the components of DNA and its three-dimensional structure

Answer 16

The components of a DNA molecule are nucleotides. These are composed of a deoxyribose sugar bonded to a phosphate and a nucleotide base (adenine, thymine, cytosine, or guanine). The three-dimensional structure of DNA is a double helix, which resembles a twisted ladder.

Question 17

What evidence enabled Watson and Crick to decipher the structure of DNA

Answer 17

The evidence included Rosalind Franklin’s X-ray diffraction photo of a crystal of DNA, plus Erwin Chargaff’s work that showed that DNA contains equal amounts of adenine and thymine and equal amounts of cytosine and guanine.

Question 18

Identify the 3′ and 5′ ends of a DNA strand

Answer 18

The 5’ end has the 5th numbered carbon in deoxyribose facing out and leading with a phosphate group attached, and the 3’ end has the 3rd numbered carbon leading with no phosphate, just the OH attached to the carbon.
3’ and 5’ are numbersmthat chemist assign to carbon atoms in deoxyribose