Question

What it approximate ratio between the width of the double helix and the length of one turn of the helix? Width : length is approx.

a.         1 : 1

b.         1: 2

c.         1 : 3

d.         1: 5

e.         1 : 10

What would the best description be for the E. coli genome.

a. metacentric

b. linear

c. telocentric

d. haploid

A short length of DNA: 5’ GCATAGCA 3’ will hybridize with which of the following sequences?

a. 5’    GCATAGCA 3’

b. 5’    CGTATCGT 3’

c. 5’    ACGATAGC 3’

d. 5’    TGCTATGC 3’

Draw a simple schematic of the molecule which is the ‘building material’, taken in by DNA polymerase in the process of replication.

Please provide full explanations!

Thank you! :)

Answer 1

What it approximate ratio between the width of the double helix and the length of one turn of the helix? Width : length is approx. =>

One single turn of DNA is 34.86 Angstrom long (10.5 bases with each 3.32 Angstrom apart for a B form of DNA) while the width of DNA is about 20 Angstrom (diameter).

Therefore, length to width ratio of DNA = (34.86 Angstrom)/(20 Angstrom) = 1.743 (approxiamtely equals 2.)

Hence Width : length is approx. = 1:2.

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What would the best description be for the E. coli genome. =>

The correct answer is "d. haploid". E. coli and most other bacteria contain one homolog of their single chromosome and are considered to be haploid.

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A short length of DNA: 5’ GCATAGCA 3’ will hybridize with which of the following sequences? =>

d. 5’    TGCTATGC 3’.

writing it from 3' to 5': CGTATCGT which is complementary to 5’ GCATAGCA 3’