DNA

Question 1

Nucleic acids are composed of repeating units called

Answer 1

Nucleotides

Question 2

List the constituent parts of a nucleotide

Answer 2

Phosphate group (PO4 3-)
Sugar group (pentase) 
Nitrogen containing base (pyrimidines and purines)

Question 3

Sugar found in both DNA and RNA

Answer 3

Pentase

Question 4

Chemical difference between deoxyribose and ribose

Answer 4

Deoxyribose has one less oxygen than ribose

Question 5

Identify the two families of nitrogen bases and explain the difference and group the pairs

Answer 5

Pyrimidines- single ring (uracil, cytosine, thymine)

Purines- double ring (adenine and guanine)

Question 6

List and explain findings of chargaff in regards to DNA structure

Answer 6

He showed in a sample:

Equal concentrations of A and T, equal concentrations of C and G, total pyrimidines=total purines.

This means that he figured out what base pairs match with each other always

Question 7

Explain roles of Wilkins and Franklin in finding structure of DNA

Answer 7

They took and mastered reading X-ray diffraction images

Question 8

10 facts learned about DNA structure from experiments

Answer 8

1. ) DNA is right handed double helix
2. ) each chain has repeating nucleotides held together by phosphodiester bonds
3. ) bases are perpendicular to the molecular axis
4. )bases are nonpolar, phosphate and sugar are polar (hydrophobic core)
5. ) 2 strands are held together by hydrogen bonds
6. ) complimentary
7. ) nitrogen bases are 0.34 nm apart
8. ) backbones are antiparallel (in opposite directions)
9. ) minor vs major groove
10. ) super coils

Question 9

Identify chemical polarity of bases and explain how this aids in molecular stability of DNA

Answer 9

Bases are nonpolar, phosphate and sugar are polar. This aids in stability of molecule in aqueous cell

Question 10

Explain how hydrogen bonds form

Answer 10

An H of one molecule is attracted to electronegative atom (O or N) of another

Question 11

Where in the DNA strand do hydrogen bonds form

Answer 11

2 Between A and T
3 between C and G
None between opposites because there’s no hydrogen bonds formed between them so they’re never paired together

Question 12

Define complementary

Answer 12

The sequence of one strand dictates sequence of other strand

Question 13

Why DNA complementary is crucial to heredity

Answer 13

DNA is capable of storing and transmitting genetic info from generation to generation through complementary

Question 14

Distance between nitrogen bases in DNA in both nm and m

Answer 14

0. 34 nm

0. 34 x 10^-9 m

Question 15

Length of one complete turn of DNA helix and number of bp in one turn

Answer 15

10 bp per turn

1 turn=3.4nm

Question 16

Define antiparallel and explain what it means in terms of DNA

Answer 16

In opposite directions. If top is 5’-3’ then bottom is 3’-5’

Question 17

Explain the significance of the two types of grooves

Answer 17

Minor and major. Transcription factors bond to either major or minor groove. This influences genetic expression.

Question 18

Describe supercoiling of DNA

Answer 18

All functional DNA is supercoiled. It is twisted like a rubber band. This compacts the DNA, most organisms have negative supercoiling.

Question 19

Evolutionary significance of supercoiling and negative supercoiling

Answer 19

It was passed down in most organisms which means it was important. All who have negative supercoiling are related. All who have normal supercoiling are related.

Question 20

Differentiate between negative and positive supercoiling

Answer 20

Negative supercoiling is to the left, compared to the right handed helix (opposite direction) positive supercoiling is vice versa of this