2.6 DNA & RNA structure

Question 1

How many pairs of chromosomes in a cell?

Answer 1

23 pairs

Question 2

How long are DNA strands coiled and uncoiled?

Answer 2

Uncoiled, it’s approx. 2m while coiled it is usually enclosed in just a 10 um diameter.

Question 3

What are nucleotides?

Answer 3

Recurring monomeric units that make up nucleic acids (genetic material)

Question 4

3 components of nucleotide

Answer 4

Nitrogenous base, phosphate group and a pentose sugar

Question 5

Which carbon is the nitrogenous base attached to?

Answer 5

1-carbon atom

Question 6

Which carbon is phosphate group attached to?

Answer 6

5-carbon atom

Question 7

Nucleic acids are linked by: condensation or hydrolysis reactions?

Answer 7

Condensation reactions

Question 8

What part of nucleotides attach to the next nucleotide?

Answer 8

Phosphate group of one molecule is attached to sugar of another at 3-carbon

Question 9

How many hydrogen bonds between A and T?

Answer 9

2

Question 10

How many hydrogen bonds between C and G?

Answer 10

3

Question 11

What direction do strands run in and why?

Answer 11

They run antiparallel to each other as bases need to face each other.

Question 12

General shape of DNA

Answer 12

Double helix

Question 13

How many bases per twist in DNA?

Answer 13

10-15 per twist

Question 14

Difference between sugar of DNA and RNA

Answer 14

DNA has a deoxyribose sugar while RNA has a ribose sugar. DNA has one fewer oxygen while RNA has a hydroxide group

Question 15

Difference between no. of strands in DNA and RNA

Answer 15

DNA is double stranded (2 polymers of nucleotides) while RNA is single stranded

Question 16

Bases in DNA and RNA

Answer 16

DNA- A, G, C, Thymine

RNA- A, G, C, Uracil

Question 17

What type of bond is formed between nucleotides? What is the by-product?

Answer 17

Phosphodiester bonds. By-product is water

Question 18

How is double helix formed?

Answer 18

As chain lengthens, atoms will organize themselves into the most stable energy configuration and arrangement will result in double helix

Question 19

If strand is 40% C, how much A is there?

Answer 19

There will be 10% (C and G will both be 40%)

Question 20

Who was the correct structure of DNA proposed by?

Answer 20

Watson and Crick (although they combined their understanding of many other’s discoveries )

Question 21

What was the shape of the original Watson-Crick model?

Answer 21

Triple helix

Question 22

Why were the early DNA models wrong?

Answer 22

• They proposed that the bases were on the outside while the sugar-phosphate was on the inside
• Nitrogenous bases were not complementary

Question 23

Whose work did Watson and Crick take without permission?

Answer 23

Rosalind Franklin