DNA

Question 1

What is the role of DNA?

Answer 1

It stores your genetic information which is used to control how you grow and function.

Question 2

What is the role of RNA?

Answer 2

Transfer genetic information from the DNA to the ribosomes.

Question 3

What is the structure of DNA?

Answer 3

DNA has a double-helix structure. The two polynucleotide chains are joined together by hydrogen bonds between the bases. The nucleotides in the chain are held together by phosphodiester bonds between the phosphate group of one nucleotide and the pentose sugar of another.

Question 4

What is the general structure of a nucleotide?

Answer 4

A phosphate group
A pentose sugar
A nitrogenous base

Question 5

What is the structure of a DNA nucleotide?

Answer 5

A phosphate group
A deoxyribose sugar
nitrogenous bases: adenine, thymine, guanine, cytosine.

Question 6

What is the structure of an RNA nucleotide?

Answer 6

A phosphate group
A ribose sugar
nitrogenous bases: adenine, uracil, guanine, cytosine.

Question 7

What are the differences between RNA and DNA?

Answer 7

1. RNA is much shorter compared to DNA
2. DNA contains a deoxyribose sugar and RNA contains a ribose sugar.
3. In RNA uracil replaces thymine as a base.
4. DNA is double-stranded and RNA is single-stranded.

Question 8

What is the purpose of DNA replication?

Answer 8

So that when cell division happens each cell has the full amount of DNA.

Question 9

Why is DNA replication considered semi-conservative?

Answer 9

Each strand of DNA is used as a template to make a new DNA strand. The new DNA contains half of the old DNA and half of the new DNA.

Question 10

Describe what happens in DNA replication.

Answer 10

DNA helicase breaks the hydrogen bonds which causes the DNA to unwind. One of the DNA strands is used as a template to make a new DNA strand. Free nucleotides line up next to their complementary base pairs due to complementary base pairing. DNA polymerase catalyses the formation of phosphodiester bonds between the nucleotides. Hydrogen bonds form between the bases which cause the DNA to recoil.

Question 11

Why does the DNA polymerase work in opposite directions when working on the different template strands?

Answer 11

1. The active site of the DNA polymerase is only complete to the 3’ end of the template strand.
2. This means it moves in a 3’ to 5’ direction and the new strand is made in a 5’ to 3’ direction.
3. Since the two template strands are antiparallel this will happens in the opposite direction on the other template strand.

Question 12

What is the evidence that DNA replication is semiconservative?

Answer 12

1. Bacteria were grown is two solutions, once containing light nitrogen and another containing heavy nitrogen.
2. The bacteria took the nitrogen in to make their DNA.
3. When the DNA was removed and placed in a centrifuge. The heavy DNA settled at the bottom of the tube since it was denser and the light DNA at the top since it was less dense.
4. The bacteria with heavy DNA was placed in a solution with light nitrogen and left to undergo on round of DNA replication.
5. Step 3 repeated.
6. If DNA replication was conservative the same thing that happened in step three would happen. However, there was only one band in the middle which shows that the DNA contains one strand of light nitrogen and another of heavy nitrogen. This means that DNA replication is semi-conservative.

Question 13

How are DNA molecules packaged into chromosomes?

Answer 13

It is wrapped around protein called histones.

Question 14

What are homologous chromosomes?

Answer 14

Chromosomes that are the same size and contain the same genes.

Question 15

What is the difference between the DNA in eukaryotes and prokaryotes?

Answer 15

1. The DNA in eukaryotes is longer.
2. The DNA in eukaryotes is packaged into chromosomes.
3. The DNA in eukaryotes is stored in a nucleus.
4. The DNA in eukaryotes has a double helix structure and in prokaryotes, it is a circular loop of DNA.