Topic 1 - Year 1 - Biological Molecules - DNA and RNA

Question 1

What are DNA and RNA ?

Answer 1

DNA and RNA are nucleic acids that are found in all living cells and carry information.

Question 2

What does DNA stand for?

Answer 2

Deoxyribonucleic acid

Question 3

What does RNA stand for?

Answer 3

Ribonucleic acid

Question 4

What is DNA used for?

Answer 4

DNA is used to store all your genetic inormation

Question 5

What is RNA used for?

Answer 5

RNA is used to transfer genetic information from the DNA to the ribosomes , it does this so that proteins can be made.

Question 6

What is the monomer of DNA and RNA ?

Answer 6

Nucleotides are the monomer that builds polymers DNA and RNA

Question 7

Describe the structure of a nucleotide:

Answer 7

A nucleotide has 3 diffrent components

1. A pentose sugar , in DNA this is deoxyribose sugar and in RNA it is ribose sugar
2. A phosphate group
3. A nitrogenous base
   (adenine , thymine , cytosine , guanine , uracil)

Question 8

What type of reaction joins nucleotides to make polynucleotide chains?

Answer 8

Condensation Reactions

Question 9

What type of bond is formed between two nucleotides

Answer 9

A phosphodiester bond , forms between the pentose sugar and the phosphate group.

Question 10

When phosphodiester bonds form , what is created?

Answer 10

A sugar phosphate backbone is created as phosphodiester bonds form between the pentose sugar and the phosphate group.

Question 11

Name 5 nitrogenous bases

Answer 11

Adenine 
Thymine 
Cytosine 
Guanine 
Uracil

Question 12

In DNA what would a nitrogenous base labelled A be?

Answer 12

Adenine

Question 13

In DNA what would a nitrogenous base labelled T be?

Answer 13

Thymine

Question 14

In DNA what would a nitrogenous base labelled C be?

Answer 14

Cytosine

Question 15

In DNA what would a nitrogenous base labelled G be?

Answer 15

Guanine

Question 16

In RNA what would a nitrogenous base labelled U be?

Answer 16

Uracil

Question 17

Cytosine makes 3 hydrogen bonds to which other nitrogenous base?

Answer 17

Guanine

Question 18

Adenine makes 2 hydrogen bonds to which other nitrogenous base?

Answer 18

Thymine

Question 19

Cytosine and Guanine make how many hydrogen bonds?

Answer 19

3

Question 20

Adenine and Thymine make how many hydrogen bonds?

Answer 20

2

Question 21

What type of structure does DNA have and how does this make it fit for purpose?

Answer 21

DNA has a double helix structure , two strands wind around each other to form a spiral , these strands are polynucleotides. DNA molecules are very long and coiled up very tightly so a lot of genetic information can fit into a small space in the cell nucleus.

Question 22

Are both polynucleotide chains oriented the same way in a molecule of DNA?

Answer 22

No the two polynucleotide chains in a double helix of DNA run antiparallel to each other , there is one forward strand which runs 5’ to 3’ and a reverse strand which runs 3’ to 5’

Question 23

The pairing of Thymine + Adenine and Guanine + Cytosine is referred to as?

Answer 23

Complimentary Base Pairing

Question 24

Which nitrogenous bases are found in DNA?

Answer 24

Adenine
Thymine
Cytosine
Guanine

Question 25

Which nitrogenous bases are found in RNA?

Answer 25

Adenine Uracil Cytosine Guanine

Question 26

What replaces Thymine as a base in RNA?

Answer 26

Uracil

Question 27

Which pentose sugar is found in DNA?

Answer 27

Deoxyribose sugar

Question 28

Which pentose sugar is found in RNA?

Answer 28

Ribose sugar

Question 29

What are the main differences between DNA and RNA?

Answer 29

1 . Their pentose sugars are different DNA=deoxyribose sugar RNA= robose sugar 2. Thymine , a base found in DNA is not found in RNA , in its place is uracil. 3. DNA is a double helix where as RNA is a single polynucleotide strand 4. RNA polynucleotide strands are much shorter than DNA polynucleotide strands.

Question 30

When does DNA replicate its self?

Answer 30

DNA replicates itself before cell division so that each new cell has the full amount of DNA.

Question 31

By which method does DNA replicate?

Answer 31

DNA replicates by the semi-conservative replication

Question 32

Why is the model known as the semi conservative model?

Answer 32

The model is known as the semi conservative model as in each piece of DNA replicated there is a strand of the parental DNA and a strand of new DNA.

Question 33

How is DNA replicated?

Answer 33

DNA is replicates as firstly the enzyme DNA Helicase breaks the hydrogen bonds between nitrogenous bases , separating the two polynucleotide strands appart , this causes the helix to unwind and form two single strands. Each original single strand acts as a template for a new strand. Complimentary base pairing means that free floating DNA nucleotides are extracted to their complimentary exposed bases that lie on the original strand. Condensation reactions (catalysed by DNA polymerase) join the new nucleotides together forming phosphodiester bonds. Hydrogen bonds form between the bases on the original strand and new strand . Each new DNA molecule contains one strand from the original DNA molecule and one new strand of DNA.

Question 34

what does the enzyme DNA Helicase do?

Answer 34

DNA helicase is an enzyme that breaks hydrogen bonds between nitrogenous bases in a double helix of DNA so that it will unzip and expose its bases.

Question 35

What does the enzyme DNA polymerase do?

Answer 35

DNA polymerase is an enzyme that catalyses the condensation reactions between nucleotides in the new strands of DNA.

Question 36

Isotopes of which element were used to prove semi-conservative replication? and which isotopes if this element were used?

Answer 36

Nitrogen | N^14 and N^15

Question 37

Explain how Meselson's and Stahl's experiment acted as evidence for semi conservative replication

Answer 37

In the experiment bacteria was grown in dishes containing nitrogen 14 (light nitrogen) and nitrogen 15 (heavy nitrogen). As the two samples of bacteria grew they took up nitrogen from the dishes to help make new nucleotides for new DNA so the nitrogen gradually became part of the bacterias DNA. A sample of each of the bacteria was taken and spun in a centrifuge . The DNA from the bacteria grown in the heavy nitrogen (15^N) settled lower in the tube than the DNA from the bacteria grown in light nitrogen (14^N) Next the DNA grown in the heavy nitrogen were transferred to a dish containing light nitrogen. The bacteria were left in this light nitrogen for enough time to allow the DNA to replicate once. Another DNA sample was taken and spun in the centrifuge. If the conservative model was correct then there would have been two layers of DNA one off heavy at the bottom made of purely original material and then a layer of light at the top made of purely new material. If the conservative model was correct and there was now one strand of original and one strand of new material in each helix of DNA then theoretically it should have settled in around the middle of the tube between where the 14^N had settled and the 15^N had settled. The result was that it settled in the middle proving the semi-conservative model.

Question 38

What is a purine?

Answer 38

A purine is a nitrogenous base it consist of two rings.

Question 39

Which two of the nitrogenous bases in DNA are purines?

Answer 39

Adenine | Guanine

Question 40

What is a pyrimidine ?

Answer 40

A pyrimidine is a nitrogenous base that consists of a singe ring

Question 41

Which two nitrogenous bases are pyrimidines?

Answer 41

Thymine | Cytosine