Topic 2.1 - DNA and RNA structure

Question 1

What pentose sugar is found in DNA?

Answer 1

Deoxyribose

Question 2

What 3 components are nucleotides made of?

Answer 2

A phosphate group, a pentose sugar and an organic base

Question 3

What organic bases are in DNA?

Answer 3

A (adenine) T (thymine) C (cytosine) G (guanine)

Question 4

What pentose sugar is found in RNA?

Answer 4

Ribose

Question 5

What organic bases are found in RNA?

Answer 5

A (adenine) U (uracil) C (cytosine) G (guanine)

Question 6

Which reaction joins nucleotides together?

What molecule does it remove?

Answer 6

Condensation reactions

Water

Question 7

What bond is formed between nucleotides?

Answer 7

Phosphodiester bonds

Question 8

What does an organic base consist of?

Answer 8

Nitrogen, Oxygen, Carbon and Hydrogen

Question 9

What 3 types of RNA are there?

Answer 9

mRNA (messenger RNA)
rRNA (ribosomal RNA)
tRNA (transfer RNA)

Question 10

How many strands does DNA have?

Answer 10

2 (double)

double helix

Question 11

How many strands does RNA have?

Answer 11

1 (single)

Question 12

What type of bond forms between complimentary organic bases?

Answer 12

Hydrogen bonds

Question 13

How many bases code for 1 amino acid?

Answer 13

3 (triple code)

Question 14

What two types of alleles are there?

Answer 14

Dominant and recessive

Question 15

Who was the man that named the alleles through pea plant experiments?

Answer 15

Gregor Mendel

Question 16

What does DNA occur in?

Answer 16

Long lengths of chromosomes

Question 17

What do chromosomes consist of?

Answer 17

Genes

Question 18

What organic bases are complimentary to one another?

Answer 18

A - T
A - U
G - C

Question 19

What is the purpose of RNA?

Answer 19

allowing the genetic code to be copied/transferring genetic information for protein synthesis

Question 20

What is the purpose of DNA?

Answer 20

Holding genetic information

Cell division

Question 21

How is the double helix formed?

Answer 21

The uprights of the phosphate and deoxyribose wind round one another (sugar-phosphate backbone). Organic bases comprise rungs (bridges).

Within the double helix, they run anti-parallel to each other.

Question 22

Explain what makes the DNA a stable molecule.

in detail, not just two points

Answer 22

• hydrogen bonds (3 between G and C, 2 between A and T)
• such hydrogen bonds connect the two strands of the double helix together
• if there are more G and C pairs in DNA molecule, it is more stable as the h bonds contribute towards overall stability and strength
• phosphodiester bonded backbone protect reactive organic bases in helix
• interactive forces between base pairs that hold molecule together

Question 23

Name the man who conducted the experiment on mice with 2 strains of pneumococcus bacteria

Answer 23

Frederick Griffiths

Question 24

How are nucleotides arranged in the double helix?

Answer 24

Numbering of carbon atoms in deoxyribose sugar (3’ and 5’)

• one strand runs 5’-3’ but the other runs 3’-5’ (anti-parallel)
• 5’ carbon has phosphate group attached
• 3’ carbon has hydroxyl group attached

Question 25

What is the structure of mRNA (messenger RNA) and how is it made?

Answer 25

It is a long, single stranded molecule that's formed into a helix. It is manufactured, in the nucleus, during transcription of a strand of DNA.

Question 26

What does mRNA do?

Answer 26

It carries the genetic code from the DNA to the ribosomes in the cytoplasm, and leaves the nucleus through a nuclear pore.

Question 27

What is the structure of rRNA (ribosomal RNA)?

Answer 27

It is found in the cytoplasm and is a large, complex molecule made up of both double and single helices.

Question 28

What does rRNA do?

Answer 28

Combines with proteins to form ribosomes

Question 29

What is the structure of tRNA (transfer RNA)

Answer 29

Small single-stranded molecule that forms a clover leaf shape. - One end of the chain ends in a cytosine-cytosine-adenine sequence at which point the amino acid it is carrying attaches itself. - The other end of the chain is a sequence of three bases called the anticodon.

Question 30

What does tRNA do?

Answer 30

transport amino acids to the ribosome so proteins can be synthesised

Question 31

Where does protein synthesis take place?

Answer 31

The ribosomes

Question 32

List the order in how proteins are synthesised.

Answer 32

``` Triplet codes in a gene - Pre-mRNA - mRNA - sequence of amino acids made by ribosomes (tRNA and rRNA) - Protein ```