2.3 Nucleic Acids

Question 1

What is the structure of a purine base?

Answer 1

2 carbon-nitrogen rings

Question 2

What is the structure of a pyrimidine base?

Answer 2

1 carbon-nitrogen ring

Question 3

How many hydrogen bonds form between Adenine and Thymine

Answer 3

2

Question 4

How many hydrogen bonds form between Cytosine and Guanine

Answer 4

3

Question 5

What is the difference between a DNA and RNA nucleotide?

Answer 5

DNA- Deoxyribose pentose sugar and A,T,C,G

RNA- Ribose pentose sugar and A,U,C,G (Uracil)

Question 6

1 DNA molecule consists of _ anti-parallel polynucleotide strand(s).

Answer 6

2

Question 7

What bond is formed/broken when polynucleotides are made or broken?

Answer 7

Phosphodiester

Question 8

What gives DNA molecules stability?

Answer 8

The double helix created by hydrogen bonds and the sugar-phosphate backbone

Question 9

What is the structure of ATP and ADP?

Answer 9

Ribose pentose sugar, nitrogenous base adenine and 2/3 phosphate groups

Question 10

Why is it important that the DNA molecule is stable?

Answer 10

To protect the coded genetic information and base sequence

Question 11

What are the complementary base pairs?

Answer 11

A-T and C-G

Question 12

How is DNA organised in Eukaryotes?

Answer 12

Each DNA molecule is wrapped around a histone protein into a chromosome.
A loop of DNA inside mitochondria and chloroplasts

Question 13

How is DNA organised in Prokaryotes

Answer 13

In a loop of ‘naked’ DNA

Question 14

How can you purify and extract DNA?

Answer 14

Precipitation

Question 15

What is precipitation?

Answer 15

Macerate the tissue, add a strong detergent then add ethanol so the DNA precipitates out of solution

Question 16

What does DNA polymerase do?

Answer 16

An enzyme that catalyses the addition of new nucleotide bases, in the 5’ to 3’ direction to the single unzipped DNA strand

Question 17

What does DNA helicase do?

Answer 17

An enzyme that catalyses breaking the hydrogen bonds between DNA polynucleotide strands

Question 18

What is semi-conservative replication?

Answer 18

How DNA replicates, making 2 new molecules, each containing 1 old strand and 1 new strand- 1 old strand is conserved in each molecule

Question 19

What is a genome?

Answer 19

All the DNA within a cell

Question 20

What is the 1st thing a DNA molecule must do before it can replicate?

Answer 20

Unwind the double helix, catalysed by DNA gyrase and unzip, catalysed by DNA helicase

Question 21

How is the leading strand synthesised?

Answer 21

Continuously

Question 22

How is the lagging strand synthesised?

Answer 22

In Okazaki fragments discontinuously, that are later joined by DNA ligase

Question 23

What are different versions of the same gene called?

Answer 23

Alleles

Question 24

What is a gene?

Answer 24

A section of DNA that codes for a particular protein

Question 25

What is a base triplet (codon)?

Answer 25

3 DNA bases which code for an amino acid

Question 26

How is the genetic code non-overlapping?

Answer 26

It is read from start to finish in triplets, and each triplet is read separate from the ones before and after

Question 27

How is the genetic code degenerate?

Answer 27

There are more than 1 base triplet for each amino acid, reducing effect of point mutation

Question 28

How is the genetic code universal?

Answer 28

Because in all organisms the same triplet codes for the same amino acid

Question 29

How does a gene determine the protein structure?

Answer 29

The order of nucleotide bases in a gene determines the order of amino acids in a protein (primary structure)

Question 30

What are the roles of RNA polymerase in protein synthesis?

Answer 30

• It’s an enzyme that attaches to DNA at the beginning of a gene to begin transcription
• It catalyses formation of temporary hydrogen bonds between RNA nucleotides and the unpaired DNA bases.

Question 31

What is messenger RNA (mRNA) for?

Answer 31

It carries the genetic code from the DNA in the nucleus to the ribosomes in the cytoplasm.

Question 32

What is transfer RNA (tRNA) for?

Answer 32

To carry amino acids that are used in protein synthesis to ribosomes during translation

Question 33

What is the structure of transfer RNA (tRNA)?

Answer 33

It has an amino acid binding site at one end and an anticodon (sequence of 3 bases) on the other end

Question 34

Where is tRNA found?

Answer 34

Cytoplasm

Question 35

What does ribosomal RNA (rRNA) do?

Answer 35

• It forms the 2 subunits of a ribosome alongside proteins

- rRNA catalyses formation of peptide bonds

Question 36

What is transcription for?

Answer 36

To make an mRNA copy of a gene in the nucleus

Question 37

What is translation for?

Answer 37

Amino acids are joined together to make a polypeptide following the mRNA codon sequence

Question 38

During transcription, one DNA strand acts as a _______ to make an mRNA copy.

Answer 38

Template

Question 39

What does RNA polymerase do in transcription?

Answer 39

Lines up free RNA nucleotides alongside the template strand, making the mRNA strand a complementary copy of the DNA template strand, and catalysing temporary hydrogen bonds between RNA nucleotides and DNA bases

Question 40

What happens in translation?

Answer 40

mRNA attaches to a ribosome, and a tRNA that’s complementary to the starting codon attaches to mRNA by complimentary base pairing, until many tRNA’s have joined similarly and rRNA catalyses formation of pepide bonds between the amino acids, and the tRNA moves away leaving a polypeptide chain