Nucleic acids - structure and function

Question 1

Where is DNA mainly found?

Answer 1

In the cells nucleus

Question 2

What does the backbone of DNA consist of?

Answer 2

Deoxyribose’s

Question 3

How is the double-stranded DNA structure held together?

Answer 3

By hydrogen bonding

Question 4

What shape does two chains of DNA wrapped round each other make?

Answer 4

Regular double helix structure (spiral)

Question 5

What base does Guanine always pair with in DNA?

Answer 5

Cytosine

Question 6

What does Adenine always pair with in DNA?

Answer 6

Thymine

Question 7

What is the general structure of RNA?

Answer 7

• same 5’-3’ backbone as DNA

Question 8

Where is RNA mainly found?

Answer 8

In the cytoplasm

Question 9

How does RDA differ from DNA?

Answer 9

1. Uracil replaced Thymine as a base
2. Ribose replaces deoxyribose
3. Single-stranded (no base pairings)

Question 10

What is a ‘hairpin loop’?

Answer 10

Local double strand formation occurring in a single strand of RNA

Question 11

What are the 3 types of RNA?

Answer 11

• Messenger RNA (5%)
• Transfer RNA (15%)
• Ribosomal RNA (80%)

Question 12

What does the base sequence of DNA contain in all cells?

Answer 12

The genetic code

Question 13

What are genes?

Answer 13

Specific stretches of DNA which code for a protein

Question 14

What is the AA sequence of each protein determined by?

Answer 14

Nucleotide sequence of its corresponding gene

Question 15

What is the whole genetic information within a single cell nucleus called?

Answer 15

The genome

Question 16

What is involved in the process of transcription and translation?

Answer 16

1. In the nucleus DNA unfolds to expose base pairs of template strand
2. Transcription: RNA polymerase copies sequence of bases in template strand of DNA to produce mRNA
3. mRNA translated by tRNA, using ribosome as a functional support in the cytoplasm

Question 17

What is a codon?

Answer 17

Sequence of 3 bases in mRNA

Question 18

What are ribosomes?

Answer 18

Small and large subunits, contain proteins and rRNA - act as a functional support and process of translation

Question 19

What is tRNA’s role in translation?

Answer 19

• Carries each amino acid to ribosome (one specific tRNA for each amino acid)
• Contains anticodon (3 bases) complimentary to sequence of 3 bases (codon) on mRNA
• AA transferred to growing polypeptide chain
• Sequence of mRNA codons determines sequence of AA in a protein

Question 20

How many possible codons are there?

Answer 20

64 possible codons

Question 21

How many amino acids exist?

Answer 21

20 possible amino acids

Question 22

What is meant by the genetic code being ‘degenerate’?

Answer 22

Some amino acids have more than 1 tRNA and hence more than one coding triplet - can be coded for by more than 1 codon

Question 23

How do many degenerate codons differ?

Answer 23

Many codons specifying the same AA are grouped together, differing only in the 3rd base position e.g. Phe = UUU and UUC

Question 24

What AA is known as the ‘universal start codon’?

Answer 24

Met

Question 25

What 3 codons are known as ‘stop’ codons?

Answer 25

UAA, UAG, UGA