PROTEINS

Question 1

What is transcription?

Answer 1

Production of mRNA from DNA.

Question 2

What is the process of transcription?

Answer 2

• DNA strand unwinds and unzips by DNA helicase
• Instead of a new DNA strand being formed, RNA nucleotide bases pair up with the exposed
DNA bases
• An enzyme called RNA polymerase forms covalent bonds between the nucleotide bases
• Unlike DNA, RNA is single-stranded
• A messenger RNA (mRNA) strand is formed and breaks away from the DNA which then rezips
itself up thanks to the natural formation of hydrogen bonds
6. mRNA is now free to migrate out of the nucleus through nuclear pores

Question 3

What enzyme unzips DNA strand?

Answer 3

DNA helicase

Question 4

What is the purpose of the enzyme RNA polymerase?

Answer 4

RNA polymerase forms covalent bonds between the nucleotide bases

Question 5

How does the mRNA leave the nucleus?

Answer 5

Through the nuclear pores

Question 6

How does DNA differ from RNA?

Answer 6

It is single stranded

Question 7

What forms covalent bonds between nucleotide bases?

Answer 7

Enzyme called RNA poylermase

Question 8

What does a gene code for?

Answer 8

• Amino acid sequence of a polypeptide

* A functional RNA ( including ribosomal RNA and tRNAs )

Question 9

Where is a gene present?

Answer 9

A gene occupies a fixed position called a locus on a DNA molecule.

Question 10

What is a triplet?

Answer 10

Sequence of three DNA bases

Question 11

What does a triplet do?

Answer 11

codes for a

specific amino acid

Question 12

What are some features of triplets?

Answer 12

The genetic code is universal, non-overlapping

and degenerate.

Question 13

What is the genome?

Answer 13

Complete set of genes in a cell

Question 14

What is the proteome?

Answer 14

Full range of proteins that a cell is able to produce

Question 15

What is the purpose of RNA polymerase?

Answer 15

Joining mRNA nucleotides

Question 16

What does transcription result in in prokaryotes?

Answer 16

Transcription results in the production of mRNA from DNA

Question 17

What does transcription result in, in eukaryotes?

Answer 17

Transcription results in the production of pre-mRNA, that is spliced to form mRNA nucleotides

Question 18

What is translation?

Answer 18

production of polypeptides from the sequence of codons carried by mRNA

Question 19

What is the process of translation?

Answer 19

1. Once mRNA has left the nucleus, it attaches to a ribosome on the rough endoplasmic
   reticulum
2. Transfer RNA (tRNA) carries the corresponding amino acid to each on the mRNA
3. The anti-codon is a triplet of bases that form part of a tRNA molecule and ensure that the
   correct amino acid is joined onto the polypeptide chain
4. This process is active and requires ATP
5. The amino acid transported by the tRNA attaches to the ribosome
6. Adjacent amino acids join together by peptide bonds, creating a polypeptide chain
7. This process continues until the ribosome reaches a ‘stop’ codon (triplet) on the mRNA. At
   this point, the polypeptide breaks loose from the ribosome and is free.

Question 20

What occurs in prokaryotic transciption?

Answer 20

• mRNA directly produced from DNA

Question 21

What occurs in eukaryotic transcription?

Answer 21

• DNA is first copied into pre-mRNA
• May contain pieces of non-useful polynucleotide
• pre-mRNA is spliced into mRNA
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