Protein Synthesis & Transcription

Question 1

What are the different types of RNA made in the nucleus?

Answer 1

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

Question 2

What type of RNA is formed in the nucleus in the same way as DNA is replicated?

Answer 2

• mRNA

Question 3

What is the process of mRNA formation called?

Answer 3

• transcription

Question 4

What is transcription?

Answer 4

• the process by which DNA makes and codes mRNA

Question 5

How does the process of transcription start?

Answer 5

• when a small piece of DNA, a gene, unwinds

Question 6

What catalyses the initial unwinding of a gene in transcription?

Answer 6

• the enzyme RNA polymerase

Question 7

What does RNA polymerase specifically do?

Answer 7

• causes the 2 strands of DNA to separate
• by breaking the hydrogen bonds between complementary DNA nucleotides

Question 8

What happens during transcription after the gene unwinds?

Answer 8

• the polymerase attaches to and moves along one of the DNA strands
• causing new nucleotides to pair up with their complementary nucleotides

Question 9

What happens during transcription after the new nucleotides pair up with their complementary nucleotides?

Answer 9

• the nucleotides join up
• a sugar-phosphate backbone is added
• a new strand of mRNA is formed

Question 10

What is the sequence of nucleotides in a strand of mRNA determined by?

Answer 10

• the sequence of the template DNA nucleotides

Question 11

What happens after a completed mRNA strand is formed during transcription?

Answer 11

• it breaks away from the DNA
  p the DNA then re-zips

Question 12

What happens to the newly formed strand of mRNA after transcription has occurred?

Answer 12

• it moves through the pores of the nuclear membrane
• carries the genetic code to the ribosomes
• which are the sites of protein synthesis

Question 13

What is a protein?

Answer 13

• a long chain (polymer) of small units (monomers) called amino acids

Question 14

How many different amino acids are there involved in protein synthesis?

Answer 14

• 20

Question 15

What determines the kind of protein that is made?

Answer 15

• the order in which the amino acids are linked

Question 16

What is the sequence of amino acids determined by?

Answer 16

• the instructions from the genetic code in the DNA molecules
• which is passed on to mRNA

Question 17

What is a genetic code?

Answer 17

• a sequence of codons

Question 18

What is a codon?

Answer 18

• codon is a sequence of three nucleotides in DNA that codes for an amino acid or a stop signal in protein synthesis

Question 19

How many different codons are there and how many form proteins?

Answer 19

• 64 different codons
• all except 3 code for one of the 20 amino acids used to form proteins

Question 20

What is the basis of the genetic code?

Answer 20

• the triplet code of bases

Question 21

What is a gene made up of?

Answer 21

• a group of codons that code for the synthesis of one protein

Question 22

What does the order of codons in mRNA determine?

Answer 22

• the sequence of the amino acids
• which determines which protein is made