RNA and Protein Synthesis

Question 1

Properties of RNA

Answer 1

• Single polynucleotide strand
• Contains uracil as a base instead of thymine
• pairs up with adenine

Question 2

What are the two types of RNA?

Answer 2

• mRNA- Messenger RNA
• tRNA - Transfer RNA

Question 3

What is mRNA made in?

Answer 3

Made during transcription

Question 4

What is the function of mRNA?

Answer 4

Carries the genetic code from the DNA to ribosomes

where it is used to make protein during translation

Question 5

What is the structure of mRNA?

Answer 5

• Single polynucleotide strand

Question 6

What are codons in mRNA?

Answer 6

Groups of three adjacent bases are called codons e.g sometimes called triplet/base triplet

Question 7

What is tRNA involved in?

Answer 7

Translation

Question 8

What is the function of tRNA?

Answer 8

It carries the amino acids that are used to make proteins to the ribosomes

Question 9

Structure of tRNA

Answer 9

• Single polynucleotide strand that is folded into a clover shape
• Hydrogen bonds between base pairs hold the molecule in space
• Each one has a specific sequence of three bases at one end called anticodon
• Also amino acid binding site on other end

Question 10

What generally happens during transcription?

Answer 10

mRNA copy of a gene is made from DNA

Question 11

Where does transcription take place in a eukaryotic cell?

Answer 11

Nucleus

Question 12

Where does transcription take place in a prokaryotic cell?

Answer 12

Cytoplasm - has no nucleus

Question 13

Instructions of transcription

Answer 13

1. RNA polymerase attaches to DNA double-helix at the beginning of a gene
2. Hydrogen bonds between DNA strands in gene break, separating strands and uncoil to expose some bases
3. One of the strands is used as a template for mRNA copy
4. RNA polymerase line up free RNA nucleotide, complementary base pairing
5. Joined together by RNA polymerase to form mRNA
6. RNA polymerase moves along the DNA, assembling the mRNA strand
7. Hydrogen bonds between uncoiled strands coil to make a double helix
8. RNA polymerase reach particular sequence - stop signal, detaches from DNA

Question 14

What happens at the end stage of transcription for eukaryotic cells?

Answer 14

• Introns and exons are both copied into mRNA during transcription
• mRNA containg introns and exons - pre-mRNA
• Spilicing - introns removed , exons joined to form mRNA strand
• mRNa moves out of the nucleus through nuclear pore , attach to ribosome in cytoplasm

Question 15

What happens to the end of transcription for prokaryotic cell?

Answer 15

• mRNA is produced directly from DNA - without spilcing as there is no introns

Question 16

Where does translation occur in eukaryotic and prokaryotic cells?

Answer 16

Ribosomes and cytoplasm

Question 17

What happens during translation?

Answer 17

Amino acids are joined together to make a polypeptide chain

following a sequence of codons (triplets) carried by the mRNA

Question 18

Steps of translation

Answer 18

1. mRNA attach itself to ribosome and transfer RNA molecules to carry amino acids
2. ATP provides energy needed for the bond between amino aicd and tRNA to form
3. tRNA carry amino acid with anticodon that is complementary to first codon on mRNA - bind with specific base pairing
4. Second tRNA attach to neext codo on mRNA in same way
5. Two amino acida attach to tRNA joined by peptide bond
6. First tRNA molecule moves away , leaving amino acid
7. Third tRNA molecule binds to next codon on mRNA , binds to first two amino acid and second tRNA molecule moves away
8. Continues until there is a stop signal in mRNA
9. Polypeptide moves away from ribosome