DNA, RNA and Protein Synthesis- RNA and Protein Synthesis

Question 1

How is RNA different to DNA?

Answer 1

It is a single polynucleotide and contains uracil instead of thymine

Question 2

What does uracil pair with?

Answer 2

Adenine

Question 3

What are the 2 main types of RNA?

Answer 3

Messenger RNA (mRNA) and transfer RNA (tRNA)

Question 4

When is mRNA made?

Answer 4

During transcription

Question 5

What is the role of mRNA?

Answer 5

Carries the genetic code from the DNA to the ribosomes where it is used to make a protein during translation

Question 6

What is the structure of mRNA?

Answer 6

Single polynucleotide strand, contains codons

Question 7

What are codons?

Answer 7

Groups of 3 adjacent bases

Question 8

What is tRNA involved in?

Answer 8

Translation

Question 9

What is the role of tRNA?

Answer 9

Carries the amino acids that are used to make proteins to the ribosomes

Question 10

What is the structure of tRNA?

Answer 10

Single polynucleotide strand folded into a clover shape- held in shape by hydrogen bonds between specific base pairs

Question 11

What does every tRNA molecule have?

Answer 11

A specific sequence of 3 bases at one end called an anticodon and an amino acid binding site at the other end

Question 12

What happens during transcription?

Answer 12

An mRNA copy of a gene is made from DNA

Question 13

Where does transcription take place in eukaryotes?

Answer 13

The nucleus

Question 14

Where does transcription take place in prokaryotes?

Answer 14

The cytoplasm

Question 15

How does transcription start?

Answer 15

When RNA polymerase attaches to the DNA double helix at the beginning of a gene

Question 16

What is the role of DNA helicase?

Answer 16

Breaks the hydrogen bonds between DNA strands which separates the strands and causes DNA molecule to unravel, exposing some bases

Question 17

What is the purpose of one strand being used as a template?

Answer 17

To make an mRNA copy

Question 18

What is the role of RNA polymerase?

Answer 18

Lines up free RNA nucleotides alongside the exposed bases on the template strand and the free bases are attracted to the exposed bases

Question 19

What does complementary base pairing mean?

Answer 19

mRNA strand ends up being a complementary copy of the DNA template strand

Question 20

What happens once the RNA nucleotides have paired up with their specific bases on the DNA strand?

Answer 20

They’re joined together by RNA polymerase to form an mRNA molecule

Question 21

What does the RNA polymerase do once the mRNA molecule is formed?

Answer 21

Moves along the DNA to separate the strands and assemble the mRNA strand

Question 22

When do the hydrogen bonds between the uncoiled strands of DNA re-form?

Answer 22

Once the RNA polymerase has passed by and the strands coil back into a double helix

Question 23

What happens when RNA polymerase reaches a stop signal?

Answer 23

It stops making mRNA and detaches from DNA

Question 24

What happens in eukaryotes to allow the next stage of protein synthesis to take place?

Answer 24

mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm

Question 25

What is the process of transcription?

Answer 25

1. RNA polymerase attaches to DNA double helix at the beginning of a gene 2. Hydrogen bonds between the 2 DNA strands in the gene are broken by a DNA helicase attached to the RNA polymerase which separates the strands and the DNA molecule uncoils, exposing some bases 3. One strand used as a template to make an mRNA copy 4. RNA polymerase lines up free RNA nucleotides alongside the exposed bases on template strand, free bases are attracted to exposed bases, complementary base pairing means mRNA strand ends up being a complementary copy of DNA template strand 5. Once RNA nucleotides have paired up with specific bases on DNA strand, they're joined together by RNA polymerase, forming an mRNA molecule 6. RNA polymerase moves along DNA, separates strands and assembles mRNA strand 7. Hydrogen bonds between uncoiled strands of DNA re-form once RNA polymerase has passed by and strands coil back into a double helix 8. When RNA polymerase reaches stop signal, stops making mRNA and detaches from DNA 9. mRNA moves out nucleus through nuclear pore and attaches to a ribosome in cytoplasm

Question 26

What is pre-mRNA?

Answer 26

mRNA strands that contain exons and introns

Question 27

What is splicing?

Answer 27

Introns are removed from pre-mRNA

Question 28

What is produced in prokaryotes from transcription?

Answer 28

mRNA is produced directly without introns

Question 29

What is the final stage of transcription?

Answer 29

Pre-mRNA is spliced to make mRNA without introns

Question 30

Where does translation occur?

Answer 30

At the ribosomes in the cytoplasm

Question 31

What happens during translation?

Answer 31

Amino acids are joined together to make a polypeptide chain following the sequence of codons carried by the mRNA

Question 32

What does tRNA do when mRNA attaches itself to a ribosome?

Answer 32

Carries amino acids to it

Question 33

What is the role of ATP in translation?

Answer 33

Provides the energy needed for the bond between the amino acid and the tRNA molecule to form

Question 34

How does a tRNA molecule attach itself to mRNA?

Answer 34

Specific base pairing- the anticodon on the tRNA is complementary to the codon on the mRNA

Question 35

What happens after one tRNA molecule has attached to the mRNA molecule?

Answer 35

A second tRNA molecule attaches to the next codon

Question 36

How are the two amino acids attached to the tRNA molecule joined?

Answer 36

By a peptide bond- first tRNA molecule moves away and the amino acid is left behind

Question 37

When does the process of tRNA molecules bonding to codons stop?

Answer 37

When there's a stop signal on the mRNA molecule

Question 38

When is translation complete?

Answer 38

The polypeptide chain moves away from the ribosome

Question 39

What is the process of translation?

Answer 39

1. mRNA attaches itself to a ribosome and tRNA molecules carry amino acids to it, ATP provides energy needed for the bond between the amino acid and the tRNA molecule to form 2. tRNA molecule with an anticodon that's complementary to the first codon on mRNA, attaches to mRNA by specific base pairing 3. Second tRNA molecule attaches to next codon on mRNA in same way 4. Two amino acids attached to tRNA molecules are joined by a peptide bond, first tRNA molecule moves away and leaves amino acid behind 5. Third tRNA molecule binds to next codon on the mRNA, amino acid binds to first two and second tRNA molecule moves away 6. Process continues, produces a chain of linked amino acids (polypeptide chain) until stop signal reached on mRNA molecule 7. Polypeptide chain moves away from ribosome and translation is complete