Structure of Ribonucleic Acid ( 2 )

Question 1

When is mRNA made?

Answer 1

During transcription

Question 2

What is the purpose of mRNA?

Answer 2

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

Question 3

What process is tRNA involved?

Answer 3

Translation

Question 4

What is the purpose of tRNA?

Answer 4

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

Question 5

What bonds hold the molecule in its shape?

Answer 5

Hydorgen molecules

Question 6

What is the structure of the tRNA molecule?

Answer 6

• Anticodon at one end

* Amino acid binding site at another end

Question 7

What occurs during transcription?

Answer 7

• Transcription starts when RNA polymerase attaches to the DNA double helix at the beginning of a gene
• The hydrogen bonds between the two DNA strands in the gene break, separating the strands, and the DNA molecule uncoils at that point, exposing some of the bases
• One of the strands is then used as a template to make mRNA copy
• RNA polymerase lines up free RNA nucleotides along the exposed bases on the template strand, free bases are attracted to the exposed bases, specific complementary base pairing means that the mRNA strand ends up being a complementary copy of the DNA template strand ( T base replaced by U in RNA )
• One of the RNA nucleotides have paired up with their specific bases on the DNA strand, joined together by RNA polymerase, forming an RNA molecule
• RNA polymerase moves along the DNA separating the strands and assembling the mRNA strand
• Hydrogen bonds between the uncoiled strands of DNA re-form once the RNA polymerase has passed by and the strands coil back into a double helix
• When RNA polymerase reaches a stop signal on the DNA, it stops making mRNA and detaches from the DNA

Question 8

When does the RNA polymerase stop making DNA?

Answer 8

When it reaches a place called the stop signal on the DNA, it stops making mRNA, and detaches from DNA.

Question 9

What separates strands and assembles the mRNA molecule?

Answer 9

RNA polymerase

Question 10

What is the purpose of RNA polymerase?

Answer 10

• RNA polymerase lines up free RNA nucleotides along the exposed bases on the template strand
• RNA polymerase moves along the DNA separating the strands and assembling the mRNA strand

Question 11

How are the strands separated?

Answer 11

• Hydrogen bonds between the two DNA strands in the gene break
• Separating the strands, and the DNA molecule uncoils at that point
• Exposing the bases

Question 12

How is the mRNA copy made?

Answer 12

One of the strands is used as a template to make an mRNA copy

Question 13

Why is the mRNA strand a complementary copy of the DNA molecule?

Answer 13

• Complementary base pairing

Question 14

What happens when RNA nucleotides have paired up?

Answer 14

• When they are paired up with specific bases on the DNA strand, they are joined together by RNA polymerase
• Forming an mRNA molecule

Question 15

What binds the nucleotides and specific bases on the DNA strand?

Answer 15

RNA polymerase

Question 16

When do hydrogen bonds between uncoiled strands of DNA reform?

Answer 16

Once the RNA polymerase has passed by the strands, they then coil back into a double helix

Question 17

What is the purpose of the stop signal?

Answer 17

Stops the RNA polymerase from making mRNA and causes it to detach from the DNA molecule

Question 18

How does the mRNA move in eukaryotes?

Answer 18

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