DNA, RNA, Transcription and Translation

Question 1

What are genes made of?

Answer 1

A single DNA molecule exists as a double helix.

Question 2

What is 1 DNA molecule made of?

Answer 2

2 polynucleotide chains, 2 strands, twisted clockwise around each other and are anti-parallel.

Question 3

What are polynucleotides?

Answer 3

Chains of nucleotides: A,T,G,C,U.

Question 4

How are 2 single-stranded DNA molecules held together?

Answer 4

By bonds between complimentary bases;

Question 5

What is a nucleotide composed of?

Answer 5

Nitrogenous base + pentose + phosphate group

Question 6

What are differences between DNA and RNA?

Answer 6

1. DNA: the 5-carbon-sugar is deoxyribose (H-OH)
   RNA: the 5 -carbon-sugar is ribose (OH-OH)
   2.DNA: Thymine (with adenine)
   RNA: Uracil (with adenine)

Question 7

Define a phosphodiester linkage.

Answer 7

It is a link between the phosphate groups of 1 nucleotide and the hydroxyl group of another nucleotide to form a single-stranded DNA molecule.

Question 8

Why are A and T complimentary bases?

Answer 8

1. 2 hydrogen bonds

2. A is bigger (2 rings) and T is smaller (1 ring).

Question 9

Why are C and G complimentary bases?

Answer 9

1. 3 hydrogen bonds

2. G is bigger (2 rings) and C is smaller (1 ring).

Question 10

What do genes do?

Answer 10

• Specify genetic information
• Control other genes
• Make RNA (transcription)

Question 11

What are the types of RNA that play a role in protein synthesis?

Answer 11

rRNA (ribosomal), tRNA (transfer), mRNA (messenger)

Question 12

What is the function of rRNA?

Answer 12

It combines with proteins to form proteins to form ribosomes. Nucleolus is the site of rRNA synthesis.

Question 13

What is the function of tRNA?

Answer 13

It carries the amino acids used to synthesize proteins and brings them to the ribosome.

Question 14

What is the function of mRNA?

Answer 14

It specifies the order of amino acids during protein synthesis.

Question 15

What are other classes of proteins?

Answer 15

Protective, Regulatory, Enzymes, Motile, Structural, Storage, Transport.

Question 16

What is transcription?

Answer 16

Using DNA as a template to make RNA (in other words, RNA synthesis)

Question 17

What is transcribed?

Answer 17

• Only genes (start at promoter; end at terminator)

- 1 strand of DNA

Question 18

Where are the new nucleotides added?

Answer 18

To the 3’ end of RNA (which is anti-parallel with DNA)

Question 19

Describe the functions of RNA polymerase in transcription.

Answer 19

• unwinds ans separates ds DNA into ss
• reads DNA template (strand)
• adds RNA nucleotides (complimentary) to the 3’ end of the growing RNA.
• recognizes promoter and terminator (with help of transcription factors)

Question 20

What is different in eukaryotic transcription that is not necessary in prokaryotic transcription?

Answer 20

• RNA polymerase needs transcription factors to find DNA and promoter/terminator
• 5’ cap added to 5’end of RNA
• Introns are removed from pre-mRNA to make mRNA
• Poly-A-tail is added to the 3’ end of RNA

Question 21

Define 5’ cap.

Answer 21

A modified guanine that is added to protect RNA from breakage and to help transport RNA out of nucleus.

Question 22

Define poly-A-tail.

Answer 22

Many adenine molecules.

Question 23

True or False. Only mRNA can be translated?

Answer 23

True. pre-mRNA is made during transcription, but it needs to undergo RNA processing where the introns are removed + 5’ cap + poly-A-tail to make it mRNA and be translated.

Question 24

During transcription, is the promoter transcribed?

Answer 24

No! Starts after the promoter.

Question 25

What is translation?

Answer 25

Using mRNA as a template to make proteins comprised of amino acids (20).

Question 26

Define codon.

Answer 26

A serie of 3 joined nucleotides that codes for an amino acid.

Question 27

What does the ribosome do in translation?

Answer 27

• It holds and captures mRNA
• Reads mRNA from 5’ to 3’
• Translates 3 nucleotides into 1 amino acid.

Question 28

Where does translation start and where does it end?

Answer 28

Start: AUG codon closest to 5’ end of mRNA
End: STOP codon (UAA, UAG, UGA)

Question 29

Describe the initiation step.

Answer 29

1. mRNA joins with ssu at 5’ end of untranslated region
2. MET-tRNA attaches to start codon (AUG on mRNA)
3. Lsu attaches and MET is at P site.

Question 30

Describe the elongation step.

Answer 30

1. Codon at A site recognized by anti-codon (tRNA)
2. Peptide bond forms between aa at A and P site.
3. Ribose moves forward on template and P moves to E.

Question 31

Describe the termination step.

Answer 31

1. STOP codon on mRNA at A-site is recognized
2. Release factor fills A-site (no aa)
3. Peptide chain is released and everything breaksdown into parts.