6.2 Transcription: Synthesizing RNA from DNA (CQ - exam)

Question 1

3 differences between DNA and RNA.

Answer 1

1. DNA has thymine and RNA has uracil
2. DNA is double stranded, RNA is single stranded
3. DNA has genetic info, RNA has info about protein structuralization

Question 2

How is RNA involved in protein synthesis?

Answer 2

ribosomes will decode mRNA—a type of RNA—to assist with making proteins. basically has the instructions of making amino acids, then the amino acids are synthesized into proteins

Question 3

three stages of transcription

Answer 3

1. Initiation of Transcription
   - RNA polymerase binds to the DNA template strand at the promoter region, then unwinds a section of the double helix
2. Elongation of mRNA
   - RNA polymerase builds mRNA in 5’ to 3’ direction
   - Moves along the DNA
3. Termination
   - When the RNA polymerase reaches the end of the gene, it reaches a terminator sequence that indicates for mRNA to be released
   - Double helix DNA reformed.

Question 4

Predict where mRNA is transported in the cell after transcription is finished. Why?

Answer 4

mRNA is transported to the ribosome for decoding

Question 5

How do cells synthesize multiple strands of mRNA from one gene simultaneously? Why is this advantageous?

Answer 5

• When it binds to the promoter, more can bind behind it,
• As long as you can fit another, it is possible
• It is beneficial because it is greatly efficient

Question 6

Are errors in transcription more or less damaging than errors in DNA replication?

Answer 6

• Error in DNA replication impacts the genome of the cell
• Therefore this is more damaging
• Transcription effects a single protein

Question 7

five ways that transcription differs from DNA replication

Answer 7

1. Transcription requires mRNA, and DNA replication requires DNA
2. Transcription forms a single stranded, and DNA replication forms 2 identical strands
3. Transcription uses uracil, and DNA replication uses thymine
4. Transcription has RNA polymerase, and DNA replication uses helicase, DNA polymerase, etc.
5. Transcription does not use primers.

Question 8

What is the promoter region? Why are promoter regions necessary for transcription?

Answer 8

The promoter region is a site where RNA polymerase binds to DNA template strands. The region contains a sequence of nucleotides that indicates if the RNA polymerase should bind.

Question 9

DNA polymerase vs RNA polymerase + similarities

Answer 9

DNA polymerase
- catalyzes the rate of DNA synthesis
- requires primers
- used in DNA replication
- has exonuclease activity

RNA polymerase
- catalyzes the rate of mRNA synthesis
- used in transcription

both
- catalysts
- in nucleus
- enzymes
- bind to strands

Question 10

In prokaryotes, protein synthesis can occur at the same time as transcription. Why is this not the case for eukaryotes?

Answer 10

In eukaryotes, it is impossible for both to occur because transcription happens in a membrane-bound nucleus. Then translation happens in the nucleus so eukaryotes are unable to occur simultaneously.

Question 11

three modifications that must occur to a precursor mRNA in Eukaryotes

Answer 11

1. Cap added
   - Allows mRNA to be recognized by protein synthesis machinery
2. Tail added
   - Protects mRNA from digestion when exiting nucleus and entering the cytoplasm
3. Introns sequence spliced out
   - If they are not removed, proteins cannot fold properly

Question 12

Why do introns exist in eukaryotic genes?

Answer 12

• Introns control transcription and allows for it to occur
• They exist to assist in the synthesis of DNA polymerase