Gene Expression

Question 1

Gene

Answer 1

Portion of DNA providing instructions for making a functional product (RNA or Protein).

Question 2

Gene Expression

Answer 2

The flow of genetic info in cells. From DNA to RNA to protein.
Central dogma of molecular biology.

Question 3

What are the steps of Gene expression?

Answer 3

Transcription

Translation

Question 4

What are the steps of Gene expression?

Answer 4

Transcription

Translation

Question 5

What is the purpose of transcription in gene expression?

Answer 5

To copy a particular portion of the DNA nucleotide sequence (Gene) into an RNA nucleotide sequence.
3 steps:
Initiation
Elongation
Termination

Question 6

Transcription initiation

Answer 6

Cells regulate which proteins are to be produced and at what rate. 
General Transcription Factors: 
Recognize promoter.
Position RNA polymerase.
Unwind DNA.
Release RNA polymerase.

Question 7

Distal gene regulating protein

Answer 7

Activation | Repression of specific genes. (Part of initiation transcription).

Question 8

Promoter

Answer 8

Stretch of DNA upstream from a gene.

Question 9

Transcription Elongation

Answer 9

-Capping of the 5’ end of the RNA with a modified guanine nucleotide, in order to protect the 5’ end and so that ribosome can recognize it.
-Splicing: Removal of introns leaving the exons(contain the info to make protein).
Position of the 3’ end of each mRNA is specified by a signal encoded in the genome. The signals are transcribed into RNA and recognized by RNA-processing enzymes.
- RNA cleaved at the 3’ end, Poly-A polymerase added on. 200-300 Adenine nucleotides added to primary transcript. Important for translation and stability of mRNA.

Question 10

Transcription termination

Answer 10

Unprotected RNA attached to RNA polymerase (no 5’ cap). RNA is degraded an exonuclease which causes the RNA polymerase to
dissociate from the DNA.

Question 11

RNA polymerase

Answer 11

Enzyme that performs transcription.

Unwinds DNA, immediate release of RNA, synthesis in 5’ to 3’ direction.

Question 12

Translation

Answer 12

Passage of info encoded in the mRNA into a protein sequence.

Question 13

Genetic code

Answer 13

Set of rules that assign how the 4 letter co code of DNA can be translated in the 20 letter language of proteins.

• Universal: all living organism use the same code.
• Unambiguous: each codon codes for 1 amino acid, or a START or STOP signal.
• Redundant: most AA are encoded by more than one codon

Question 14

mRNA in translation

Answer 14

Specify the sequence of the proteins.

Question 15

Ribosome in translation

Answer 15

Catalyze formation of peptide bonds.
Site of translation.
A site: bind to a tRNA loaded with an amino acid.
P site: contains the tRNA with the growing polypeptide chain attached
E site: contain the tRNA without an amino acid, which is ready to exit.

Question 16

tRNA in translation

Answer 16

Anticodon reads the codon on mRNA to specify which amino acids should be brought into the ribosome. Attached to the 3’ end.

Question 17

Codon

Answer 17

3 nucleotide sequence.
mRNA is composed of 4 letters
and needs codons to code for 20 amino acids.
64 codons for 20 AA.

Question 18

Translation initiation

Answer 18

Initiatior tRNA binds to the small subunit of the ribosome. Binds to the 5’ end of mRNA. Finds start codon and binds. Large subunit of ribosome recruited to form initiation complex (initiator tRNA in P site). Protein synthesis can begin.

Question 19

Translation Elongation

Answer 19

Codon recognition.
New tRNA enter A site.
Formation of peptide bonds.
Translocation: tRNA in A site with protein attached. in P site the protein is released and in E site tRNA leaves the ribosome.

Question 20

Translation Termination

Answer 20

Stop codon enters A site.
Codon recognized by a releasing factor.
Ribosome adds water molecule instead of amino acid, releasing the newly synthesized protein.
Ribosome dissembles.