Tutorial #19: From Gene to Protein (transcription and translation)

Question 1

What is the central dogma (prevailing theme) of molecular biology?

Answer 1

DNA is transcribed to mRNA which is then translated into proteins.

DNA>RNA>PROTEIN!

Question 2

Template strand

Answer 2

The strand of DNA that is used as a template to make messenger RNA (mRNA).

Question 3

Coding strand

Answer 3

The other strand of DNA (not the template strand). This strand is identical to the mRNA made from the template strand except for the substitution of all Thymine nucleotides to Uracil.

Question 4

Where does transcription happen in eukaryotic cells?

Answer 4

The nucleus

Question 5

Where does translation happen in eukaryotic cells?

Answer 5

At a ribosome

Question 6

Genetic code

Answer 6

The sequence of nucleotides in DNA and RNA that determines the amino acid sequence of proteins.

Question 7

Codon

Answer 7

A specific sequence of three consecutive nucleotides on a mRNA molecule that corresponds to a specific amino acid or a stop signal during the translation of a protein.

Question 8

“Genetic code is said to be both unambiguous and redundant.”

What does this mean?

Answer 8

• “unambiguous” means that the codons are fixed and that each codon specifies only one amino acid.
• “redundant” means that several codons code for the same amino acid.

Question 9

Transcription

Answer 9

• The first stage of protein synthesis where one of the two strands of DNA (the template strand) is transcribed into a single strand of complementary RNA termed mRNA.
• happens in the nucleus
• RNA polymerase, with the help of transcription factors, binds to the promoter region of the gene and separates the two strands of DNA. RNA polymerase then reads the template strand from 3’ to 5’ and builds the complimentary strand of mRNA in the 5’ to 3’ direction, adding RNA nucleotides to the 3’ end as it goes.
• RNA polymerase zips the DNA double helix back up as it goes, keeping only 10-20 base pairs exposed at a time.
• once RNA polymerase reaches the end of the gene, termination occurs; the enzyme detatches from the gene and the DNA is returned to its original state.

Question 10

mRNA

Answer 10

(Messenger RNA) caries the code found in the gene

Question 11

Translation

Answer 11

• happens at a ribosome
• during translation, the mRNA acts as a code for a specific protein. This happens because each set of three bases on the mRNA (called a codon) will code for a specific anticodon, which will be carried by tRNA (each different tRNA is covalently linked to a particular amino acid)

Question 12

Reading frame

Answer 12

Refers to the arrangement of the nucleotides on a strand of mRNA into codons