Gene transcription and translation

Describe the Central Dogma of Life

• DNA> Transcription > RNA > translation > Protein

• RNA> translation> DNA> transcription > Protein

• Protein> translation>RNA> translation> DNA

• DNA> translation>RNA>transcription> Protein

Unlike DNA polymerase, RNA does not need ___ to start

• Ligase

• Primer

• Helicase

• Histones

Which are the three STOP codons?

• UCU, UCC, UCA

• UAA, UAG, UGA

• CGU, CGC, CGA

• GGU, GGC, GGA

Answer explanation

These codons do not code for any amino acid but instead signal the termination of translation.

What is the start codon?

(a)  

Answer explanation

AUG also codes for the amino acid (Met), but if encountered in conjunction with other signals, AUG also indicates the start of translation.

What carries amino acids to the ribosome, the site of protein synthesis?

(a)  

Answer explanation

Each tRNA molecule has a specific amino acid attached to one end and an anticodon attached to the other end. The nucleotides in the anticodon pair with the complementary codons on the mRNA in antiparallel orientation (codon: 5'-GCU-3' pairs with anticodon: 3'-CGA-5').

Aminoacyl-tRNA synthetases do what?

• Enzymes that join ribosomes to tRNAs

• Enzymes that synthesize tRNA

• Enzymes that charge tRNA molecules with their appropriate amino acid

Answer explanation

Match the appropriate ribosome sites to their specific function:

(1) where the charged tRNA carrying the next AA to be added enters

(2) where the growing polypeptide chain is held by the tRNA

(3) where the tRNA exits

• (1) A site: Aminoacyl-tRNA binding site

  (2) P site: Peptidyl-tRNA binding site

  (3) E site: Exit site

• (1) P site: Peptidyl-tRNA binding site

  (2) A site: Aminoacyl-tRNA binding site

  (3) E site: Exit site

• (1) E site: Exit site

  (2) A site: Aminoacyl-tRNA binding site

  (3) P site: Peptidyl-tRNA binding site

Answer explanation

Which of the following are subtypes of chromosomal mutations?

• germline, somatic, point

• missense, nonsense, silent

• duplications, deletions, inversions, translocations

Answer explanation

DNA mutations: germline (occurs in cells that produce gametes); somatic (occur in non-gamete cells); point (single base pair is altered)

Point mutations (single nucleotide): transition (purine for purine, pyrimidine for pyrimidine); transversion (pyrimidine for purine, purine for pyrimidine); missense (new nucleotide alters codon to produce diff. AA); nonsense: (changes a codon so that chain termination occurs); silent (doesn't change AA)

Frameshift mutations (1/more nucleotides, shift over)

Chromosomal mutations (large scale): duplications (doubling of genome section-result of unequal crossing over); deletions (result of chromosome breaking at 2 points and rejoining causing deletion of DNA at breaking point); inversions (piece of chromosome breaks off and reattaches in reverse direction); translocations (piece of chromosome is abnormally moved to another location on another chromosome)

A sequence of RNA shown below

5' CAA AAU GCG AUC 3'

• His-Asn- Ala-Met

• Val-Leu-Arg-Stop

• Gln-Asn-Ala-Ile

• Gln-Asn-Pro-Tyr

Protein Subunit that binds to the core RNA polymerase to create what is known as the RNA polymerase holoenzyme. Binds to the promotor to initiate transcription (in prokaryotes)

• Beta

• Sigma

• Alpha

• Gamma