Week 8 - DNA translation

Question 1

What is DNA translation

Answer 1

process by which the genetic information RNA is used to synthesize proteins in ribosomes

Question 2

What is the genetic code

Answer 2

The genetic code is a set of rules that governs the translation of the nucleotide sequence of mRNA into the amino acid sequence of a protein. It tells us what sequence of mRNA is equivalent to what amino acid.

Question 3

What are the characteristics of the genetic code

Answer 3

• Redundancy - some codes equate to the same amino acid
• No ambiguity - there are no exceptions
• Non-overlapping three letter sections

Question 4

What is tRNA

Answer 4

are single RNA molecules which read mRNA than provide an Amino acid according to the genetic code

Question 5

What is the structure of tRNA

Answer 5

cloverleaf like secondary structure which consist of 3 hair pin loops when flattened. It 3D structure is not a double helix as it contains imperfect base pairs. It also contains anticodon which is complementary to each codon on the mRNA

Question 6

What is the structure of a ribosome

Answer 6

• E, P and A sites
• Facilitate coupling to tRNA to mRNA and catalyzes formation of the peptide bond
• Large and small units combine only when forming on a mRNA
• 1/3 of the mass of a ribosome is made up of RNA associated proteins

Question 7

What are the 3 steps in DNA translation

Answer 7

1. Initiation
2. Elongation cycle
3. Termination

Question 8

Explain initiation step in DNA translation

Answer 8

The small ribosomal subunit binds to the start of the RNA molecule, which is called the start codon. The start codon codes for the amino acid methionine, which is the first amino acid in the protein chain.

-A small subunit binds to the start codon AUG
- Initiation factors bind
- Large subunit assembly
- Beginning of peptide bond formation

Question 9

Explain the elongation cycle in the translation process

Answer 9

The large ribosomal subunit binds to the small subunit, and transfer RNA (tRNA) molecules bring the appropriate amino acids to the ribosome, based on the codons in the RNA sequence. The amino acids are linked together by peptide bonds to form a polypeptide chain.

• Codon recognition - the ribosome moves along the mRNA molecule (codon matching)
• Peptide bond formation - the ribosome catalyzes the formation of a peptide bond
• Translocation - the ribosome moves one codon along the mRNA sequence

The tRNA carrying the growing polypeptide chain shifts from the A site to the P site and the empty tRNA from the P site to the E site. Frees the A site.

• Release of uncharged tRNA - the empty tRNA is released from the E site
• Repeat

Question 10

Explain the termination step in DNA translation

Answer 10

Termination occurs when a stop codon (UAA, UAG, or UGA) is encountered in the mRNA sequence. Stop codons do not code for amino acids but instead signal the termination of translation.
- Release factors - proteins which bind to the ribosome when a stop codon is encountered
- Dissociation of the ribosome - ribosome breaks apart for recycling

Question 11

How do amino acids influence protein structure

Answer 11

Proteins are comprised of different sequences of amino acids. Amino acids are consist of an amide group connected to are carboxyl group and a varying side chain. This side chain adds a variety of chemical properties such as hydrophobic, hydrophilic, polar, non-polar
The type of amino acid that goes into the polypeptide chain is dependent on the job that the protein needs to do, and if you incorporate the incorrect type of amino acid which is most of the time detrimental and can result in cancer.