Lecture 28 - Gene Expression

Question 1

There is much variability in the human genome. Support this statement.

Answer 1

Gene content (in terms of density and number) in chromosomes differs, gene sizes differ, gene can encode proteins, while other encode other RNA

Question 2

Explain how gene expression is related to the conformation of the DNA.

Answer 2

Gene expression requires access between the transcription machinery and the DNA sequence itself. This access is provided when the DNA are in a “open configuration” rather than a closed one.

Question 3

How does RNA differ from DNA?

Answer 3

RNA:

• Many copies per cell
• Sugar is ribose
• Nucleotide: U, A, C, G
• mostly single stranded

DNA:

• One copy per cell
• Sugar is deoxyribose
• Nucleotide: T, A, C, G
• double-stranded

Question 4

How does RNA structures like hairpins occur?

Answer 4

It is formed by the bond between complementary sections of a ssRNA.

Question 5

Mention all known type of RNA (both used in translation and regulatory RNAs)

Answer 5

RNA in Translation
- Messenger RNA= mRNA
- Transfer RNA= tRNA
- Ribosomal RNA =rRNA

Regulatory RNAs
- Micro RNA= miRNA
- Small interfering RNA = siRNA

Question 6

What is the main function of mRNA?

Answer 6

It carries the coding “message” of DNA, as it is formed as a RNA complement to the DNA template.

Question 7

Ribosomes are called the _______. It is made up of two subunits, each containing ______ and ________.

Answer 7

translation machinery, rRNA, ribosomal proteins

Question 8

Describe the structural elements of tRNA. Answer in context of its specificity.

Answer 8

There are two important sites in a tRNA: the amino acid attachment site and the anticodon . Each tRNA can only bind one specific amino acid at the 3’ end (base sequence always CCA) and matches that to a corresponding anticodon sequence.

Question 9

Binding of amino acid to each tRNA is termed as ______. It is carried out by an enzyme called ________.

Answer 9

charging, amino-acyl-tRNA-synthase

Question 10

What is an example of an interference RNA? How does it work?

Answer 10

siRNA is an example of an interference RNA. It perfectly binds to transcribed mRNA. The resulting complex are then degraded

Question 11

What are the building blocks of proteins? How are they arranged

Answer 11

Amino acids are the building blocks of protein. They have the same backbone consisting of an amino group, carboxyl group, and a variable side chain specific to each type of amino acid.

Question 12

Differ how miRNA and siRNA differ in their features and regulatory actions.

Answer 12

miRNA are transcribed form DNA and are processed to become single stranded, before binding imperfectly to mRNA targeted for degradation.

siRNA are synthetic and double-stranded(requires unwinding) It perfectly binds to mRNA to form a complex that are degraded.

Question 13

Mention the organisation levels of a protein structure.

Answer 13

Primary: Amino acid sequence
Secondary (folding)
Tertiary (packing)
Quaternary (interaction): proteins with multiple tertiary subunits