27. DNA, RNA and polypeptide

Question 1

Where does the variability in the human genome come from?

Answer 1

1. Gene content (density and number) in each chromosome differs
2. Gene sizes differ
3. Genes can encode proteins
4. Genes can encode other RNA

Question 2

How does gene expression generate diversity of cells/organs?

Answer 2

220 cell types in humans forming distance organs

- Differential gene expression

Question 3

How does open/condensed dna regulate gene expression?

Answer 3

• Dna has various levels of organisation and gene expression controlled by physical properties
• More open it is, the more it is expressed

Question 4

What does each nucleotide consist of?

Answer 4

• A phosphate group
• A sugar
• A nitrogenous base

Question 5

What sort of secondary structures can RNA form?

Answer 5

• Rna is mainly single stranded but can also form secondary structures
• Hairpins are double stranded regions formed by complementary sections on the single stranded RNA

Question 6

What are the three types of RNA involved in translation?

Answer 6

• Messenger RNA=mRNA
• Transfer RNA=tRNA
• Ribosomal RNA=rRNA

Question 7

What are the two types of regulatory RNAs?

Answer 7

• Micro RNA=miRNA

- Small interfering RNA= siRNA

Question 8

What does messenger RNA do?

Answer 8

• It carries the coding message of the DNA

- Formed by transcription, template used during protein synthesis

Question 9

What does ribosomal RNA do?

Answer 9

• It formed part of the ribosome
• Each ribosome is made of a large and small subunit
• Both rRNA and ribosomal proteins make up these subunits

Question 10

What are the two key structural elements in transfer RNA?

Answer 10

• The 3’ end is the CCA sequence where a specific amino acid will attach
• The anticodon is when he tRNA matches to the mRNA template

Question 11

What is the process of ‘charging’?

Answer 11

Where a specific amino acid is added to the 3’ CCA of the tRNA

Question 12

What is the enzyme that facilitates this charging?

Answer 12

Amino-acyl-tRNA-synthase
- There are different versions of amino-acyl-tRNA syntheses that can only bind specific tRNAs and their matching amino acids

Question 13

What does microRNA (miRNA) do?

Answer 13

• It is an endogenous type of RNA interference
• Transcribed from DNA and requires processing to become single stranded
• Binds imperfectly to mRNA and blocks translation/marking mRNA for degradation

Question 14

What does small interfering RNA do? siRNA

Answer 14

• These are synthetic and double stranded types of RNA interferences
• Require unwinding
• Perfectly bind mRNA transcribed from DNA to degrade siRNA-mRNA complexes

Question 15

How does RNA interference affect X inactivation?

Answer 15

1. The Xist gene is on the X chromosome
2. Transcription of the Xist gene makes an interference RNA
3. The RNA binds to the X chromosome from which it was transcribed
4. Methylation and histone deacetylation attract chromosomal proteins that form heterochromatin, inactivating the chromosome

Question 16

What is the secondary structure of the protein?

Answer 16

• Folding due to amino acid interactions

- The carboxyl and amino groups can form bonds to give rise to alpha helices and beta sheets

Question 17

What is the tertiary structure of the protein?

Answer 17

3D packaging due to amino acid interaction