Topic 5

Question 1

What are different parts of the nucleus?

Answer 1

• nucleolus
• euchromatin
• heterochromatin
• nuclear membrane
• nuclear pore
• nucleoplasm

Question 2

What is the nucleolus and what is its function?

Answer 2

• dense, non-membranous sub organelle

- site of synthesis of RNA

Question 3

What is the euchromatin and what is its function?

Answer 3

• uncondensed chromatin
• strains poorly
• used in transcription

Question 4

What is the heterochromatin and what is its function?

Answer 4

• condensed chromatin strains well
• nuclear envelope & nucleolus
• some remain packed, others can be activated in special tissue

Question 5

What is the nuclear membrane and what is its function?

Answer 5

• double membrane
• separated by 200-400nm inner nuclear membrane
• contiguous with rough ER

Question 6

What is the nuclear pore and what is its function?

Answer 6

• double membrane fused together at various points => pores

- sites allow for transport in/out of nucleus

Question 7

What is the nucleoplasm and what is its function?

Answer 7

• matrix for nucleus
• similar to cytoplasm
• contains enzymes, hormones receptors & precursors

Question 8

What are the components of DNA?

Answer 8

• DNA is double helix & made up of nucleotides

- phosphate backbone, 5’ carbon sugar & nitrogenous base (A-T, C-G)

Question 9

Describe molecular structure of DNA, according to Watson and Crick, including types of bonds that maintain this structure.

Answer 9

Phosphodiester bond between individual nucleotides

Question 10

What is the process of transcription?

Answer 10

Process whereby DNA is used as a template to synthesise RNA
Facilitated by RNA polym.
1. Binding
2. Initiation
3. Elongation
4. Termination

Question 11

What is the role of RNA polymerase in transcription?

Answer 11

• enzyme that catalyses RNA synthesis from DNA
• uses 1 of 2 strands as template
• reads DNA 3’ => 5’
• synthesises 5’ => 3’
• causes unwinding & rewinding of DNA
• needs a promotor sequence to begin reading DNA for RNA synthesis

Question 12

What are the start and stop codons

Answer 12

Start: AUG
Stop: UAA, UAG, UGA

Question 13

What are the different types of RNA?

Answer 13

ALL PRODUCTS OF TRANSCRIPTION

• rRNA: constitutes major part of ribosomes => site of protein
• tRNA: decoders info in mRNA into aa
• mRNA: messenger RNA, codes for aa sequence of protein

Question 14

What is template strand?

Answer 14

• template => gene
• 3’ => 5’
• codes for aa sequence of corresponding protein

Question 15

What is coding strand?

Answer 15

• segment within double-stranded DNA that runs 5’ => 3’

- synthesised strand

Question 16

What is the steps in translation?

Answer 16

1. Initiation
2. Elongation 1
3. Elongation 2
4. Termination of translation

Question 17

What is rRNA and its role in translation?

Answer 17

• ribosomal RNA

- codes of aa sequence of protein

Question 18

What is mRNA and its role in translation?

Answer 18

• messenger RNA

- code of aa sequence of protein

Question 19

What is tRNA and its role in translation?

Answer 19

• transfer RNA

- decodes info in mRNA into aa

Question 20

What is aminoacyl-tRNA synthetases and its role in translation?

Answer 20

• enzyme that attaches the appropriate amino acid onto its tRNA
• important role in RNA translation, the expression of genes to create proteins

Question 21

What is peptide transferase and its role in translation?

Answer 21

• primary enzymatic function of ribosome

- forms peptide bonds between adjacent amino acids using tRNAs during translation process

Question 22

What is the process of translation?

Answer 22

1. Initiation: small subunit bind wi/ mRNA
2. Elongation 1: translating a polypeptide
3. Elongation 2: translating a polypeptide
4. Termination: UAA, UAG, UGA, triggered by polypeptide releasing enzyme