Cellular Replication: Division, Cycle, DNA, RNA, Protein Synthesis

Question 1

What can increased cell proliferation be caused by ?

Answer 1

• shortening the cell cycle
• recruiting quiescent (sleeping) cells to divide & proliferate

Question 2

What are different cell types?

Answer 2

• Labile cells
• stable cells
• non-dividing (permanent) cells

Question 3

What are labile cells?

Answer 3

• Constantly dividing, regenerate rapidly e.g. Surface epithelium

Question 4

What are stable cells?

Answer 4

• Low level of replicative activity but can rapidly divide in response to stimuli e.g. Liver damage

Question 5

What are non dividing cells?

Answer 5

-Terminally differentiated , unable to proliferate (neurons)

Question 6

What has increased proliferation & decreased proliferation?

Answer 6

• Increased proliferation: cancer
• decreased proliferation: chronic wound

Question 7

What are the main events of the cell cycle?

Answer 7

• Interphase
• mitosis
• cytokinesis: cytoplasm division

Question 8

What are the phases of interphase?

Answer 8

• G 1: sure environment is correct e.g. O2, nutrients, phase before synthesis of DNA
• s phase: synthesis, nuclear DNA is synthesised, chromosomes are duplicated
  -G2: after DNA synthesis is complete, lasts until mitosis. Makes sure duplicated DNA is correct for mitosis

Question 9

What are the main stages of mitosis?

Answer 9

1. Prophase: centrioles move to poles
   2, prometaphase: microtubules attach to chromosomes
2. Metaphase: chromosomes align nuclei disappear
   4.anaphase: chromosomes divide and move to poles
3. Telophase: nuclear membrane reappears and cytokinesis occurs

Question 10

What different Cyclins are required for which parts of the cell cycle?

Answer 10

• Cyclin D: for Go and G1
• Cyclin A: for S phase and G2
  -Cyclin B: for mitosis

Question 11

What is the cyclin/cdk action?

Answer 11

1. CDK protein is always present but its active site isn’t exposed - cyclin protein is only made at a certain point of the cycle
2. Cyclin binds to CDK exposing its active site
3. A protein substrate and ATP binds to CDK, The protein substrate is phosphorylated
4. The phosphorylated protein regulates the cell cycle. Each CDK has different protein targets

Question 12

What are some characteristics of DNA?

Answer 12

-deoxyribonucleic acid
- base pairs, phosphate / deoxyribose sugar
Instructions needed for an organism to develop, survive & reproduce
- double stranded

Question 13

What are some characteristics of RNA?

Answer 13

• Ribonuleic acid
  -base pairs, phosphate, ribose sugar
• protein synthesis
  -Single strand

Question 14

What are the different types of RNA?

Answer 14

• Messenger RNA
• transfer RNA
• ribosomal RNA

Question 15

What are the components of a nucleotide?

Answer 15

• phosphate group
• pentose sugar
• nitrogenous base

Question 16

What are the purine bases?

Answer 16

-Adenine
- guanine

Question 17

What are pyrimidine bases?

Answer 17

• Uracil
  -Cytosine
• thymine

Question 18

What are the differences between RNA & DNA?

Answer 18

• RNA has uracil while DNA contains thymine
  -RNA contains ribose and DNA contains deoxyribose
• DNA is double stranded

Question 19

How do nucleotides join and the base pairs?

Answer 19

• Phosphodiester bonds
• 5’, 3’ by DNA polymerase
• Between A & T (2 hydrogen bonds)
• Between C & G (3 hydrogen bonds)

Question 20

What are chromosomes?

Answer 20

• Thread like structures inside the nucleus
• Human body contains 46 chromosomes (23 pairs)
• Each section of a chromosome contains the code for the production of a gene (section of polypeptide chain that codes for a protein)

Question 21

What is DNA helicase and polymerase?

Answer 21

• DNA Helicase: separate double stranded DNA into single strands
• DNA Polymerase: Contain 5 types: a, B, Y, 5, E (don’t exactly look like these symbols) add nucleotides

Question 22

What is Transcription?

Answer 22

• Initiation
• Before start of gene to be coded = promoter
• Need transcription factors

Question 23

What are the units in a Ribosome?

Answer 23

• 2 units, 1 small and 1 large
• Large unit has 3 subunits:
• A-site (amino acyl) accepts incoming amino acids. Joins the ribosome
• P-site (peptide) peptide is made
• E-site (Exit) holds the tRNA before it leaves the ribosome

Question 24

What are the happens when the ribosome reaches the stop codon in translation?

Answer 24

• When a ribosome reaches a stop codon on mRNA, the A site on the ribosome accepts a protein called release factor instead of tRNA
• The release factor hydrolyses the bond between the tRNA in the P-site and the last amino acid. Polypeptide is freed from ribosome
• 2 ribosomal subunits and the other components of the assembly dissociate

Question 25

What are the stages of translation?

Answer 25

• mRNA leaves the nucleus via nuclear pores and attaches to ribosome
• tRNA carries a single amino acid and an anticodon
• Complementay anticodon binds with codon on mRNA
• A 2nd tRNA binds on adjacent codon and peptide bond is formed by condensation. Ribososme moves along until reacjing a stop codon

Question 26

What are the stages of translation?

Answer 26

• mRNA leaves the nucleus via nuclear pores and attaches to ribosome
• tRNA carries a single amino acid and an anticodon
• Complementary anticodon binds with codon on mRNA
• A 2nd tRNA binds on adjacent codon and peptide bond is formed by condensation.
• Ribosome moves along until reaching a stop codon

Question 27

What components do tRNA have?

Answer 27

• Amino acid attachment site
• Anticodon (opposite side)