Protein synthesis + cell division

Question 1

Describe how gene activation occurs

Answer 1

Requires DNA to be uncoiled to expose sites required to start transcription
-> gene kept inactive by being tightly coiled + bound to histones

Question 2

Describe the structure + function of DNA

Answer 2

Stores all info required for protein synthesis
- wound around histone proteins + forms complex called nucleosome

Question 3

Define gene

Answer 3

A section of DNA that has the instructions for one protein (sequence of amino acids)

Question 4

Describe transcription

Answer 4

Where DNA is transcribed into mRNA in the nucleus
-> mRNA then transported to free-floating ribosomes or RER

Question 5

Describe translation

Answer 5

mRNA translated into protein in the cytoplasm + at ribosomes
-> proteins destined for mod. + transport enter RER -> golgi app. -> secretory vesicles

Question 6

Explain how a ribosome translates mRNA

Answer 6

• Small + large ribosomal units join together + enclose mRNA + tRNA
• Large unit has 3 sites for tRNA building (E site, P site + A site)
• Once ribosome reaches stop codon, termination occurs
• subunits separate, freeing mRNA strand

Question 7

State what happens if a protein is misfolded

Answer 7

Retention + transport out of the cell -> degradation by ubiquitin-proteosome system

Question 8

State the steps of the cell life cycle

Answer 8

-G1= normal cell functions, growth + protein synthesis
-S= DNA replication
-G2= protein synthesis
-mitosis = division of nuclei in parent cell into daughter cells
-cytokinesis = cytoplasm splits -> 2 new cells

Question 9

Describe the process of DNA replication

Answer 9

• Helicase unwinds DNA helix
• DNA polymerase attaches to start site + travels along strand making new strand w/ comp bases

Question 10

Describe prophase of mitosis

Answer 10

Chromosomes become visible, centrioles move to opposite sides of the cell, nuclear envelope disappears, spindle fibres attach to chromosomes

Question 11

Describe metaphase of mitosis

Answer 11

Chromosomes align along metaphase plate, equidistant from poles

Question 12

Describe anaphase of mitosis

Answer 12

Centromere splits, sister chromatids move to opposite sides of the cell

Question 13

Describe telophase of mitosis

Answer 13

Nuclear envelope forms, chromosomes change to chromatin

Question 14

Describe cytokinesis

Answer 14

Splitting of cytoplasm w/ formation of 2 identical cells

Question 15

Describe how a cell ages

Answer 15

Telomeres = cap @ end of chromosome which protects from damage
-> as cell divides, loses section of telomere
-> cell eventually stops dividing

Question 16

Describe apoptosis

Answer 16

Programmed cell death
-> activation of ‘suicide genes’
-> DNA fragments + cell ingested by phagocytes

Question 17

Describe necrosis

Answer 17

When cell is injured, cellular contents flow into interstitial fluid -> causes inflammatory response

Question 18

State how cell differentiation occurs

Answer 18

Genes not required at that specific cell are turned off

Question 19

Differentiate b/t benign + cancerous tumours

Answer 19

Benign tumours = cells are contained
malignant tumours = cells not contained