Pages 80-81 Specification area 2.2 The Cell Cycle The Cell Cycle Pages 80-81 Specification area 2.2

Syllabus

Resources Text book Summary worksheet Link to APBI website Cell Cycle Revision podcast on Kerboodle

Objectives Know the three stages of the cell cycle. Be able to describe the main processes occurring during each stage of the cell cycle. Explain how mitosis is controlled Describe how cancer and its treatment relates to the cell cycle.

The Cell Cycle Know the three stages of the cell cycle The cell cycle is divided into three major phases: Interphase The M phase or mitotic phase when Nuclear Division occurs The C phase or cell division stage

The Cell Cycle Describe the main processes occurring during each stage of the cell cycle Cytoplasm divides and 2 ‘daughter’ cells separate Nucleus Divides Production of new proteins and organelles DNA replicates

The Cell Cycle (Extension only) INTERPHASE G1 G2 S Cytokinesis Interphase is divided into G1, S and G2 phases MITOSIS (M PHASE)

Interesting facts about Variations in duration of the Cell Cycle G1 is the most variable of all the phases The rapidly dividing epithelial cells lining the human intestine remain in the G1 phase for only about 2 hours G1 G2 S M Slowly dividing liver cells may take many months to move through G1 to the S phase Some cells, such as nerve and muscle cells never divide; they may be considered to be permanently in the G1 phase and never enter the S phase

To do:- Figure 2 Page 80 : Copy Graph showing how Cell Mass and the mass of DNA changes during the cell cycle (lower graph) and add labels to show which stage of the cell cycle is on each part of the graph (5 minutes).

Interphase MITOSIS Interphase MITOSIS G2 S G1 G1 Interphase

There are 75 cells in this field of view. How do you think you might calculate the “MITOTIC INDEX”? Hint: it is a proportion of cells in any stage of nuclear division

The Timing of the Cell Cycle The different phases of the cell cycle last for different periods of time An onion root slide was examined for the different stages of the cell cycle and the number of cells in each phase was recorded The percentage of cells in each stage was then calculated The percentage of cells in each stage is used as a measure of the percentage of time that the cells spend in each phase of the cell cycle Stage of Cell Cycle Number of Cells Cell % (approx) Interphase 138 66 Prophase 56 27 Metaphase 6 3 Anaphase 2 1 Telophase 7 Total 209 100 Interphase is the longest stage of the cell cycle with anaphase being the shortest 3/100 * 72 = 2.16h OR 7/209 x 72 = 2.16h If cell cycle takes 72 hours to complete, how long is Telophase?

Genetic Control of The Cell Cycle Out The division of cells is a closely regulated process Cell division is under genetic control, and it is known that there are TWO specific genes which code for proteins that ‘switch on’ and ‘switch off’ the process Cancer is a disease that results from uncontrolled cell divisions When a MUTATION occurs in one of the genes that control Normal cell division, the resulting cells become transformed into cancer cells Environmental factors such as cancer-causing agents (carcinogens like those in cigarette smoke), IONISING RADIATION (X-rays / UV / α ß ɣ), INCREASE THE RISK of these gene mutations

Click to goto link on causes of cancer

Scanning Electron Micrograph of Dividing Cancer Cells

Cancer: The Cell Cycle Out of Control When a gene controlling division in a normal body cell mutates – the cell continues to divide uncontrolled to produce a clone of cells that form a tumour normal body cell mutated tumour Uncontrolled mitosis mutation Many such tumours are found to be BENIGN and do not spread from their site of origin – they may nevertheless compress and damage adjacent tissues Malignant, cancerous tumours are less stable and break apart so may spread from their site of origin These tumours develop their own blood and lymph supply which can transport malignant cells from the tumour to other sites in the body malignant tumour malignant cancer cells carried to other body sites secondary tumour This is called metastasis these cells invade other body regions to form secondary cancers

Describe how cancer and its treatment relates to the cell cycle. To Do:- Read the information about Cancer treatment. Write down the effects of the TWO main types of drug used in Chemotherapy treatment Copy the graph in figure 3 on p81 Give TWO features that are similar between the ‘normal’ and ‘cancer’ cell trends What are the main DIFFERENCES between the effects of treatment on the normal and cancer cell numbers?

To Do:- answers Read the information about Cancer treatment. Write down the effects of the TWO main types of drug used in Chemotherapy treatment Prevent DNA replication during interphase of the cell cycle Inhibit nuclear spindle formation so chromosomes cannot attach during metaphase of mitosis (thereby interfering with cell division) Copy the graph in figure 3 on p81 Give TWO features that are similar between the ‘healthy’ and ‘cancer’ cell trends Both cells types show declining numbers over time with repeated doses In both cell types, there is a recovery period during after each dose has taken effect during which numbers remain stable before increasing again What are the main DIFFERENCES between the effects of treatment on the healthy and cancer cell numbers? The length of the recovery stage is shorter in healthy cells than in the cancer cells The decrease in cancer cell numbers is greater after each dose than the decrease in healthy cell numbers

Homework Answer summary questions and Question 5 in the application box on page 81. Goto the following website and write the FIVE ways cancer can be caused Also list all the different ways that cancer can currently be treated http://www.abpischools.org.uk/page/modules/celldiv_cancer/index.cfm?age=Age%2520Range%252016%252D19&subject=Biology Great link to cancer info

Outcomes I Know the stages of the cell cycle. I can describe the main processes occurring during each stage of the cell cycle. I can describe how cell division is controlled. I am able to describe what cancer is and how it relates to the cell cycle.

Keywords Cell cycle Interphase Cytokinesis Cancer Chemotherapy drugs Risk factors