The image shows a cancerous tumor in the lungs. Tumors are caused by uncontrolled cell division.

1.6 Cell division

Cell division is essential but must be controlled.

Essential idea

1.6 Cell Division Quizlet

1.6 Cell division

Vocabulary

1.6 Cell division

Understandings

1.6 Cell division

Applications and Skills

1.6 Cell division

Why do cells undergo mitosis?

1.6.U1 Mitosis is division of the nucleus into two genetically identical daughter nuclei.

1.6 Cell division

1.6.U4 Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.

G2 (Gap 2)

• Increase the volume of cytoplasm
• Organelles produced
• Proteins synthesised

S (Synthesis)

• DNA replicated

G1 (Gap 1)

• Increase the volume of cytoplasm
• Organelles produced
• Proteins synthesised

G1

G2

S

Mitosis

(Synthesis)

1.6 Cell division

Outline the stages of interphase.

1.6.U4 Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.

• DNA replication – DNA is copied during the S phase of interphase
• Organelle duplication – Organelles must be duplicated for twin daughter cells
• Cell growth – Cytoplasmic volume must increase prior to division
• Transcription / translation – Key proteins and enzymes must be synthesized
• Obtain nutrients – Vital cellular materials must be present before division
• Respiration (cellular) – ATP production is needed to drive the division process

1.6 Cell division

List three metabolic reactions that occur during interphase.

1.6.U4 Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.

Chromatin

• DNA is usually loosely packed within the nucleus as unravelled chromatin
• DNA is accessible to transcriptional machinery
• Genetic information can be translated (Euchromatin and Heterochromatin)

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1.6 Cell division

Explain why cells need to supercoil their DNA molecules.

1.6.U2 Chromosomes condense by supercoiling during mitosis.

Chromosome:

• DNA is temporarily packaged into a tightly wound and condensed chromosome prior to division (via supercoiling)
• DNA is able to be easily segregated
• Inaccessible to transcriptional machinery

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1.6 Cell division

Explain why cells need to supercoil their DNA molecules.

1.6.U2 Chromosomes condense by supercoiling during mitosis.

1.6 Cell division

1.6 Cell division

Get the terminology right

centromere is the part of a chromosome that links sister chromatids

Sister chromatids are duplicated chromosomes attached by a centromere

centrioles organise spindle microtubules

Spindle microtubules (also referred to as spindle fibres)

In animal cells two centrioles are held by a protein mass referred to as a centrosome

After anaphase when the sister chromatids separate they should then be referred to as chromosomes

1.6 Cell division

Prophase

1.6.U1 Mitosis is division of the nucleus into two genetically identical daughter nuclei.

DNA supercoils chromatin condenses and becomes sister chromatids, which are visible under a light microscope

The centrosomes move to opposite poles of the cell and spindle fibres begin to form between them

The nuclear membrane is broken down and disappears

1.6 Cell division

Metaphase

1.6.U1 Mitosis is division of the nucleus into two genetically identical daughter nuclei.

Spindle fibres from each of the two centrosomes attach to the centromere of each pair of sister chromatids

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Contraction of the microtubule spindle fibres cause the sister chromatids to line up along the centre (equator) of the cell.

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1.6 Cell division

1.6.U1 Mitosis is division of the nucleus into two genetically identical daughter nuclei.

Continued contraction of the microtubule spindle fibres cause the separation of the sister chromatids

Chromosomes move to the opposite poles of the cell

The chromatids are now referred to as chromosomes

1.6 Cell division

Telophase

1.6.U1 Mitosis is division of the nucleus into two genetically identical daughter nuclei.

Now cytokinesis begins!

New nuclear membranes reform around each set of chromosomes

Microtubule spindle fibers disappear

The chromosomes uncoil de-condense to chromatin (and are no longer visible under a light microscope).

Chromosomes arrive at the poles.

1.6 Cell division

1.6.U1 Mitosis is division of the nucleus into two genetically identical daughter nuclei.

Prophase

Metaphase

Anaphase

Telophase

Mitosis is the division of the nucleus whereas, cytokinesis is the division of the cytoplasm and the cell.

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1.6 Cell division

Cytokinesis

1.6.U3 Cytokinesis occurs after mitosis and is different in plant and animal cells.

1.6 Cell division

1.6.S1 Identification of phases of mitosis in cells viewed with a microscope or in a micrograph.�1.6.S2 Determination of a mitotic index from a micrograph.

http://www.nuffieldfoundation.org/practical-biology/investigating-mitosis-allium-root-tip-squash

A very good, well explained lab outline for creating slides and calculating the mitotic index.

Verify you are human:

DEAB

Name and Draw the stages of mitosis

Label all of the important structures

Annotate what is happening at each stage.

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Challenge: Describe cytokinesis in plants versus animals

1.6 Cell division

1.6.U1 Mitosis is division of the nucleus into two genetically identical daughter nuclei.

1.6 Cell division

Annotate the images below

1.6.U3 Cytokinesis occurs after mitosis and is different in plant and animal cells.

A kinase is an enzyme that adds phosphate groups (PO43−) to other molecules.

Phosphorylation is the process of adding a phosphate. This makes it phosphorylated

1.6 Cell Division

Progression through parts of the cell cycle are affected in various ways by specific cyclins

1.6.U5 Cyclins are involved in the control of the cell cycle.

1.6 Cell Division

Progression through parts of the cell cycle are affected in various ways by specific cyclins

1.6.U5 Cyclins are involved in the control of the cell cycle.

• Target Protein is needed for a stage of the cell cycle. Eg Centrosome
• It needs to be activated (phosphorylated)
• Cyclins bind to Cyclin Dependent Kinases which phosphorylate the target protein.
• Target protein does it’s specific job.
• Cyclin is destroyed and levels decrease until it is required again.

1.6 Cell Division

Cyclins are a family of regulatory proteins that control the progression of the cell cycle

1.6.U5 Cyclins are involved in the control of the cell cycle.

Cyclins activate cyclin dependent kinases (CDKs), which control cell cycle processes through phosphorylation

Tumours are abnormal cell growths resulting from uncontrolled cell division

1.6 Cell division

Define the term tumour.

1.6.U6 Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

• Tumour cells may either remain in their original location (benign) or spread and invade neighbouring tissue (malignant)

1.6 Cell division

1.6.U6 Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

1.6 Cell division

What is metastasis?

1.6.U6 Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

Mutation

Primary Tumour

Vascularisation

Detachment

Invasion

Secondary Tumour

Vascularisation

• An oncogene is a gene that has the potential to cause cancer.
• Two types of genes include: proto-oncogenes and tumour suppressor genes

1.6 Cell division

What is the name given to the few genes that can become cancerous after mutating?

1.6.U6 Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

• Mutagens that lead to the formation of cancer are further classified as carcinogens

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• Physical – Sources of radiation including X-rays (ionising), ultraviolet (UV) light and radioactive decay
• Chemical – DNA interacting substances including reactive oxygen species (ROS) and metals (e.g. arsenic)
• Biological – Viruses, certain bacteria and mobile genetic elements (transposons)

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1.6 Cell division

State the collective name given to chemicals that cause mutations.

1.6.U6 Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.

• Cancer of the lung
• Cancers of the mouth, throat, nose and sinuses
• Cancers of the oesophagus
• Cancers of the bladder, kidney and ureter
• Cancer of the pancreas
• Cancer of the stomach
• Cancer of the liver
• Cancer of the cervix and ovary
• Cancer of the bowel (colorectal cancer)

1.6 Cell division

Cancers more common in smokers than non-smokers

1.6.A1 The correlation between smoking and incidence of cancers.

1.6 Cell division

1.6.A1 The correlation between smoking and incidence of cancers.

1.6.A1 The correlation between smoking and incidence of cancers.

http://en.wikipedia.org/wiki/File:Smoking_lung_cancer.png

1. Describe the relationship shown.
2. What type of correlation is shown
3. How strong is the correlation? Justify your answer by discussing the evidence.
4. The correlation shown here is lagged. A lag is a time gap between the factors. Estimate the size of the lag between cigarette consumption and lung cancer death.

There are many other similar surveys in different countries, with different demographics that show similar results. Along with lung cancer, cancers of mouth and throat are very common as these areas are in direct contact with the smoke too. It might surprise you that the following cancers are also more common in smokers:

• Head and neck
• Bladder
• Kidneys
• Breast
• Pancreas
• Colon

Correlation ≠ causation, however laboratory investigations have found:

• more then 20 chemicals found in tobacco have caused cancers in laboratory animals and/or humans
• More than 40 other chemicals found in tobacco have been identified as carcinogens

1.6 Cell division

1.6 Cell Division QUiz

1.6 Cell Division Kahoot