Cell cycle and mitosis

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4.1.2.2 Cell cycle and mitosis

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Learning purpose:

MUST (4):

• Label the nucleus,

chromosomes, genes and DNA in a cell and describe each

• Explain why cells need to divide by mitosis

• Name the products of mitosis

SHOULD (5):

• Explain what the cell cycle is

• Explain why DNA and

organelles are replicated in cell division

• Describe the stages of mitosis COULD (6/7):

• Explain what happens in each stage of the cell cycle

Links to prior learning:

• Year 7 "Intro to Biology" – Cell structure,

specialised cells, microscopy

• Year 7 "Humans" – Cells, tissues,

organs and systems

• 4.1.1.1 Prokaryotes and eukaryotes

• 4.1.1.2 Animal and plant cells

• 4.1.1.3/4.1.1.4 Cell specialisation and differentiation

Links to future learning:

• Stem cells

• Tissues, organs and systems

Lesson vocab

Nucleus DNA Gene Chromosome

Cell cycle Cell division

Mitosis

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Specification statements:

4.1.2.1 Chromosomes

• The nucleus of a cell contains chromosomes made of DNA molecules. Each chromosome carries a large number of genes

• In body cells the chromosomes are normally found in pairs 4.1.2.2 Mitosis and the cell cycle

• Cells divide in a series of stages called the cell cycle. Students should be able to describe the stages of the cell cycle, including mitosis

• During the cell cycle the genetic material is doubled and then divided into two identical cells

• Before a cell can divide it needs to grow and increase the number of sub-cellular

structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome

• In mitosis one set of chromosomes is pulled to each end of the cell and the nucleus divides

• Finally the cytoplasm and cell membranes divide to form two identical cells

• Students need to understand the three overall stages of the cell cycle but do not need to know the different phases of the mitosis stage

• Cell division by mitosis is important in the growth and development of multicellular organisms

• Students should be able to recognise and describe situations in given contexts where mitosis is occurring

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Starter:

Put these parts of a cell into size order, smallest to largest

Cell

Nucleus Chromosome

Gene DNA

Extension:

Write a short description of each component

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Genes, chromosomes & DNA

The nucleus of a cell contains all the genetic information

needed to make

and organise a

new cell

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Genes, chromosomes & DNA

This information is carried on

chromosomes and organised in genes – each gene codes for one

characteristic

Chromosomes are

usually found in

pairs – one copy

from each parent

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Genes, chromosomes & DNA

Genes also come in

pairs – one on each

chromosome

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Task:

Use the textbooks to help you write definitions for:

• Chromosome

• Gene

• DNA

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• Cells divide in a series of stages called the cell cycle

• During the cell cycle the DNA is copied and then divided

into two identical cells

• Before a cell can divide it needs to grow and increase the number of organelles such as ribosomes and

mitochondria

• This is to ensure that each of the two new cells receives

copies of all the organelles

What is the "cell cycle"?

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Note: the times depend on the type of cell and available nutrients

G1 Synthesis of organelles

10 hours

S Synthesis - DNA is copied 9 hours

G2 Growth 4 hours

M Mitosis (nucleus divides)

1 hour

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Tasks:

1. What is the cell cycle?

2. Why must DNA and organelles be copied before the cell divides?

3. Label your diagram of the cell cycle to

show what happens at each stage

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Mini-plenary:

1

2

3

4

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All complex organisms originate from a single fertilised egg

Every cell in your body started from this

fertilised egg. Through cell division the numbers of cells are increased

Cells then specialise and change into their various roles

Cell division

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Mitosis is a type of cell division

Mitosis occurs

wherever more cells are needed

It produces two new cells that are

identical to each other, and to the parent cell

Mitosis

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Why do cells need to divide?

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How do we go

from one cell

to many?

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For the first week, humans don’t actually grow – the

fertilized egg cell (zygote) splits in two every day to

make a bundle of smaller cells

mitosis

After about 1 week, the zygote is called an embryo

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Mitosis

Mitosis is needed for growth and repair,

and to replace worn- out cells

Mitosis produces two genetically identical

“daughter” cells It is also used in

asexual reproduction

in some organisms

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Mitosis

Before the cell divides,

every chromosome is copied During division, one copy moves to one side (pole) of the cell and the other copy moves to the

other side

Finally the cytoplasm and cell membranes divide to form two identical cells

Each new cell has the same DNA as the original

(parent) cell

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2 daughter cells identical to original

Parent cell

Chromosomes are copied and double in number

Chromosomes now split

Note: Bacteria do not have chromosomes, so do

not replicate by mitosis.

They use a method called

“binary fission” instead

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Mitosis – bone cell slides

1 2 3

4 5

Parent cell Chromosomes copied Copies separating

Cells split

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Tasks:

1. Name the four purposes of mitosis 2. What are the products of mitosis?

3. Annotate the diagram on your worksheet to explain what is happening during mitosis

Extension: Complete the sheet by placing the stages of mitosis in the correct order, with a description of each stage

AQA Biology pages 202-203

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