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Flashcards in Cell Division Deck (21):

In body cells what do they contain?

Chromosomes in matching pairs


Explain why the chromosomes have to be copied to produce new cells for growth

To replace damaged cells and repair worn out tissue


What is mitosis needed for?

- replacement of worn out cells
- repair to damaged tissue
- asexual reproduction


What is sexual reproduction?

When gametes join in fertilisation


What do gametes contain?

Half the number of chromosomes of body cells


Explain why sperm cells are produced in large numbers?

To increase the chance of fertilisation


In sexual reproduction what s needed to produce a unique individual?

Half the genes from each parent


Explain the advantages or being multicellular

Allows organisms to be larger
Allows for cell differentiation
Allows organisms to be more complex


What are new cells for growth produced by?



Explain why new cells are genetically identical in mitosis?

Because the DNA replicates


In mammals what type of body cells do they have?

Diploid (two copies of each chromosome)


Explain why DNA replication must take place

So that all new cells produced have all the DNA of the original cell otherwise the cells would not receive all the chromosomes and genes necessary for life processes


What are gametes produced by?



Describe gametes

Haploid (contain one chromosome from each pair)


Explain how the structure of a sperm cell is adapted to its function

Many mitochondria to provide energy
An acrosome that releases enzymes to digest the egg membrane


Explain why fertilisation results in genetic variation

- gametes combine to form a diploid zygote
- genes on the chromosome combine to control the characteristics of the zygote


Explain why in meiosis the chromosome number is halved and each cell is genetically different

- one chromosome from each pair separate to opposite poles of the cell in the first division
- chromosomes divide and the copies move to opposite poles of the cell in the second division


Describe what happens in mitosis

- chromosomes line up along the centre of the cell
- they then divide
- the copies more to opposite poles of the cell


Describe how DNA replication occurs

- the double helix unzips
- new bases pair up with exposed bases on each strand
- an enzyme bonds the new bases together to form complementary strands
- two identical strands of DNA are formed


Explain why becoming multicellular requires the development of specialised organ systems

Communication between cells
Supplying the cells with nutrients
Controlling exchanges with the environment


Describe the difference between simple organisms which are unicellular and more complex organisms which are multicellular

Single-cell organisms are very small and have to rely on diffusion to obtain glucose and oxygen, to remove waste products
- multicellular are larger and more complex. Require specialised organs to carry out functions like gas exchange and digestion.