B2: Cell Division and Inheritance

Here is a document for students taking AQA Additional Science. This is a document based on cell division and inheritance, including mitosis, meiosis, fertilisation, inheritance of sex, alleles and genetic disorders from the B2 (biology) section. I hope this helps you to revise! The document has been written in easy revision format. Please rate and comment on how to improve :) Also, I have a study group called AQA Additional Science where we discuss topics such as this one and more. Feel free to become a member, the more the merrier! Study Group: http://getrevising.co.uk/studygroups/aqa_additional_science

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  • Created by: I P B
  • Created on: 05-01-10 18:36
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B2: Inheritance
Cell Division
In body cells the chromosomes are normally found in pairs
Body cells divide by mitosis to produce additional cells during
growth or to replace other cells.
Mitosis also occurs during asexual reproduction.
Before each cell divides, a copy of each chromosome is made so
the new cell has exactly the same genetic information.
This means that the cells of asexually produced offspring have the
same genes as the parents.
When gametes join at fertilisation, one chromosome comes from
each parent and a single body cell with new pairs of
chromosomes is formed.
This then divides repeatedly by mitosis to form a new individual.
This causes variation between people and animals.
Sexual reproduction gives rise to variation because each pair of
alleles comes from each parent.
Body cells have two sets of genetic information sex cells
(gametes) have only one set.
Cells in reproductive organs (testes and ovaries in humans) divide
to form gametes
This is done by the process of meiosis

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When a cell divides to form gametes:
Copies of the chromosomes are made
Then the cell divides twice to form four gametes, each with a
single set of chromosomes
Inheritance of sex ­ the sex chromosome
In human body cells, one of the 23 pairs of chromosomes is the
sex chromosomes
In females the sex chromosomes are the same (XX) and in males
the sex chromosomes are different (XY)
In males, one is much shorter than the other, the shorter one is
called the Y…read more

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This type of inheritance is referred to as monohybrid inheritance
Differentiation of cells
When cells develop a specialised structure to carry out a specific
structure, this is called differentiation.
Most type of animal cells differentiate at an early stage in life so
quickly become muscles, nerves etc.…read more

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Each person has unique DNA (apart from identical twins who have
the same DNA)
A way of identifying each individual is using DNA fingerprinting
Genetic Disorders
Some disorders are inherited such as cystic fibrosis and
Huntington's disease.…read more

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Embryos provide the most Stem cells are cultivated using
useful stem cells: the cells are nutrients from animal sources,
nonspecialised, which means which could carry diseases that
they can become any specific could be passed on to humans
type of cell (adult stem cells are
more limited in their potential
They can act as a repair kit for People who receive cell
damaged tissue transplants through stem cell
therapy could be infected with
Stem cells may be able to treat Stem cells may…read more



A good set of notes on inheritance which has usefully included tables to compare the advantages and disadvantages of  stem cells and genetic engineering which often forms the basis of some of the longer questions in the GCSE Biology syllabus.

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