Biology: Year 11

While the year 10 module may have been pretty dull, this is all good stuff.

The Menstrual Cycle

This random topic doesn't really fit in anywhere, but it's in the syllabus, so you'll just have to learn it. You know already, the monthly cycle, but do you know exactly how it works? Well, here's some enlightenment...

  • FSH is produced in the pituitary gland (Follicle Stimulating Hormone). This caused:
    • An egg to develop in the ovaries.
    • Oestrogen to be produced in the ovaries
  • Oestrogen caused the lining to build up in the uterus.
    • It also stops the production of FSH.
    • But it causes the pituitary gland to produce LH.
  • LH stimulates the release of the egg around the middle of the cycle.
    • It also causes progesterone production.

If the egg is fertilized, progesterone will continue to be produced, which inhibits LH, and keeps the egg growing. If the egg is not fertilized, the cycle begins again with the production of FSH.

The "pill" is an oral contraception of oestrogen. The hormone level remains high, and this stops FSH from being produced. No FSH, no more egg production, so no pregnancy.

 Advantages  Disadvantages
Gives the woman control. Unwanted side effects, e.g. deep vein thrombosis, increased risk of cancer.
The most effective contraception. Doesn't protect against STIs.
Only on prescription.
May not always work: e.g. if sick.

FSH can be given to women as a form of fertility treatment, stimulating egg production.

However, it's very expensive, often doesn't work, and can tear apart couples.

Go to top!


Deoxyribonucleic acid (DNA to the normal human) is the stuff that we're made up of. Each of the 46 chromosome in the nucleus of every cell is a tight strand of DNA. DNA split into sections, or genes.

DNA is structured like a twisted ladder. Each of the 'rungs' of the ladder are made up of two bases. These bases are A T G and C. A and T always go together and G and C always combine. You can see this in the diagram to the left.

Because of this, if the DNA is split in half, it it able to replecate its other half. A will be a base design for T and this will happen likewise will happen with G and C.

Bases are essential, because they code proteins. Three bases in a row, e.g. AAA will make a certain kind of protein, while GAG will make a different one. (Note, the 'other half' of the DNA isn't included here). This is what allows any creature to develop. Pretty awesome really.



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All text copyright © 2006 to EJ Taylor. Page Template created by James Taylor. Site created: 10 April, 2006. Last revised: 2 August, 2015