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To answer this two-part question students must be able to understand two concepts: what a gene can do; and what constitutes a gene.

For the first part, a mutation in the genetic code of the tumour ...

So if we start off by looking at the structure of a typical phospholipid inside a cell membrane, we can see that it is made up of two components: a hydrophilic phosphate head, which means it is 'water lov...

• Structure formed after multiple cell divisions of zygote. • Inner cell mass (ICM) - forms the embryo. • The outer layer - trophoblast. This layer surrounds the inner cell mass and a fluid-filled cavity ...

• Ovulation stimulated by hormones at spec dose to cause follicles to develop simultaneously• Oocytes collected from female using tube inserted through vagina into oviducts - ultrasound used; semen collec...

Biology A-level is examined by year. Year 1 is examined in paper 1 and year 2 is examined in paper 2. Paper 3 consists of content from both years 1 and 2. When revising content for the papers it is impera...