Post on 24-Feb-2016
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Starter1. Give three main causes of
variation within a population2. Define the term ‘mutation’3. Can ‘skin cancer’ be inherited?
Explain your answer.4. Give one advantage of mutation
(hint: read the pages 30 & 31)
Sex chromosomes
X = Female ChromosomeY = Male Chromosome
All female gametes (e.g. eggs) will contain an ‘X’ chromosome.Half of all male gametes (e.g. sperms) will contain an ‘X’ and half will contain a ‘Y’.
Sex Determination
X = Female ChromosomeY = Male Chromosome
EGG SPERM ZYGOTE
X X XX = Girl
X Y XY = Boy
However, occasionally sperms carrying BOTH the ‘X’ and the ‘Y’ chromosomes are produced.
X + XY = XXYXXY is known as Klienfelter Syndrome
EGG SPERM ZYGOTE
X XY XXY
Even sperms carrying no sex chromosome are produced
X + nothing = XJust having an ‘X’ chromosome is known as Turner Syndrome
EGG SPERM ZYGOTE
X none X