SEX CHROMOSOMES

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SEX CHROMOSOMES

1. What are sex chromosomes?
2. Why are sex chromosomes important in the study of
   inheritance of gender?
3. Explain the term inheritance of gender.
4. Explain why a human babys gender is determined
   by the sperm that fertilises the egg cell.

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Ivan Ukiwah
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Sex Chromosomes And Gender Determination

• Contents of Power point
• Sex Chromosomes
• What I Need to know
• Genetic or Environmental Variation (1 and 2)
• Continuous and Discontinuous Variation
• Quick Quiz
• Clones (Identical Twins)

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www.sciencetutors.zoomshare.com Compilation By
Ivan Ukiwah
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WHAT I NEED TO KNOW

• A human babys gender is determined by the sperm
  that fertilises the egg cell.
• The male Y chromosome carries a gene called the
  'sex-determining region Y also know as SRY.
• Genetic information are passed from parents to
  offspring's in their sex cell
• Sex cells are egg cells and sperm cells
• When egg cells and sperm cells join together in
  fertilisation the contain full 23 pairs of
  chromosomes.
• One pair of chromosome (23) comes from the mother
  and the other pair (23) comes from the father.

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4
GENETIC OR ENVIRONMENTALVARIATION?

• Mark and John are identical twins and are
  genetically the same. Mark takes regular exercise
  and have better muscle tone than John who does
  not. However there are some differences between
  John and Mark - for example, in personality,
  fashion tastes or dress sense, intelligence,
  relationships, likeability factor, confidence,
  and aptitude
• Underline environmental variation using red pen
  or pencil
• Which of these differences are due to their a)
  experiences or environment b) genes.

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Ivan Ukiwah
5
CONTINUOUS AND DISCONTINUOUS VARIATIONThink back
to some of the difference between people in your
class

• Explain the meaning of the following
• Continuous Variation
• Discontinuous Variation
• Write down six examples continuous variation
• Write down three examples of discontinuous
  variation.

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CONTINUOUS AND DISCONTINUOUS VARIATION

• A variation with a progressive range of values
  which change gradually is called CONTINUOUS
  VARIATION.
• A variation in which there is not a continuous
  range of options is called a DISCONTINUOUS
  VARIATION.

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QUICK QUIZ

• Which of these graph represents a continuous and
  a discontinuous variation and explain why?

No. of Pupils
No. of Pupils in 10f1/SC
Attached Ears Detached Ears
10FI/SC Height of students (cm)
Say whether each variation is a continuous or
discontinuous Natural eye colour, a scar, tongue
rolling, attached ear lobes, free or detached ear
lobes, height, hair length.
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Distribution Pattern in Variation

• Height is affected by several genes, so more
  complicated than being either tall or short. Also
  affected by the environment.

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HUMAN CLONES

• Explain why identical twins are clones of each
  other but not of their parents.
• Ask students if there will be variation between
  offspring. Draw out that variation between clones
  has environmental cause.
• Define CLONING