Transcript sex chromosomes

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 baby’s gender is
determined by the sperm that fertilises the
egg cell.
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www.sciencetutors.zoomshare.com Compilation By Ivan Ukiwah
Sex Chromosomes And Gender
Determination
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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
WHAT I NEED TO KNOW
• A human baby’s gender is determined by the sperm that
fertilises the egg cell.
• The male Y chromosome carries a gene called the 'sexdetermining 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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www.sciencetutors.zoomshare.com Compilation By Ivan Ukiwah
GENETIC OR ENVIRONMENTAL
VARIATION?
• 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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www.sciencetutors.zoomshare.com Compilation By Ivan Ukiwah
CONTINUOUS AND DISCONTINUOUS
VARIATION
Think back to some of the difference between people in your class
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Explain the meaning of the following:
Continuous Variation
Discontinuous Variation
Write down six examples continuous
variation
Write down three examples of
discontinuous variation.
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.
QUICK QUIZ
• Which of these graph represents a continuous and a discontinuous
variation and explain why?
No. of
Pupils in
10f1/SC
Attached Ears
No. of
Pupils
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.
Distribution Pattern in Variation
• Height is affected by several genes, so
more complicated than being either tall or
short. Also affected by the environment.
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