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Sex determination

Sex determination. We can use a genetic diagram to show how sex (gender) can be determined. The diagram shows how there is an equal chance that each baby will be a girl or a boy. Click to advance the diagram.

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Sex determination

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  1. Sex determination

  2. We can use a genetic diagram to show how sex (gender) can be determined. The diagram shows how there is an equal chance that each baby will be a girl or a boy. • Click to advance the diagram.

  3. We can use a genetic diagram to show how sex (gender) can be determined. The diagram shows how there is an equal chance that each baby will be a girl or a boy. • Click to advance the diagram.

  4. We can use a genetic diagram to show how sex (gender) can be determined. The diagram shows how there is an equal chance that each baby will be a girl or a boy. • Click to advance the diagram.

  5. We can use a genetic diagram to show how sex (gender) can be determined. The diagram shows how there is an equal chance that each baby will be a girl or a boy. • Click to advance the diagram.

  6. We can use a genetic diagram to show how sex (gender) can be determined. The diagram shows how there is an equal chance that each baby will be a girl or a boy. • Click to advance the diagram.

  7. You should note that: • Half the male gametes (sperm) have an X chromosome and half have a Y chromosome. • However, all the female gametes (eggs) have an X chromosome. • Fertilization is random and either type of sperm could fertilize an egg. • At each pregnancy, there is a 50:50 chance of conceiving a girl or a boy. • In a large population, there will be equal numbers of male and female offspring.

  8. When constructing a genetic diagram for a monohybrid cross, it is important to follow these conventions: Show the characteristic of the parents (phenotype). Show the alleles present in the parents’ cells (genotypes). Use upper case letters to represent a dominant allele. Use the lower case version of the same letter to show a recessive allele. Put gametes in circles. Show all the different possible combinations of alleles at fertilization. Put an ‘x’ to show a cross (mating).

  9. Below is an example of how you might construct a genetic diagram to explain a monohybrid cross between a father who has two alleles for free earlobes and a mother who has two alleles for attached earlobes. Which conventions of drawing genetic diagrams do you recognize? Offsprings’ characteristics: all have free earlobes but have one dominant and one recessive allele

  10. Below is an example of how to write the last genetic diagram as a punnet square.

  11. Now have a go at your own punnet squares • A Blue eyed mum (bb) crossed with a Brown eyed father (BB) • A Tortoise shell cat (TT) crossed with a Ginger hair cat (tt) • A brown eyed mum (Bb) crossed with a Brown eyed father (Bb) • A Red flowered pea plant (Rr) crossed with a Yellow pea plant (rr) • A Wrinkled pea (WW) With a Smooth pea (ww)

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