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CHROMOSOMES

CHROMOSOMES. GENES. A Credit card has a chip and is in a wallet . Sex cells ( gametes ). FERTILISATION. Hypertrichosis. Progeria. MUTATIONS. Why do offspring get half their genes from each parent ?. Answer.

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CHROMOSOMES

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  1. CHROMOSOMES

  2. GENES

  3. A Creditcard has a chip and is in a wallet.

  4. Sex cells (gametes)

  5. FERTILISATION

  6. Hypertrichosis

  7. Progeria

  8. MUTATIONS

  9. Why do offspringgethalftheir genes fromeachparent?

  10. Answer • Because Sex Cellscontainhalfthechromosomes and they fuse to form a new set of chromosomes.

  11. Why are brothers and sisters similar?

  12. Answer • Becausetheymighthavesome genes in common.

  13. How do identicaltwinsform?

  14. Answer • Iftheearlyembryosplitsappart.

  15. Thesetwins are ‘geneticallyidentical’. What do youthinkthismeans?

  16. Answer • Theyhavethesamegeneticinformation.

  17. How do you think the differences between identical twins are caused?

  18. Answer • Identical twins have differences in their environment; this can cause differences between them even before being born. (fingerprints, weight, etc)

  19. FocusonChromosomes

  20. Chromosomes

  21. AllelesRecessive - Dominant

  22. Genotypes (Alleles) and phenotypes

  23. PunnettSquare

  24. Eyes color of anoffspringfromparentswhohavedifferenteye color. • Father has blue eyes (bb) • Mother has Brown eyes – onerecessive blue(Bb)

  25. 6a Whatpercentage of thiscouple’schildren are likely to have Brown eyes? • According to the chart, 50% of thecouple’schildrenwillhave Brown eyes.

  26. 6b. Redrawdiagramfor a manwitheye color allelesBb and a womanwithalleles BB. Whatpercentage of thiscouple’schildren are likely to havebrowneyes? • According to the chart, 100% of thecouple’schildrenwillhavebrowneyes.

  27. 6c. Redrawdiagramsfor a man and a womanwhobothhaveallelesBb. Whatpercentage of thiscouple’schildren are likely to have Brown eyes? • According to the chart, 75% of thecouple’schildrenwillhavebrowneyes.

  28. Cystic fibrosis iscausedby a recessiveallele. Twoparents are bothcarriersforthedisease and bothhaveallelesCc (C isthe normal allele and c istheallelethat causes thedisease). Whatpercentage of childrenwouldthe be likely to havecystic fibrosis? • According to the chart, 25% of thecouple’schildrenwillhavecystic fibrosis.

  29. The tall trait is dominant (T) in pea plants, while short pea plants is a recessive trait (tt). Use a punnett square and probability table to determine the possible genotypes and phenotypes of offspring from a cross between a tall male pea plant (TT) and a short female pea plant (tt).

  30. PunnettSquare

  31. Benefits of Punnett Square • Predict possible genetic diseases • Combine genes to have new varieties of plants and animal breeds • Can you list another possible benefit?

  32. Whiskers in seals In seals, the gene for the length of the whiskers has two alleles. The dominant allele (W) codes long whiskers & the recessive allele (w) codes for short whiskers. a) What percentage of offspring would be expected to have short whiskers from the cross of two long-whiskered seals, one of them with Genotype Ww and the other with WW? • If one parent seal is a non pure long-whiskered (Ww) and the other is short-whiskered, what percent of offspring would have short whiskers?

  33. Blue eyes In humans, brown eyes (B) are dominant over blue (b). A brown-eyed man marries a blue- eyed woman and they have three children, two of whom are brown-eyed and one of whom is blue-eyed. Draw a Punnett square that illustrates this marriage. • What is the man’s gentoype? • What are the genotypes of the children?

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