5. Every nucleus in every cell of an organism contains identical copies of these chromosomes. The number of chromosomes present in an organisms’ cells depends on its species. e.g Human Male 46 Chromosomes
10. Activity Daughter Son On your worksheet, label whether each family member has night blindness or normal vision. Trim sheet and stick into your notes. Grandmother Grandfather Grandmother Grandfather Daughter Son Grandson Grandaughter Grandson Grandaughter Night blindness is always masked by normal vision
11. Tongue rolling = Dominant Non-Tongue rolling = Recessive (R) (r) (R) (R) (R) (r) (r) (r) Tongue roller Tongue roller Non-Tongue roller Notes The alleles can be shown as letters. The DOMINANT allele is always in CAPITAL letters. The recessive allele is always the same letter but a small letter.
12. Activity Using the letters: N for normal vision n for night blindness Add the correct letters to your night blindness family tree. For example: Grandmother Grandfather Daughter Son n n n n
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14. Genotype: The alleles an organism carries for a particular characteristic. e.g RR Rr rr Phenotype is dependant upon genotype and environment ! Notes
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16. Black hair (B) is the dominant allele. White hair (b) is the recessive allele. Copy and complete using what you have learned. 1 allele for black hair and 1 allele for white hair White Hair bb Black Hair BB 2 Black hair alleles Phenotype Homo/ heterozygous Genotype Alleles carried by guinea pigs Notes
17. This means that the offspring of true breeding black mice are always black and the offspring of true breeding white mice are always white. Animals that always pass on the same characteristics to their offspring from generation to generation are know as True-breeding. True Breeding Notes
18. X P (parents) X F 1 (first generation) F 2 (second generation) Notes Add the names of the generations to your copy of the true breeding, black haired mice.
19. Lets look at this in terms of genotype: Black coat colour is dominant (B) White coat colour is recessive (b) All offspring (F 1 ) BB BB BB Parents x BB BB x Second generation (F 2 ) BB Gametes all B B Gametes all B B Notes
20. What about true breeding for white coated mice? Label the generations on your diagram for the white mice. X X
21. -Draw the cross for the true breeding white mice using the genotypes -Work through exactly as we did for the black mouse Answer All offspring (F 1 ) bb bb bb Parents x bb bb x Second generation (F 2 ) bb Gametes all b b Gametes all b b Notes
22. Another type of cross is when each parent is a true breeding individual, but each has a different phenotype. X P (parents) F 2 (second generation) X F 1 (first generation) Monohybrid Cross Notes
23. Where did the white mouse come from? P bb x BB Bb x Bb Gametes: (F 2 ) Bb BB Bb Bb bb Punnett Square = Gives a ratio of 3 : 1 black white (F 1 ) All Bb BB Bb bb B b B b Gametes all b B B b B b Notes
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28. How can we tell if an organism is true breeding ? BB or Bb True breeding Not True breeding A test cross is used to identify the genotype of an individual by crossing it with a homozygous recessive individual… bb If a black coat in mice is dominant (B) it’s genotype could be: Notes
29. All offspring: black Ratio= Black: white 1 : 1 BB or Bb? B B b b Bb Bb Bb Bb B b b b Bb bb Bb bb X BB bb X Bb bb
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31. Cystic Fibrosis Healthy female Affected female Healthy male Affected male Mhairi Molly Henry Katie Joe Ben Zoe Chloe Sue Chris Erin Tom Doug Polly Steve Rab Jim
35. XX X Y Female Female Male X X X Y XX X Y X Y XX Female Male Male Egg Sperm
36. Sex Determination Using page 81 of the Success Guides: -make notes on the sex chromosomes -add your completed cut out of the sex determination diagram. Notes
37. Check Test 1. Describe the term Genotype 2. Describe the term Phenotype 3. What do we mean by a homozygous organism? 4. What do we mean by a heterozygous organism? 1 mark 1 mark 1 mark 1 mark
38. 5. Breeding experiments (crosses) which focus on just one characteristic are called ______ crosses. 6. Organisms which pass on the same characteristics to their offspring over many generations are described as …… 1 mark 1 mark
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42. 10. Which sex chromosomes do males carry? 1 mark 14 Total
