allele? (2 marks) First letter of the dominant characteristic with a capitol letter (1) First letter of the dominant characteristic but this time with a lower case letter (1) 8) What do we mean by the terms homozygous and heterozygous? (2 marks) Homozygous 2 alleles that are the same – Heterozygous 2 alleles that are different – 9) What do we mean by the term genotype and phenotype? Give examples (2+2 marks) Genotype the alleles that have been inherited (1) e.g. Bb or CC or ff (1) – Phenotype the physical characteristic that shows through (1) e.g. Blue eyes, brown eyes, – cystic fibrosis, sickle cell trait, (1) 10) Describe the following genotypes e.g. HH = homozygous dominant – (3 marks) a) Bb Heterozygous – b) BB homozygous dominant – c) bb homozygous recessive – 11) What must the genotype be if the recessive trait is going to show through? Explain your answer (2 marks) Homozygous recessive (1) 2 recessive alleles are needed for the characteristic to come through, if a dominant allele is passed on then it would show through rather than the recessive allele(1) 12) Carry out a pedigree analysis for a cross between the following genotypes Bb and bb (2 marks) 1 mark for correct genotypes in the correct box (boxes 1-4 all correct 1 mark for correct offspring (boxes 5-8 all correct) B b (1) (2) b Bb bb (3) (5) (6) b Bb bb (4) (7) (8) 13) B codes for brown eyes and b codes for blue eyes. What is the probability that the offspring of the cross above will have blue eyes? Represent as a ratio and a percentage and a chance out of 4
allele? (2 marks) First letter of the dominant characteristic with a capitol letter (1) First letter of the dominant characteristic but this time with a lower case letter (1) 8) What do we mean by the terms homozygous and heterozygous? (2 marks) Homozygous – 2 alleles that are the same Heterozygous – 2 alleles that are different 9) What do we mean by the term genotype and phenotype? Give examples (2+2 marks) Genotype – the alleles that have been inherited (1) e.g. Bb or CC or ff (1) Phenotype – the physical characteristic that shows through (1) e.g. Blue eyes, brown eyes, cystic fibrosis, sickle cell trait, (1) 10) Describe the following genotypes – e.g. HH = homozygous dominant (3 marks) a) Bb – Heterozygous b) BB – homozygous dominant c) bb – homozygous recessive 11) What must the genotype be if the recessive trait is going to show through? Explain your answer (2 marks) Homozygous recessive (1) 2 recessive alleles are needed for the characteristic to come through, if a dominant allele is passed on then it would show through rather than the recessive allele(1) 12) Carry out a pedigree analysis for a cross between the following genotypes Bb and bb (2 marks) 1 mark for correct genotypes in the correct box (boxes 1-4 all correct 1 mark for correct offspring (boxes 5-8 all correct) B (1) b (2) b (3) Bb (5) bb (6) b (4) Bb (7) bb (8) 13) B codes for brown eyes and b codes for blue eyes. What is the probability that the offspring of the cross above will have blue eyes? Represent as a ratio and a percentage and a chance out of 4
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