REPRODUCTION. NAME.. Page 1. Q1.Figure 1 shows the stages in the transmission of the malaria parasite by mosquitoes to humans.

Transcription

1 REPRODUCTION. Thornton College NAME.. Q.Figure shows the stages in the transmission of the malaria parasite by mosquitoes to humans. Figure (a) Where in the mosquito does Stage 2 happen? Draw a ring around the correct answer. Page

2 brain salivary glands stomach () (b) What is Organ A in the human? Draw a ring around the correct answer. liver pancreas small intestine () (c) What happens in the human at Stages 5 and 6? (4) (d) Sickle-cell anaemia is an inherited disease caused by a mutation in the haemoglobin gene. (i) Genes are small pieces of DNA. The DNA in a gene consists of a sequence of bases. Figure 2 shows part of the base sequence in the DNA of a normal haemoglobin gene and the same section in the sickle-cell gene. A, C, G and T represent the different bases. Figure 2 Page 2

3 Normal gene Sickle-cell gene GGACTCCTC GGACACCTC Describe how the mutation causes a change in the shape of the haemoglobin protein molecule. (4) Sickle-cell anaemia is caused by a recessive allele, a. The normal haemoglobin allele is dominant, A. Use a genetic diagram to find the probability that two heterozygous parents will produce a child who is homozygous for sickle-cell anaemia. Probability =... (4) Page 3

4 (iii) What is the benefit of the heterozygous genotype in areas where malaria is common? () (Total 5 marks) Q2.The diagram shows some of the cell divisions that occur during human reproduction. (a) (i) Name the type of cell division that produces cell D from cell B. () Which organ in the male body produces cell C from cell A? () (b) (i) Cells A and B each contain 46 chromosomes. Page 4

5 How many chromosomes would there be in the nucleus of cell C? () Why is it important that cell C has this number of chromosomes? (2) (Total 5 marks) Q3.Polydactyly is an inherited condition caused by a dominant allele. (a) The figure below shows the hand of a man with polydactyly. The man has an extra finger on each hand. The man s mother also has polydactyly but his father does not. Ifness/iStock (i) The man is heterozygous for polydactyly. Explain how the information given above shows that the man is heterozygous for polydactyly Page 5

6 (3) The man marries a woman who does not have polydactyly. What is the probability that their first child will have polydactyly?... () (b) The man has red hair. His sister has brown hair. Both of their parents have brown hair. Brown hair is caused by the dominant allele, B. Red hair is caused by a recessive allele, b. Complete the genetic diagram below to show how the man s parents were able to have some children with red hair and some with brown hair. Father Mother Parental phenotypes Parental Genotypes Gametes Offspring genotypes:... Offspring phenotypes:... (5) (Total 9 marks) Page 6

7 Page 7 Thornton College

8 M.(a) salivary gland (b) liver (c) any four from: merozoites released (from liver) and enter the red blood cells (some of these) turn into schizonts (which) burst the red blood cells releasing (more) merozoites coincides with fever attacks. points credited must be in correct sequence 4 (d) (i) three bases code for one amino acid middle code of CTC is now CAC / T changed to A so will be a different amino acid (in the chain) (and so chain / protein will have a different shape) due to a different sequence of amino acids correct parental genotypes (both Aa) allow ecf for 2 nd and 4 th marking points or correct gametes (A+a A+a) allow alternative symbols if defined correct derivation of offspring genotypes from gametes aa identified (homozygous for) SCA 0.25 allow 25% or in 4 or :3 or / 4 (iii) (Aa) less likely to get malaria (than homozygous dominant / AA) Page 8

9 allow resistance or protection if correctly qualified eg some protection do not accept immune Thornton College [5] M2.(a) (i) meiosis allow mieosis testis / testes allow testicle (b) (i) 23 fuses / joins with cell D / with egg cell or used in fertilisation allow fuse with another cell prevents doubling of chromosome number / restores original no. / 46 / diploid no. / normal no. / full no. accept 23 from each parent / from each gamete [5] M3.(a) (i) man has (inherited) polydactyly (PD) allele (from mother) man has (inherited) other / normal / recessive allele from father because father does not have PD allele or if father had it father would have had PD or father only has normal allele or father is homozygous recessive Page 9

10 allow gene for allele Thornton College 0.5 / ½ / in 2 / : / 50% do not allow :2 or 50/50 allow 50:50 (b) parental phenotypes: both brown parental genotypes: both Bb gametes: B b and B b allow only on gametes answer line allow ecf from genotypes offspring genotypes: BB (2)Bb bb allow ecf from gametes offspring phenotypes correctly assigned to genotypes: BB & Bb = brown bb = red do not penalise confusion of phenotypes & genotypes here [9] Page 0