Unit B2, B2.7. Cell division and inheritance. Stage 1. Ovary. Cell Q. Cell P. Cell R. Cell S. 7 Embryo A B C

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Harvey Lindsey
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1 Cell division and inheritance 1. A woman gives birth to triplets. Two of the triplets are boys and the third is a girl. The triplets developed from two egg cells released from the ovary at the same time. The diagram shows how triplets A, B and C developed. Stage 1 2 Cell P Ovary Cell Q 3 Cell R Cell S Embryo A B C Which stages on the diagram show gametes? Draw a ring around your answer. 1 and 2 2 and 3 3 and 7 1 and 7 Embryo B is male. Which of the following explains why embryo B is male? Tick ( ) one box. Cell P has an X chromosome; cell R has an X chromosome. Cell P has a Y chromosome; cell R has an X chromosome. Cell P has an X chromosome; cell R has a Y chromosome. Page 1 of 6

2 (c) The children that develop from embryos A and C will not be identical. Explain why. You may use words from the box in your answer. egg genes sperm (d)..... Single cells from an embryo at Stage 7 can be separated and grown in a special solution. (i) What term describes cells that are grown in this way? Draw a ring around your answer. alleles screened cells stem cells (ii) What happens when the cells are placed in the special solution? Tick ( ) two boxes. The cells divide The cells fertilise The cells differentiate (iii) The cells separate Give one use of cells grown in this way.. (iv) Some people might object to using cells from embryos in this way. Give one reason why... (Total 9 marks) Page 2 of 6

3 2. The diagram shows one of the experiments performed by a scientist called Mendel in the 1850s. He bred pea plants which had different coloured pea seeds. Key Green Yellow Green-seeded pea plant bred with yellow-seeded pea plant First generation offspring are all yellow-seeded Yellow-seeded offspring bred together Second generation offspring are a mixture of yellow-seeded and green-seeded pea plants Use words from the box to help you to explain the results of this experiment. dominant factor recessive..... Mendel explained these results in terms of inherited factors. (i) What do we now call inherited factors? (ii). Where, in a cell, are these inherited factors found?. (Total 5 marks) Page 3 of 6

4 3. The diagram shows three types of cells in a life history of a simple animal. How do the chromosomes of the body cells compare with the chromosomes in the fertilised egg from which they came? Describe what happens to chromosomes in the nucleus of a body cell when it forms reproductive cells. 4. Cystic fibrosis is a disease which affects 1 in 1600 babies. What are the symptoms of cystic fibrosis? (4) (Total 5 marks) Page 4 of 6

5 Two parents with normal characteristics have a child who was born with cystic fibrosis. Explain, as fully as you can, how this can happen. You may use a genetic diagram if you wish. 5. The black pigment in human skin and eyes is called melanin. A single gene controls the production of melanin. A person who is homozygous for the recessive allele of the gene has no melanin and is said to be albino. The diagram shows the inheritance of albinism in a family. P Q Key affected male unaffected male affected female (4) (Total 7 marks) R S unaffected female? Use a genetic diagram to explain the inheritance of the albino allele by children of parents P and Q. R and S decide to have a child. What is the chance that this child will be an albino?... Use a genetic diagram to explain your answer. (Total 6 marks) Page 5 of 6

6 6. Chromosomes contain molecules of DNA. Genes are small sections of DNA. Each gene contains a code. What does a cell use this code for? DNA fingerprints can be used to identify people. One example of the use of DNA fingerprints is to find out which man is the father of a child. The diagram shows the DNA fingerprints of a child, the child s mother and two men who claim to be the child s father. The numbers refer to the bars on the DNA fingerprints. Man A Man B Child Mother (i) Which man, A or B, is more likely to be the father of the child? (ii) Use the numbers on the DNA fingerprints to explain your choice. In your answer you should refer to all four people. Only half the bars of the child s DNA fingerprint match the mother s DNA fingerprint. Explain why. (Total 7 marks) Page 6 of 6

Page 2. Q1.Figure 1 shows a human body cell. Figure 1. Which part in Figure 1 contains chromosomes? Tick one box. A B C

Page 2. Q1.Figure 1 shows a human body cell. Figure 1. Which part in Figure 1 contains chromosomes? Tick one box. A B C Q1.Figure 1 shows a human body cell. Figure 1 (a) Which part in Figure 1 contains chromosomes? Tick one box. A B C (b) Humans have pairs of chromosomes in their body cells. Draw one line from each type