Cell Division

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(d) TMV can cause plants to produce less chlorophyll. This causes leaf discoloration. Explain why plants with TMV have stunted growth. Page 3 (2) (Total 8 marks) (e) (f) Tick one box. Cheaper Higher magnification Lower resolution The cheek cell in Figure 2 is magnified 250 times. The width of the cell is shown by the line D to E. Figure 2 real size D Calculate the width of the cheek cell in micrometres (μm). Complete the following steps. Measure the width of the cell using a ruler Use the equation to work out the real width of the cell in mm: image size magnification Convert mm to um A red blood cell is 8 pin diameter. A bacterial cell is 40 times smaller. Calculate the diameter of the bacterial cell. E Page 3 mm mm μm (1) (3) (b) Describe what is happening in photograph A. (c) (d) A student wanted to find out more about the cell cycle. The student made a slide of an onion root tip. She counted the number of cells in each stage of the cell cycle in one field of view. The table below shows the results. Number of cell S Non-dividing cells Reason 20 Stages in the cell cycle Stage 1 Stage 2 Stage 3 Stage 4 9 Each stage of the cell cycle takes a different amount of time. Which stage is the fastest in the cell cycle? Give a reason for your answer. Stage Page 3 The cell cycle in an onion root tip cell takes 16 hours. 4 2 1 Total 36 (1) (2) (2) (e) Calculate the length of time Stage 2 lasts in a typical cell. Give your answer to 2 significant figures. Time in Stage 2 = Bacteria such as Escherichia coli undergo cell division similar to mitosis. Figure 2 shows a growth curve for E. coli grown in a nutrient broth. Figure 2 Log10 number of live cells 10- 5- 1 2 P Page 4 -O 3 4 5 Time in hours What type of cell division causes the change in number of E. coli cells at P? Q minutes 6 7 8 (3) Q2. Tick one box. 0.02 μm 0.2 μm 2.0 μm 20.0 μm Diagram 1 shows the nucleus of a body cell as it begins to divide by mitosis. Page 4 (1) (Total 9 marks) Q2.(a) In humans there are two types of cell division: mitosis and meiosis. The table below gives statements about cell division. Tick (✓) one box in each row to show if the statement is true for mitosis only, for meiosis only, or for both mitosis and meiosis. The first row has been done for you. Statement How cells are replaced How gametes are made How a fertilised egg undergoes cell division How copies of the genetic information are made How genetically identical cells are produced (b) Stem cells can be taken from human embryos. In therapeutic cloning, an embryo is produced that has the same genes patient. (i) (ii) Both mitosis Mitosis only Meiosis only and meiosis Name one source of human stem cells, other than human embryos. the Stem cells from embryos can be transplanted into patients for medical treatment. Page 4 Give one advantage of using stem cells from embryos, compared with cells from the source you named in part (i). (4) (1) (1) (Total 6 marks) (f) Suggest why the number of cells levels out at Q. Page 5 (1) (2) (Total 11 marks) (a) (b) (c) Use a word from the box to label Diagram 1. alleles Diagram 1 chromosomes ● gametes Complete Diagram 2 to show what the nucleus of one of the cells produced by this mitosis would look like. Diagram 2 Stem cells from a recently dead embryo can be grown in special solutions. Some facts about stem cells are given below. Stem cells from an embryo can grow into any type of tissue. Stem cells may grow out of control, to form cancers. Page 5 (1) (1) Q3. (a) (b) The photograph shows some cells in the root of an onion plant. Cell X Cell Y By UAF Center for Distance Education [CC BY 2.0], via Flickr Cells X and Y have just been produced by cell division. (i) Name the type of cell division that produced cells X and Y. (ii) What happens to the genetic material before the cell divides? A gardener wanted to produce a new variety of onion. Explain why sexual reproduction could produce a new variety of onion. Page 5 (1) (1) Q3. ● ● Large numbers of stem cells can be grown in the laboratory. Stem cells may be used in medical research or to treat some human diseases. Patients treated with stem cells need to take drugs for the rest of their life to prevent rejection. Collecting and growing stem cells is expensive. Use only the information above to answer these questions. (i) Give two advantages of using stem cells. 1 (ii) 2 Give two disadvantages of using stem cells. 1 2 Some students grew one species of bacterium in a flask. Page 6 (2) (2) (Total 6 marks) Q4. X The genetic diagram shows how the chromosomes divide and combine in human reproduction. XX XX (a) (b) XX (d) XY XY XY Draw circles around the symbols for the two male gametes. State the chance of a child being a girl. (c) (i) How many pairs of chromosomes are there in a human body cell? (ii) How many chromosomes are there in a human egg cell? Chromosomes contain genes. From what substance are genes made? (3) (Total 5 marks) Page 6 (2) (1) (1) (1) Q2. The diagram shows two patterns of cell division. Cell division type A is used in gamete formation. Cell division type B is used in normal growth. Male Female Parents: (a) (b) (c) Sperm cells Sperm and egg join together Offspring: 12 13 (16) Egg cell Cell division type A Cell division type B Name the two types of cell division, A and B, shown in the diagram. Type A Type B Name the process in which an egg and sperm join together. Cell 1 contains 46 chromosomes. How many chromosomes will there be in: Page 6 (2) (1) (i) (ii) cell 10; cell 14? Page 7 (1) (1) (Total 5 marks) Diagram 1 shows the flask. Culture medium containing bacteria The students wanted to find the number of bacteria in 1 cm³ of the culture medium. The students: diluted 1 cm³ of the culture medium from the flask with 999 cm³ of water added 1 cm³ of diluted culture to sterilised nutrient agar in a Petri dish placed the Petri dish in an incubator at 25 °C. ● Diagram 1 Cotton wool ● Diagram 2 shows the Petri dish after 3 days in the incubator. Diagram 2 Sticky tape Colonies of bacteria Glass Petri dish (a) Each colony of bacteria is formed where one bacterium landed on the agar jelly. How is each colony formed? Page 7 (1) (e) In the process of mitosis, how do the number of chromosomes in the daughter cells compare to that in the original cell? Page 7 (1) (1) (Total 7 marks) (b) Complete the following calculation to find how many bacteria there were in 1 cm³ of the undiluted culture. (d) Number of colonies of bacteria in the Petri dish = These colonies were formed from 1 cm³ of the culture diluted x 1000. Therefore, number of bacteria in 1 cm³ of undiluted culture= (c) It is important to sterilise the culture medium and all the apparatus before use. Explain why. The bacteria would grow faster at 35 °C. In a school laboratory, the Petri dish should not be incubated at a temperature higher than 25 °C. Why? (e) The students decided to repeat their investigation. Why? Page 8 (2) (2) (1) (1) (Total 7 marks) Q3. The diagram shows how an immature egg could be used either to produce cells to treat some human diseases or to produce a baby. Immature egg extracted from ovary Egg treated chemically so that it starts to divide Blastocyst - a group of about 100 cells Cells used to treat some human diseases Blastocyst could be implanted into the mother's womb. She would later give birth Scientists may be allowed to use this technique to produce cells to treat some human diseases, but not to produce babies. Page 8 Using information from the diagram, suggest an explanation for this. (Total 4 marks) Q4. Meiosis and mitosis are different types of division in human cells. Compare the two processes by referring to where each takes place and the kind of products that are made. Page 9 (Total 6 marks) Q4. The parent plant grows side shoots. New plants grow on the side shoots. New plant. The diagram shows a strawberry plant. gametes (a) (b) (c) Parent plant The new plants will all have the same inherited characteristics as the original parent plant. Complete the sentences to explain why. Use words from the box. asexual Mackean differentiation embryos mitosis genes The new plant is produced by reproduction. In this type of reproduction, body cells divide by The new plant has the same plant. fertilisation Page 9 Side shoot sexual D.G. as the parent (1) (1) (1) (Total 3 marks) Q5. Stage 1 2 3 4 5 6 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. 7 (a) (b) Cell P Cell R or A B 3 and 7 Ovary Cell Q Cell S Which stages on the diagram show gametes? Draw a ring around your answer. 1 and 2 2 and 3 Page 10 Embryo 1 and 7 Embryo B is male. Which of the following explains why embryo B is male? Tick (v) one box. Cell P has an X chromosome; cell R has an X chromosome. (1) Q5. The table shows the number of chromosomes found in each body cell of some different organisms. Fruit fly Goat Species Number of chromosomes in Species Number of chromosomes in each body cell each body cell Human (a) Animals (b) 8 60 46 Tomato Potato Rice Chromosomes contain DNA molecules. Describe the function of DNA. Plants (c) Gametes are made in the testes by meiosis. (i) Look at the diagrams. Page 10 24 Nearly every organism on earth has an even number of chromosomes in its body cells. Suggest why. 44 24 (1) (2) (c) (d) Cell P has a Y chromosome; cell R has an X chromosome. Cell P has an X chromosome; cell R has a Y chromosome. 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 (ii) Single cells from an embryo at Stage 7 can be separated and grown in a special solution. (i) sperm What term describes cells that are grown in this way? Draw a ring around your answer. lleles The cells divide The cells fertilise screened cells What happens when the cells are placed in the special solution? Tick (v) two boxes. stem cells Page 11 (1) (2) (1) gametes in the testes? (d) A C Which diagram, A, B, C or D, represents how cell division by meiosis produces (ii) How many chromosomes will each goat gamete contain? Body cells divide by mitosis. (i) Why is the ability of body cells to divide important? B Page 11 D (1) (1) (1) (ii) When a body cell of a potato plant divides, how many chromosomes will each of the new cells contain? Page 12 (1) (Total 7 marks) Q6. (iii) (iv) The cells differentiate The cells separate Give one use of cells grown in this way. Some people might object to using cells from embryos in this way. Give one reason why. Stem cells can be collected from human embryos and from adult bone marrow. Stem cells can develop into different types of cell. Page 12 (2) (1) (1) (Total 9 marks) The table gives information about using these two types of stem cell to treat patients. Stem cells from human embryos It costs £5000 to collect a few cells. Stem cells from adult bone marrow It costs £1000 to collect many cells. There are ethical issues in using embryo Adults give permission for their own stem cells. bone marrow to be collected. The stem cells can develop into most other types of cell. Each stem cell divides every 30 minutes. There is a low chance of a patient's immune system rejecting the cells. More research is needed into the use of Use of these stem cells is considered to these stem cells. be a safe procedure. (b) Scientists are planning a new way of treating a disease, using stem cells. Use only the information above to answer these questions. (a) Give three advantages of using stem cells from embryos instead of from adult bone marrow. 1 2 3 The stem cells can develop into only a few types of cell. Each stem cell divides every four hours. There is a high chance of a patient's immune system rejecting the cells. 1 2 Give three advantages of using stem cells from adult bone marrow instead of from embryos. 3 Q7. Human cells and yeast cells have some parts that are the same. Page 13 (3) (3) (Total 6 marks) Q6. Read the information about stem cells. Stem cells are used to treat some human diseases. Stem cells can be collected from early embryos. These stem cells have not begun to differentiate, so they could be used to produce any kind of cell, tissue or organ. The use of embryonic stem cells to treat human diseases is new and, for some diseases, trials on patients are happening now. Stem cells can also be collected from adult bone marrow. The operation is simple but may be painful. Stem cells in bone marrow mainly differentiate to form blood cells. These stem cells have been used successfully for many years to treat some kinds of blood disease. Recently there have been trials of other types of stem cell from bone marrow. These stem cells are used to treat diseases such as heart disease. Evaluate the use of stem cells from embryos or from adult bone marrow for treating human diseases. You should give a conclusion to your evaluation. Page 13 (5) (Total 5 marks) Q7. The photographs show the flowers of two closely-related species of plant. Species A Species B Images: © iStock/Thinkstock The drawings show chromosomes from one cell in the root of each plant during cell division. *** (((((() (a) One chromosome Species A Species B (ii) The drawings show that each chromosome has two strands of genetic material. (i) How does a chromosome become two strands? One chromosome Explain why each chromosome must become two strands before the cell divides. Page 14 (1) (a) (b) (c) The diagram shows a yeast cell. Cell wall- Vacuole Parts A and B are found in human cells and in yeast cells. On the diagram, label parts A and B. Many types of cell can divide to form new cells. Some cells in human skin can divide to make new skin cells. Why do human skin cells need to divide? Human stem cells can develop into many different types of human cell. (i) Use the correct answer from the box to complete the sentence. (ii) embryos hair Human stem cells may come from nerve cells Use the correct answer from the box to complete the sentence. Page 14 (2) (1) (1) cystic fibrosis paralysis Human stem cells can be used to treat Page 15 polydactyly (1) (Total 5 marks) (b) For sexual reproduction, the plants produce gametes. (i) Name the type of cell division that produces gametes. (ii) How many chromosomes would there be in a gamete from each of these two plant species? (c) (i) Species A (iii) It is possible for gametes from Species A to combine with gametes from Species B to produce healthy offspring plants. How many chromosomes would there be in each cell of one of the offspring Species B plants? Look back at the information at the start of the question and the information from part (b). What evidence from these two pieces of information supports the belief that Species A and Species B evolved from a common ancestor? Page 15 (2) (1) (1) (1) (2) (ii) For successful gamete production to take place, chromosomes that contain the same genes must pair up. The drawings showing the chromosomes of Species A and of Species B are repeated below. Species A Species B *****) The offspring plants cannot reproduce sexually. Suggest an explanation for this. 00 Page 16 (2) (Total 10 marks) Q8.CADASIL is an inherited disorder caused by a dominant allele. CADASIL leads to weakening of blood vessels in the brain. The diagram shows the inheritance of CADASIL in one family. (a) 1 6 (ii) 2 10 7 11 3 8 12 CADASIL is caused by a dominant allele. (i) What is a dominant allele? 9 Key Male with CADASIL Female with CADASIL Male without CADASIL Female without CADASIL What is the evidence in the diagram that CADASIL is caused by a dominant allele? Page 17 (iii) Person 7 has CADASIL. Is person 7 homozygous or heterozygous for the CADASIL allele? Give evidence for your answer from the diagram. (1) (1) (1) (b) (c) Persons 7 and 8 are planning to have another baby. Use a genetic diagram to find the probability that the new baby will develop into a person with CADASIL. Use the following symbols to represent alleles. Dallele for CADASIL d = allele for not having CADASIL Probability = Scientists are trying to develop a treatment for CADASIL using stem cells. Specially treated stem cells would be injected into the damaged part of the brain. (i) Why do the scientists use stem cells? (ii) Embryonic stem cells can be obtained by removing a few cells from a human embryo. In 2006, scientists in Japan discovered how to change adult skin cells into stem cells. Suggest one advantage of using stem cells from adult skin cells. Page 18 (4) (2) (1) (Total 10 marks)