001-028 U2-AK BIO11TR

Answer Key

Unit 2 Genetic Processes

Unit Preparation Questions (Assessing Readiness) (Student textbook pages 154?7)

1. b

2. In both animal and plant cells: A?cell membrane B?cytosol C?mitochondrion E?endoplasmic reticulum (smooth and rough) G?Golgi apparatus H?nucleus (or nuclear envelope) L?nucleus (or nuclear envelope) In plant cell only: I?central vacuole J?cell wall (or membrane) K?chloroplast In animal cell only: D?ribosomes F?vesicle

3. For efficient movement of materials the ratio of a cell's surface area to volume must stay within a range that permits diffusion to all parts of the cell within a short amount of time (to support the metabolic activity of the cell).

4. d

5. Nucleus (contains) chromosomes (composed of) DNA (which is made up of) genes (which code for) proteins

6. d

7. Students should draw a double helix and label any small piece as a gene.

8. a

9. c

10. Mitosis involves the division of the nuclear material in the nucleus and cytokinesis is the process that divides the cytoplasm (including all organelles).

11. During cell division, DNA is tightly coiled in chromosomes and looks "bunched." The rest of the time, the DNA looks more like long, loose threads.

12. A?centrosome B?chromosomes C?spindle fibres D?centromere

13. Daughter cells formed during cell division are genetically identical to the parent cell.

14. In plant cells, a cell plate is formed during cytokinesis and divides the cytoplasm into two. Animal cells are divided by a contractile ring rather than a cell plate.

15. A?interphase B?growth and preparation (G1) C?DNA replication D?growth and preparation (G2) E?mitosis F?cytokinesis

16. Any two of: the DNA may be damaged; DNA replication may not have occurred; there were not enough nutrients to support cell growth; no additional cells of that type are needed; cell death may have been signalled

17. Sample answer: Skin cells have a short life span--skin is easily damaged and must often be replaced. Nerve cells have a long life span--these internal cells are rarely damaged and, once an organism is full size, there is no need to divide for growth.

18. Cancer results from uncontrolled cell reproduction and the lack of cell death triggered by errors in DNA.

19. Sample answer: The digestive system is made of organs including the stomach and small intestine, and tissues like muscle (which move food along) or epithelium (which line the tract). Muscle tissue is made of muscle cells and epithelial tissue is made of epithelial cells.

Diagrams could look like the one that accompanies question 38 on student textbook page 437.

20. Cell differentiation describes the process by which a cell specializes to perform a specific function. Because they perform different jobs, muscle cells look very different from skin cells and nerve cells, for example. If cells didn't differentiate, they would all be generalists--they would be able to do all functions, but not very well.

21. Stem cells can specialize to become many types of cell. Other types of adult cells can only divide to produce cells identical to themselves.

Biology 11 Answer Key Unit 2 ? MHR TR 1

Chapter 4 Cell Division and Reproduction

Learning Check Questions

(Student textbook page 164) 1. Interphase, mitosis, and cytokinesis

2. Interphase

3. At prophase, the cell's chromatin condenses into chromosomes. Each chromosome exists as two copies of one chromosome, joined at a centromere.

4. When mitosis is inhibited, healing times increase.

5. Interphase would differ in length between cell types because different cells have different functions that are carried out during interphase. Mitosis and cytokinesis are processes that would likely be consistent for all cell types.

6. The daughter cells would either have twice as much DNA as a healthy cell, or no DNA. Neither cell would be viable. One would lack genetic material and the other would have too much to be able to survive.

(Student textbook page 172) 7. A gamete is a haploid sex cell and a zygote is a

diploid cell.

8. Thirty-nine chromosomes; gametes are haploid, meaning they contain half the number of chromosomes that are in a diploid cell

9. See Figure 4.14 on student textbook page 172 for illustration; each homologous chromosome still consists of two sister chromatids. In mitosis, the sister chromatids are separated during anaphase.

10. The gametes would have 46 chromosomes (23 pairs). After fertilization, the zygote would have 92 chromosomes (four sets of 23).

11. The phases in meiosis II (metaphase II, anaphase II, and telophase II) are most like the phases of mitosis because, during these stages, the chromosomes align on the equator of the cell, sister chromatids are separated, and a new nucleus forms for each new cell.

12. During anaphase I and anaphase II, because this is when the homologous chromosomes and sister chromatids, are each separated

(Student textbook page 176) 13. The outcome of mitosis is genetically identical

offspring, whereas the outcome of meiosis is one (or four) haploid cells with a genetically diverse

representation of the parent cell. This leads to genetically unique offspring. 14. 27 = 128 different gametes

15. Students may redraw the figure showing chromosomes that are mixes of pieces of blue and yellow.

16. Because of independent assortment and crossing over, all children will have some genetic material from each of their ancestors.

17. Alleles that are found close together on the same chromosome will be inherited together more often than those that are either far apart on a chromosome or on different chromosomes.

18. The ideal donor is an identical twin, because they are genetically identical.

(Student textbook page 185) 19. Artificial insemination allows wider access to high-

quality male donors.

20. Both of these processes allow for the introduction of genetic variation from different parts of the world.

21. A vector carries the gene of interest into the foreign cell.

22. They are much less expensive to produce in large quantities.

23. A company may use embryo transfer so that they can choose desirable characteristics for their animals, and shipping embryos is much easier than shipping animals. This also allows offspring to grow up in their permanent environment.

24. Sample answer: The bacteria do or do not do something to the protein that would normally occur in the human tissue.

Caption Questions

Figure 4.4 (Student textbook page 162): Unequal distribution in anaphase could lead to unequal distribution of chromosomes between new cells. This would lead to chromosomal disorders or cells that were not viable.

Figure 4.10 (Student textbook page 167): They are homologous because they are two X chromosomes that are the same length and carry genes for the same traits at the same location.

Figure 4.12 (Student textbook page 169): six chromosomes

Figure 4.13 (Student textbook page 171): Meiosis I would produce cloned cells, resulting in less genetic diversity introduced into the cell and the organism.

2 MHR TR ? Biology 11 Answer Key Unit 2

Figure 4.25 (Student textbook page 184): The vector DNA contains DNA only from one source, while recombinant DNA contains the vector DNA and the DNA being cloned.

Figure 4.26 (Student textbook page 185): The nucleus is removed from the egg cell so that it will only contain the nucleus with the desired (inserted) genes.

Figure 4.28 (Student textbook page 187): Reduced crop loss due to disease will result in larger harvests. This saves the farmer money and allows lower prices.

Figure 4.29 (Student textbook page 188): Students may suggest that animal genes should not be manipulated for human benefit, period; that the welfare of the animals should be considered; or that any method available should be used to alleviate human suffering. Any answer supported by an argument is acceptable.

Section 4.1 Review Questions (Student textbook page 168)

1. All living things are composed of one of more cells. Cells are the smallest units of living organisms. New cells come only from pre-existing cells, by cell division.

2. Sample answer: Skin cells undergo mitosis more frequently than nerve cells do. The skin cells will divide and repair the cut before the nerve cells are replaced.

3. In a child, because a child is growing in addition to repairing and replacing tissue

4. G1 is a period of rapid growth and normal cell duties. S is a period of DNA replication so that each cell produced receives a full set of DNA. During G2, cells prepare for division; organelles are made so that new cells have full complement of information.

5. a. anaphase b. prophase c. telophase

6. Sketches should look like Figure 4.4.

7. Sample answer: DNA replicates and I am connected to my twin; we condense to make chromosomes, line up along the equator, are pulled apart to opposite sides, and are then surrounded by a new nuclear membrane. We relax and get to work.

8. Mitosis duplicates and divides the nuclear material and cytokinesis divides the cytoplasm, producing two daughter cells.

9. Daughter cells are genetically identical to parent cells (except in the case of a mutation).

10. Since microtubules are responsible for the accurate division of the chromosomes, it is likely that the chromosomes would not move to the poles, and

that when cytokinesis occurred, there would be a completely random division of the genetic material or that cell division would stop.

11. The error most likely occurred during anaphase, when the chromosomes are divided for the new daughter cells. The centromere did not divide or spindle fibres only formed from one centrosome, resulting in all of the chromosomes moving to the same pole. When cytokinesis occurred, all of the chromosomes were on one side of the cell. The other daughter cell had no chromosomes.

12. Students should sketch the basic structure of DNA, indicating nucleotides and that a certain section of the DNA contains a gene. Thin threadlike substances should represent chromatin, and something resembling the chromosome structure. Sketches should show that DNA is a component of both chromatin and chromosomes, such as in Figure 4.7 on student textbook page 165.

13. Chromosome pairs are not necessarily identical (due to copying errors, etc.) but the pairs are homologous, meaning their genes are in corresponding locations but may have different coding.

14. Diagrams should combine Figures 4.5 (on student textbook page 163) and 4.9 (on student textbook page 167).

15. Diagram should show an entire set of chromosomes, with three that are identical in both size and banding.

16. The X and Y chromosomes determine the sex of the individual; a female has two Xs and a male has one X and one Y.

17. a. This is a karyotype, prepared by collecting a cell sample that is treated to stop cell division during metaphase of mitosis, then stained to produce a banding pattern on the chromosomes that is clearly visible under a microscope. Chromosomes are then sorted and paired. The autosomes are numbered 1 through 22 and the sex chromosomes are labelled as X or Y.

b. Male

c. Yes, this individual has the correct number of chromosomes (23 pairs, 46 altogether).

18. By matching homologous chromosomes (which should be the same size and pattern), the doctor would see that one chromosome is shorter than it should be.

Biology 11 Answer Key Unit 2 ? MHR TR 3

Section 4.2 Review Questions (Student textbook page 181)

1. a. meiosis b. fertilization c. mitosis

2. a. 2n = 64 b. n = 32 c. 32 d. 64

3. fertilization

4. Meiosis produces cells that: ? are genetically diverse; and ? contain half the number of chromosomes (are haploid)

5. a. Metaphase II b. Sketches should show that the sister chromatids separate and move to opposite poles of the cell. c. Different colours illustrate that genetic material was exchanged during crossing over. d. 2n = 8

6. Meiosis takes place in the reproductive organs (ovaries and testes).

7. Homologous pairs line up next to each other to make a tetrad. This leads to chromosomes becoming tangled (synapse) and DNA trading places. This leads to increased variation in the daughter cells.

8. Mitosis and meiosis II are very similar in that the chromosomes line up on the equator and are separated during anaphase. The significant difference is that mitosis separates the chromosomes of a diploid cell, but in meiosis II the cell is haploid.

9. Sample answer:

Spermatogenesis

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TFYDFMMT TQFSN

rDFMMTQSPEVDFE rPDDVSTJO

UIFUFTUFT rTUBSUTXJUI

TQFSNBUPHPOJVN

rQSPEVDFTIBQMPJE HBNFUFTGSPN EJQMPJEDFMMT CZNFJPTJT

rFWFODZUPQMBTNJD

EJWJTJPO

Oogenesis rQSPEVDFTGFNBMF

TFYDFMMT FHHT

rDFMMBOEQPMBS

CPEJFTQSPEVDFE rVOFWFODZUPQMBTNJD

EJWJTJPO rTUBSUTXJUI

PPHPOJVN rPDDVSTJO

UIFPWBSJFT

10. 25 = 32 distinct gametes

11. Independent assortment refers to the fact that the orientation of each pair of chromosomes along the equator is independent of the orientation of the other pairs (ensuring a mix of maternal and paternal DNA goes to each pole). Crossing over refers to the

entanglement of chromatids during prophase 1 that leads to pieces of chromosome changing places.

Both lead to variation by creating unique combinations of chromosomes and genes in the sex cells. Sketch should combine information from Figures 4.18 and 4.19 on student textbook page 175.

12. Sketches should accurately represent the errors in chromosome structure as shown in Table 4.1 on student textbook page 177.

13. Chromosomes do not separate evenly during nondisjunction. During anaphase II, a centrosome may not divide, leading to sister chromatids both going to the same pole. During anaphase I, a spindle fibre may attach to both homologous chromosomes and pull them to the same pole. This results in one cell having one too many chromosomes (called trisomy) or one too few chromosomes (called monosomy).

14. By looking at the homologous pairings in a karyotype, a clinician can quickly see if one of the chromosomes is missing its homologue (monosomy) or has two homologues/three identical chromosomes (trisomy).

15. Invasive methods of prenatal genetic testing pose a risk to the fetus. If there are no indications of genetic abnormality, there is no reason to put the fetus at risk of miscarriage (i.e., invasive methods can be avoided).

16. Students' arguments should be supported by statements from either the textbook or individual research. Students will likely find that it was difficult to be entirely in favour of or against this type of testing, illustrating the dilemmas faced by many.

Section 4.3 Review Questions (Student textbook page 190)

1. Selective breeding. Farmers choose the best animals to breed with each other by looking at the traits that they considered favourable (for example, the fastest or those which produced the most milk).

2. Ways to produce these traits should relate to finding parent animals with the same traits. Students may mention selective breeding or artificial insemination.

3. Answers should contain supporting information such as: In favour--anything that makes us better should be encouraged; taking the best characteristics and allowing people to pick and choose their skills will make us more productive Opposing--it is not right to interfere with nature; everyone could end up being highly skilled in the same areas and we wouldn't have people who would want to or be able to do other jobs

4 MHR TR ? Biology 11 Answer Key Unit 2

4. Both embryo transfer and IVF involve in vitro fertilization of egg by sperm. In humans, there is usually no genetic basis for choosing the egg and sperm donor. Most human IVF procedures are undertaken as a result of a fertility problem. Usually in humans, the embryo is implanted into the female that donated the egg, whereas in animals, the embryo is usually implanted in an unrelated female

5. Vectors act as carriers of DNA that a scientist wants to clone, enabling that DNA to be copied to a foreign cell. This is important for applications such as gene therapy and making insulin.

6. Gene cloning copies a segment of DNA, usually for the purpose of protein production or study. Therapeutic cloning produces genetically identical cells, usually for medical treatments. Reproductive cloning produces genetically identical individuals.

7. Flowcharts and diagrams should accurately represent the process as shown in Figure 4.25 on student textbook page 184.

8. Binary fission; some cells underwent conjugation or had vectors inserted into them

9. Somatic cell nuclear transfer uses an egg cell (with its nucleus removed) and the nucleus from a somatic cell. The daughter cells are genetically identical to the somatic cell.

10. Producing insulin through transgenic plants is less expensive.

11. The animals produced through reproductive cloning suffer from health problems and reduced lifespan, and many are not even born alive.

12. He can choose to breed his schnauzer with another prize-winning dog (selective breeding) or he could clone it. Cloning would produce the most exact copy.

13. Stem cells are used in regenerative medicine because they are undifferentiated. When they are placed into a patient, they can be stimulated to differentiate and replace the defective cells of the patient.

14. Students may choose examples such as transgenic animals like goats which are designed to produce medical protein products like HGH in their milk, or pigs that can act as organ donors.

15. a. Sample answer: The Canadian government should consider the benefits of the transgenic carrots over regular carrots: are the worms and insects a significant crop risk? Will it cause more economic success? Where did the genes come from? Are the genes naturally-occurring in the area? Will pesticide eliminate desirable bugs as well? Might the pesticide genes cross over to other plants? Are there any possible health risks to those who eat the carrots?

b. Sample answer: The biggest advantage is that crops will be larger and of a better quality. Other advantages may be that fewer pesticides are needed, and that pesticides are delivered at the site of concern and in the smallest possible amounts, reducing toxic runoff. Disadvantages might include a higher seed cost, resulting in higher market prices and fewer sales. The public may also be reluctant to buy transgenic food.

c. Answers should show an understanding of the arguments mentioned in the subsection entitled "Regulating the Use of Transgenic Organisms" on student textbook page 188.

16. Students may agree or disagree. If they agree, arguments might include that it will save lives (prevent deadly allergic reactions). If they disagree, arguments might include that there are more pressing issues than creating a peanut that doesn't cause an allergic reaction, or that the causes of allergies are more complex than a simple allergen?reaction relationship, and that other solutions are possible.

Chapter 4 Review Questions (Student textbook pages 195?7)

1. d

2. d

3. e

4. e

5. c

6. a

7. e

8. b

9. growth, repair, and maintenance

10. The bases in DNA connect to each other in a way that looks like the rungs of a ladder. The sugar and phosphate make the rails of the ladder, joining the rungs. The comparison is limited because a real ladder is flat but DNA is twisted in a helix.

Biology 11 Answer Key Unit 2 ? MHR TR 5

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