001-028 U2-AK BIO11TR

Answer Key

Unit 2 Genetic Processes

13. Daughter cells formed during cell division are

genetically identical to the parent cell.

Unit Preparation Questions

(Assessing Readiness)

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.

(Student textbook pages 154¨C7)

1. b

2. In both animal and plant cells: A¨Ccell membrane

B¨Ccytosol

C¨Cmitochondrion

E¨Cendoplasmic reticulum (smooth and rough)

G¨CGolgi apparatus

H¨Cnucleus (or nuclear envelope)

L¨Cnucleus (or nuclear envelope)

In plant cell only: I¨Ccentral vacuole

J¨Ccell wall (or membrane)

K¨Cchloroplast

In animal cell only: D¨Cribosomes

F¨Cvesicle

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) ¡ú chromosomes (composed of) ¡ú

DNA (which is made up of) ¡ú genes (which code for)

¡ú 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¨Ccentrosome

B¨Cchromosomes

C¨Cspindle fibres

D¨Ccentromere

15. A¨Cinterphase

B¨Cgrowth and preparation (G1)

C¨CDNA replication

D¨Cgrowth and preparation (G2)

E¨Cmitosis

F¨Ccytokinesis

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¡ªskin

is easily damaged and must often be replaced. Nerve

cells have a long life span¡ªthese 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¡ªthey 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

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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

2

MHR TR ? Biology 11 Answer Key Unit 2

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 highquality 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.

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).

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.

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

Biology 11 Answer Key Unit 2 ? MHR TR

3

entanglement of chromatids during prophase 1 that

leads to pieces of chromosome changing places.

Section 4.2 Review Questions

(Student textbook page 181)

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.

1. a. meiosis

b. fertilization

c. mitosis

2. a. 2n = 64

b. n = 32

c. 32

d. 64

12. Sketches should accurately represent the errors in

chromosome structure as shown in Table 4.1 on

student textbook page 177.

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

r
QSPEVDFT
NBMF


TFY
DFMMT
TQFSN

r

DFMMT

QSPEVDFE r
QSPEVDFT
IBQMPJE


r
PDDVST
JO


HBNFUFT
GSPN


UIF
UFTUFT

EJQMPJE
DFMMT


r
TUBSUT
XJUI


CZ
NFJPTJT

TQFSNBUPHPOJVN

r
FWFO
DZUPQMBTNJD


EJWJTJPO

Oogenesis

r
QSPEVDFT
GFNBMF


TFY
DFMMT
FHHT

r

DFMM
BOE

QPMBS


CPEJFT
QSPEVDFE

r
VOFWFO
DZUPQMBTNJD


EJWJTJPO

r
TUBSUT
XJUI


PPHPOJVN

r
PDDVST
JO


UIF
PWBSJFT

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

4

MHR TR ? Biology 11 Answer Key Unit 2

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¡ªanything 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¡ªit 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. 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¨Creaction relationship,

and that other solutions are possible.

Chapter 4 Review Questions

(Student textbook pages 195¨C7)

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

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