Cell Division

Jan 96,27

Use the following information to answer the next question

1. Meiosis occurs in this life cycle when

A. an egg and a sperm fuse to form a zygote

B. a mature polyp produces a medusa

C. a planula produces a young polyp

D. a medusa produces gametes

Jan 96,28

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2. Which structures normally have a haploid number of chromosomes?

A. Seed plant spores and animal zygotes

B. Seed plant spores and animal gametes

C. Seed plant zygotes and animal zygotes

D. Seed plant gametes and animal zygotes

In the life cycle of this jellyfish, the polyp stage is sessile. The medussa is a diploid, free-

swimming animal. The planula is ciliated and motile.

Jan 96,4

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Some Events that Occur During Meiosis

1. Gametes are produced

2. Spindles form and homologous pairs of chromosomes separate

3. Centromeres divide and chromatid pairs separate

4. Chromosomes are replicated

Numerical Response

1. Provide the correct sequence of these four events that occur during meiosis

(Record your four-digit answer in the numerical-response section of the answer sheet.)

Answer: ___________

Jan 96,29

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3. Which statement best explains why the umber of red blood cells in the human body can be maintained?

A. Mature red blood cells retain sufficient mRNA for replication and transcription

B. Pluripotent stem cells undergo cell division continuously to produce new red blood cells

C. Other types of mature blood cells undergo differentiation to form new red blood cells

D. Mature red blood cells, before they are destroyed, undergo cytoplasmic cleavage

repeatedly to produce more red blood cells

Mature red blood cells lack a nucleus. Approximately 2 million red blood cells are destroyed every

second in the circulatory system. All blood cells differentiate from a common source – a population of

pluripotent stem cells in the bone marrow. Pluripotent refers to the potential of these cells to form any

type of blood cell.

Jun 96,24

Use the following information to answer the next three questions

4. Which row correctly identifies processes I, II, III and IV?

Row

Process

I II III IV

A fusion mitosis meiosis mitosis

B fusion meiosis mitosis mitosis

C fission meiosis mitosis meiosis

D fission mitosis meiosis meiosis

Jun 96,25

5. Processes II and IV illustrate budding. The information in the diagram indicates that budding is a type

of

A. asexual reproduction that produces haploid or diploid cells

B. asexual reproduction that produces diploid cells

C. sexual reproduction that produces haploid or diploid cells

D. sexual reproduction that produces haploid cells

The Life Cycle of Baker’s Yeast

The life cycle of baker’s yeast demonstrates a number of biological processes. Gene a and its allele a+

are present in this yeast population. Genotypes of cells are shown below each cell or group of cells.

Jun 96,26

6. Which genetic principle is best demonstrated by process III?

A. Dominance

B. Segregation

C. Crossing-over

D. Incomplete dominance

Jun 97,25

Use the following information to answer the next two questions

7. What does process Y represent?

A. Oogenesis

B. Fertilization

C. Gastrulation

D. Spermatogenesis

Jun 97,26

8. The cell processes diagrammed are more advantageous than budding because

A. new genetic combinations are produced

B. recessive gene combinations cannot occur

C. less variation occurs increasing survival rates

D. only successful genetic combinations are produced

Jun 97,27

Use the following information to answer the next two questions.

9. According to this karyotype, his individual has

A. one less autosome than normal

B. one more autosome than normal

C. one less sex chromosome than normal

D. one more sex chromosome than normal

Jun 97,28

10. This unusual number of chromosomes is the result of

A. synapsis during gametogenesis

B. crossing over during gametogenesis

C. nondisjunction during gametogenesis

D. lack of cytokinesis during gametogenesis

Jun 98,23

Use the following information to answer the next two questions

11. Which of the following statements about cell types and chromosome numbers is correct?

A. The ovum of a horse contains 66 chromosomes

B. A somatic cell of a cat contains 76 chromosomes

C. The spermatid of a dog contains 39 chromosomes

D. A somatic cell of a human contains 23 chromosomes

Organism Chromosome Number (2n)

Horse 66

Dog 78

Cat 38

Human 46

To prepare a karyotype, cells are broken open and the chromosomes are stained with a dye.

A photograph of the chromosomes is taken, and the chromosomes are arranged in pairs.

Below is an example of a human karyotype that provides information about an individual.

Jun 98,24

Use the additional information to answer the next question

12. Which process illustrates reduction division, as in spermatogenesis?

A. Process 1

B. Process 2

C. Process 3

D. Process 4

Jun 98,4

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Numerical Response

2. Four events that occur in both human asexual and sexual cell reproductions are represented by

numbers __________

(Record your four-digit answer in lowest-to-highest numerical order in the numerical-response

section of the answer sheet.)

Answer: _____ _____ _____ _____

Jun 98,25

13. In a human cell cycle, the event that occurs before mitosis begins and the event that occurs at or near

the completion of mitosis are, respectively,

A. crossing over and synapsis

B. cytokinesis and crossing over

C. replication of DNA and synapsis

D. replication of DNA and cytokinesis

Some Events That Occur During Cell Division

1 Centromeres divide

2 Cytokinesis occurs

3 Identical cells are produced

4 DNA is replicated

5 Haploid cells are produced

6 Spindle fibres form

Jun 98,26

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14. The modern-day interpretation of Mendel’s law of segregation is that

A. alleles are expressed independently during mitosis

B. alleles are expressed independently during meiosis

C. paired alleles separate during mitosis and are distributed into different gametes

D. paired alleles separate during meiosis and are distributed into different gametes

During his study of genetics, Gregory Mendel cross-pollinated many pea plants. He recorded the

number and types of offspring produced and applied his knowledge of mathematics to create

explanations for his observations. He hypothesized that factors are inherited separately and

proposed the law of segregation.

Jan 00,23

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15. Which structures in the life cycle of the Ulva are haploid (monoploid)?

A. Zoospores and the zygote

B. The sporophyte and zygote

C. Zoospores and the gametophytes

D. The sporophyte and the gametophytes

Jan 00,24

Use the following information to answer the next four questions

16. In humans, what process must have occurred to obtain the cells at U?

A. Mitosis

B. Meiosis

C. Fertilization

D. Differentiation

Jan 00,25

17. In humans, what process occurs between U and V?

A. Mitosis

B. Meiosis

C. Fertilization

D. Differentiation

Jan 00,26

18. In humans, what process must occur before cell V forms cells W and X?

A. Mitosis

B. Meiosis

C. Recombination

D. Nondisjunction

Jan 00,27

19. In humans, cells Y and Z represent individual cells that

A. are two eggs

B. will no longer divide

C. will become a 4n cell

D. could develop into identical twins

Chromosome Content of Human Cells During a Series of Events

Jan 00,3

Use the following information to answer the next question

Numerical Response

3. The phases of mitosis in the sequence in which they occur are _____, _____, _____, and _____.

(Record your four-digit answer in the numerical-response section on the answer sheet.)

Jun 00,30

Use the following information to answer the next three questions

20. Which of the structures numbered above was replaced by the beads in the experimental setup?

A. 1

B. 2

C. 3

D. 4

Phases of Mitosis

1 Anaphase

2 Metaphase

3 Prophase

4 Telophase

Investigators were interested in determining the role chromosomes play in the formation of the

mitotic spindle. Using extracts of eggs from the African frog Xenopus laevis, they monitored

spindle assembly in a test tube. The researchers replaced the chromosomes with beads, coated with

random sequence of DNA. The beads served as substitute genetic material, but centrosomes

(centrioles) were absent. As well, a part of the centromere was missing.

Simplified Diagram of Normal Mitotic Cell

-from Travis, 1996

Jun 00,31

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21. Based on the results of this research, the structure or molecule that does not appear to be necessary for

mitosis is

A. DNA

B. a spindle

C. centrosomes

D. microtubules

Jun 00,32

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22. The phase that is delayed and the phase where the chromosomes line up at the equator are,

respectively,

A. telophase and anaphase

B. metaphase and prophase

C. interphase and telophase

D. anaphase and metaphase

The investigators observed that the genetic material on the beads condensed and microtubules

began to form. Within 90 minutes, the microtubules formed a spindle-like structure that lined

up the beads along the centre of the cell.

-from Travis, 1996

Other studies showed that the phase that involves pulling chromosomes to the two poles of

mitotic cells can be delayed for up to 4.5 h by pulling a chromosome out of line from the

centre of the cell.

-from Travis, 1996

Jan 01,23

Use the following information to answer the next three questions.

23. Process Z represents

A. fertilization

B. crossing-over

C. nondisjunction

D. spermatogenesis

Meiosis is a process that results in the reduction of the chromosomes number from diploid to haploid.

Sometimes chromosomes fail to separate, which results in an abnormal number of sex chromosomes.

Jan 01,24

Use the following additional information to answer the next question

24. This evidence best supports which of the scientists’ hypotheses about gender determination?

A. The presence of a Y chromosome causes maleness

B. The lack of a second X chromosome causes maleness

C. The presence of two X chromosomes causes femaleness

D. The Y chromosome is not involved in gender determination

Jan 01,25

Use the following additional information to answer the next question

25. This partial human karyotype represents the last six chromosome pairs, in numerical order. The

karyotype presented is that of a

A. male with trisomy 21

B. female with trisomy 21

C. male with Turner syndrome

D. female with Turner syndrome

Scientists studying Klinefelter and Turner syndromes wanted to determine which of several

hypotheses about gender determination was most likely. These hypotheses were:

presence of a Y chromosome causes maleness

lack of a second X chromosome causes maleness

the presence of two X chromosomes causes femaleness

the Y chromosome is not involved in gender determination

Evidence noted by the scientists included the following points.

Individuals with Klinefelter syndrome (XXY) have genitalia and internal ducts that are

usually male, but their testes are underdeveloped.

Individuals with Turner syndrome (XO) have female external genitalia and internal ducts;

however, the ovaries are underdeveloped.

-from Cummings and Klug, 1997

Partial Human Karyotype

Jan 01,26

Use the following information to answer the next four questions

26. What type of inheritance is demonstrated in Tay-Sachs disease?

A. Autosomal recessive

B. Autosomal dominant

C. Sex-linked recessive

D. Sex-linked dominant

Jan 01,27

27. If tuberculosis regained its former role as one of the world’s deadliest diseases, then the frequency of

the Tay-Sachs allele over time would

A. decrease because of a decreased selective advantage

B. increase because of an increased selective advantage

C. decrease because of an increased selective advantage

D. remain the same as a result of Hardy – Weinberg equilibrium

Jan 01,4

Numerical Response

4. A young couple decided to have genetic screening done to determine if they were carriers of Tay-

Sachs disease. if both individuals were carriers, what percentage of their offspring would be predicted

to have protection from tuberculosis but not have Tay-Sachs disease?

Answer: __________%

(Record your answer as a whole number percentage in the numerical-response section on the answer

sheet.)

Tay-Sachs disease is a hereditary disease that kills 1 in 360,000 individuals in the general

population, but 1 in 4,800 among the Ashkenazi (Eastern European) Jews. The disease

disrupts or halts proper formation of lysosomes and increases fat deposition around the nerve

sheath. Individuals that are homozygous for the defective allele have Tay-Sachs disease and

die at an early age. Studies suggest the heterozygous individuals have a higher survival rate

against tuberculosis than the rest of the population. Biochemical tests can be done to

determine if parents are carriers.

-from Cummings 1994

Jan 01,5

Use the following information to answer the next question

Numerical Response

5. Identify the stages in the conifer life cycle, as numbered above, that correspond with the letters that

represent these stages on the diagram.

Stages: _____ _____ _____ _____

Diagram: A B C D

(Record your four-digit answer in the numerical-response section on the answer sheet.)

Jan 02,35

Use the following information to answer the next six questions

28. The probability of two carriers parents having a child with sickle cell anemia is

A. 25 %

B. 50 %

C. 75 %

D. 100 %

Jan 02,36

29. If scientists are successful in significantly reducing or eliminating malaria, the best prediction for what

will happen to the allele for sickle cell anemia in the population is that it will

A. not be affected by the elimination of malaria

B. increase as its selective advantage is increased

C. be reduced as its selective advantage is decreased

D. quickly disappear as its selective advantage is increased

Sickle cell anemia is an autosomal recessive genetic disorder. Because individuals affected by

sickle cell anemia have defective hemoglobin proteins, their blood cannot transport oxygen

properly. There appears to be a relationship between the incidence of malaria and sickle cell

anemia. Individuals with sickle cell anemia and carriers of the sickle cell allele have some

resistance to malaria. Malaria is caused by the parasite Plasmodium and is transmitted between

humans by mosquitoes.

Jan 02,37

Use the following additional information to answer the next two questions

30. The row below that identifies process 1 and process 2 is

Row Process 1 Process 2

A. mitosis meiosis

B. mitosis mitosis

C. meiosis mitosis

D. meiosis meiosis

Jan 02,38

31. The row below that identifies the chromosome number at the first stage and the chromosome number

at the second stage is

Row First stage Second stage

A. diploid haploid

B. diploid diploid

C. haploid diploid

D. haploid haploid

Jan 02,39

Use the following additional information to answer the next two questions

32. Some investigators have suggested that some strains of Plasmodium have become chloroquine-

resistant because these strains have an increased ability to pump chloroquine from their bodies. Other

investigators suggest that the resistance stems from changes in some strains of Plasmodium that

prevent chloroquine from entering the parasites in the first place. These two suggestions can best be

described as

A. theories

B. hypotheses

C. conclusions

D. observations

Jan 02,40

33. A possible reason that the Plasmodium parasite may have resistance to chloroquine is that the cg2 gene

codes for protein that seems to play a role in membrane transport of the drug. If this true, researchers

may want to develop compounds that specifically block this resistance mechanism by

A. preventing mutation of the cg2 gene

B. stimulating translation of the cg2 gene

C. preventing transcription of the cg2 gene

D. stimulating DNA replication of the cg2 gene

Insecticides have been used to control mosquito populations in order to prevent the spread of

malaria, but mosquitoes in malaria-infested areas are developing resistance to these insecticides.

In addition, the antimalarial drug chloroquine, once very effective in protecting individuals

against Plasmodium, has become ineffective, which ahs resulted in a resurgence of malaria.

Scientists have identified a gene, called cg2, in Plasmodium that allows the Plasmodium to

mount resistance to chloroquine. This research could be used by scientists to develop new

versions of chloroquine that will sidestep the parasite’s resistance and, therefore, efffectively

protect people against malaria.

- from Travis, 1997