Ch 6 online exam bio 101

1- The DNA in linear eukaryotic chromosomes is wrapped around proteins called _____________, which keep the DNA from getting tangled and enable an orderly, tight, and efficient packing of the DNA inside the cell. A-telomeres B-ribosomes C-histamines D-centromeres E-histones

1- E histones . ......... correct

10-Naturally occurring chemicals in plants may be useful in inhibiting cancer. One of these chemicals that is found in grapes and peanuts is called A-resveratrol. B grape inhibition hormone. C erythropoietin. D insulin. E cancer inhibition hormone.

10-A resveratrol.... correct

11-In humans, the haploid number, n, equals A 46. B 44. C 23. D 2n. E 3n.

11- C 23

12-A karyotype of one of your skin cells would reveal a total of 46 chromosomes. How many of these are maternally inherited autosomes? A-22 B- 23 C-20 D-46 E-24

12- A-22 ....... correct

13-In the ______________ process of DNA replication, each of the single strands becomes a double strand as an enzyme connects the appropriate complementary base to the exposed base. A-duplication B- error correction C- rebuilding D- unwinding E- attachment

13- C- rebuilding ...... correct

14-During meiosis, chromatin A- unwinds to allow synapsis between homologous pairs of chromatids. B- condenses, becoming more tightly coiled. C- unwinds to allow tetrads to form. D- reduces the incidence of crossing over. E- binds to the metaphase plate, enabling chromosome division.

14-B condenses, becoming more tightly coiled..... correct

15-Separation of the chromatids at the end of metaphase leads into the next phase, which is A- anaphase. B- interphase. C- postmetaphase. D- prophase. E- telophase.

15- A Anaphase.... correct

16-In order for a eukaryotic cell to undergo reproduction and divide, certain steps must be successfully completed. Select the choice below that is NOT one of these necessary steps. A-Replication of the DNA within the nucleus must occur. B-Proper division of the cytoplasm must occur. C-Proper packaging and segregation of the replicated DNA must occur. D-Proper reshuffling of the genetic material must occur in order to provide diversity within the gametes. E- All of the above answer choices are necessary steps in eukaryotic cellular replication.

16- D Proper reshuffling of the genetic material must occur in order to provide diversity within the gamete

17-In a cell in which 2n = 46, the independent assortment of chromosomes during meiosis can by itself give rise to how many genetically different gametes? A-46 B-184 C-23 D-92 E-There is insufficient information to answer this question.

17- C-23 ....... maybe correct

18-Mitosis results in A-eight daughter cells. B-daughter cells with the same number of chromosomes but different combinations of alleles. C-daughter cells with twice as much genetic material and a unique collection of alleles. D-gametes. E-daughter cells with the same number and composition of chromosomes.

18-E daughter cells with the same number and composition of chromosomes....... correct

19-Bacteria reproduce asexually, whereas most plants and animals reproduce sexually. Which is the better method? A-Neither method is better—each is effective in different environments for different kinds of organisms. B- Sexual reproduction is the better method because it produces more variation. C-Sexual reproduction is the better method because more plants and animals than bacteria are present. D-Asexual reproduction is the better method because more bacteria than plants and animals are present. E-Asexual reproduction is better because binary fission is more efficient.

19- A-Neither method is better—each is effective in different environments for different kinds of organisms..... correct

2- In most bacteria, the DNA is carried in A-multiple linear chromosomes. B-multiple circular chromosomes. C-a single circular chromosome. D-a single linear chromosome. E-two circular chromosomes.

2- C a single circular chromosome ........ correct

20- Anaphase of mitosis occurs when A-the cell enters interphase. B-the chromatin coils into thicker, visible chromatids. C-crossing over begins. D-the chromatids begin to separate from the metaphase plate. E-the nuclear envelope first breaks down.

20-D The chromatids begin to separate from the metaphase plate...... correct

21- In many species of birds, males are XX and females are XZ. With birds like this, who is most likely to display a sex-linked recessive trait? A-Females are more likely to display a sex-linked recessive trait. B-Males are more likely to display a sex-linked recessive trait. C-Males and females are equally likely to display a sex-linked recessive trait. D-No Y chromosome exists, so they are not affected by sex-linked recessive traits. E- The gender that is incubated at a higher temperature is more likely to display a sex-linked recessive trait.

21-A Females are more likely to display a sex-linked recessive trait

22- Prokaryotic cells generally have a single circular chromosome attached to A-proteins called histones. B-the cell membrane. C-the ribosome. D-the nuclear membrane. E- the telomere.

22- B the Cell membrane .......... correct

23- In female gamete development in humans and other vertebrates, the net result of meiosis is the production of one large egg and three small cells with very little cytoplasm. These three small cells A- divide to form secondary egg cells. B-fuse together to form the placenta. C-fertilize the egg. D-act to nurse the egg cell. E-degrade almost immediately.

23-E degrade almost immediately.... correct

24- Some fertility clinics now promise that a couple can choose the sex of their baby. What technique might allow for this? A-Separating the father's sperm according to weight, because the X chromosome weighs more than the Y chromosome. B-Separating the father's sperm according to weight, because the Y chromosome weighs more than the X chromosome. C-Add a fluorescent dye to the father's sperm—sperm that show more fluorescence contain a Y chromosome. D-Add a fluorescent dye to the father's sperm—sperm that show more fluorescence contain an X chromosome. E-Both the first and fourth answer choices are correct.

24-E Both the first and fourth answer choices are correct....... correct

25- DNA replication occurs during the _____________ phase of the cell cycle. A-Gap 2 B-S (DNA synthesis) C- prophase D-Gap 1 E- M

25-B- S (DNA synthesis) .... correct

26- Sex cells having the ___________ number of chromosomes are called ____________. A- haploid; gametes B- diploid; gametes C- diploid; zygotes D- haploid; zygotes E- diploid; somatic cells

26-A haploid; gametes... correct

27- A cell is said to have reached the metaphase stage of mitosis when A- the nuclear envelope disappears. B- the centromeres have arrived at the equatorial plate. C-separation of the chromatids begins. D- the cell physically divides in two. E- None of the above answer choices is correct.

27-B the centromeres have arrived at the equatorial plate....... correct

28- In DNA replication, when the DNA molecule separates into two strands, A- it is possible to reconstruct perfectly all the information on the missing strand because one strand carries all the information needed to construct its complementary strand. B- the rebuilding process begins, in which an enzyme connects the appropriate complementary base to the exposed base. C- the mitotic phase begins. D- All of the above answer choices are correct. E- Only the first and second answer choices are correct.

28-E Only the first and second answer choices are correct. ... correct

29- Between the stage in the cell cycle where the genetic material is replicated and the process of cell division begins, there is a stage referred to as A- Gap 2. B- Gap 1. C- Gap 3. D- mitotic phase. E- None of the above is correct; there is no stage between the replication and division stages in the cell cycle.

29-A Gap 2. ..... correct

3- A karyotype is a physical representation (usually a photograph) of all of the chromosomes in a single cell; however, the cell must be in mitotic metaphase when the karyotype is made. Why? A- Metaphase is the only stage of the cell cycle in which both sets of homologous chromosomes are present in the cell. B-Metaphase is the only stage of the cell cycle in which the nuclear envelope is degraded. C-Metaphase is the only stage of the cell cycle in which the cell membrane is permeable to dye. D-Metaphase is the only stage of the cell cycle in which both sister chromatids of each chromosome are present in the cell. E-Metaphase is the only stage of the cell cycle in which the chromosomes have condensed and aligned, but have not yet separated.

3-E Metaphase is the only stage of the cell cycle in which the chromosomes have condensed and aligned, but have not yet separated.... correct

30- During meiosis but NOT during mitosis, A- genetic variation among the daughter cells is increased. B- duplication of the cytoplasm occurs. C- two identical daughter cells are produced. D- haploid gametes are produced that are all identical in their allelic composition. E- chromosomes line up in the center of the cell during metaphase.

30-A genetic variation among the daughter cells is increased.

31- Hermaphrodites are individuals with functioning male and female reproductive organs capable of producing both male and female gametes. Which of the following statements about hermaphrodites is INCORRECT? A- Hermaphrodites are common among invertebrates. B- Some vertebrate hermaphrodites exist. C- An XXY human is a hermaphrodite. D- Humans with Klinefelter syndrome are not hermaphrodites. E- No human hermaphrodites exist.

31- C- An XXY human is a hermaphrodite...... correct

32- Errors sometimes occur when DNA duplicates itself. Why might that be a good thing? A- Most errors are, in fact, good for the organism in which they occur. B- The rebuilding process proceeds much more quickly when a few errors occur. C- Errors in DNA replication can never be a good thing. D- The DNA replication process becomes more fine-tuned, the more errors it makes. E- New genes can enter the population and be acted upon by evolution.

32-E New genes can enter the population and be acted upon by evolution...... coorect

33- How many sex chromosomes does the normal human female inherit from her mother? A- 1 B- 23 C- 46 D- 22 E- 2

33-A 1.... correct

34- Chromosomes on which recombination takes place A- have a mixtures of maternal and paternal chromosomes. B- are created during meiosis. C- usually result in aborted fetuses. D- lead to the condition known as Down syndrome. E- Both the first and second answer choices are correct.

34-E Both the first and second answer choices are correct..... correct

35- A diploid cell undergoes meiosis. What are the products of this division? A- four diploid cells B- two haploid cells C- one polyploid gamete D- two diploid cells E- four haploid cells

35-E four haploid cells. ...... correct

36- Animal cells have "counters" that keep track of how many times a cell has divided. These counters are called A- centromeres. B- odometers. C- telomeres. D- nuclei. E- chromosomes.

36-C telomeres. correct

37- Non-disjunction A- is the division of cytoplasmic constituents. B- is the cause of sex determination in birds and mammals. C- is the unequal division of the genetic material during cell division. D- is the exchange of genetic material between the chromatids from homologous chromosomes. E- occurs during mitosis but not meiosis.

37-C is the unequal division of the genetic material during cell division

38- Cytokinesis A- occurs during mitosis but not meiosis. B- refers to the division of a cell's cytoplasm. C- occurs during prophase. D- results in greater genetic diversity among daughter cells. E- All of the above answer choices are correct.

38-B refers to the division of a cell's cytoplasm...... correct

39- A human skin cell contains 46 chromosomes (23 paternally inherited and 23 maternally inherited). Before mitosis begins, this cell must duplicate its genetic material. What are the products of this duplication? A- 92 chromatids, each consisting of 2 sister chromosomes connected by a kinetochore. B- 23 chromosomes, each consisting of a maternal and a paternal chromatid connected by a centromere. C- 92 chromosomes, each consisting of 2 homologous chromatids connected by a centromere. D- 92 sister chromatids, in 46 pairs that are connected by a centromere. E- None of the above answer choices is correct.

39-D 92 sister chromatids, in 46 pairs that are connected by a centromere. ...... correct

4- Down syndrome results from which of the following chromosomal abnormalities? A-two Y chromosomes B-inversion of the long arm of chromosome 8 C- the absence of a second copy of chromosome 10 D-all or part of a third copy of chromosome 21 E-a truncated copy of chromosome 3

4- D all or part of a third copy of chromosome 21

40- During which phase of the cell cycle do the chromosomes align in one plane at the center of the cell? A- interphase B- prophase C- metaphase D- anaphase E- telophase

40-C metaphase

41- Cancer cells are different from other cells in that they have lost their "contact inhibition." "Contact inhibition" means that A- DNA replication in most cells stops when the double helix comes in contact with particular enzymes. B- most cells stop dividing when they bump up against other cells or collections of cells. C- DNA replication in most cells doesn't begin until the double helix comes in contact with particular enzymes. D- most cells don't begin to divide until they bump up against other cells or collections of cells. E- most cells stop dividing when they have reached 50 cell divisions.

41-B most cells stop dividing when they bump up against other cells or collections of cells...... correct

42- In mitosis, telophase occurs when A- the chromosomes begin to uncoil. B- the chromosomes reach opposite poles and stop moving. C- chromosome condensation occurs. D- crossing over occurs. E- Both the first and second answer choices are correct.

42-E Both the first and second answer choices are correct..... correct

43- Crossing over is the mixing of chromosomes, which results in the recombination of genes on the same chromosome. Which of the following correctly describes the process of crossing over? A- During replication, a chromosome from one tetrad breaks off from its pair, as does a chromosome from another tetrad. The two chromosomes switch places. B- Two chromatids (one maternal and one paternal) break off at corresponding points on homologous chromosomes. The pieces of chromatid rejoin to the chromosome in each other's places. C- Two alleles exchange positions on a chromosome, creating new recombination frequencies. D- One paternal tetrad switches places with a maternal tetrad, so that they occupy places on opposite ends of the spindle fibers. E- While homologous chromosomes are splitting apart and separating to either end of the new nucleus, two chromosomes switch positions and move toward the ends opposite from where they were originally headed.

43-B- Two chromatids (one maternal and one paternal) break off at corresponding points on homologous chromosomes. The pieces of chromatid rejoin to the chromosome in each other's places....... correct

44- In humans, both sexes have the same number of autosomes but different ratios of sex chromosomes. Males are XY and females are XX. Which of the following statements comparing the X and Y chromosomes is FALSE? A- Certain regions on the Y chromosome are unique and not found on the X chromosome. B- Genetic instructions on the Y chromosome instruct the fetal gonads to develop as testes instead of ovaries. C- The Y chromosome is much smaller than the X chromosome, with 85 genes and 1,000 genes respectively. D- Certain regions on the Y chromosome are identical to the genes on the X chromosome. E- Genetic instructions on the X chromosome instruct the fetal gonads to develop as testes instead of ovaries.

44-E- Genetic instructions on the X chromosome instruct the fetal gonads to develop as testes instead of ovaries..... correct

45- Somatic cells can include A- kidney cells. B- heart cells. C- sperm cells. D- All of the above answer choices are correct. E- Both the first and second answer choices are correct.

45-E Both the first and second answer choices are correct....... correct

46- Crossing over means the same as A- sex-linked inheritance. B- heterozygosity. C- the process by which pieces of homologous chromosomes are exchanged. D- incomplete dominance. E- independent assortment.

46-C the process by which pieces of homologous chromosomes are exchanged....... correct

47- In asexual reproduction, daughter cells inherit their DNA from A- two separate parents. B- a single parent. C- a single offspring. D- multiple offspring. E- None of the above is correct; in asexual reproduction, the DNA is not inherited.

47-B a single parent. ..... correct

48- In some species, sex is determined by environmental, instead of genetic, factors. This is TRUE of A- dogs. B- birds. C- bees. D- humans. E- turtles.

48-E turtles.

49- Eukaryotic cells can divide by A-mitosis only. B-fission only. C-meiosis only. D-synthesis only. E-both mitosis and meiosis.

49-E both mitosis and meiosis.

5- During DNA replication, each strand serves as a _____________ for the new ________________ strand. A-proofreader; complementary B-blueprint; template C-template; supplementary D-master model; identical E-template; complementary

5-E Template; complementary

50- Chemotherapy is one common treatment for cancer. Which of the following are aspects of chemotherapy? A-Drugs that interfere with cell division are administered to the patient. B-Chemotherapy drugs circulate throughout the entire body. C-Chemotherapy drugs disrupt normal systems that rely on the rapid and constant production of new cells. D-All of the above answer choices are correct. E-Only the first and third answer choices are correct.

50-D-All of the above answer choices are correct....... correct

6- If a cell becomes arrested within the cell cycle because it is unable to replicate its DNA, in which of the stages would you predict it would become arrested? A-mitotic phase B-Gap 2 phase C- Gap 1 phase D- S phase E- None of the above is correct; the cell would simply die.

6- C- Gap 1 phase ......... correct

7- Some animals are primarily asexual in their reproduction, but have the ability to switch to sexual reproduction under certain conditions. Why might an animal that generally reproduces asexually make this switch to sexual reproduction? A-to better compete in crowded situations B-to confuse its predators C-to increase the genetic diversity of its offspring during periods of stress D- to increase its own likelihood of survival E- None of the above answer choices is correct.

7-C- to increase the genetic diversity of its offspring during periods of stress......... correct

8-A karyotype A-reveals the autosomes but not the sex chromosomes. B-can be produced only from cells in telophase of mitosis or telophase II of meiosis. C-requires a haploid gamete. D-can be produced only from cells in telophase of mitosis. E- can be used to diagnose Down syndrome in humans.

8-E can be used to diagnose Down syndrome in humans..... correct

9-Crossing over takes place during A-cytokinesis. B-mitosis. C-meiosis. D-mitosis and meiosis. E-None of the above answer choices is correct.

9-C meiosis..... correct