UNIT V STUDY GUIDE KEY

I. DNA

A. adenineG. covalent bond (phosphodiester linkage)

B. guanineH. cytosine

C. phosphate groupI. thymine

D. deoxyriboseguanine & adenine = purines

E. nucleotidethymine & cytosine = pyrimidines

F. hydrogen bond

II. Scientists

1. Meselson & Stahl

2. Rosalind Franklin

3. Hershey & Chase

4. Chargaff

5. Griffith

6. Watson & Crick

7. Avery, McCarty, and MacLeod

III. DNA Replication

1. 3’ end of parental strand

2. 3’ end of parental strand

3. 5’ end of daughter strand

4. where DNA ligase will unite pieces

5. Okazaki fragment

6. 3’ end of daughter strand

7. 5’ end of parental strand

DNA replication occurs in the nucleus of eukaryotic cells during S phase of the cell cycle. First, the hydrogen bonds between the nitrogen bases are split with the enzyme, helicase, opening the double helix at points called origins of replication. Another enzyme known as topoisomerase makes small cuts in the DNA, then re-joins them to alleviate twisting of the DNA ahead of the replication fork. After separation of the parental strands, single-stranded binding proteins hold them apart to prevent the hydrogen bonds from re-forming. The enzyme, DNA polymerase then moves in nucleotides according to Chargaff’s (base pairing) rules, adenine with thymine and guanine with cytosine. Nucleotides can only be added to an existing strand of nucleotides, so first the enzyme, primase adds a short RNA primer at the point where replication begins. Synthesis always occurs in a 5’ to 3’ direction, so one new strand is synthesized continuously producing the leading strand; however the other strand is forming away from the replication fork. This strand is known as the lagging strand and it is synthesized in short pieces known as Okazaki fragments. The fragments are then joined together by the enzyme, DNA ligase to form a continuous strand of nucleotides. Another DNA polymerase follows and proofreads the newly synthesized strand of nucleotides. Each time replication takes place, a small portion of DNA is left unreplicated due to the removal of the RNA primer combined with the fact the DNA polymerase can only add nucleotides to an existing strand; thus, a small, single-stranded segment of DNA is lost at the 5’ end of each newly-synthesized strand with each cell cycle. The integrity of the genetic material is preserved by sequences of non-coding nucleotides at the tips of chromosomes known as telomeres. As cells divide, the tips shorten, leading to cell aging and eventually, cell death. Two types of human cells, stem cells and cancer cells produce an enzyme known as telomerase that lengthen the end-caps, essentially making these cells capable of unlimited cell division.

IV. Vocabulary Check

1. W21. H

2. KK22. L

3. LL23. T

4. D24. M

5. Q25. V

6. R26. J

7. CC27. U

8. GG28. E

9. K29. HH

10. JJ30. Y

11. F31. II

12. NN32. Z

13. BB33. FF

14. DD34. I

15. AA35. C

16. G36. X

17. S37. MM

18. P 38. A

19. EE39. N

20. D40. B

V. DNA Content

1. C

2. H

3. D, J

4. I, J, K (and by the end of H)

VI. Chromosome Number

1. 46. 4

2. 47. 4

3. 28. 2

4. 89. 2

5. 810. 4

VII. Identification

1. anaphase II6. anaphase

2. prophase I7. prophase

3. telophase II8. metaphase I

4. metaphase II9. anaphase I

5. telophase10. metaphase

VIII. Mitosis vs Meiosis

MITOSIS / MEIOSIS
Definition: Cell division that results in
2 cells identical to parent cell / Definition: Cell division that results in
4 cells with half the chromosome number of the parent (germ) cell
Cells Where Process Occurs:
somatic cells / Cells Where Process Occurs:
germ cells in ovaries, testes
Number of DNA Replications:
1 / Number of DNA Replications:
1
Number of Cell Divisions:
1 / Number of Cell Divisions:
2
Number of Resulting Daughter Cells:
2 / Number of Resulting Daughter Cells:
4
Chromosome Number in Original Cell:
46 / Chromosome Number in Original Cell:
46
Chromosome Number in Daughter Cells:
46 / Chromosome Number in Daughter Cells:
23
Purpose:
To replace damaged cells, enable growth & development, maintain genetic continuity of all cells / Purpose:
To produce gametes, ensure genetic variability, ensure fertilized zygote has correct chromosome number.
2n
2n
2n 2n / 2n
2n
n n
n n n n

IX. Cell Cycle Control

  • Density-dependent inhibition – G1
  • Alignment of sister chromatids at metaphase plate - M
  • Proper replication of DNA – G2
  • Presence of growth factors - G1
  • Integrity of spindle apparatus - M
  • Nutrient availability - G1
  • Damage to DNA - G1
  • Anchorage dependence - G1
  • Cell Size - G1
  • Please Note: Many of the controls monitored at G1 are also factors at G2 checkpoint

X. Chi Square Problems

  1. There is no significant difference in aggressive behavior in baboons due to light intensity.

Chi2 = 4.83

1 degree of freedom

P value ≤ 0.05

Null hypothesis is rejected; light intensity does have an effect on aggression in baboons

  1. There is no significant difference between the expected number of kittens with the defect as compared to the number actually born with the defect.

Chi2 = 6.93

1 degree of freedom

P value ≤ 0.05

Null hypothesis rejected; there is a significant difference in the actual number of kittens with the defect as compared to the expected number.

  1. There is no significant difference in test results in students using the traditional math textbook as compared to students using the new textbook.

Chi2 = 2.73

1 degree of freedom

P value > 0.05

Null hypothesis is accepted; the new textbook made no significant difference in test results.

  1. There is no significant difference between the expected number of heads versus tails and the observed number of each.

Chi2 = 1.92

1 degree of freedom

P value > 0.05

Null hypothesis is accepted; the penny is a fair penny.

  1. There is no significant difference on the number of 12s rolled when blowing on the dice as compared to not blowing on the dice.

Chi2 = 0.11

1 degree of freedom

P value > 0.05

Null hypothesis is accepted; there is no advantage to blowing on the dice.