1. UNIT V - DNA & CELL DIVISION
Baby Campbell – Ch 9 , 10, 13
Big Campbell – Ch 12, 13, 16

2. I. CHI SQUARE ANALYSIS
Statistical tool that evaluates variation in categorical data
Used to determine if variation is significant or instead, due to random error, chance by calculating the sum of the variation in the data
Specifically, used to support or reject null hypothesis

3. I. CHI SQUARE, cont
The sum, or Chi2, is then compared to the critical value in the Probability Table using the correct degrees of freedom.
Degrees of freedom = n – 1 where n represents # categories, possible outcomes
The p value represents the probability that the null hypothesis is correct; that is, the probability that the differences seen are random and due to chance alone.
By convention, the accepted probability value in science is > In other words, the p value must be > 0.05 to accept the null hypothesis.,

4. I. CHI SQUARE, cont
To determine whether null hypothesis is accepted or rejected,
Calculate Chi Square
Find the p(0.05) Critical Value for the correct degrees of freedom,
If your calculated Chi Square value is less than the critical value,
This means the calculated variation is less than the amount accepted as due to chance; therefore, there is greater than a 95% probability the differences seen are random
Null hypothesis is accepted
If your calculated Chi Square value is greater than or equal to the critical value,
This means the calculated variation is greater than the amount accepted as due to chance; in other words, the probability the differences are due to random chance does not exceed 95%; therefore they must be considered significant.
Null hypothesis is rejected

5. I. CHI SQUARE, cont
A poker-dealing machine is supposed to deal cards at random, as if from an infinite deck. In a test, you counted 1600 cards and observed the following:
Spades = 404
Hearts = 420
Diamonds = 400
Clubs = 376
Is the machine dealing randomly?
Null Hypothesis:
Chi Square Formula:
Expected =

6. I. CHI SQUARE, cont Chi Square = Degrees of Freedom =
Chi Square Value vs Critical Value:
Interpretation:

7. II. ASEXUAL REPRODUCTION
Purpose
Unicellular Organisms
Multicellular Organisms

8. III. THE CELL CYCLE
Can be divided into:

9. III. CELL CYCLE, cont Interphase
Portion of cell cycle in which cell is carrying out normal activities.
~ 90% of normal cell cycle is spent in interphase.
DNA found in chromatin form
3 sub-phases

10. III. CELL CYCLE, cont A closer look at S of Interphase
Produces 2 identical DNA molecules known as ________________
Term is only used when identical DNAs are physically attached; correctly described as one chromosome made up of two sister chromatids
Centromere
Kinetochore 10

11. III. CELL CYCLE, cont Mitosis Nuclear division
Requires all the cells energy, resources
Last step is cytokinesis – splitting of the cell

12. III. CELL CYCLE, cont

13. III. CELL CYCLE, cont
Cytokinesis

14. IV. MEIOSIS – A SPECIAL TYPE OF CELL DIVISION
Somatic Cells
Body cells
Human somatic cells contain 46 chromosomes, 23 from mom, 23 from dad
2n or diploid
Matched pairs of chromosomes called homologous pairs. Each chromosome making up a homologous pair is known as a homologue. Both carry genes for same traits. The location of a gene on a chromosome is known as a locus.
44 Autosomes
2 Sex chromosomes
XX =
XY =

15. IV. MEIOSIS, cont Gametes Egg and sperm cells Haploid or n
Contain 23 chromosomes
In fertilization, haploid (n) sperm fuses with haploid (n) egg → diploid (2n) zygote

16. IV. MEIOSIS, cont Description of Meiosis
Special type of cell division that occurs to produce gametes
Involved specialized cells
DNA replicated once, cell divides twice
Produces 4 cells with ½ the original chromosome number
In humans,
Occurs in ovaries, testes only

17. IV. MEIOSIS, cont

18. IV. MEIOSIS, cont

19. IV. MEIOSIS, cont Crossing Over Further increases genetic variability
Occurs during prophase I when tetrads are forming
Piece of one sister chromatid breaks off & exchanges places with piece of sister chromatid of homologue
Known as chiasma
Occurs very frequently

20. IV. MEIOSIS, cont

21. IV. MEIOSIS, cont Spermatogenesis vs Oogenesis in Humans

22. V. A COMPARISON OF MEIOSIS & MITOSIS

23. VI. DNA – THE MOLECULE OF INHERITANCE
Discovery
Structure of DNA
Each strand of nucleotides held together with
Double helix
2 nucleotide strands are antiparallel
Each strand has a 3’ end (terminus) and a 5’end; named for carbon on deoxyribose 23

24. VI. DNA, cont
Base Pairing 24

25. VI. DNA, cont
Chromosome
Single molecule of DNA wrapped in histone proteins. Proteins maintain chromosome structure & control DNA activity
Gene 25

26. VI. DNA, cont Genome All of an organism’s DNA
Provides working instructions for cell through ______________________
Must be copied prior to cell division 26

27. VII. DNA REPLICATION DNA Replication
Prior to cell division, DNA must be replicated
Occurs during _____ or ________________ phase of mitosis, meiosis
Known as semiconservative model of replication
Meselson-Stahl Experiment 27

28. VII. DNA REPLICATION, cont.
Steps of Replication:
DNA helicase unwinds the DNA double helix
Replication begins at specific points on the DNA molecule known as origins of replication. The Y-shaped region where new strands of DNA are elongating are called replication forks 28

29. VII. DNA REPLICATION, cont.
As DNA is “unzipped”, single-strand binding proteins hold the DNA open
A topoisomerase relieves tension creating by unwinding of DNA by making cuts, untwisting, & rejoining the nucleotide strand.
DNA polymerase can only add nucleotides to an already-existing strand so an RNA primer is synthesized to get replication going 29

30. VII. DNA REPLICATION, cont.
DNA polymerases add complementary nucleotides to each side of the DNA molecule.
DNA polymerase can only add nucleotides to the 3’ end of the growing strand, so the daughter DNA is synthesized 5’ – 3’, which means parental DNA is “read” _______________.
This means only one side of the DNA (3’ – 5’) molecule can be replicated as a continuous strand. Known as the leading strand. 30

31. VII. DNA REPLICATION, cont.
Synthesis of lagging strand
To synthesize the other new strand of DNA, DNA polymerase must work away from the replication fork. Leads to synthesis of short pieces of DNA known as Okazaki fragments.
DNA ligase binds fragments together to form a continuous strand of nucleotides. 31

32. VII. DNA REPLICATION, cont.
An Overview of Replication 32

33. VII. DNA REPLICATION, cont.
Proofreading & Repair
DNA Polymerase proofreads nucleotides as they are added

34. VII. DNA REPLICATION, cont.
Telomeres
5’ ends of daughter strands cannot be completed because DNA polymerase can only add nucleotides to the 3’ end
Results in shorter and shorter DNA molecules with jagged ends
To protect genetic integrity, ends of chromosomes do not contain genes – instead there are nucleotide sequences known as telomeres

35. VII. DNA REPLICATION, cont.
Telomeres, cont
Telomeres shorten each time cell divides - limits the number of times a cell can divide; thought to protect organism from cancer
Telomerase 35

36. IX. REGULATION OF CELL CYCLE
Highly regulated by __________________.
Cell Signaling
Autocrine Signaling
Paracrine Signaling
Endocrine Signaling
Allosteric Regulation

37. IX. CELL CYCLE REGULATION, cont
Internal Signals
Three major checkpoints in cell cycle G1 G2 M

38. IX. CELL CYCLE REGULATION, cont
Regulated by enzymes known as cyclin-dependent kinases or Cdks
Activated when bound to proteins known as cyclins
Kinase concentrations fairly constant; cyclin concentrations vary

39. IX. CELL CYCLE REGULATION, cont

40. IX. CELL CYCLE REGULATION, cont
External Signals
Growth Factors
Proteins released by certain cells that stimulate other cells to divide.
Cells stop dividing when growth factor is depleted.
Examples include erythropoetin, interleukin, pdgf

41. IX. CELL CYCLE REGULATION, cont
External Signals
Density-dependent Inhibition
Results from crowded conditions
When one cell touches another, cell division stops
Anchorage Dependence
Most cells must be in contact with solid surface to divide

42. IX. CELL CYCLE REGULATION, cont
Cell Cycle Out of Control = CANCER
Uncontrolled growth
Deprive normal cells of nutrients
Cancer cells do not respond to normal cell cycle controls

43. IX. CELL CYCLE REGULATION, cont
Cancer cells do not respond to normal cell cycle controls
Apoptosis

44. IX. CELL CYCLE REGULATION, cont