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

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

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 > 0.05. In other words, the p value must be > 0.05 to accept the null hypothesis.,

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

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 =

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

II. ASEXUAL REPRODUCTION Purpose Unicellular Organisms Multicellular Organisms

III. THE CELL CYCLE Can be divided into:

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

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

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

III. CELL CYCLE, cont

III. CELL CYCLE, cont Cytokinesis

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 =

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

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

IV. MEIOSIS, cont

IV. MEIOSIS, cont

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

IV. MEIOSIS, cont

IV. MEIOSIS, cont Spermatogenesis vs Oogenesis in Humans

V. A COMPARISON OF MEIOSIS & MITOSIS

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

VI. DNA, cont Base Pairing 24

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

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

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

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

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

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

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

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

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

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

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

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

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

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

IX. CELL CYCLE REGULATION, cont

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

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

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

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

IX. CELL CYCLE REGULATION, cont