Cell Division and Mitosis Chapter 8
HOMEWORK • 12/13 Pre/post,Read pages 126-129 • 12/14 Compare and contrast asexual and sexual reproduction from a cellular viewpoint ESSAY and yes, this is a quiz) • 12/14 Mitosis Lab • 12/17 Complete lab
Math moments • If you made $ 30,000 per hour, what would you make in a day? • If you were given $ 8.00 per year from the year you were born what would you have now? What would you have when you are 75 years old?
Science Moments • If you lost 30,000 skin cells per hour, what would you lose in a day? • If you lost 8.00 lbs. of skin per year from the year you were born how many lbs. would you have lost by now? How much would you have lost when you are 75 years old?
Buzz Words • Genes • Chromosomes • Asexual • Sexual • Generation • Cell division • Reproduction
Why is it necessary for cells to divide? • DNA overload • To improve material exchange • Surface area to volume
Ratio of Surface Area to Volume in Cells Section 10-1 Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume
Understanding Cell Division • What instructions are necessary for inheritance? • How are those instructions duplicated for distribution into daughter cells? • By what mechanisms are instructions parceled out to daughter cells?
Reproduction • Parents produce a new generation of cells or multicelled individuals like themselves • Parents must provide daughter cells with hereditary instructions, encoded in DNA, and enough metabolic machinery to start up their own operation • Like begets like..
Division Mechanisms Eukaryotic organisms • Mitosis • Meiosis Prokaryotic organisms • Prokaryotic fission (Binary fission)
Roles of Mitosis • Multicelled organisms • Growth • Cell replacement • Some protistans, fungi, plants, animals • Asexual reproduction EXPLAIN!!!
Chromosome • A DNA molecule & attached proteins • Duplicated in preparation for mitosis • When the chromosomes are just a mass of fibers it is called a Chromatin one chromosome (unduplicated) one chromosome (duplicated)
Chromosome Number • Sum total of chromosomes in a cell • Somatic cells • Chromosome number is diploid (2n) • Two of each type of chromosome • Gametes • Chromosome number is haploid (n) • One of each chromosome type
Human Chromosome Number • Diploid chromosome number (n) = 46 • Two sets of 23 chromosomes each • One set from father • One set from mother • Mitosis produces cells with 46 chromosomes--two of each type
Lots of DNA • Stretched out, the DNA from one human somatic cell would be more than two meters long • A single line of DNA from a salamander cell would extend for ten meters
Organization of Chromosomes DNA one nucleosome DNA and proteins arranged as cylindrical fiber histone
Cell Cycle • Cycle starts when a new cell forms • During cycle, cell increases in mass and duplicates its chromosomes • Cycle ends when the new cell divides
Interphase • Usually longest part of the cycle • Cell increases in mass • Number of cytoplasmic components doubles • DNA is duplicated
Stages of Interphase • G1 • Interval or gap after cell division • S • Time of DNA synthesis (replication) • G2 • Interval or gap after DNA replication
Control of the Cycle • Once S begins, the cycle automatically runs through G2 and mitosis • The cycle has a built-in molecular brake in G1 • Cancer involves a loss of control over the cycle, malfunction of the “brakes”
Stopping the Cycle • Some cells normally stop in interphase • Neurons in human brain • Arrested cells do not divide • Adverse conditions can stop cycle • Nutrient-deprived amoebas get stuck in interphase
Cell Cycle Regulators • Cyclin (protein) regulate the timing of the cell cycle • Cancer cells do not respond to these “signals” • This results in masses called tumors
Effect of Cyclins The sample is injected into a second cell in G2 of interphase. A sample of cytoplasm is removed from a cell in mitosis. As a result, the second cell enters mitosis.
Skin Cancer Asymmetrical, Borders, Color, Diameter, Elevation
Essay Question 1 • Compare and contrast mitosis and meiosis. Pay extra attention to crossing over, number of daughter cells and chromosome number. Based on your comparison, explain how these two processes play an important role in reproduction and evolution. • List and describe the main events of the cell cycle.
Mitosis • Period of nuclear division • Usually followed by cytoplasmic division • Four stages: Prophase Metaphase Anaphase Telophase
MITOSIS pair of centrioles plasma membrane nuclear envelope nucleus chromosomes TRANSITION TO METAPASE Now microtubules penentrate the nuclear region. Collectively, they form a bipolar spindle apparatus. Many of the spindle microtubules become attatched to the two sister chromatids of each chromosome. CELL AT INTERPHASE EARLY PROPHASE LATE PROPHASE The cell duplicates its DNA, prepares for nuclear division Mitosis begins. The DNA and its associated proteins have started to condense. The two chromosomes color-coded purple were inherited from the female parent. The other two (blue) are their counterparts., inherited from the male parent. Chromosomes continue to condense. New microtubules become assembled. They move one of the two pairs of centrioles to the opposite end of the cell. The nuclear envelope starts to break up. Fig. 8.7a, p. 132
INTERPHASE METAPHASE ANAPHASE TELOPHASE All chromosomes have become lined up at the spindle equator. At this stage of mitosis (and of the cell cycle), they are most tightly condensed Attachments between the two sister chromatids of each chromosome break. The two are separate chromosomes, which microtubules move to opposite spindle pores. There are two clusters of chromosomes, which decondense. Patches of new membrane fuse to form a new nuclear envelope. Mitosis is completed. Now there are two daughter cells. Each is diploid; its nucleus has two of each type of chromosome, just like the parent cell. Fig. 8.7b, p. 133
The Spindle Apparatus • Consists of two distinct sets of microtubules • Each set extends from one of the cell poles • Two sets overlap at spindle equator • Moves chromosomes during mitosis
Spindle Apparatus one spindle pole one of the condensed chromosomes spindle equator microtubules organized as a spindle apparatus one spindle pole
Stages of Mitosis Prophase Metaphase Anaphase Telophase
Early Prophase - Mitosis Begins Duplicated chromosomes begin to condense
Late Prophase • New microtubules are assembled • One centriole pair is moved toward opposite pole of spindle • Nuclear envelope starts to break up
Transition to Metaphase Spindle forms Spindle microtubules become attached to the two sister chromatids of each chromosome
Metaphase • All chromosomes are lined up at the spindle equator • Chromosomes are maximally condensed
Anaphase • Sister chromatids of each chromosome are pulled apart • Once separated, each chromatid is a chromosome
Telophase • Chromosomes decondense • Two nuclear membranes form, one around each set of unduplicated chromosomes
Results of Mitosis • Two daughter nuclei • Each with same chromosome number as parent cell • Chromosomes in unduplicated form
Cytoplasmic Division • Usually occurs between late anaphase and end of telophase • Two mechanisms • Cell plate formation (plants) • Cleavage (animals)