 Role of DNA  1. Info. In DNA must be present in each cell after division  2. Stores info for which proteins to make and when  3. Directs cell activities  4. DNA gets copied and redistributed during division

 Role of DNA  A single chromosome contains thousands of genes that code for proteins involved in determining how a person’s body develops and function

 Pro vs. Eu  How many chromoso mes do we have?  1. What is the main difference between Prokaryotic and Eukaryotic organisms?  2. How does cell reproduction occur in prokaryotic organisms?  3. Where does cell reproduction occur in eukaryotic organisms?

 Chromo- somes  1. Each human somatic (body) cell has 23 pairs of chromosomes ( = 46 total chromosomes)  Chromosomes differ in size, shape  Contain thousands of genes that determine how the body functions and develops

 Chromo- somes  2. Homologous chromosomes- Each 23 pairs of chromosomes consists of 2 homologues  Similar in size, shape and genetic content (chromatids that are connected)

 Chromo- somes  3. One half of each chromosome pair comes from the mother and the other half from the father

 Chromo- somes  A somatic cell, that contains 2 sets of chromosomes is diploid  Gametes (sex cells) only have 1 set of chromosomes - haploid  Zygote - a fertilized egg cell  We use the symbol “n” to represent one set of chromosomes

 Chromosome numbers in common species Chromosome numbers in common species  Haploid and Diploid Chromosome Numbers Haploid and Diploid Chromosome Numbers

 Autosomes  22 of the chromosome pairs in humans are called autosomes - not directly involved in determining the gender of an individual

 Sex Chromosom es  One of the chromosome pairs containing genes that determine the sex of the individual X and Y XX - female XY- male The sex is determined by the male

 Changes in chromo- some number  1. Presence of all 46 chromosomes is essential for normal development and function  2. Humans missing one chromosome typically do not survive

 Changes in chromo- some number  Can detect this in Karyotype  3. More than two copies of a chromosome - trisomy (improper development occurs)  Ex: Down Syndrome (21)

 Non- disjunction  When chromosomes don’t separate properly when egg and sperm form  One gamete ends up with both chromosomes, the other has none  Trisomy results when abnormal gamete fuses with another

 How many chromosomes do humans have? How many pairs?  What is the difference between “haploid” and “diploid”?  Give the sex chromosomes for females & males

 Why is it essential to have all 46 chromosomes?  Draw a pair of homologues, draw a gene on one of the homologues, and label the chromatids

 Change in chromo- some structure  MUTATION - change in chromosome structure (4 TYPES)

 Change in chromo- some structure  1. Deletion- piece of chromosome completely breaks off (often fatal)

 Change in chromo- some structure  2. Duplication- chromosome fragment attaches to its homologue (doubles the info - 2 copies of a gene)

 Change in chromo- some structure  3. Inversion- chromosome piece reattaches to original chromosome in reverse orientation

 Change in chromosom e structure  4. Translocation- chromosome piece attaches to non- homologous chromosome

 All of the four mutations discussed could prove fatal for the individual

 Cell Cycle  Repeating sequence of growth and division in the life of an organism

 Cell Cycle  A cell spends 90% of its time in the first three phases – called Interphase G1 S G2

 Cell Cycle  G1- First Growth Phase Rapid cell growth and development, routine functions Major part of cell life spent here Non-dividing cells remain here Muscle cells and nerve cells always here, cannot be replaced

 Cell Cycle  S- Synthesis phase DNA copied, end up with sister chromatid

 Cell Cycle  G2- Second Growth Phase Cell prepares nucleus to divide Microtubules assembled for moving chromosomes during mitosis

 Cell Cycle  Mitosis- nucleus divides into two Each nucleus ends up with same type and number of chromosomes Allows organisms to:  Grow  Replace damaged tissue  Asexually reproduce

 Cell Cycle  Cytokinesis- cytoplasm divides in half

 Control of the cell cycle  1. Cell growth checkpoint (G1) decides whether the cell will divide A. Cell must be healthy and large enough first B. Proteins will stimulate transition to S phase

 Control of the cell cycle  1. Cell growth checkpoint (G1) decides whether the cell will divide C. If conditions are unfavorable or cells need a rest, growth will stop here D. Nerve and muscle cells remain here forever

 Control of the cell cycle  2. DNA synthesis G2 checkpoint- DNA repair enzymes check the DNA replication A. Once past this point, proteins trigger mitosis

 Control of the cell cycle  3. Mitosis checkpoint- triggers end of mitosis Signals beginning or G1 phase again

 Losing Control of the cell cycle  Cancer- uncontrolled growth of cells caused by: A. Mutagens- readily damage DNA (pollutants, radiation, other environmental factors) B. When gene coding for proteins that regulate cell cycle are mutated

 Losing Control of the cell cycle  Cancer- uncontrolled growth of cells caused by: C. When growth promoting proteins are mutated and actually speed up the rate of cancer  Oncogenes- accelerate rate of cell division

 Losing Control of the cell cycle  Cancer- uncontrolled growth of cells caused by: D. When mutations inactivate the control proteins that normally slow/stop cell cycle  Tumor Suppressor Genes- releases the “brakes” on cell division

 Differentiate between the G1, G2 and S phases of the eukaryotic cell cycle  Relate what occurs at each of the three principal checkpoints in the cell cycle  Why are individual chromosomes more difficult to see during interphase than during mitosis?

 Mitosis: Spindles  Made of centrioles and microtubule fibers that move chromosomes during cell division A. Extra set made right before division B. Travel to opposite ends of cell C. Only animal cells have centrioles D. Animals and plant cells both have spindle fibers

 Mitosis: Spindles  E. Microtubules attach to cell poles and chromosome centromeres  F. Chromosomes begin to move towards opposite ends of cell  G. Spindle fibers reel in the attached chromosomes as the ends of the fibers at the poles are broken down  H. Each pole gets a full set of chromosomes

46 X’s 92 X’s 46 X’s Fertilized Cell Chromosomes copied

 Mitosis: Stages  1. PROPHASE Chromosomes uncoil, become visible Nuclear envelope disappears Spindle forms

 Mitosis: Stages  2. METAPHASE Chromosomes move to center of cell and attach to spindle fibers along equator

 Mitosis: Stages  3. ANAPHASE Centromeres divide Sister chromatids split and move to opposite poles as spindle fibers shorten

 Mitosis: Stages  4. TELOPHASE Nuclear envelope reforms Chromosomes recoil Spindle and fibers break down

 Mitosis: Stages  5. CYTOKINESIS Cytoplasm divided in half, cell membrane reforms Animal: cell pinches in half by belt of protein Plant: vesicles from golgi line down middle of cell to make a cell plate  New cell wall grows on either side of plate  Plate breaks cell into two

 Mitosis: An Interactive Animation Mitosis: An Interactive Animation  Molecular Expressions Cell Biology: Mitosis Interactive Java Tutorial Molecular Expressions Cell Biology: Mitosis Interactive Java Tutorial

 Home(page) Movies - QT and Flash to illustrat... Home(page) Movies - QT and Flash to illustrat...  Dr Chromo's school: mitosis Dr Chromo's school: mitosis  Molecular Expressions Photo Gallery: Mitosis Molecular Expressions Photo Gallery: Mitosis  Mitosis Mitosis  The Cell Cycle & Mitosis Tutorial The Cell Cycle & Mitosis Tutorial  Mitosis: An Interactive Animation Mitosis: An Interactive Animation

 Describe the function of the microtubules during anaphase  Describe the events that occur during each of the four stages of mitosis  Compare how cytokinesis occurs in plant cells and how it occurs in animal cells