DNA Mitosis

Key Concepts for DNA Unit All cells come from other cells, passing on their DNA from parent cell to daughter cell The cell cycle consists of a series of stages Mitosis consists of one cell division, produces 2 identical diploid cells, and produces somatic cells for cell growth and repair. Meiosis produces different haploid sex cells (gametes) Uncontrolled cell division results from mutations in the DNA and results in cancer

Key Terms Mitosis Telophase Meiosis Cytokinesis Haploid Gamete Diploid Cell Cycle Interphase Prophase Metaphase Anaphase Telophase Cytokinesis Gamete Somatic Cell Fertilization Zygote Cancer Carcinogen Mutation

What makes us get bigger? Do our cells grow larger and larger or do they divide and multiply??? In most cases living things grow by producing more cells. There’s no real cell size difference between baby and adult animals. Adults just have many more cells.

REVIEW

DNA structure DNA is a long chain of simple units called nucleotides Nucleotides: base, sugar & phosphate

Sugar-Phosphate Backbone Composed of deoxyribose sugar and a simple phosphate molecule Forms a strong bond that creates the backbone Exactly the same in all DNA

DNA Structure There are only 4 types of bases in ALL DNA molecules Adenine, Cytosine, Guanine, and Thymine Each bond with complimentary bases in other nucleotides to form the rungs of the DNA ladder. BASE PAIR RULE Adenine + Thymine Cytosine + Guanine

DNA Structure

DNA Form DNA nucleotides combine in cells to form long strands in the shape of a double helix The order of the nucleotides is the determining factor in the expression of genes in organisms

Characteristics of DNA DNA accounts for the genetic variation between different organisms by the use of different Sequences of DNA segments Lengths of DNA segments Numbers of chromosomes and amounts of DNA in an organism

Characteristics of DNA DNA replication is the process through which cells copy DNA for transmission to daughter cells during cell division The double helix structure allows DNA to easily unzip down the center between nitrogenous bases Free floating nucleotides attach to each of the separated DNA strands forming 2 new strands of DNA, each an exact copy of the original

Characteristics of DNA A mutation is an unexpected change in a DNA sequence, usually occurring during replication/division Mutations are common in most organisms (especially simple organisms) though only a small percentage produce noticeable changes in organisms

Mutations Often result from increased levels of stress on cells prior to or during cell division Stress include: radiation, UV rays, environmental

Genetic Hierarchy A group of nucleotides= a gene (45-150 base pairs) A group of genes = 1 strand of DNA Several condensed strands of DNA = 1 chromosome

The Chromosome Chromosome: A compact spool of DNA Humans have 46 chromosomes 23 from father 23 from mother Individuals with Downs Syndrome have 1 extra chromosome

Chromosome Chromosomes are important in the mapping of the human genome Scientists look at chromosomes to diagnose or predict genetic disorders

Genetic disorders A genetic disorder is a disease or other problem resulting from errors in the transmission of genetic information or the expression of certain negative gene sequences

Limits to Cell Growth There are 3 reasons cells divide rather than continue to grow: The larger the cell becomes, the more demands the cell places on its DNA Larger cells have more trouble moving things like nutrients and wastes across the cell’s membrane Repair of damaged tissue

Division of the Cell Cells divide before they get too large. Cell Division — process by which a cell divides into 2 new cells Each new cell is IDENTICAL to the original and has the same number of chromosomes Diploid number = 2n (two sets)

The original cell is called the parent cell; 2 new cells are called daughter cells Before cell division occurs , the cell replicates (copies) all of its DNA, so each daughter cell gets complete set of genetic information from parent cell Each daughter cell is exactly like the parent cell – same kind and number of chromosomes as the original cell 2 Daughter Cells Parent Cell

Many organisms, especially unicellular organisms, reproduce by means of cell division – called asexual reproduction – Ex: bacteria

DNA DNA is located in the nucleus and controls all cell activities including cell division Long and thread-like DNA in a non-dividing cell is called chromatin Doubled, coiled, short DNA in a dividing cell is called chromosome Consists of 2 parts: chromatid and centromere

2 identical “sister” chromatids attached at an area in the middle called a centromere When cells divide, “sister” chromatids separate and 1 goes to each new cell

Coils up into chromosomes Chromatin to chromosomes illustration: Chromatin Coils up into chromosomes Duplicates itself Why does DNA need to change from chromatin to chromosome? More efficient division

Chromosome number Every organism has its own specific number of chromosomes Examples: Human = 46 chromosomes or 23 pairs Dog = 78 chromosomes or 39 pairs Goldfish = 94 chromosomes or 47 pairs Lettuce = 18 chromosomes or 9 pairs

All somatic (body) cells in an organism have the same kind and number of chromosomes Examples: Human = 46 chromosomes Human skin cell = 46 chromosomes Human heart cell = 46 chromosomes Human muscle cell = 46 chromosomes Fruit fly = 8 chromosomes Fruit fly skin cell = 8 chromosomes Fruit fly heart cell = 8 chromosomes Fruit fly muscle cell = 8 chromosomes

Mitosis – division of the nucleus into 2 nuclei, each with the same number of chromosomes Mitosis occurs in all the somatic (body) cells Why does mitosis occur? So each new daughter cell has nucleus with a complete set of chromosomes

Cell Cycle -- series of events cells go through as they grow and divide Cell grows, prepares for division, then divides to form 2 daughter cells – each of which then begins the cycle again

IPMATC “I play music at the concert” Interphase Prophase Metaphase Anaphase Telophase Cytokinesis I put my alligator there carefully

Interphase—period of cell growth and development DNA replication (copying) occurs during Interphase During Interphase the cell also grows, carries out normal cell activities, replicates all other organelles The cell spends most of its life cycle in Interphase

4 phases of nuclear division (mitosis), directed by the cell’s DNA (PMAT) Prophase Metaphase—(Middle) Anaphase—(Apart) Anaphase—(Apart) Telophase—(Two)

Prophase Longest part of Mitosis Chromosomes become visible Centrioles near the nuclear envelope move toward opposite poles Spindle fibers form Condensed chromosomes become attached to spindle fibers at their centromeres Nucleolus disappears and the nuclear envelope breaks down

Metaphase (middle) Chromosomes line up across the center of the cell (metaphase plate) Spindle fibers connect to chromosomes

Anaphase (apart) Chromosome copies divide Centromeres split move toward opposite sides of the cell - (pulled by spindle fibers)

Telophase (two) Chromosomes uncoil Nuclear envelope re-forms 2 New nuclei are formed Spindle fibers disappear Mitosis is complete

What’s Next? What we’ve got: Final task: 2 nuclei with duplicate chromosomes in the cytoplasm of a single cell Final task: Divide the cytoplasm

Cytokinesis — the division of the rest of the cell (cytoplasm and organelles) after the nucleus divides After mitosis and cytokinesis, the cell returns to Interphase to continue to grow and perform regular cell activities

Cytokinesis In animal cells the cell membrane draws inward and is pinched off forming two separate cells In plants, a cell plate forms between the nuclei, turns into a separating membrane and eventually a cell wall http://www.youtube.com/watch?v=VlN7K1-9QB0 http://www.youtube.com/watch?v=s4PaOz7eWS8

Summary: Cell Cycle Interphase Mitosis (PMAT) Cytokinesis When cells become old or damaged, they die and are replaced with new cells

Controls on Cell Division Scientists have observed what is “supposed to happen” in petri dishes. Cells should grow until the bottom is covered and then stop. They are also regulated by the surrounding cells.

Cell Division Control DNA controls all cell activities including cell division Some cells lose their ability to control their rate of cell division – the DNA of these cells has become damaged or changed (mutated) These super-dividing cells form masses called tumors

Cancer is the result of cells not being able control their growth. Cancer cells DO NOT respond to the signals that regulate the growth of most cells

Benign tumors are not cancerous – these cells do not spread to other parts of the body Malignant tumors are cancerous – these cells break loose and can invade and destroy healthy tissue in other parts of the body (called metastasis)

What causes Cancer? Smoking tobacco, radiation exposure, viral infections These all have uncontrolled cell growth in common with one another http://www.youtube.com/watch?v=A1Fkdt-2veM

Cancer is not just one disease, but many diseases – over 100 different types of cancers

DNA damage vs mutation DNA damage is distinctly different from mutation, although both are types of error in DNA. DNA damage is an abnormal chemical structure in DNA, while a mutation is a change in the sequence of standard base pairs.

Cancer http://www.youtube.com/watch?v=keIs5aIAG8o&src_vid=A1Fkdt-2veM&feature=iv&annotation_id=annotation_455857775

Chromosome Appearance & Location Phase Chromosome Appearance & Location Important Events Interphase Prophase Metaphase Anaphase Telophase Cytokinesis DNA replication, cell grows and replicates organelles DNA copies itself; chromatin Nuclear envelope disappears, spindle fibers form Chromosomes coil up Chromosomes line up in the middle Spindle fibers connect to chromosomes Spindle fibers pull chromosome copies apart to opposite poles Chromosome copies divide and move apart Nuclear envelopes reform, 2 new nuclei are formed, spindle fibers disappear Chromosomes uncoil back into chromatin Division of the rest of the cell: cytoplasm and organelles Chromatin

Unit project Research a genetic disorder Causes Genetics Prevention? Treatment Clinical trials/Research