See http www sci sdsu edumultimediamitosis Cardiff UniversityGeneticsCSAN

See http: //www. sci. sdsu. edu/multimedia/mitosis/ ©Cardiff University/Genetics/CSAN Team/

"DNA is, . . so precious and so fragile that we now know that the cell has evolved a whole variety of repair mechanisms to protect its DNA from assaults by radiation, chemicals and other hazards. This is exactly the sort of thing that the process of evolution by natural selection would lead us to expect. " Francis Crick in What Mad Pursuit. ©Cardiff University/Genetics/CSAN Team/

Basic concepts • • • Gene: unit of heredity, residing at a specific point on a chromosome; a length of DNA that specifies a product Chromosome: condensed, linear DNA and protein, containing genes and intervening sequences DNA: the genetic material in all living organisms; , located in the nucleus onchromosomes in eukaryotes ©Cardiff University/Genetics/CSAN Team/

Mitosis Somatic cell division ◦ Define somatic cell. Controlled by: ◦ Genes (indirectly) ◦ Hormones (directly) ◦ Environment (directly) ©Cardiff University/Genetics/CSAN Team/

CANCER IS UNCONTROLLED MITOSIS! ©Cardiff University/Genetics/CSAN Team/

Genetics 1 The Cell Cycle, Cell division and Cell Work ©Cardiff University/Genetics/CSAN Team/

Cell Regeneration food water oxygen Cell renewal Supporting life/ life quality environment Communication ©Cardiff University/Genetics/CSAN Team/

Why cells divide Growth Development Repair of the organism ©Cardiff University/Genetics/CSAN Team/

Cell cycle function includes: Detection and repair of genetic damage Prevention of uncontrolled cell division ©Cardiff University/Genetics/CSAN Team/

Learning outcomes State 2 key factors that control frequency of cell division Describe the different phases of the cell cycle Discuss the primary importance of Interphase in respect of nursing interventions State the 4 phases of mitosis List the changes that occur in each phase of mitosis State the differences between natural and pathological cell death ©Cardiff University/Genetics/CSAN Team/

R E P L I C A T I O N ©Cardiff University/Genetics/CSAN Team/

Why and when is mitosis important? (why should you care about cell division) • How does a one-celled embryo grow into a multicellular organism? • When do cells need to be made in adults? ex. skin cells in humans are continuously being sloughed off and replaced • - as many as 100 billion (1011) cells are lost daily In abnormal situations, cells may divide “out of control” = cancer ©Cardiff University/Genetics/CSAN Team/

The Cell Cycle and Cell division ©Cardiff University/Genetics/CSAN Team/

The Cell Cycle The cell cycle is cyclically events that has set of reaction sequences that both trigger and coordinate key events in the cell cycle The system (e. g. in animal cells) is driven by a built-in clock that can be adjusted by external stimuli (chemical messages) Checkpoint - a critical control point with ‘stop’ and ‘go-ahead’ signals that regulate the cell cycle Three Major checkpoints are found in the G 1, G 2, and M phases of the cell cycle ©Cardiff University/Genetics/CSAN Team/

G 1 checkpoint - the Restriction Point ◦ The G 1 checkpoint ensures that the cell is large enough to divide, and that enough nutrients are available to support the resulting daughter cells. ◦ If a cell receives a go-ahead signal at the G 1 checkpoint, it will usually continue with the cell cycle ◦ If the cell does not receive the go-ahead signal, it will exit the cell cycle and switch to a non-dividing state called G 0. ◦ Most cells in the human body are in the G 0 phase ©Cardiff University/Genetics/CSAN Team/

External Signal for Cell Division PDGF For Example - Platelet-Derived Growth Factors – (PDGF ) required for the division of fibroblasts which are essential in wound healing When injury occurs, platelets (blood cells important in blood clotting) release PDGF Fibroblasts are a connective tissue cells The binding of PDGF leads to a proliferation of fibroblasts and a healing of the wound ©Cardiff University/Genetics/CSAN Team/

Cell cycle When a cell population reaches a certain density, the amount of required growth factors and nutrients available becomes insufficient to allow continued cell growth E. g. Cells grown in culture will rapidly divide until a single layer of cells is spread over the area of the petri dish, after which they will stop dividing If cells are removed, those bordering the open space will begin dividing again and continue to do so until the gap is filled ©Cardiff University/Genetics/CSAN Team/

Cancer Cells These are the cells which no longer respond to cell-cycle controls – Cancer cells do not respond normally to the body's control mechanism. ◦ They divide excessively and invade other tissues ◦ If left unchecked, they can kill the organism Cancer cells do not exhibit contact inhibition ◦ If cultured, they continue to grow on top of each other when the total area of the petri dish has been covered ©Cardiff University/Genetics/CSAN Team/

Cancer cells May produce required external growth factor themselves or possess abnormal signal which falsely convey growth signals thereby bypassing normal growth checks Cancer cells exhibit irregular growth sequences If growth of cancer cells does cease, it does so at random points of the cell cycle Cancer cells can go on dividing indefinitely if they are given a continual supply of nutrients Normal mammalian cells growing in culture only divide 20 -50 times before they stop dividing ©Cardiff University/Genetics/CSAN Team/

INTERPHASE AND CELL DIVISION The length of this period varies in different cell types Certain cells divide very frequently Examples Blood forming cells divide rapidly Epithelial slower cells divide frequently though much than RBC producing cells ©Cardiff University/Genetics/CSAN Team/

Cells that do not divide readily These tend to remain within Interphase until death Nerve cells ? Muscle cells? ©Cardiff University/Genetics/CSAN Team/

Interphase This is the longest period of the complete cell cycle May appears to the eye to be a resting stage between cell divisions It is in fact a period of diverse activities Interphase activities are indispensible in making the next mitosis possible ©Cardiff University/Genetics/CSAN Team/

INTERPHASE- general cellular activities During this period, it also carries out metabolic activities example– burning glucose for energy ◦ It performs specialised functions example – preparing molecules, to secrete ©Cardiff University/Genetics/CSAN Team/

PREPARATION –Interphase Is the "resting" or non-mitotic portion of the cell cycle It is comprised of G 1, S, and G 2 stages of the cell cycle. ◦ Chromatin condenses the nuclear envelope begins to disperse. ◦ Production of m. RNA and t. RNA – ©Cardiff University/Genetics/CSAN Team/

Interphase - preparation for cell division During which: DNA replicates or makes copies the DNA strings. DNA is Deoxyribonucleic Acid The Centriole divide Performs specialised functions – ◦ Creates more cellular material, for example ◦ Proteins are actively produced. Carries out metabolic activities ◦ e. g. creating energy, producing waste products ©Cardiff University/Genetics/CSAN Team/

Interphase - preparation for cell division Replication of DNA must occur◦ mistakes occur and are corrected, Mistakes are corrected by enzymes that chop out the defective bit, using the undamaged strand as a template, it assembles correct codes. If not corrected, successive generations will appear as mutations. ©Cardiff University/Genetics/CSAN Team/

RECAP The Cell Cycle includes: 1. MITOSIS (a period of active division called the M phase); - the nucleus divides into 2 nuclei. 2. INTERPHASE (a period of non-division) which is divided into three parts. ©Cardiff University/Genetics/CSAN Team/

Interphase - 3 parts: G 1 & S G 1 (gap 1 18 or more hours) - Cells increase in size. Some cells miss this stage - there is of DNA protein synthesis assembly of new molecules & reproduction of m. RNA & t. RNA S (DNA synthesis 6 + hours) DNA (chromosome) replication, there is also continued duplication of some organelles. ©Cardiff University/Genetics/CSAN Team/

Interphase - 3 parts: 2 & 0 G 2 (gap 2 (2 -5 hours premitotic) ) – - preparation for Mitosis. - Chromatin condenses & the nuclear envelope begins to disperse. - There is also production of m. RNA and t. RNA - similar to G 1 & some cells miss this stage G 0 (stop phase (indefinite) ) arrest of cell division ©Cardiff University/Genetics/CSAN Team/

Mitosis P-Prophase M-Metaphase A- Anaphase T- Telophase ©Cardiff University/Genetics/CSAN Team/

Mitosis-are these in correct order A- Anaphase P-Prophase T- Telophase M-Metaphase ©Cardiff University/Genetics/CSAN Team/

Prophase Metaphase • Centrosomes migrate • Spindle fibers form • Chromatin condenses • microtubules attach to chromosomes • Chromosomes move to midline/metaphase plate Telophase Anaphase • Links break • Daughter chr. move to poles Cytokinesis • Chr. reach poles and decondense • Nuclear envelope reforms • Spindle fibers disappear

How are chromosomes duplicated during cell division? • When do somatic cells divide? ie. Why do cells divide? • What is this cell division called? • MITOSIS (2 n to 2 n) • • • What happens if chromosomes are not duplicated correctly? ex. Cri-du-Chat syndrome Small part of chromosome 5 is lost: results in heart problems, mental retardation, and other problems ©Cardiff University/Genetics/CSAN Team/

Chromosome structure ©Cardiff University/Genetics/CSAN Team/

Key Phase 1: Prophase Chromosomes appear – condensed- Chromatids. (2 identical chromatids were formed during S phase) These attach to centromere. 2 Centrioles (tiny microtubular organelles ) duplicate, move and stop on opposite sides of the cell. Chromatids tighter, disappears, envelope disintegrates. coil nucleolus nuclear ©Cardiff University/Genetics/CSAN Team/

©Cardiff University/Genetics/CSAN Team/

Key Phase 2: Metaphase Chromatids ◦ align in the middle of the cell- pulled by spindle fibres They line up along spindle fibres Nuclear Membrane now disappears ©Cardiff University/Genetics/CSAN Team/

©Cardiff University/Genetics/CSAN Team/

Key Phase 3: Anaphase Chromatids ◦ pulled by spindle fibres ◦ to opposite ends of the cell. ◦ And renamed Chromosomes Result: twice as many Chromosomes as in the parent cell ©Cardiff University/Genetics/CSAN Team/

©Cardiff University/Genetics/CSAN Team/

Key Phase 4: Telophase Chromosomes extend they become visible nuclear membranes reform Nucleoli reappear Spindles disappear ◦ around each group of newly divided chromosomes ©Cardiff University/Genetics/CSAN Team/

©Cardiff University/Genetics/CSAN Team/

The Finale: Cytokinesis The cell membrane pinches inward like a belt tightening between two poles until 2 daughter cells are formed ©Cardiff University/Genetics/CSAN Team/

©Cardiff University/Genetics/CSAN Team/

Whole PROCESS ©Cardiff University/Genetics/CSAN Team/

Control of cell division All cellular activity is controlled by genes This is influenced by Genetic Inheritance The Environment ©Cardiff University/Genetics/CSAN Team/

Optimal homeostatic conditions Insufficient O 2 & nutrition slows ◦ cellular respiration ◦ cell renewal processes Mitosis stop at G 1 or G 2 phase This phase is called G 0 ©Cardiff University/Genetics/CSAN Team/

Cell Death Occurs in 2 ways: ◦ Necrosis occurs when pathological changes kill a cell ◦ Apoptosis occurs as a normal physiological response Also called programmed cell death ©Cardiff University/Genetics/CSAN Team/ 3 -53

Cell Division- conditions apply CONTACT INHIBITION Dividing cells will divide until they run out of space = contact inhibition. Example = Wound healing ©Cardiff University/Genetics/CSAN Team/

Meiosis Reductive cells division No Duplication of Genetic material The process results in 23 single chromosomes instead of pairs of chromosomes Genetic material halved The chromosomes are cross over & randomly sorted & this gives rise to genetic diversity in normal situations ©Cardiff University/Genetics/CSAN Team/ 3 -67

Biological flow of information (central dogma) DNA RNA Protein Trait

Genetics: Work of the Cell Reading DNA & making Protein ©Cardiff University/Genetics/CSAN Team/

Learning Outcomes Briefly explain base paring Briefly explain triplet coding for amino acids Name 2 amino acids Define transcription & translation of DNA ©Cardiff University/Genetics/CSAN Team/

DNA ©Cardiff University/Genetics/CSAN Team/

Reading the DNA code within the nucleus= Transcription BASE PARING PURINES PYRIMIDINES Adenine pairs with Thymine Guanine pairs with ©Cardiff University/Genetics/CSAN Team/ Cytosine

Base paring Allows molecules to act as templates for replication of amino acids It allows for transmission of a genetic code ©Cardiff University/Genetics/CSAN Team/

BASE PARING PURINES PYRIMIDINES Adenine pairs with Thymine Guanine pairs with & Uracil Cytosine ©Cardiff University/Genetics/CSAN Team/

Transcription: Reading The Genetic Code for protein Adenine(A) Thymine(T) Cytosine(C) Guanine(G) letters A T C G ” = DNA code Copying the code in the nucleus. ©Cardiff University/Genetics/CSAN Team/

TRANSLATION G is read as C A is read as T But ribosome's change T to ‘U’ (uracil) In the Cytoplasm ©Cardiff University/Genetics/CSAN Team/

You do not have to remember these codes - the concept is important though ©Cardiff University/Genetics/CSAN Team/

Ribosome functions Translation occurs in the cytoplasm where the Ribosomes are located. Ribosomes bind to messenger RNA and read triplet codes for amino acids in the correct sequence to form a polypeptide chain; ©Cardiff University/Genetics/CSAN Team/

PROTEIN SYNTHESIS There are 50. 000 different protein containing compounds in the body forming a part of enzymes, hormones or structural proteins ©Cardiff University/Genetics/CSAN Team/

GENES Control Protein Production PROTEINS ◦ DETERMINE THE FUNCTION OF THE CELL GENES CONTROL CELL DIVISION ©Cardiff University/Genetics/CSAN Team/

‘Aging cells' DNA -repeatedly refreshed ◦ Genetic information is renewed in its original format: If this does not occur - then chaos can occur within the cellular environment. Viruses for example can alter protein synthesis, this is the basis for viral disease. ©Cardiff University/Genetics/CSAN Team/

Guarding the Codes on DNA Tight coiling Only uncoiling specific sections for protein synthesis. e. g. from viruses and prions – ? how do they affect the DNA strand? ©Cardiff University/Genetics/CSAN Team/

http: //www. youtube. com/watch_popup? v=f. Kyljuk BE 70 ©Cardiff University/Genetics/CSAN Team/

Basic definitions gene - basic unit of heredity; codes for a specific trait locus - the specific location of a gene on a chromosome (locus - plural loci) genome - the total hereditary endowment of DNA of a cell or organism somatic cell - all body cells except reproductive cells gamete - reproductive cells (i. e. sperm & eggs) chromosome - elongate cellular structure composed of DNA and protein - they are the vehicles which carry DNA in cells diploid (2 n) - cellular condition where each chromosome type is represented by two homologous chromosomes haploid (n) - cellular condition where each chromosome type is represented by only one chromosome homologous chromosome - chromosome of the same size and shape which carry the same type of genes chromatid - one of two duplicated chromosomes connected at the centromere - region of chromosome where microtubules attach during mitosis and meiosis Allele - alternate forms of the same gene Homozygous - having two identical alleles for a given gene Heterozygous - having two different alleles for a given gene Genotype - genetic makeup of an organism Phenotype - the expressed traits of an organism ©Cardiff University/Genetics/CSAN Team/