Cell cycle & division

Vocabulary Chromosome- DNA bound to proteins forming a threadlike structure containing genetic information arranged in a linear sequence, visible during mitosis & meiosis Chromatid- one individual chromosome Sister Chromatids-2 identical copies of a chromatid Centromere- the middle of the chromatids where the spindle fibers hook for cell division Daughter Cell- are the end product of cell division Homologous chromosomes- chromosomes that are identical with respect to their genetic information (traits they code for) and centromere placement, sets of sister chromatids that pair during meiosis Centromere

 Haploid- cell of organism having a single set of unpaired chromosomes, cells have half the diploid amount of chromosomes  Gametes- specialized reproductive cell (sperm & egg cells)  Diploid- a condition in which each chromosome exists in pairs, having two of each chromosome.  Somatic cells- everything besides gametes.  Depending on the organisms that amount of chromosomes changes  In Humans our diploid cells have 46 chromosomes and haploid cells have 23 chromosomes  In house flies, diploid has 12 and haploid has 6 chromosomes  Crossing over- the exchange of genetic material between homologous chromosomes during meiosis

Centromere Centriols Sister Chromotides Chromosome/Chromatid Spindle fibers

Cell Cycle and Cell division Cell cycle - has 2 phases/stages. Interphase and M phase Interphase. Consists of G 1, S, G 2. G 1 phase – This is where cell growth occurs G0 (G not) phase- is the waiting stage, most cells spend most of their time here S phase- this is where DNA replicates itself, only happens if the cell is going to divide G 2 phase- is when the cell prepares to start mitosis/meiosis

M phase Mitosis/ Meiosis Consists of Prophase, Metaphase, Anaphase and Telophase is the division of the nucleus and all the genetic information within Cytokinesis is the division of the cytoplasm The actual splitting of the two cells into new ones

1 st phase is Prophase this is when chromosomes coil and become visible centrioles move to the poles (opposite ends of the cell) the nuclear envelope breaks down spindle fibers start to grow from the centrioles 2 nd phase Metaphase sister chromatids line up across the midline (middle of the cell) spindle fibers attach to the centromere. 3 rd phase Anaphase centromeres split the sister chromatids separate to become individual chromosomes Those chromosomes move towards the centrioles (poles/ends of the cell)

4 th phase Telophase chromosomes gather to the poles the nuclear envelope begins to reappear around the chromosomes the chromosomes begin to uncoil the cells begin to separate/ cleave. The cleavage furrow begins In the plants the cell plate begins Cytokinesis this is when the cleavage furrow is completed and the cytoplasm pinches in half And each daughter cell has an identical set of chromosomes. In plants the cell plate finishes

Meiosis This is how sex cells/gametes are made It has the same phases as Mitosis, it goes through them twice (meiosis I and meiosis II. The first time the homologous chromosomes separate and the sister chromatids move to one opposite sides of the cell It is then divide into 2 diploid cells Then it starts the process over again but this time the sister chromatids split into individual chromosomes Moving to opposite end of the cell Ends with 4 cells all genetically different and haploid

Meiosis I Prophase I- Nuclear envelope breaks down, Chromosomes coil and form sister chromatids, Homologous chromosomes form a tetrad and preform crossover Metaphase I- Homologous chromosomes line up down the midline, and the spindle fibers attach to the centromere Anaphase I- Homologous chromosomes split into sister chromatids and begin to the move towards the poles Telophase I- Sister chromatids are pulled towards the poles, cell begins to cleave Cytokinesis I- The cytoplasm splits and two diploid genetically different cells are formed

Meiosis II Prophase II- Chromosomes begin to move from the poles Metaphase II- The sister chromatids line up down the midline and the spindle fibers attach to the centromere Anaphase- The centromere is broken and the sister chromatids are separated into individual chromosomes Telophase- The individual chromosomes are pulled toward the poles, the cells begin to cleave, the nuclear envelope begins to reappear, the chromosomes begin to uncoil Cytokinesis II- The cytoplasm splits completely and 4 haploid cells are made genetically different

Crossover First part of meiosis. Crossover happens. The homologous chromosomes separate and the sister chromatids move to opposite sides of the cell. And split into 2 diploid cells Second part of meiosis. The sister chromatids split into individual chromosomes and into 4 haploid daughter cells

Regulators Cyclins- Are proteins that regulate cell division. Help tell cells when to divide and when to stop. There are 2 types of regulators internal and external growth factors. Cancer is uncontrolled cell growth. Because it doesn’t respond to the internal and/or external growth factors.

Internal growth factors- are proteins that respond to events inside the cell. I.E. not letting the cell move to a new phase until the previous is complete. External growth factors- proteins that respond to events outside the cell. Tell it to speed up or slow down the cell cycle Growth factors stimulate cell growth and division of cells. Molecules found on the surface of neighboring cells that tell the cell to slow down or stop dividing when they get close. These prevent excessive cell growth

Cancer A group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body Causes Environmental factors (anything not inherited) Diet, Alcohol, Tobacco, Pollutants Infections (hepatitis B & C, HPV) Ionizing radiation and non-ionizing radiation (UV) Heredity

Sexual and Asexual reproduction Asexual reproduction- is the process by which a single parent reproduces by itself. Plants sometimes (self pollination) bacteria mostly (fission) Pros- don’t have to find a mate, faster, Cons- no genetic variation Sexual reproduction- is the process by which cells from 2 different parents unite to produce the first cell of a new organism Pros- more genetic variation, Cons- genetic variation, finding a mate

Spermatogenesis The basic function of spermatogenesis is to turn each one of the diploid spermatogonium into four haploid sperm cells. The germ cells progress first from the diploid to haploid state and then change shape to become spermatozoa, then into functioning sperm cells.

Oogenesis Oogenesis involves the formation of haploid cells from an original diploid cell, called a primary oocyte. First of all, oogenesis only leads to the production of one final ovum, or egg cell, from each primary oocyte. Of the four daughter cells that are produced when the primary oocyte divides meiotically, three come out much smaller than the fourth. These smaller cells, called polar bodies, eventually disintegrate, leaving only the larger ovum as the final product of oogenesis.