The Cell Cycle

• The division (separation) of a cell into two daughter cells with the same genetic material. 
• Organism use cell division in order to grow, replenish (repair) and reproduce.

The series of events that takes place in a cell that cause it to divide into daughter cells.

All cells arise from pre-existing cells

Any cell of living organisms other than the reproductive cells

somatic cells arise from mitosis

• Binary fission is the forming of two daughter cells from a parent cell. 
• two major steps are
• - Replication and separation of nuclear material
• - Division of cytoplasm and organelles (Cytokinesis)

Mitosis is a type of cell division that results in two daughter cells (/when two daughter cell are formed from a parent cell), each having the same number and kind of chromosomes as the parent nucleus.

A special type of cell division of germ cells in sexually-reproducing cells that produces the gametes, such as spleen and egg cells.

Germ cells are the only type of cells capable of generating entirely new organism.

Gametes is/are the reproductive cells of a human, animal or plant.

Meiosis

• Mitosis
• Growth
• Meiosis
• Gametes 
• sperm and egg cells

Deoxyribonucleic acid gives of information and codes for traits. DNA sits for most a cell life cycle as chromatin.

• Chromatin is the material of which chromosomes of organisms are composed. It looks like a jumble (puddle) of DNA. 
• It consist of Proteins, RNA, DNA

Chromosome.

One of the two identical halves of chromosome that had been replicated in preparation for cell division.

• Chromosomes are condensed DNA (chromatid) and protein (Histones). 
• It’s a thread like structure located in the nucleus of animal and plants.

Centromere

Histones are proteins for DNA to wrap itself  around (acts as a guide to help DNA to wrap up/organize.

Human somatic cells have 22 pairs of homologous chromosomes (autosomes) and 1 pair of sex cells

Autosomes are chromosomes that code for body

Areas of the chromosome with similar coding (DNA).

Information that is present, which can vary between homologous pairs.

23 chromosome pairs.

• Diploid are complete pair of chromosomes, 46 chromosomes or 23 paired chromosomes.
• Somatic cells are diploid

• Karyotype is an individuals complete set of chromosomes.
• The chromosomes vary in length, location of centromere and staining properties (different locus stain produces different banding) Unique BP (bonding pair?) sequence = different chemical properties.

• Karyotyping is a laboratory procedure that allows doctor to examine your set of chromosomes
• karyotyping procedures are
• - obtain cell and isolate one between prophase and metaphase
• - stain the cell (to show chromosomes)
• - Organize the chromosomes (pair them up)

• G1 (11h): growth 1 - develop interior
• S phase (7h): synthesis of new DNA (copies are made producing sister chromatids)
• G2 (4h): rebuild energy reserves, produces proteins.

• Mitosis (2h)
• - Prophase
• - Metaphase
• - Anaphase
• -Telophase and (Cytokinesis)

• - Parent genetic material is duplicated
• - Replicated Chromatin is condensed to form chromosomes
• - Each daughter cells receive one copy of chromatid. 
• - Cell Cytoplasm and Organelles must be divide equally.

• - Interphase is 90% of cell cycle
• - Cell growth, maintenance, repair time
• - Cell makes structural proteins that moves around nutrients and waste 
• - Prepare for cell division building new proteins (enzymes, membranes)

• - 1st phase of cell division, chromosome shortens and thickens(become visible) 
• - Centriole grow microtubule spindle fibers (forms aster/ spindle apparatus) that extends into the nucleus where the chromosomes are
• - Nuclear membrane fades away.

• Metaphase (the “line up” phase) 
• - Chromosomes (paired chromatid, joined in the middle by a centromere) move toward the centre of the cell (equatorial plate
• - centrioles move to the end of the cell
• - spindle fibre attaches to centromere

• Anaphase otherwise known as the “pull phase. 
• - Chromosome move toward the centriole that pulls them with its spindle fibers
• - Should have an equal number of chromatid s at each end.

• Telophase otherwise known as the return phase.
• - Chromosome reach the opposite poles of the cell
• - spindle fibers dissolve 
• - Nuclear membrane begins to reform around the mass of Chromatin

• Cytokinesis occurs at the end of telophase.
• - Cytoplasm begins to divide into each daughter cell

• Animals - membrane pinches off in the center (like endocytosis)
• Plants - Cell plate (which later become cell wall) starts to form between daughter cell. Between daughters
• - plants lack centrioles, but they do form spindle apparatus during mitosis.

Cell cycle is affected by hormones, nutrient levels, contact with other cells

uncontrollable cell duplication of non-functioning cells.

• - The form of cell division by which gametes, with half the number of chromosomes are produced.
• - 1x Diploid ——-Meiosis——-> 4x Haploid
• - Gametes (male + female) combine to form zygote (sexual reproduction). Ensuring differentiation (/variability); traits from each parent
• - it has two divisions (meiosis I and meiosis II

• 1) Reduction division - produce daughters with fewer chromosomes than parent. 2n —> n
• 2) Recombination - chromosomes mix and cells have different genetic combinations than parent (variation).

In mammals, meiosis occurs in the gonads (testes or ovaries)

• Asexual reproduction is mitosis. 
• It is the reproductive process in which parent organism produces identical offsprings.

Sexual reproduction uses meiosis. The production of gametes by meiosis, followed by fertilization of genetically different parent gametes to produce genetically different offsprings.