BIOTECH REVIEWER2nd quarter

I.CELL CYCLE is required for cell growth and cell division into two new daughter cells.~ Cell Cycle

1st – G1 or Gap 1 = is required for cell growth and preparation of DNA synthesis.2nd – S1 or Sythesis = replicates the DNA (genome)3rd – G2 or Gap 2 = is needed for cell growth and preparation for mitosis.4th – M or Mitosis (Karyokinesis) = where cells separate duplicated chromosomes5th – C or Cytokinesis = cells divide

~Dividing stage Karyokinesis – nuclear division

M Phase which can be byMitosis or Meiosis

Cytokinesis – cytoplasmic division involving the formation of Cleavage furrow and Cell plate

II. MITOSIS is the process whereby cells divide to form new cells (daughter cells) which are identical to the original cell (parent cell).~ The process includes 5 stages 1) Prophase 2) Prometaphase 3) Metaphase 4) Anaphase 5) Telophase~Eukaryotic Chromosomes

All eukaryotic cells store genetic information in chromosomes Most eukaryotes have between 10 and 50 chromosomes in their body cells Human body cells have 46 chromosomes or 23 identical pairs Eukaryotic Chromosomes Each chromosome is composed of a single, tightly coiled DNA molecule Chromosomes can’t be seen when cells aren’t dividing and are called chromatin DNA is tightly coiled around proteins called histones Duplicated chromosomes are called chromatids & are held together by the centromere

~Karyotype First 22 pairs are called autosomes Last pair are the sex chromosomes XX female or XY male

~ Types of Cell Reproduction1.) Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells2.) Mitosis & binary fission are examples of asexual reproduction3.) Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells. Meiosis is an example

~Four Mitotic Stages1.) Prophase - Chromatin in nucleus condenses to form visible chromosomes

Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal)*Prometaphase - Nuclear membrane & nucleolus are broken down

Chromosomes continue condensing & are clearly visibleSpindle fibers attach to kinetochores at the centromere of each chromosomeSpindle finishes forming between the poles of the cell

2.) Metaphase - Chromosomes, attached to the kinetochore fibers, move to the center of the cell

Chromosomes are now lined up at the equator3.) Anaphase - Occurs rapidly

Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers4.) Telophase - Single-stranded chromosomes reach opposite poles

Spindle disassemblesNuclear envelope forms around each set of single-stranded chromosomesNucleolus reappearsChromosomes reappear as chromatin

~Comparison of Anaphase and Telophase

~Uncontrolled MitosisIf mitosis is not controlled, unlimited cell division occurs causing cancerous tumorsOncogenes are special proteins that increase the chance that a normal cell develops into

a tumor cell

III. MEIOSIS - Combines genetic material from 2 parents (sperm & egg) so offspring are genetically different from parents~ Human Chromosomes

Humans have 46 (23 pairs) chromosomes 44 chromosomes (22pairs): autosomal 2 chromosomes (1 pair): sex chromosomes (XX, XY) All human cells have 46 chromosomes except for the egg & sperm Egg = 23 Sperm = 23 All other cells = 46 (2 sets of chromosomes) (liver, cardiac, blood cells) Diploid (2N) = 2 sets of chromosomes (46) Haploid (1N) = 1 set of chromosomes (23) N = haploid #

~If egg and sperm had same number of chromosomes as other body cells . . . baby would have too many chromosomes! If egg and sperm had half the number of chromosomes than other body cells . . . baby would have just the right amount!~ Meiosis is a special kind of cell division that halves the number of chromosomes in gametes. This insures that the correct number of chromosomes are passed on.

Makes 4 cells genetically different from parent cell & from each other Production of gametes = sperm & egg Contain half the number of chromosomes = haploid (1N) Called the “reduction” division =

o Diploid Haploido 2N 1N

Used in sexual reproduction~Where does it happen?

In males- in the testesIn females- in the ovaries

~Homologous Chromosomes Pair of chromosomes - maternal & paternal - similar in shape & size. Homologous pairs – tetrads - carry genes controlling the same inherited traits. Each locus - position of a gene - is in the same position on tetrads.

~GametogenesisSpermatogenesis: production of spermOogenesis: production of egg

~Phases of Meiosis *Meiosis I

Interphase I -Cells undergo a round of DNA replication, forming duplicate chromosomes. Prophase I - Each chromosome pairs with its corresponding homologous chromosome to

form a tetrad.o There are 4 chromatids in a tetrad.o Crossing-over: Homologous chromosomes exchange portions of their chromatids

in a processo Crossing-over produces new combinations of alleles.

Metaphase I - Spindle fibers attach to the chromosomes.o Tetrads line up in the middle: metaphase plate.

Anaphase I - Spindle fibers pull the homologous chromosomes toward opposite ends of the cell.

o Tetrads split into single chromosomes. Telophase I / Cytokinesis - Nuclear membranes form.

o Cell separates into two cells.o The two cells produced have chromosomes and alleles that are different from each

other and from the diploid cell that entered meiosis I.*Meiosis II - The two cells produced by meiosis I now enter a second meiotic division.

Unlike meiosis I, neither cell goes through chromosome replication.Each of the cell’s chromosomes has 2 chromatids

Prophase II - Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original cell.

Metaphase II - The chromosomes line up in the center of cell. Anaphase II - The sister chromatids separate and move toward opposite ends of the cell. Telophase II and Cytokinesis - Meiosis II results in four haploid (N) daughter cells.

~ Gamete Formation In male animals, meiosis results in four equal-sized gametes called sperm. In many female animals, only one egg results from meiosis. The other three cells,

called polar bodies, are usually not involved in reproduction. Interphase I - DNA replicates forming duplicate homologous chromosomes. (S phase).

Centriole pairs also replicate.Nucleus & nucleolus visible.

Meiosis I - Cell division that reduces the chromosome number by one-half.4 Phases:A. Prophase I - Longest and most complex phase (90%).

Homologous chromosomes come together to form a tetrad = SynapsisTetrad is two chromosomes or four chromatids (sister and nonsister

chromatids).B. Metaphase I - Shortest phase

Tetrads align on the metaphase plate.INDEPENDENT ASSORTMENT OCCURS:Orientation of homologous pair to poles is random.Leads to variation

C. Anaphase I - Homologous chromosomes separate and move towards the poles.

Sister chromatids remain attached at their centromeres.D. Telophase I & Cytokinesis - Each pole now has haploid (1n) set of

chromosomes.Cytokinesis occurs and two haploid daughter cells are formed.

Meiosis II - No interphase II Similar to mitosis

4 Phases:A. Prophase II - Centrioles separate

Nuclear envelope disappearsB. Metaphase II - Sister chromatids line up at metaphase plate

Spindle fibers attach at centromereC. Anaphase II - sister chromatids separate & move toward opposite ends of

the cellD. Telophase II & Cytokinesis - Nuclei form

Cytokinesis occurs.Four haploid daughter cells produced.gametes = sperm or egg

II. CANCER ppt. tnamad nko hahaha sorry labyu ol.,