2Introduction What is Genetics? What level of organization is being examined?molecular, cellular, species, or populationWhat is the purpose of this lab?
3Somatic versus Reproductive Cells Somatic cells:all except the reproductive cells2 copies of each chromosomediploidexample: in humans, the diploid number is 46Reproductive or sex cells:haploid1 copy of each chromosome
4Nuclear Division Mitosis prior to mitosis chromosomes are duplicated nuclear division in somatic cellsgenetic info from “parent” to daughterscancer: uncontrolled cell division
5Nuclear Division Meiosis prior to meiosis: chromosomes are duplicated nuclear division in the sex cellsgenetic diversity
6Cytokinesis division of the cytoplasm occurs at the end of mitosis occurs at the end of meiosis Ioccurs at the end of meiosis II
8Interphase no nuclear or cell division DNA replication, chromosome duplication, and cell growth“chromosomes,” not visible inside nucleusbut can see nucleolus inside nucleus
9Mitosis Four phases of mitosis: prophase metaphase anaphase telophase End result of mitosis: 2 daughter cells
10ProphaseDuplicated chromosomes condense and become visible as sister chromatids joined at the centromerenuclear membrane disintegrates; neither the nucleus nor the nucleolus is distinctspindle apparatus of the cell is formed
11Prophase Chromatin condenses into discrete chromosomes two identical “sister chromatids”joined at the centromereEarly prophaseProphase
12MetaphaseChromosomes are aligned along the cell’s equator at their centromeresspindle fibers are visible
13MetaphaseChromosomes convene on the metaphase plate, an imaginary “equator” located between the two poles of the spindle. Centromeres are aligned, and sister chromatids of each chromosome straddle the metaphase plate.Metaphase plateSpindle fibers
14Anaphase Migration of the chromosomes: Each chromatid -- a chromosome centromeres splitmove along the spindle fibers towards opposite polespulling the sister chromatidEach chromatid -- a chromosome
15AnaphaseThe sister chromatids separate from each other and move along the spindle fibers towards opposite poles. Each chromatid is now considered a chromosome.Spindle polesEarly anaphaseAnaphase
16AnaphaseBy the end of anaphase, each pole has an equivalent and complete set of chromosomes.Late anaphase
17TelophaseChromosomes are aggregated at the poles and begin to thin out and extend in lengthnew nuclear membrane forms; nucleolus and nucleus begin to reappearspindle disintegratescytoplasm divides (cytokinesis occurs); daughter cells begin to form
18Telophase The “daughter” nuclei begin to form at the two poles Nuclear membranes begin to formchromosomes lose their distinct appearance.TelophaseCytokinesis begins, separating the cytoplasm into 2 “daughter cells”.Late telophase
19Telophase formation of 2 daughter cells Each daughter cell has same genetic material as parentDaughter Cells
20Meiosis: Reproductive or Sex Cells Gametesfemale gametes: “eggs” or “ova” (ovum, singular)male gametes: “sperm”HAPLOID, have 1 copy of each chromosome (i.e., 1/2 as many chromosomes as somatic cells)example, in humans, the haploid number is 23.
21Meiosis in the Lily Anther male reproductive organ in flowering plants.meiosis takes placeresult: haploid pollen grains
22Meiosis in the Lily Anther A very thin cross-section of a lily antherstain itexamine with a compound light microscope:
23Meiosis in the Lily Anther Each anther contains 4 pollen sacs where meiosis takes place.
24Meiosis in the Lily Anther Study the various phases of meiosis in prepared slides of the lily anther.look at the cells inside the pollen sacslocate the different phases.
25Stages of Meiosis Meiosis I: Meiosis II: Meiosis consists of meiosis I and meiosis II and both have 4 stages leading up to the actual cell division.Meiosis I: Meiosis II:Prophase I Prophase IIMetaphase I Metaphase IIAnaphase I Anaphase IITelophase I Telophase II
26Meiosis: Prophase IChromatin condenses into discrete chromosomes. Chromosome is actually composed of 2 sister chromatids.Homologous chromosomes come together as pairs.
27Meiosis: Metaphase IMetaphase plateChromosomes are arranged on the metaphase plate, still in homologous pairs.Spindle fibers from each pole attach to one chromosome of each pair of the homologue.Spindle fibers
28Meiosis: Anaphase Ieach homologous pair of chromosomes separate and move toward opposite poles.each chromosome still consists of 2 sister chromatids joined together at the centromere.
29Meiosis: Telophase I Chromosomes have moved to opposite poles. Cytokinesis separates the cytoplasm into 2 daughter cells.Each cell is now haploid.HaploidHaploid
30Meiosis: Prophase IIIn prophase II, the chromatin again condenses so the chromosomes have a distinct shape.
31Meiosis: Metaphase IIIn metaphase II, chromosomes align on the metaphase plate.
32Meiosis: Anaphase IIsister chromatids separate, and move towards opposite polessister chromatids are now individual chromosomes.
33Meiosis: Telophase IInuclei begin to form at opposite poles, and cytokinesis occurs4 daughter cells, each with the haploid number of chromosomes.HaploidHaploidHaploidHaploid
34Meiosis I: ReviewProphase IMetaphase ITelophase IAnaphase I
35Review: Meiosis IIProphase IIMetaphase IIAnaphase IITelophase II
36Chromosomes and Genes one long strand of DNA associated proteins “chromatin”thousands of genesgenediscrete unit of hereditylocusphysical location of a gene
37Homologous Chromosomes, Genes, and Alleles Chromosome pair:“homologous chromosomes”pair has genes at the same loci“alleles”may be the same or different
38Human Genetics Genotype Phenotype heterozygoushomozygousPhenotypeObserve traits and identify which form you possessMake a table
39Heredity and Genetic Disorders Video, “Healthy, Heredity, and Genetic Disorders”Extra 21st chromosome
40Mechanics of Mitosis Answer questions use instructional materials availablevideo: Mechanics of MitosispostersPhoto Atlas of Biology
41Mitosis in the Onion Root Tip Today’s lab exercisesexamine the tip of an onion rootfind and identify the 4 different phases of mitosis.Root tips are useful material because the cells are frequently dividing as the root grows.
42Growth and Mitosis in Onion Root Tips A) Examine onion (Allium) root tip under low power objective (10x)answer questionsB) Examine same slide under high power objective (40x)follow instructions
43Meiosis: The basis of Genetic Inheritance and Sexual Reproduction Mechanics of MeiosisAnswer questionsuse instructional materials availablevideo: Mechanics of MeiosispostersPhoto Atlas of Biology
44Meiosis and Gamete Formation in Lily Anthers Observe first and second meiotic division in demonstration slidesNote:DO NOT move the slides out of positionUse only FINE focus