1 Chapter 13 – Campbell’s 6th Edition Meiosis and Sexual Life Cycles
2 Definitions Heredity: transmission of traits from generation to the nextVariation:slight differences in appearanceGenetics:scientific study of heredity and hereditary variation
3 GenesGenes:coded information in the form of hereditary units (lots of genes on each chromosome)Where else can you find DNA beside the nucleus of the cell?MitochondriaChloroplast
4 Asexual Reproduction Asexual reproduction single individual is sole parent and passes copies of all its genes to its offspringClonethe offspring of asexual individuals
5 Sexual reproductionTwo parents give rise to offspring with unique combinations of genes; results in more variation
6 Animals Life Cycle Plants and some algae Fungi and some algae sequence of stages from an organisms conception to production of its own offspringAnimals
7 More Vocab somatic cell: body cells; any cell other than sperm or ovum karyotype:micrograph of the 46 human chromosomes in which they are lined up in pairs starting with the longesthomologous chromosomes:same length, centromere position, staining pattern; carry genes governing the same inherited characterssex chromosomes:X and Y chromosomesautosomes:all non-sex chromosomes (1 through 22)
10 Meiosis and Sexual Reproduction Sexual Reproduction – chromosomes of two parents combine to form offspring2323+ (N)+GametesFertilization(2N)46Zygote
11 About Chromosomes(2N) = diploid – any cell with 2 complete sets of chromosomes(N) = haploid – a cell with 1 complete set of chromosomesZygote (2N) – egg cell after fertilzation = egg + spermEach chromosome in egg has a matching chromosome from spermHomologous Pairs – matching chromosomes
12 Homologous pairs chromosomes occur in pairs one set from each parent Diploid or 2NCells that contain both sets of chromosomes.Haploid =1NSex cells have only half the chromosome number
13 Just before Meiosisbegins, duringinterphaseidentical sisterchromatidsare attached atthe centromere, andcentrioles havebeen duplicated.Centrioles
14 Meiosis: Prophase I During Prophase I: chromosomes condense nucleus breaks downspindle fibers formHomologous chromosomes form tetrads (fours)
15 Meiosis: Prophase I the chromosomes condense centrioles move to opposite poles of the parent cell and begin building the spindle microtubules.the nuclear envelope breaks down
16 Meiosis: Prophase I Homologous chromosomes pair up, forming tetrads.
18 Meiosis: Prophase I …. and crossing over may occur. Crossing over- pieces of DNA are exchanged with the matching homologous chromosome
19 Meiosis: Prophase Icentrioles begin building the spindle fibers.
20 Meiosis: Prophase ISpindle fibers grab each chromosome at the centromere.Move the chromosomes towards the poles.
21 Meiosis: Metaphase I During Metaphase I: Homologous chromosomes line up in the middle.Equator = metaphase plate
22 Meiosis: Metaphase I Each pair is assorted independently; this means that the maternalhomolog in each pairrandomly faces up or down.And this pair could have assortedlike this.So this pair could haveassorted like this.
23 Meiosis: Anaphase I During Anaphase I: Homologous pairs of separate. Sister chromatids remain attached at the centromere.
47 A comparison of mitosis and meiosis Mitosis and MieosisChromosomes replicate only onceMitosisCell divides onceProduces 2 identical daughter cellsMeiosisCell divides twiceDaughter cells with half the number of chromosomesDaughter cells are not all alikeProduces 4 cells (gametes)