Cellular Reproduction Mitosis (Asexual) and Meiosis (Sexual)

DNA refresher Stores genetic info Contained in nucleus Macromolecule made up of repeating NUCLEOTIDES (monomer) –Sugar –Phosphate –Nitrogen Base

DNA Between cell divisions, DNA in the form of chromatin. –Looks like string (not organized) Prior to cell division…DNA needs to be in chromosome form. –Looks like an “X” (more organized) Chromosomes are rod shape –made of DNA and protein –DNA wraps around protein (histones)

Chromosomes come in different sizes and complexity based on the chromosome capacity. Eukaryotes more complex than prokaryotes –Prokaryotes only have 1 chromosome and it is circular 23 pairs

HAPLOID- Sperm and egg cells (gametes) are haploid cells Contain only HALF set of chromosomes Haploid number = n Humans: n = 23 DIPLOID – Cells with two sets of chromosomes –All normal cells except reproductive cells are diploid cells –“Body cells” – somatic cells –Diploid number = 2n –Humans: 2n = 46

“Fertilization” = union of sex cells (two haploid cells), which will result in diploid cell.

Asexual Reproduction –Only one source of DNA –Produces 2 diploid cells that are EXACT copies – identical DNA. –Chromosome # is maintained!

Cell Division of Prokaryotes (no nucleus) Binary Fission – a type of asexual reproduction –Division of a prokaryotic cell into 2 offspring cells (daughter cells) –DNA copied –Results in two identical cells

Mitosis –Type of Asexual Reproduction –Division of nucleus –Tissue repair (Body Cells/Somatic Cells) –Grow and develop –Budding

Division of Eukaryotic Cells (Cells with a nucleus) Interphase - prepare Prophase Metaphase Anaphase Telophase Cytokinesis - finish CELL CYCLE

Mitosis (ASEXUAL) Division of the nucleus-DNA “PMAT” Prophase Metaphase Anaphase Telophase

Interphase - the time between cell division Longest phase-cells spend most time here Subdivided into 3 subgroups

Interphase G1 – cells grows S – DNA copied (replicated) G2 – cell grows, protein synthesis, increase in organelles

Prophase  DNA coils into chromosomes  Nucleolus and nuclear membrane break down and disappear Centrosomes start to move toward opposite poles Spindle fibers appear (mitotic spindle)

Metaphase –Chromosomes meet in the middle of the cell (equator of cell) –Spindle fibers attach to chromatids Spindle fibers

Anaphase Chromatids separate at the centromere –Get pulled towards opposite poles by the spindle fibers

Telophase Spindle fibers disappear Chromosomes return chromatin  Nuclear membrane (envelope) reforms around the chromatin Spindle fibers chromatin

Cytokinesis Occurs after telophase How the cytoplasm of a cell divides Cytokinesis in Animal cells Cleavage furrow – area of cell membrane that pinches in through the action of microfilaments Cleavage furrow

Cytokinesis Plant cells –Vesicles from Golgi apparatus fuse at the midline of the dividing cell to form a cell plate which divides the two cells –cell plate eventually turns into cell wall Cell wall

Cell Cycle or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication (replication).

Asexual Reproduction Budding

Asexual Reproduction Budding

Tissue Repair Body Cells! Aka: Somatic Cells

Asexual Reproduction Regeneration

Growth and Development

Binary Fission Bacteria/Prokar yotes

Asexual Reproduction Advantages vs. Disadvantages Identical Cells made quickly If there is a mistake then that mistake will be copied. Tumors Cancer

Which one correctly represents Asexual Reproduction?

How many chromosomes would be in EACH offspring cell?

Sexual Reproduction –GENETIC VARIATION!!!!! –Words associated with ONLY sexual reproduction Gametes Egg/sperm Fertilization Haploid

Meiosis –A type of sexual reproduction –Produces 4 HAPLOID cells that are genetically different!!! –Creates gametes –Chromosome # is reduced by half.

Meiosis (SEXUAL) Cells undergoing meiosis will divide twice. Go through 4 main phases of mitosis (PMAT) two times. Two Divisions –Meiosis I (prophase 1, metaphase 1, anaphase 1, telophase 1/cytokinesis 1) –Meiosis II (prophase 2, metaphase 2, anaphase 2, telophase 2/cytokinesis 2) Results?  Produces 4 cells that are DIFFERENT than parent cell Reduction of chromosome number by half!  One diploid cell (2n) will produce FOUR haploid cells (n)

Homologous chromosomes –Homologous Chromosomes – two chromosomes (one from mother and one from father) that carry corresponding genes.

Prophase I The phase that really makes sexual (meiosis) different from asexual (mitosis) Homologous chromosomes will line up side by side “Crossing over” –A genetic scramble of DNA

Crossing Over exchange of genetic material Portions of chromatids randomly break off and attach to adjacent chromatids

Karyotype photomicrograph of chromosomes SEX Chromosomes Normal Female: XX Normal Male: XY

What is special about Sexual Reproduction? Genetic Recombination – random scrambling of genes….results in genetic diversity!

Meiosis The phases are the same as what occurred in Mitosis but it will go through each phase twice. –Interphase – cell growth, DNA copied –Prophase 1 – nuclear membrane disappears, crossing over!!!! This phase is very different than prophase in mitosis due to the crossing over. –Meta 1 – homologous chromosomes in middle –Ana 1 – homologous chromosomes pulled apart –Telo 1 & Cyto 1 – pinch in, 2 new nuclei (haploid) Now those 2 cells each go through the phases AGAIN –Pro 2 – nuc. mem disappears –Meta 2 – single chromosomes in middle –Ana 2 – chromatids pulled apart –Telo 2 & Cyto 2 – pinch in, 4 new nuclei (haploid!) *notice Interphase only happens once at the beginning

Fertilization Union of gametes (sex cells)

Sexual Summary Meiosis 2 divisions Chromosome # reduced by half in new cells Produces 4 new “haploid” cells Genetic variation/recombination- allows species to adapt rapidly to new conditions Offspring are genetically different from the parents Fertilization –Union of a sperm and an egg (gametes)

Sexual Reproduction Advantages vs. Disadvantages Genetic Diversity Natural Selection (survival) Larger chance of mistakes

You should be able to understand both types of reproduction and tell the difference between the two types.

What type of reproduction would be in “process 1”? What type of reproduction would be in “process 2”? What type of reproduction would be in “process 3”?