Growth and Reproduction l Characteristic of all living

Growth and Reproduction l Characteristic of all living things – Growth l 2 options Cells can become larger (unicellular and multicellular) – More cells produced (multicellular) – l – Needed for success of the individual Reproduction l 2 options – l Asexual or sexual Needed for the success of the species/population

Growth and Reproduction l Based on portion of cell theory – All cells come from preexisting cells l Genes and chromosomes were inherited from previous generations – l Parents, grandparents, great-grand, etc Continuation of life is dependant on this – Information must be passed from cell to cell, generation to generation l Information is in the form of DNA for all living things l DNA stored in chromosomes

Cell Size l Cells are small – – Surface area to volume limitation 0. 0004 -0. 0008 inches l – – All cells are about the same size Cell size and shape relate to function l – 100 trillion cells in a typical human Remember: Structure determines function Cells of organisms are all about the size l l Muscle cells of a whale is the same size as that of a mouse Whale just has more cells

Limitations on Cell Size l l All base on surface area to volume ratio Limited by 4 main factors – – Availability of nutrients How much cytoplasm the cell can control l – – Supply with nutrients/remove waste Relation of surface area and volume Location of the cell l Different cells have different jobs different size

Differentiation/Specialization l l Found in multicellular organisms Have cells designed to complete specific task Cells take on characteristics to help the organism meet needs All cells have the same genetic info within an organism – DNA in a muscle cell is the same as a nerve cell

Major Terms for Mitosis l Traits: daughter and parent cells have the same traits – – Characteristics passed from parent to offspring Height, eye color, hair color, facial structure, blood type, to many more to list

Major Terms for Mitosis l Heredity: transmission of traits between generations – – Information is carried in the chromosome Asexual l l – All genetic information comes from one parent Offspring are identical to the parent Sexual l l ½ genetic info from each parent Human: 23 chromosomes from mom, 23 from dad

Major Terms for Mitosis l Genes: Segment of DNA which controls hereditary traits – – Points on chromosomes that control certain traits Estimated number of human genes is currently at 20, 000 -25, 000 l Human genome project

Major Terms for Mitosis l Chromatin – How the genetic information is organized when a cell is not dividing l l l Uncoild Genes available to read Nucleic acid wraps around proteins – Proteins called histones

Major Terms for Mitosis l Chromatid – – – Identical copies of the same genetic information Each cell gets one when cell divides Held together by a centromere

Binary Fission l l 1 parent cell divides into 2 daughter cells Binary Fission – – Carried out by bacteria Method of asexual reproduction Bacteria only have 1 chromosome, no nucleus Very simplistic division l l Can happen very rapidly E. Coli will colinize infant gastrointestinal tract within 40 hours (needed for survival)

Mitosis l l Process of cell division when chromosomes in the nucleus of the parent divide into 2 identical sets Cells produce daughter cells that contain same DNA as the parent – l Daughter cells are genetic copies of the parent Involved in asexual reproduction of eukaryotes

Stages of the Cell Cycle l l Interphase (G 1, G 0, S, G 2) Mitosis (M) – – l Prophase Metaphase Anaphase Telophase Cytokinesis(C)

Interphase l l Period between division Genetic info in the form of chromatin Majority of a cells life When normal cell function is carried out

Interphase l G 1: Cell grows – – l G 0: When a cell does not divide – l Nerve, muscle (in adults), kidney, liver S: Synthesis of DNA – – l Right after cell was produced from parent Must get to functional size DNA is copied in preperation for division Each new cell will need its own copy G 2: Growth and preparation for division

Prophase l l l l First stage of mitosis Chromatin shorten and thicken making visible chromosomes Each chromosome consist of 2 chromatids Chromatids held together by centromere Nuclear envelope starts to break down Nucleolus breaks down Centrioles (Centrosome) become visible

arm centromere arm

sister chromatids daughter chromosomes

Prophase

Metaphase l l Chromosomes move to the middle of the spindles between the two poles Line up side by side at the equator Chromatids attach to spindle fibers at the centromere Chromosomes are thick and coiled

Metaphase

Anaphase l l Chromatids separate and are pulled to opposite poles Ends when chromatids reach the sides Once they are split from each other they are considered a chromosome Each pole contains the same number of chromosomes as the parent cell

Anaphase

Telophase l l l Exact opposite of prophase Chromosomes become fine threads (chromatin) Spindle fibers disappear Nuclear membrane reforms Nucleolus begins to reform

Cytokinesis l l Cytoplasm of the cell divides Produces 2 new daughter cells Cell pinches in forming a cleavage furrow Cell plate is formed in organisms with a cell wall

Cytokinesis

Reproduction l Sexual reproduction – – – Union of 2 reproductive cells to form new cells Requires meiosis Reproductive cells called gametes l Male = sperm Female = egg

Reproductive Terms l Gamete – – – Cell with only half the number of chromosomes Sperm/egg Why do they need ½ genetic information?

Reproductive Terms l Fertilization – l Fusion of 2 gametes Zygote – – Result of 2 gametes being fused First cell of a sexually reproduced organism

Reproductive Terms l Diploid – – – l Cell with the complete number of chromosomes Called somatic cells 46 in a human (2 n) Haploid – – Cell that has half the number of chromosomes 23 in human (n)

Reproductive Terms l Meiosis – – Cell reproduction that produces cells with haploid number of chromosomes Broken into Meiosis I and Meiosis II l l Similar to mitosis cell cycle Everything happens twice Except intephase – Do not need to reproduce genetic information between – – – Meiosis I Separates homologous pairs Meiosis II separates chromatids

Asexual Reproduction l l 1 parent Offpring are exact copies of parent – l l Several types based on organism Benefits – l One get copies of one parents chromosomes Quick, large amount of offspring, low energy input, difficulty of finding mate (sessile) Draw backs – Little/no genetic variation

Binary Fission l l Simple form of asexual reproduction Unicellular organism splits into two identical organisms

Budding l l Growth of a reproductive fragment from a parent Contains complete genetic information – Limited cytoplasm

Spore production l l Spores protected by hard shells Can survive harsh conditions

Vegatative Propagation l l l Asexual in plants Make clone of themselves Why do plants need to be able to reproduce a sexually?

Meiosis Cycle l l l Interphase Meiosis I Cytokinesis I Meiosis II Cytokinesis II

Meiotic Interphase l l Very similar to interphase for somatic cells Cell grows, DNA copied, cell prepares for division

Prophase I l l Very similar to Prophase from mitosis Crossing over happens – – Homologous pairs exchange genetic information Group together in a tetrad l – – Tetra = 4 Allows for more diversity in the population What are homologous pairs?

Prophase I

Metaphase I l l Homologous pairs line up on metaphase plate Moved by spindle just like mitosis

Metaphase I

Anaphase I l l Separates the homologous pairs Creates huge possibility for genetic variation – Called independent assortment l l Amount of possible combinations is 2 n For Humans: 223 = 8, 388, 608 possible combinations

Metaphase II l Chromosomes align on the metaphase plate again

l Sister chromatids separated

Overall Meiosis l l Meiosis I : Separates Homologous Pairs Meiosis II: Separates sister chromatids