Textbook Notes (362,766)
Canada (158,052)
Biology (308)
BIOL 1090 (72)
Chapter 2

Bio 1090 chapter 2

6 Pages
Unlock Document

University of Guelph
BIOL 1090
Andrew Bendall

Bio 1090 Chapter 2 p.23-26, p.27-36 Cell division - clone; population of cells (one cell divide into 2 cells ect.) - cell division is an integral part of the growth of multicellular organism, basis or reproduction - mother cell; cell about to divide. Daughter cells; products of division - When prokaryotic cells divide, the contents of the mother cell are more or less equally apportioned between the 2 daughter cells; fission - Mother cell’s chromosome is duplicated prior to fission and copies of it are bequeathed to each of the daughter cells - Optimal conditions; E. coli divides every 20-30 minutes, 1 cell could form a clone of 2 50 cells. As cells accumulate, rate of division – because nutrients are exhausted and waste products pile up - E. coli can produce enough progeny in 1 day to form a mass visible to unaided eye; colony - Mitochondria and chloroplasts randomly apportioned to daughter cells - Division in eukaryotic more elaborate than in prokaryotic cells - Eukaryotic cell divides goes through series of phases that collectively form the cell cycle (G1SG2M) - S is the period in which the chromosomes are duplicated- an event that requires DNA synthesis - M is the time when the mother cell actually divides (M= mitosis) (1) Mitosis: process that distributes the duplicated chromosomes equally and exactly to the daughter cells (2) Cytokinesis: process that physically separates the 2 daughter cells from each other - G1 and G2 phases are “gaps” between the S and M phases - In embryos, growth is rapid  cycle 30 minutes - In slow-growing adult tissues, cycle last several months - Cells in nerve and muscle tissues cease to divide once they reached their specialized functions. Progressions of eukaryotic cells through cycle is controlled by types of proteins (activities disrupted; cells divide in an unregulated fashion cancer) Mitosis - When eukaryotic cells divide, they distribute their genetic material equally and exactly to their offspring - Each chromosome in mother cell is duplicated prior to onset of mitosis (during S phase) - Chromatin: network of thin strands formed by all the chromosomes within the nucleus - Chromosomes shorten and thicken  condense out of the chromatin network and individual chromosomes become recognizable - After mitosis, chromosome decondense and chromatin network is reformed  Interphase: individual chromosomes cannot be seen (lengthy; between successive mitotic events) - When it begins, chromosomes are already duplicated. Duplicates; sister chromatids, remain associated with each other and are joined at the chromosomes centromere - (term sister =misnomer because these chromatids are copies of original chromosome) - distribution of duplicated chromosomes to daughter cells organized and executed by microtubules (components of cytoskeleton) - fibers composed of proteins; tubulins, attach to the chromosomes and move them about within dividing mother cell - microtubules assemble in a complex; spindle (formation of spindle is associated with microtubule organizing centers, found in cytoplasm of eukaryotic cells, near nucleus) - In animal cells, MTOCs are differentiated into small organelles; centrosomes (not present in plant cells). Each centrosomes contains 2 barrel-shaped centriole (aligned at right angles to each other) - Centrioles surrounded by diffuse matrix; pericentriolar material, initiates the formation of the microtubules that will make up the mitotic spindle - Single centrosome in an animal cell; duplicated during interphase - Cell enter mitosis, microtubules develop around each of the daughter centrosomes to form a sunburst pattern; aster - Centrosome then move around to nucleus to opposite positions in the cells, establish the axis of the upcoming mitotic division - Final positions of centrosomes define the poles of dividing mother cell - In plants, MTOCs that do not have distinct centrosomes define these poles and establish the mitotic spindle 1. Prophase: initiation of spindle formation and the condensation of duplicated chromosomes from the diffuse network of chromatin are hallmarks of the first stage of mitosis - formation of spindle is accompanied by fragmentation of many intracellular organelles (ER and Golgi) - Nucleolus: dense body involved in RNA synthesis within the nucleus disappears but other such as mitochondria and chloroplasts remain intact - Concomitant with fragmentation of ER, nuclear membrane breaks up into small vesicles and microtubules formed within the cytoplasm invade the nuclear space - Some of these microtubules; attach to kinetochores (protein structures associated with the centrosomes of the duplicated chromosomes) - Attachment of spindle microtubules to kinetochores  cell is entering metaphase of mitosis 2. Metaphase: duplicated chromosomes move to positions midway between the spindle poles; movement leveraged by changes in the length of the spindle microtubules and by the action of force-generating motor proteins that work near the kinetochores - spindle apparatus contains microtubules not attached to kinetochores (additional microtubules stabilizes the spindle apparatus) - operation of spindle apparatus; duplicated chromosomes come to lie in single plane in middle of the cell, equatorial plane called metaphase plate. Each sister chromatid of duplicated chromosome connected to different pole via microtubules attached to kinetochore (crucial for equal and exact distribution of genetic material to daughter cells) 3. Anaphase: sister chromatids of duplicated chromosome are separated from each other during this phase - accomplished by shortening the microtubules attached to kinetochores and by degrading materials that hold the sister chromatids together (microtubules shorten sister chromatid pulled to opposite poles of cell= chromosomes) - chromosome move toward pole, poles being to move apart  separates the 2 sets of chromosomes into distinct spaces within the dividing cell. The chromosomes decondense into a network of chromatin fibers and organelles re-form - set of chromosomes becomes enclosed by nuclear membrane 4. telophase: decondensation of chromosomes and the restoration of internal organelles are characteristic of this phase - when mitosis completed, 2 daughter cell are separated by formation of membrane between them - physical separation of the daughter cells = cytokinesis - daughter cells that are by division of a mother cell are genetically identical (daughter has set of chromosomes that derived by duplicating the chromosomes originally present in mother cell; genetic material transmitted between the 2) - mistakes during mitosis: chromatid may become detached form mitotic spindle and may not be incorporated in daughter cells or may be entangle, lead to breakage and loss of chromatid parts (causes genetic differences in daughter cells) Meiosis - zygote produced by union of 2 gametes has 2n chromosomes - n chromosomes  haploid state and 2n diploid state - meiosis: process that reduces the diploid state to the haploid state (reduces the number of chromosomes in a cell by half) - resulting haploid cells becomes gametes or divide to produce cells that becomes gametes - plays a role in reproduction among eukaryotes (without this, organisms would double their chromosome number every generation) - chromosomes in diploid cell  comes in pairs (human cells have 23 pairs of chromosomes, each are distinct, different pairs carry different sets of genes) - Homologues: numbers of a pair, carry the same set of genes, they may carry different alleles of these genes - Heterologues: chromosomes from different pairs (homologues associates intimately with each other basis of an orderly process that reduces the chromosome number to the haploid state; reduction number of chromosomes occurs so each of resulting haploid cells receives one member of each chromosome pair) - Involves 2 cell divisions  chromosome duplication, associated with DNA synthesis, occurs prior to the first of these divisions (not between the 2) chromosome duplication  meiotic division I  meiotic division II - if we represent the haploid amount of DNA by letter c, then in sequence these double the amount of DNA (from 2c to 4c), cut in half (from 4c to 2c) and cut i
More Less

Related notes for BIOL 1090

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.