Topic 8: Asexual Reproduction and Mitosis

asexual reproduction

how many unicellular organisms reproduce via cell division to create genetically identical offspring

cell cycle

the life of a cell from the time it is first formed from a dividing parent cell until its own division into two daughter cells

clone

when a parent and offspring have identical DNA blueprints (genomes)

prokaryotic cell division

binary fission: DNA is replicated, cell grows and splits in half to create two identical daughter cells

nucleolus

a dense structure within the nucleus where ribosomal RNA is synthesized and assembled into ribosomes

chromosome

DNA double helix + associated proteins; the structure that carries genetic information and is visible during cell division

chromatid

one of two identical halves of a duplicated chromosome

sister chromatids

chromatids joined together at the centromere

telomere

the ends of chromosomes

chromatin

generic term for DNA plus associated proteins

centromere

region where sister chromatids are joined together

kinetochore

structure made up of proteins that have assembled on specific sections of chromosomal DNA at each centromere

histones

types of proteins that help package and order DNA into nucleosomes (H2A, H2B, H3, H4)

nucleosome

basic unit of chromatin; short segment of DNA wrapped around an octamer of histone proteins, with 2 copies of each histone

linker histone (H1)

package nucleosomes into 30 nm fibers; fibers are then packaged into increasingly compact structures

interphase (G1, S, G2, G0)

appearance of cell is constant as it grows in size

mitosis

dramatic changes as cell divides

prophase

(1) interphase microtubules break down, centrosomes separate, and the mitotic spindle forms outside the nucleus

prometaphase

(2) nuclear envelope breaks down, and microtubules attach to kinetochores of chromosomes

metaphase

(3) kinetochore microtubules line up paired chromatids at the metaphase plate

anaphase

(4) sister chromatids are pulled toward opposite poles of the cell by microtubules

telophase

(5) chromatids separate at poles of the cell, kinetochore microtubules disassemble, nuclear envelope begins to reform, chromosomes begin to decondense; nucleus reforms

cytokinesis

(6) contractile ring of microfilament forms cleavage furrow that splits cells in two; nuclear envelope is fully visible, interphase microtubules reform

plant cell division

due to rigid plant cell wall, no cleavage furrow will form; instead, vesicles form at cell plate and fuse to form new membranes

metaphase plate

imaginary plane where chromosomes align during metaphase in mitosis