BIOL1000 chapter 8

gametes

eggs and sperm cells

zygotes

fertilized egg

binary fission

dividing in half

chromosome

single strand of dna many genes long

chromatin

structure of dna and proteins, long thin fibres

Cell cycle

ordered events from instant cell is formed to moment it divides into daughter cells

interphase (mitosis)

growing phase

g1 phase (mitosis)

first gap, normal cell function takes place

s phase (mitosis)

synthesis phase, dna replication

g2 phase (mitosis)

normal cell functions, finishes preparing for cell division

mitosis

produces 2 identical daughter cells

prophase (mitosis)

nucleus - chromatin coils and folds into chromosomes, chromosomes are 2 sister chromatins bound

cytoplasm - mitotic spindle emerges from centrosome, centrosomes seperate

Mitotic spindle

microtubule fibres and proteins that guide seperation of daughter chromosomes

Prometaphase (mitosis)

nuclear envelop fragments disappear, mitotic spindles reach chromosomes, some microtubules attach to kinetochores and some attach to microtubules from opposite pole

Metaphase (mitosis)

Centrosomes at opposite poles, chromsomes line up on metaphase plates, kinetochores are linked to microtubules of opposite poles

Anaphase (mitosis)

sister chromatids seperate, daughter chromosomes walked to opposite ends of cell,cell elongates

Telophase (mitosis)

Cell elongates, nuclei forms, chromatins uncoil, mitotic spindle disappears

Cytokinesis

division of cytoplasm, same time as telophase, daughter cells separate completely

somatic cells

typical body cells

homologous chromosomes

match in length, centromere position, and staining pattern

diploid cell

cell that contains 2 sets of each chromosomes, total number of chromosomes in organisms, number is 2n

Haploid cells

single set of chromosomes, 1n, occurs in gametes

interphase (meiosis)

chromosomes duplicated, centrosome duplicated

Prophase I

Homologous chromosomes pair up, crossing over

metaphase I

chromosome tetrads align with metaphase plate

anaphase I

Chromosomes migrate to opposite poles, sister chromatids stay attached and tetrads seperate

telophase I and cytokinesis

chromosomes arrive at pole of cell, each pole has haploid chromosome set, 2 haploid daughter cells produced

prophase II

Spindle forms and chromosomes move to center

metaphase II

chromosomes align with metaphase plate

anaphase II

Centreomeres of sister chromatids split and chromatids move towards opposite poles

telophase II and cytokinesis

nuclei for at cell poles and 4 haploid daughter cells are formed

Crossing over

happens in prophase I, shuffling at level of individual genes during meiosis

recombinant chromosomes

carry dna from 2 different parents