gen bio - lecture 10: cell cycle

cell theory ( + definition of a cell)

• all cellular life is made of one or more cells

• cell: basic organizational and functional units of all organisms!! all cells come from other cells

2 functions of cell division for multicellular organisms

1. growth/development

2. repair

main function/goal of cell division

distribute genetic material into daughter cells accurately and fully intact

genome (diff in prokaryotes vs eukaryotes)

a cell’s total genetic material

• prokaryotes: usually 1 circular DNA molecule

• eukaryotes: usually more than 1 linear DNA molecule

chromosome

• molecule of DNA in a cell wrapped around proteins

• highly organized, high density

ONLY PRESENT DURING CELL DIVISION

chromatin

• DNA/histone complex in a dispersed state

• spaghetti like

PRESENT IN THIS STATE WHEN NOT DIVIDING

ploidy

the # of sets of chromosomes in the nucleus of a cell

haploid (n)

having one complete set of chromosomes

• haploid cells = have ONE OF EACH CHROMOSOME

• ex. gametes

diploid (2n) and definition of homologous pair/chromosomes

having two complete sets of chromosomes

• ex. somatic cells (body cells)

homologous pairs/homologous chromosomes: 2 of the same chromosome

• have the same length, genes, centromere location

what types of cells can undergo mitosis?

both HAPLOID and DIPLOID

prokaryotes divide through…

binary fission

interphase OVERVIEW

• time between cell divisions

• has three subphases, each with their own checkpoint

  • G1 (gap one), S (synthesis), G2 (gap two)

interphase definition

• time between cell divisions

• NOT RESTING! cells are highly active

  • growth, synthesis, metabolic activity

• LONG, about 90% of cell cycle

• DNA is in CHROMATIN FORM

G1 (gap one) phase

• growth and normal development and functions occurring

• preparing for S phase

  • many cells spend their whole lives in this phase

S (synthesis) phase

• genetic material is DUPLICATED but DOES NOT CHANGE PLOIDY!!

  • DNA + histone synthesis

• centrosome duplication

• after replication = 2 sister chromatids connected @ centromere BUT STILL IN CHROMATIN FORM

G2 (gap two) phase

• high metabolic activity

• preparing for mitosis

• usually shortest phase + DNA = still chromatin

M phase OVERVIEW

• mitosis and cytokinesis

• shortest part of cell cycle

mitosis DEFINITION + OVERVIEW

• nuclear division of SOMATIC cells

• continuous process

• divided into four stages (PMAT - prophase, metaphase, anaphase, telophase)

prophase (define mitotic spindles + kinetochores)

4 big steps:

1. chromosomes condense (chromatin to chromosomes)

2. nucleus breaks down

3. mitotic spindle forms

• mitotic spindles: fibers within cell that are oriented from pole to pole to guide chromosome movement

4. kinetochores form

• kinetochores: handles that from near centromeres

metaphase

• chromosomes align @ metaphase plate

• longest phase of mitosis

anaphase

• “away”

• sister chromatids separate + move to opposite poles

• pulled by kinetochores

  • AFTER SEPARATION, each chromatid = considered to be a chromosome

telophase

• opposite of prophase

• chromosomes start to de-condense

• nuclear envelope reforms

• GOAL: new nuclei identical to parent nucleus

cytokinesis

• cytoplasmic division (2 cells each with 1 nucleus)

• animal cells: cleavage furrow forms and pinches cell into 2

• plant cells: cell plate forms w a new membrane @ location of the metaphase plate to separate and divide daughter cells