biology 121 lab

Cell Division Terminology Definition

  karyokinesis nuclear division   cytokinesis cell division   haploid 1 set of chromosomes (1 copy of each)   diploid 2 sets of chromosomes (2 copies of each)   polyploidy > 2 sets of chromosomes   chromatin DNA + protective histone proteins   chromosome molecule of DNA   chromatid molecule of DNA

(ss = chromosome; ds = sister chromatids)

  centromere point at which sister chromatids are joined   genes units of heredity; each codes for 1 polypeptide   alleles alternate forms of genes   centrioles (aka centrosomes) the structures from which the

spindle apparatus originates   spindle apparatus structure of microtubules; allows for proper

chromosome separation

  Cell division occurs in eukaryotic cells

  Mitosis = cell division that occurs in somatic cells (n or 2n)

  Meiosis = cell division that occurs in reproductive cells (2n) to produce gametes (ALWAYS n)

Why Mitosis?   ↑Complexity ⇒ ↑DNA ⇒ ↑Organization

  Each cell MUST have the same complement of genetic information

Cooper 2000

= 3,000,000,000 bp

= 4,600,000 bp

  Too much or little information = severe problems [often lethal effects]

  anueploidy (1 chromosome)1   sickle cell anemia (1 aa)2   phenylketonuria (1 enzyme)3

The Cell Cycle

Interphase (The “Resting” Phase)

G1 → increased biochemical activity – cell volume x2 S → replication (“synthesis”) of chromosomes (ss → ds) G2 → structures involved with chromosome separation develop (e.g., centrioles & spindle apparatus)

Mitosis Karyokinesis (1 nucleus → 2 daughter nuclei) Prophase

o  centrioles & spindle apparatus visible

o  nuclear envelope disintegrates

o  sister chromatids evident

⇒ REMEMBER…plant cells do NOT have centrioles!

Metaphase

o  ds chromosomes are aligned along “equator”

Anaphase

o  chromatids separate

o  ds → ss chromosomes

Telophase

o  daughter chromosomes become enclosed; nuclear envelope(s) form

o  2 daughter nuclei

o  centrioles & spindle apparatus disintegrate

Cytokinesis

  Differs among organisms…

o  animals: cleavage furrow

o  plants: cell plate

Importance of Control

  Cell proliferation (= formation of new cells)

Critical for:

o  embryological development o  repair of damaged tissue o  immune response

⇒ uncontrolled proliferation = cancer

Meiosis (= Gametogenesis)

  Gametogenesis (= “origin of gametes”) o  spermatogenesis → sperm cells

- 4 sperm cells - continual

o  oogenesis → egg cells - 1 egg cell - cyclical

Why Meiosis?

  Maintenance of genetic composition   each generation MUST have the same

complement of genetic information   too much/little information = severe problems

  Introduction of variation   persistence of population(s) through time   evolution of population(s) via natural selection

Oogenesis vs. Spermatogenesis

Development

  Zygote → Multicellular organism   Mitotic process

  Differentiation: gene expression

Development (cont.)

  Proceeds in ordered phases throughout the animal life history.   Gametogenesis   Fertilization   Cleavage   Gastrulation

  endoderm   mesoderm   ectoderm

  Organogenesis

Exercises: Mitosis   Exercise 8.1

o  Observe mitotic phases - whitefish blastula - onion root tip

o  Draw and describe your observations

  Exercise 8.2 o  Observe and count every cell in the field of view o  Tabulate cell stages o  A minimum of 100 cells AND 2 fields of view should be

examined and tabulated o  Calculate…

- percentage of cells per stage - amount of time spent in each phase