4.1 CELL DIVISION AND GENETIC MATERIAL

GENETICS

Field of biology

Study how genetic information is passed

from one generation of organism/cells to the next

THE CELL THEORY

developed in mid-1800s

1. All living things are composed of one or more cells.

2. Cells are the smallest units of living organisms.

3. New cells come only from pre-existing cells by cell division.

Thus, traits must be passed from a parent cell to new daughter cells

SOMATIC CELL

a plant/animal body cell

go through cell cycles: 1 cell 2 cells

cell cycle duration depends on:

1. the cell type

2. the organism

Most healthy, actively dividing cells: 12-24 hrs

THE CELL CYCLE

3 main stages

1. interphase: growth and intense cell activity

2. mitosis: nucleus and genetic material divide

3. cytokinesis: division of the cell cytoplasm and creation of new cells

THE CELL CYCLE

3 functions

1. growth of the organism

2. repair of tissues and organs

3. maintenance to replace dead cells

• Specific checkpoints

1. monitor growth

2. ensure the cycle continues or stops appropriately.

•Regulation is the key to preventing uncontrolled and rapid growth, such as cancerous growth.

INTERPHASE

the cell carries out its normal functions:

1. grows

2. makes copies of its genetic material.

3 phases: Growth 1 (G1), Synthesis (S), and Growth 2 (G2).

• Growth 1 (G1): major period of growth.

• Synthesis (S): DNA (also called chromatin) is replicated.

• Growth 2 (G2): further growth and molecule synthesis.

MITOSIS separation of the cell’s replicated genetic material.

•chromosome: a structure in the nucleus that contains DNA

• sister chromatid: one of two chromosomes

that are genetically identical and held together at

the centromere

• centromere: the region where two sister chromatids are held together in a chromosome

• spindle fibre: a microtubule structure that facilitates the movement of chromosomes within a cell

• centrosome: a structure that helps to form the spindle fibres

MITOSIS (VIDEO 3:08)

CYTOKINESIS

different in different cell types.

animal cells:

microfilaments constrict

Furrow forms in cell membrane along the equator of the cell.

deepens and pinches off into two cells. This transmission

electron micrograph

shows two identical

kidney cells forming.

Magnification: 1700x

CYTOKINESIS

plant cells:

rigid cell wall does not pinch inward

a cell plate forms between the daughter nuclei

A cell wall forms on each side of the cell plate.

PROKARYOTIC CELLS no nucleus

complete cell division with binary fission

DNA is pulled apart cell separates into two prokaryotic cells.

THE STRUCTURES OF GENETIC MATERIAL

DNA

Made of nucleotides

long, spiraling double helix

Nucleotide:

a sugar (deoxyribose),

a phosphate group,

a base.

4 bases: adenine (A), guanine (G), cytosine (C), thymine (T).

A - T and C - G

DNA REPLICATION

during interphase

double helix unwinds

each strand of DNA serves as a template

Each new double helix contains one original strand and one new strand and one new strand

Semi-conservative

CHROMOSOMESNO relationship between # of chromosomes and complexity of organism.

HUMAN CHROMOSOMESEach somatic cell has 2 sets of 23 chromosomes

one set from father and one set from mother.

The 2 sets are homologous same sequence of genes (traits)

same length, location of the centromere, and stain banding pattern.

However, they can contain different alleles(forms) of a gene.

CHROMOSOMES 22 pairs are called autosomes

true homologous pair

1 pair is the sex chromosomes

determine the sex of the individual

The two chromosomes (X and Y) are not homologous.

XX = female

XY = male

KARYOTYPES

a person’s particular set of chromosomes

chromosomes are collected and stained when a cell is in metaphase so they appear as sister chromatid “Xs.”

This is a human karyotype. The chromosome pairs are arranged and numbered in order

of their length, from longest to shortest. The sex chromosomes are placed last in a

karyotype. Note that the banding patterns between homologous chromosomes are

different in this image because of the type of dye that was used.

HOMEWORK

p. 168 #1,3-6, 8, 9, 11,13,14,16, 17