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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