3. Tanveer Saeed
Nucleus and Nuclear Envelop
Control center of cell.
Contains
Nucleoplasm
Chromosomes
Nucleolus
Double membrane has pores
Separates nucleus from rest of
cell
Nucleoli
Most cells have 2 or more.
Directs synthesis of RNA
Form component of ribosomes
4. Tanveer Saeed
Chromosome Structure( DNA)
DNA stored in the nucleus of a
single human cell.
over six feet in length if stretched
from end to end.
Hereditary material
Chromosomes----Genes
DNA
Proteins
Form for cell division
Chromatin
6. Tanveer Saeed
Chromosomes and Genes
Chroma color soma bodies
Inside the nucleus the chromatin material condense to form
chromosome.
Human cell contain 46 chromosome arrange in pair in the
nucleus of each cell.
Each chromosome is a long molecule of DNA that is coil
together with several proteins. the complex of DNA,protein
and some RNA is called chromatin.
GENES:
Gene is the segment of DNA
each chromosome carries many genes
The site on chromosome on which a particular gene is
located is called locus
Genome all gene possessed by one individual.
9. Tanveer Saeed
Nucleic Acids
They are huge organic molecule contain
carbon hydrogen oxygen nitrogen and
phosphorus.
There are 2 types of nucleic acids
1. DNA 2. RNA
consists of 3 parts
1. Nitrogenous bases 2.Pentose sugar
3.Phospate group
12. Tanveer Saeed
Transcription
Step 1:Two DNA strands separate, RNA
polymerase binds to the control segment of the
gene.
Step 2: RNA PM moves from one triplet to another
along the length of the gene. At each site,
complementary RNA nucleotides form hydrogen
bonds with DNA nucleotides of the gene. The
RNA PM then strings the arriving nucleotides
together into a strand of mRNA.
Step 3 :On reaching the stop signal RNA PM and
mRNA strand detach and two DNA strands
reattach.
13. Tanveer Saeed
Translation
mRNA then moves from the nucleus into the
cytoplasm & is used to produce a protein.
requires mRNA, tRNA (transfer RNA), amino
acids,
sequence of amino acids in a protein is
determined by sequence of codons (mRNA).
Codons are 'read' by anticodons of tRNAs &
tRNAs then 'deliver' their amino acid.
Amino acids are linked together by peptide bonds.
Codons :A sequence of 3 Nitrogenous bases along new
mRNA strand
14. Tanveer Saeed
Translation cont’d
As mRNA slides through ribosome, codons are
exposed in sequence & appropriate amino acids
are delivered by tRNAs. The protein (or
polypeptide) thus grows in length as more amino
acids are delivered.
The polypeptide chain then 'folds' in various
ways to form a complex three-dimensional
protein molecule that will serve either as a
structural protein or an enzyme.
mutations Permanent alterations in the cell
16. Tanveer Saeed
Mitosis
Mitosis is a process of cell division which
results in the production of two daughter
cells from a single parent cell.
The daughter cells are identical to one
another and to the original parent cell.
Occurs in somatic cells
19. Tanveer Saeed
Meiosis
Meiosis is a reductive cell division.
It involves two divisions to produce four non-
identical daughter cells each containing half
the number of chromosomes of the parent
cell.
Takes place in reproductive cells
21. Tanveer Saeed
Mitosis
Interphase
Cells may appear inactive
during this stage.
longest period of the complete
cell cycle during which DNA
replicates, the centrioles divide,
and proteins are actively
produced.
22. Tanveer Saeed
Prophase
During this first mitotic stage,
the nucleolus fades.
chromatin condenses into chromosomes.
Each replicated chromosome comprises two
chromatids, both with the same genetic
information.
the mitotic spindle from the region of the
centrosomes appears
23. Tanveer Saeed
Prometaphase
the nuclear envelope breaks.
Nucleus almost disappear
mitotic spindle fibers elongate from the
centrosomes and attach to kinetochores
Other spindle fibers elongate but instead of
attaching to chromosomes, overlap each other at
the cell center.
24. Tanveer Saeed
Events of Mitosis
Metaphase: Tension applied by the spindle fibers
aligns all chromosomes in one plane at the center of
the cell.
Anaphase: Spindle fibers shorten, the kinetochores
separate, and the chromatids (daughter
chromosomes) are pulled apart and begin moving
to the cell poles.
Telophase: The daughter chromosomes arrive at
the poles and the spindle fibers that have pulled
them apart disappear.
25. Tanveer Saeed
Cytokinesis
The spindle fibers not attached to
chromosomes begin breaking down until only
that portion of overlap is left.
It is in this region that a contractile ring
cleaves the cell into two daughter cells.
Microtubules then reorganize into a new
cytoskeleton for the return to interphase.
27. Tanveer Saeed
Events During Meiosis
Diploid Cell (2N): From a preceding mitotic
division, the Oogonium (Spermatogonium)
enters meiosis with DIPLOID (2N)
chromosomes but TETRAPLOID (4N)
DNA.
Chromosomes then duplicate to produce
SISTER CHROMATIDS (or
HOMOLOGOUS DYADS).
28. Tanveer Saeed
Meiosis cont’d
Prophase I: Homologous pairing of chromosomes
align to create "TETRADS", non-sister chromatids connect
"CHIASMA“ formation, "CROSSING OVER".
Metaphase I: SPINDLE FIBERS attach to each
homologous pair at the KINETOCHORE. Tension from
spindle fibers aligns the tetrads at the cell equator.
Anaphase I: Chiasmata break apart and sister chromatids
begin migrating toward opposite poles.
Telophase I: CYTOKINESIS (cell division). Resulting
daughter cells are HAPLOID (1N).
29. Tanveer Saeed
Meiosis cont’d
Prophase II: Spindle formation begins and centrosomes
begin moving toward poles.
Metaphase II: Tension from spindle fibers aligns
chromosomes at the metaphase plate.
Anaphase II: CHROMATIDS separate and begin
moving to the poles.
Telophase II: CLEAVAGE FURROW forms beginning
CYTOKINESIS.
Each haploid cell divides and net result is four haploid cells
all genetically different.
In female only one haploid cell will have the potential to to
develop unto an ovum and other three called polar bodies do
not function as gametes.
31. Tanveer Saeed
Gamete (1N): NUCLEAR ENVELOPES form and
chromosomes disperse as CHROMATIN. Meiosis
has produced 4 DAUGHTER CELLS, each with
1N chromosomes and 1N DNA. Later, in
fertilization, male and female 1N gametes will fuse
to form a 2N ZYGOTE.
32. Tanveer Saeed
Why Mitosis?
Growth: for repairing damaged tissues and it helps maintain
the surface area
Cell Replacement
Regeneration : Tissue growth by reproducing of cells that
need to be replenished constantly like in skin or cells lining
digestive system.
purpose of mitosis is not to create a new variety of organism,
but merely to aid in the development of an existing organism
mitosis produces genetically identical cells whereas meiosis
does not.
33. Tanveer Saeed
Why Meiosis?
Genetic Variation. Meiosis provides opportunities for
new combinations of genes to occur in the gametes.
This leads to genetic variation in the offspring
produced by random fusion of the gametes.
Sexual reproduction is not needed for the individual
to survive, but it helps the species survive as a whole.
make the end products of sexual reproduction
unique.
