Download Mitosis and Meiosis Powerpoint presentation

Why is Reproduction so
important?
• Preserves the continuity of
the species
• Essential to the
transmission of hereditary
information which is
carried in the DNA
Cells reproduce for many reasons:
• In single-celled organisms, the division of ONE cell
to form TWO makes a whole NEW organism
• In multicellular organisms, cell division allows
growth and development of the fertilized egg and
replacement of damaged or dead cells
There are 2 kinds
of reproduction:
•Asexual Reproduction
•Sexual Reproduction
Asexual •
Reproduction
This type of reproduction
involves only ONE parent
organism (either unicellular
or multicellular).
• Occurs by MITOSIS and
cytoplasmic division
• The offspring contains the
same DNA as the parent and
is therefore a CLONE
• Ex: An ameba reproduces
asexually by splitting in two
Three types of Asexual
Reproduction:
1. Binary Fission
2. Budding
3. Regeneration
Binary Fission
• Splitting of an
organism into 2 or
more individuals
of EQUAL SIZE
• Ex: paramecium,
bacteria
Budding
• A new individual
splits off its parent
• Split is not of equal
size
• Ex: Hydra, jellyfish
Vegetative Propagation
• This process grows
a new PLANT
using mitosis or
asexual
reproduction!
• It is the production
of a new individual
plant from
horizontal stems
and underground
roots
Regeneration
• A new individual can
grow from a segment or
piece of an existing
organism
• Helpful for replacement
of injured or lost body
parts
• Ex: Sea Star, worms
Mitosis
• Our body cells, such as
skin and hair, reproduce
asexually by splitting and
dividing through
MITOSIS
• Mitosis is used when
cells/tissues need to grow
and repair
• Mitosis creates clones of
the parent cell
• Body cells contain 46
chromosomes (the Diploid
number)
What is DNA?
• All the information
needed to create an
entire organism is
encoded in DNA
• DNA is made up of
Genes
• A single molecule of
DNA has thousands of
genes lined up like
train cars
Chromosomes
• DNA is coiled into a
structure called a
chromosome
• When DNA is
copied – the exact
copy is called a
chromatid.
• Two chromatids are
joined by a
centromere
In humans, the rate of
mitosis is about 25 million
cells every second!
Calculate the number of cells
produced by mitosis in 3
minutes.
3 min = 180 seconds (3 x 60)
180 sec x 25 million = 9 x 1010 cells
= 90,000,000,000
Single-Stranded
Chromosomes
Stages of Mitosis
Mitosis
Cell Division Animation
Mitosis in Animal Cell
Mitosis in
Plant Cell
What is Cancer?
• Sometimes body cells do not respond to normal
control mechanisms, and continue to divide as long as
nutrients are available
• Eventually a tumor forms
• If cancer cells remain at the original site they are
considered benign
• If they spread to neighboring tissues, they are
considered malignant
Sexual Reproduction
• This type of reproduction
involves the fusion
(joining) of nuclei from
two parents
• The cells used during
sexual reproduction are
called gametes
• Male gametes are
SPERM,Female gametes
are EGG cells
Gametogenesis
•
The production of gametes by the process of
MEIOSIS in males and females.
•
Gametogenesis is the ONLY process that uses
MEIOSIS in the body.
•
Production of Sperm is called
Spermatogenesis; Production of Egg cells is
called Oogenesis
Meiosis
• Meiosis is the process by which sex cells (sperm and
egg) from 2 parents are created
• These cells contain HALF the number of chromosomes
of the parent cell known as the haploid number (23
each)
• Fertilization restores the diploid number (46)
Meiosis creates 4 cells with
23 chromosomes for every
ONE that is divided
Diploid Number of some
Commonly Studied Organisms:
•
•
•
•
•
•
•
•
•
•
•
•
•
Humans – 46
House Mouse – 40
Corn – 20
Fruit Fly – 8
South African clawed Frog – 36
Microscopic Roundworm – 12
Budding Yeast – 32
Domestic Dog – 78
Deer – 23
An Ant –2
Parasitic Roundworm – 2
A Crayfish – 200
Field Horsetail (plant) - 216
Crossing Over
• During meiosis,
chromosomes cross
over each other
• This allows for
genetic shuffling and
increases genetic
variability
• Offspring have a
unique combination
of genes inherited
from both parents
Crossing Over
Why crossing over is important…
• A male bird with large wings
and weak muscles mated with
a female bird with small
wings and strong muscles.
• Describe all the possible
characteristics that could
occur in their offspring.
• Would any combination(s) be
advantageous?
• Would any combination(s) be
disadvantageous?
• How could these variations
affect the survival of the
Meiosis Animation
Meiosis Animation
Asexual
Reproduction
• Single Parent
• Single parent passes on
ALL of its genes to its
offspring
• Offspring are genetically
identical to parent
• Results in a clone
• No crossing over occurs
Sexual
Reproduction
• Two Parents
• Each parent passes on half its
genes to its offspring
• Offspring have a unique
combination of genes inherited
from both parents
• Results in offspring with greater
genetic variation
• Crossing over occurs which
increases genetic variability