Download Cell Division

Reproduction
WHY REPRODUCE?
Why Reproduce?
• Survival of the species
Species - a group of closely related
organisms that can produce fertile
offspring.
• Transfer genetic information from
one generation to the next.
2 Types of Reproduction
• Asexual Reproduction- Mitosis
– one parent
– results in one or more offspring
that are identical to parent.
2 Types of Reproduction
• Sexual reproduction- Meiosis
– two parents
– offspring that have ½ their
genetic material from each
parent.
– Offspring will NOT be identical to
either parent.
Cell Cycle and Chromosomes
CELL CYCLE
DNA Copied
Cells
Mature
Cells prepare for
Division
6
Cell Cycle
– The cell cycle consists of
four phases:
G1, S, G2, and M.
Cell Cycle
– Interphase is the time
between cell divisions.
– Period of growth that
consists of the G1, S,
and G2 phases
Cell Cycle
– The M (Mitotic) phase
is the period of cell
division.
G1 Phase: Cell Growth
G1 phase -cells
increase in size
S Phase: DNA Replication
S (synthesis) phase
New DNA is synthesized
when the chromosomes are
replicated.
G2 Phase
G2 phase
Many of the organelles
required for cell division
are produced.
M Phase: Cell Division
– In eukaryotes, cell
division occurs in two
stages
– Mitosis: the division of
the cell nucleus.
– Cytokinesis: the division
of the cytoplasm.
Chromosomes
• Chromosome – organized, tightly coiled
bundle of DNA (Chromatin) around a protein.
• Found in a cell’s nucleus
• Instructs the cell what proteins to produce
and how to function
• Contains ALL the GENETIC information
Chromosomes
• They occur in PAIRS
• Called Homologous Chromosomes
Karyotype: ( Picture of Chromosomes )
The number and appearance of chromosomes in the nucleus
of a cell. Homologous Pairs
16
Present in pairs containing genes for the
same trait.
Pair of homologous
replicated chromosomes
Centromere
Sister
chromatids
5 µm
An allele is an alternative form of gene
(one member of a pair) that is located at
a specific position on a specific
chromosome.
Chromosomes
• Centromere: Place where replicated
chromosomes attach
• Chromatid: The Single Strand of the
chromosome
Chromosomes
Vocabulary
• Diploid: Number of chromosomes in “body
cells” of an organism – 2n (human = 46)
• Haploid: Number of chromosomes in an
organism’s gamete ( Sex Cell ) - n (human = 23)
• Body cells: Somatic Cells -(skin cells, nerve
cells, liver cells) of an organism contain a
diploid number of chromosomes (2n = 46)
• Gamete cells (sperm and eggs) contain a
haploid number of chromosomes (n = 23)
Types of Cell Division
Mitosis
• Mitosis
Song
26
Mitosis Animation
• mitosis animation 2
Interphase
Prophase
Prophase
Metaphase
Metaphase
Anaphase
Anaphase
Telophase
Telophase
Cytokinesis
In plant cells, a cell plate forms
• new membranes and cell walls are formed in
the center of the cell to separate the TWO
new cells
• plant cells have no centrioles
→ spindle fibers connect to cell wall
A Cell Plate is formed between two new cells
Mitosis in Plant Cells
Differences between plant and
animal cell cytokinesis
Cleavage of an animal cell
Cleavage
furrow
Contracting ring of
microfilaments
Daughter cells
Differences between plant and animal cell cytokinesis
Cell plate formation in a plant cell
Sexual Reproduction
• How do we get HALF
of the genetic
information from
each parent?
MEIOSIS
Meiosis: “Double Cell Division”
• Involves ONE replication and
TWO divisions.
Meiosis
• Meiosis Song and Dance
Meiosis I: First Division
• Prophase I
– Homologous pairs of chromosomes come
together, form tetrads
–
crossing over occurs !!!!!!!
Prophase 1
Meiosis I: First Division
• Metaphase I
– Tetrads line up along the equator.
Meiosis I: First Division
• Anaphase I
– Disjunction- the tetrads are separated
– The Homologous pairs separate
– INDEPENDENT ASSORTMENT - Leads to variation
• Telophase I
– Two daughter cells are formed.
Meiosis II: Second Division
• Prophase II
• As the cells enter prophase II, Chromosomes visible.
Metaphase II
• During metaphase II, chromosomes line
up in the center of each cell.
Anaphase II
• As the cell enters anaphase, the paired
chromatids separate.
Telophase II, and Cytokinesis
• These four daughter cells now contain the
haploid number (N)
The Results….
• Meiosis I : 2 haploid (n) daughter cells,
with ½ the number of chromosomes as
the original cell.
• Meiosis II : 4 haploid (n) daughter cells,
basically the 2 cells from above just a
mitotic cell division!!!
Meiosis – Animation ON WEBSITE
• Animation : Meiosis
Fig. 13-7-3
Interphase
Homologous pair of chromosomes
in diploid parent cell
Chromosomes
replicate
Homologous pair of replicated chromosomes
Sister
chromatids
Diploid cell with
replicated
chromosomes
Meiosis I
1 Homologous
chromosomes
separate
Haploid cells with
replicated chromosomes
Meiosis II
2 Sister chromatids
separate
Haploid cells with unreplicated chromosomes
Vocabulary
Crossing Over: When homologous
chromosomes exchange some genetic
information during meiosis
HAPPENS DURING PROPHASE I
Crossing Over
Disjunction
Disjunction 
When fibers pull
homologous
chromosomes
toward poles.
During Anaphase
Nondisjunction
When spindle fibers
FAIL
to pull
homologous
chromosomes
toward poles.
This can result in chromosome
abnormalities
Example: Trisomy 21 – Downs
Syndrome
Meiosis I: Reduction Division
• DIPLOID cell in an ovary or testes is divided into
two HAPLOID cells.
46
23
23
Meiosis II:
• Those 2 HAPLOID cells each divide again
resulting in FOUR gametes that are all
genetically different.
23
23
23
23
23
23
Comparing Mitosis & Meiosis
Mitosis
Meiosis
Asexual reproduction growth and repair
Sexual reproduction making sperm and eggs
Daughter cells are identical
to the parent
Daughter cells have ½ the
# of chromosomes of
parent cell
One Replication, One
Division
One Replication, TWO
Divisions
Two daughter cells are
produced
Four gametes are produced
Gametogenesis
• Formation of the gametes (sperm
and egg)
• Gametes are made in the gonads
(testes and ovaries)
• Involves meiosis – cells produced
are haploid (n)
Gametogenesis
Spermatogenesis
Oogenesis
Some Sexual Reproduction Vocabulary
• Gametes: Specialized sex cells
(sperm & eggs)
• Fertilization: Fusion of the nuclei
of sperm and egg
• Zygote: Fertilized egg cell
Cancer
• Uncontrolled cell division
• Cancer cells are frequently "immortal":
• Normal cells divide about 50 times and then die,
cancer cells can go on dividing indefinitely if
supplied with nutrients
Uncontrolled Cell Growth
–Cancer cells form masses of cells called tumors
that can damage the surrounding tissues.
–Cancer cells may break loose from tumors and
spread throughout the body called Metastasis
Copyright Pearson Prentice Hall
Cell Cycle Regulation and When It goes Wild . . . .
Cell Cycle Regulation and When It goes Wild . . . .
Copyright Pearson Prentice Hall
•Controls on Cell Division
Contact Inhibition
• normal cells will reproduce until they come into contact with
other cells.
• They respond by not growing.
•This demonstrates that controls on cell division can be turned on
and off.
Copyright Pearson Prentice Hall
Controls on Cell Division
•Contact Inhibition
Copyright Pearson Prentice Hall
Controls on
Cell Division
•Cell Cycle Regulators
–The cell cycle is regulated by a specific protein
–The amount of this protein in the cell rises and falls
in time with the cell cycle.
–Scientists called this protein cyclin because it
seemed to regulate the cell cycle.
Copyright Pearson Prentice Hall
Cyclins were discovered during a similar experiment to this one.
A sample of cytoplasm
is removed from a cell
in mitosis.
The sample is injected
into a second cell in
G2 of interphase.
Copyright Pearson Prentice Hall
As result, the second
cell enters mitosis.
ASEXUAL REPRODUCTION
TYPES OF ASEXUAL REPRODUCTION
Binary Fission
• the EQUAL division of
nucleus and
cytoplasm.
• Occurs in Bacteria,
some Protists (ameba,
paramecium, algae)
Example of Binary Fission
Binary Fission of Bacteria
Budding
• UNEQUAL division of
cytoplasm.
• EQUAL division of nucleus
• Occurs in hydra and yeast
Budding
• The buds develop as small outgrowths on the
outer surface of the parent organism
• The buds may break off OR they may remain
attached to the parent to form a colony
Budding in Yeast Cells
Sporulation
• Production and release
of spores to reproduce
• Occurs most commonly
in bread mold
Spore formation
• Spores are single, specialized cells
produced by mitosis
• Spores are released from the parent
organism
• Spores are often surrounded by a hard
outer wall that protects them from the
environment
Examples of Mold
Regeneration
• Re-growth of lost or
damaged body parts
-Lobster claw, Starfish
• Regeneration decreases as an animal becomes
more complex
Starfish Regeneration
• Each part of a starfish can regenerate into a
complete organism if each part contains a
piece of the central disk.
Planaria Regeneration
• Planaria are flatworms that can regenerate
lost body parts because they have
undifferentiated tissue
• A planarian can be cut into several pieces,
and each will grow into a complete worm
• If the head is sliced down the center, the
result is a two headed planaria!
Vegetative Propagation
Producing new identical
plants from a leaf cutting,
or a runner – the new
plant has same genetic
makeup as donor plant.
Natural Means of Vegetative
Propagation
• No human intervention
3. Runners
• Stems that grow along the ground
• New roots form where the stem meets the
ground and develop into a new plant
Artificial Vegetative Propagation
Human Intervention
1. Cuttings
• Any part of the plant (stem, leaf, root) is used
to produce a new individual
2. Grafting
• A stem is removed from one plant and joined
permanently to another plant
• Stock: provides the root system
• Scion: added piece
Advantages
• Plants that grow from seeds do not always
show the same characteristics
• Faster
• Higher yields of fruits
MALE REPRODUCTIVE SYSTEM
Functions of the Male Reproductive System
1. Produce Sperm (gamete)
2. Deposits sperm in female for fertilization.
3. Produces the hormone called testosterone.
• Testosterone produces the secondary sex
characteristics.
The Male Reproductive System
Figure 28.1
Structures & Function
1. Testes- produce the sperm and testosterone
2. Epididymus- sperm fully mature and are stored
here.
3. Vas deferens- carries sperm from epididymis to
urethra.
4. Urethra- tube leading outside body through penis.
5. Scrotum- External sac that holds testes. Lower
temperature allows sperm to mature.
6. Penis – Organ that deposits sperm into the female
Hormones
• FSH : Stimulates Spermatogenesis
• LH: Stimulates production of testosterone by
the testis ( Leydig Cells )
• Testosterone: Secondary Sex Characteristics
and maintaining the accessory sex organs
COMPONENT OF SEMEN
• 1. Seminal fluid - Seminal vesicles and prostate
gland secrete a fluid for sperm to travel through a
nourishes the sperm.
• 2. Sperm-
FLUID + SPERM = SEMEN
FYI: About 200 to 600 million sperm, are released
in an average ejaculation. This increases the
chances of fertilization.
Sperm travel from testes, through vas deferens
down the urethra and out of the penis.
SPERM
• 1. Produced in the testes
by meiosis.
• 2. Haploid(n)
• 3. A sperm cell consists
of a head (DNA); a
midpiece, and a
flagellum.
Acrosome
• An organelle that develops over the anterior half
of the head the sperm
• It is a cap-like structure derived from the Golgi
apparatus.
• Contains digestive enzymes that break down the
outer membrane of the ovum
The Female Reproductive System.
The Female Reproductive System.
FUNCTIONS OF THE FEMALE
REPRODUCTIVE SYSTEM
• Produces eggs (gamete)
Ovulation- one egg is released per month
• Prepares the female’s body to nourish a
developing embryo
• Female secondary sex characteristics are
regulated by estrogen & progesterone.
Main Structures and Functions
Female Reproductive System
• 1. Ovaries- Paired structures
that produce eggs & hormones.
• 2. Fallopian tubes ( Oviduct) Carries egg to uterus. Where
egg is fertilized.
• 3. Uterus- Fetal Development
takes place here.
• 4. Endometrium: Lining of
uterus
• 5. Cervix- Lower part of Uterus
• 6. Vagina- Where sperm is
deposited & the birth canal.
Female Reproductive System
Ectopic Pregnancy
• A pregnancy NOT in the uterus
Fibroids
• Benign tumors in the uterine wall
Egg Development
• Eggs are produced within
the ovaries of females. In
a follicle
• Females are born with
over 400,000 eggs.
• Only about 450 of these
eggs will mature and be
released.
Ovulation: The egg that is maturing in a follicle is released from the
ovary
Menstrual Cycle
• The secretion of hormones in females is cyclic
• Prior to ovulation, the endometrium thickens with
blood vessels in preparation for embryo
implantation
• If an embryo does not implant, the endometrium is
shed in a process called menstruation
Stages of the Menstrual Cycle
• Follicle Stage Days 5-13 - egg matures inside follicle,
estrogen is released to start thickening uterine
lining.
• Ovulation Stage Day 14- Release of egg from follicle
• Luteal Stage Days 14-28- Corpus luteum forms from
leftover follicle after ovulation; progesterone gets
released to further build-up uterine lining
• Menstruation Days 1-5- shedding of uterine lining –
occurs only when fertilization has NOT occurred!
Fig. 46-12f
Ovary
Primary
oocyte
within
follicle
Growing
follicle
Ruptured
follicle
Ovulated
secondary oocyte
Corpus luteum
Mature follicle
Degenerating
corpus luteum
Menstrual Cycle
Sexually Transmitted Diseases
•
•
•
•
•
Chlamydia
Gonorrhea
Syphilis
HPV
HIV
The Coming Together….
Fertilization
Fertilization
• Formation of zygote.
• Occurs in upper
portion of oviduct
Development of the Zygote
Zygote divides by MITOSIS  known as CLEAVAGE!
Morula: Solid ball of cell
Blastula :hollow ball of single layered
cells that develops
Morula
Blastula
Fig. 46-15
3
Cleavage
Cleavage
continues
4
Ovary
2
Fertilization
The blastocyst
implants
5
Uterus
1
Ovulation
(a) From ovulation to implantation
Endometrium
Endometrium
Inner cell mass
Cavity
Blastocyst
(b) Implantation of blastocyst
Trophoblast
Formation of the Gastrula
The infolding of the Blastula is called Gastrulation
Gastrula : 3 layers of cells are formed: Ectoderm,
Endoderm, & Mesoderm.
•Video of Sea Urchin Gastrulation
Differentiation
When unspecialized (stem cells) cells become
specialized!
The 3 layers of the Gastrula develop into
various tissues and organs.
– Ectoderm: Nervous system and Skin
– Mesoderm : organ systems such as
muscular, circulatory, reproductive,
excretory and Bone
– Endoderm : lining of the digestive tract
and respiratory tract. Liver and pancreas
If body cells have the same DNA –Why do
they look different and have different
functions?
BECAUSE ONLY PART
OF THE DNA IN EACH
CELL IS EXPRESSED or
USED.
Adaptations for Sexual Development
•
Two Types of Fertilization:
- External Fertilization
- Internal Fertilization
Internal vs. External Fertilization
• External Fertilization
• Internal Fertilization:
– Sperm and egg fuse
– Sperm and egg fuse
outside body
inside
reproductive
– Large numbers of
tract
of
the
female
sperm and egg to
ensure fertilization
– Occurs in most
– Used by aquatic
terrestrial
(land)
organisms (fish & frogs)
:
organisms
External Fertilization
Internal Fertilization
Adaptations for Development
Development- All embryos depend on certain needs that
must be met for survival.
-Nourishment
-Oxygen
-Temperature
-Remove Waste
-Protection
• Two Places Development Occurs:
- External Development
- Internal Development
External Development
External vs. Internal Development
• External Development:
– Water : – little or no care by parent – many
eggs are eaten or destroyed
– Land : (birds and reptiles) – fertilized egg
contains a large yolk (for nourishment)
enclosed by a protective shell
Marsupials
• No Placenta
• Fetus born early and then moves into pouch
for further development
Internal Development
Internal Development
• Embryos develop within uterus
• Offspring are well protected & a
high percentage survive
• Placental Mammals (humans)
Fig. 46-15
3
Cleavage
Cleavage
continues
4
Ovary
2
Fertilization
The blastocyst
implants
5
Uterus
1
Ovulation
(a) From ovulation to implantation
Endometrium
Endometrium
Inner cell mass
Cavity
Blastocyst
(b) Implantation of blastocyst
Trophoblast
Internal Development
Placenta
• Site of diffusion; materials are
exchanged here between mother
and child. Ex. glucose, water, CO2, O2
*****Through the BLOOD
Drugs, alcohol and certain Viral Diseases can
cross the placenta
Fig. 46-16
Maternal
arteries
Maternal
veins
Placenta
Maternal
portion
of placenta
Umbilical cord
Chorionic villus,
containing fetal
capillaries
Maternal blood
pools
Uterus
Fetal arteriole
Fetal venule
Umbilical cord
Fetal
portion of
placenta
(chorion)
Umbilical
arteries
Umbilical
vein
Placenta
• During its first 2 to 4 weeks, the embryo obtains
nutrients directly from the endometrium
• A layer of the blastocyst, called the trophoblast,
mingles with the endometrium and eventually
forms the placenta
• Blood from the embryo travels to the placenta
through arteries of the umbilical cord and returns
via the umbilical vein
*******Picture next slide
Things that cross the Placenta
•
•
•
•
Drugs – Birth Defects, addicted babies, stillborns
Alcohol- Fetal Alcohol Syndrome, stillborns
Cigarette smoke – Slow growth, stillborns
Viruses - Blindness, Mental Retardation,
stillborns
• Food: Good nutrition is very important while
pregnant
Drugs can cross the placenta and cause birth defects
and harm the fetus
Thalidomide Baby
Alcohol can cross the placenta and cause birth defects
and harm the fetus
Fetal Alcohol Syndrome
Viruses can cross the placenta and cause birth defects
and harm the fetus
Examples:
Chicken Pox
German Measles
Zika
Internal Development
Amniotic Sac
• Nourishing and protecting sac containing liquid
(Amniotic Fluid)
• Grows and begins to fill, mainly with water, around
two weeks after fertilization.
• After 10 weeks it contains proteins, carbohydrates,
lipids which aid in the growth of the fetus.
• In the late stages of gestation much of the amniotic
fluid consists of fetal urine.
Fig. 46-17
(a) 5 weeks
(b) 14 weeks
(c) 20 weeks
First Trimester
• The first trimester ( 1- 12 weeks ) is the main
period of organogenesis : major period of time for
development of the body organs
• All the major structures are present by 8 weeks,
and the embryo is now called a fetus
• Changes occur in the mother
– Growth of the placenta
– Cessation of ovulation and the menstrual cycle
– Breast enlargement
Second Trimester
• During the second trimester (12-27)
– The fetus grows and is very active
– The mother may feel fetal movements
Fig. 46-17c
(c) 20 weeks
Third Trimester
• During the third trimester (28-40), the fetus grows
and fills the space of uterus
• A complex interplay of local regulators and
hormones induces and regulates labor, the process
by which childbirth occurs Oxytocin
Fig. 46-18
from
ovaries
Oxytocin
+
from fetus
and mother’s
posterior pituitary
Positive feedback
Estradiol
Induces oxytocin
receptors on uterus
Stimulates uterus
to contract
Stimulates placenta
to make
Prostaglandins
Stimulate more
contractions
of uterus
+
Fig. 46-19-1
Placenta
Umbilical cord
Uterus
Cervix
1
Dilation of the cervix
Fig. 46-19-2
2
Expulsion: delivery of the infant
Fig. 46-19-3
Uterus
Placenta
(detaching)
Umbilical
cord
3
Delivery of the placenta
Detecting Disorders During
Pregnancy
• Amniocentesis and chorionic villus sampling are
invasive techniques in which amniotic fluid or fetal
cells are obtained for genetic analysis
• Noninvasive procedures usually use ultrasound
imaging to detect fetal condition
• Genetic testing of the fetus poses ethical questions
and can present parents with difficult decisions
Reproductive Technologies
Artificial Insemination
– Used to treat
infertility
– Sperm are injected
into female with
probe
(NO INTERCOURSE)
In Vitro Fertilization
• Sperm and egg are
joined in lab and
then zygote is
implanted in
woman’s uterus.
Surrogate Pregnancy
• In vitro fertilization is performed
• Embryo is implanted in woman who has
no genetic attachment
• Woman will house embryo and deliver
baby to term
Sex Selection
• DNA of sperm and egg
are screened for X and Y
chromosomes for desired
combination.
Sperm carry X or Y
Eggs carry only X
• Sorting Technique or
genetically test for X or Y
• It’s a Girl  XX
• It’s a Boy  XY
•
How do twins form???
Monozygotic Twins
(Identical Twins)
• One egg is fertilized by one sperm
• Embryo splits into two during the early stages of
development
• Have identical genes and must be of the same sex
• (Incidence: about 3 in every 1000 births)
Dizygotic Twins
(Fraternal Twins)
• Two eggs are ovulated and each is fertilized by a sperm cell
• No more genetically similar than any other sibling in the
family (can be same/different sexes)
• Maternal age, use of assisted reproductive technologies are
factors
• Incidence (6.7/1000 births in Japan to 40/1000 births in
Nigeria)