Transcript Unit 3 (ch 8)

The Cellular Basis of Reproduction and
Inheritance
Life cycle – the sequence of events that occur
between an adult of one generation to an adult
of the next.
Sexual Reproduction – involves the union of a
sperm and an egg, each containing one half of
the genetic information.
Usually involves genetic information from two
parents, but always two gametes a sperm and
an egg.
This type of reproduction requires more energy,
but produces valuable differences, or variation,
in the offspring.
The Cellular Basis of Reproduction and
Inheritance
Asexual Reproduction – Is reproduction
involving only one parent and no egg or
sperm. This process is quick and easy, but
produces little or no variation in offspring.
Prokaryotes reproduce by Binary Fission
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Binary fission“dividing in half”
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Prokaryotic organisms
have only one circular
strand of DNA that is
their singular
chromosome.
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This process produces
two genetically identical
daughter cells.
Eukaryotic Chromosomes are more Complex
Chromosome – Chroma (colored)
soma (body)
Chromatin – active threadlike
strands of DNA
Chromosomes are duplicated long
before the cell divides. This
forms Sister Chromatids, which
are identical chromosomes that
are attached at the centromere.
They will be separated and pulled
into different cells in cell
division.
The Cell Cycle
The Cell Cycle
Cell Cycle – The cell’s lifecycle.
Interphase – The part of the cycle in
between cell divisions.
G1 – Cell increases in size, produces
organelles, and produces proteins.
S – Cell copies or synthesizes DNA
G2 – Cell produces proteins for division.
Mitotic or M phase – Is the division of the
nucleus.
Cytokinesis – The division of the cell,
cytoplasm and organelles.
Functions of Mitosis
Growth – mitosis adds new cells to
growing tissues.
Replacement – Mitosis replaces worn
out or damaged cells.
Asexual Reproduction
Mitosis is used to produce copies of
individuals in asexual reproduction.
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http://www.youtube.com/watch?v=IlV9hExXZ
nM
http://www.youtube.com/watch?v=CrTpRILtV
Yc&feature=related
Mitosis
Prophase – The 1st stage of
mitosis
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Prepares the nucleus for
division,
the nuclear envelope dissolves,
the chromosomes condense
becoming visible,
The mitotic spindle forms and
attaches to each chromosome
at the kinetochore.
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Metaphase – the mitotic spindle
pulls the chromosomes from each
side so that they line up in the
Middle on an imaginary line called
the Metaphase plate.
Anaphase
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Anaphase – The mitotic spindle keeps
pulling until the sister chromatids are
pulled Apart at the centromeres. This
doubles the number of chromosomes in a
cell.
Telophase
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Telophase – Two new nuclei form
The opposite of prophase
Chromosomes unwind, nuclear envelope
reforms
Cytokinesis in Animal Cells
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Cytokinesis is the
division of the cell’s
organelles, cytoplasm
and membrane.
In animal cells this
starts when a band of
microfilaments is
formed around the cell
and begins to contract
producing a cleavage
furrow.
The band contracts
until the cell is pinched
into two new cells.
Cytokinesis in Plant Cells
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Plant Cells have a
cell wall so they
cannot be
pinched in half.
Instead they form
a cell plate made
of cellulose that
divides the two
daughter cells.
Controlling Cell Division
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Anchorage Dependence
normal cells will not divide
unless they are attached to
a surface.
Density-Dependent
Inhibition Cells stop
dividing when they are
surrounded by other cells.
Growth Factor Proteins
that stimulate cell growth
Cell Cycle Control System
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The Red Barriers represent
three checkpoints in the cell
cycle.
G1 checkpoint – The go
ahead signal that starts
the S phase.
G2 Checkpoint intiates
the M phase or mitosis.
M Checkpoint –
indicates that all of the
chromosomes are
correctly attached to the
mitotic spindle.
Mitosis video
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http://www.youtube.
com/watch?v=VlN7
K1-9QB0
Cancer Cells are Growing out of Control
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A Tumor is an abnormal mass of cells, it can be either
benign or malignant.
Benign – Always remain in the original site, they do not
spread.
Malignant – Cells are able to break off and start new
tumors where they land, this is called Metastasis, and is
what is meant by cancer.
Cancer Cells are Growing out of Control
Carcinomas – Cancers of the skin or body covering.
Sarcomas – Cancers of the supporting tissues, bones and
muscle.
Lymphomas and Leukemias – Cancers of the blood forming
tissues, spleen, bone marrow or lymph nodes.
Chemotherapy
Taxol – prevents the spindle
from forming, stopping cell
division
Vinblastin - isolated from
periwinkle
Mitosis Activity (LAB SHEET)
Homologous Pairs
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A somatic cell, or typical body cell,
in a human has 46 chromosomes.
These are 23 pairs of homologous
chromosomes.
Homologous chromosomes carry
the same genes on the same locus,
or place on the chromosome.
One chromosome from each of
these pairs is inherited from each
parent.
22 pairs of our chromosomes are
autosomes, the other pair is the
sex chromosomes.
Gametes have half the chromosomes
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Cells that contain 23 pairs of
homologous chromosomes are referred
to as diploid cells.
All human cells are diploid except
gametes or sex cells.
Gametes only contain one chromosome
from each pair so they are referred to as
haploid cells.
Two haploid cells fuse during fertilization
producing a diploid zygote.
This new individual will produce gametes
by undergoing meiosis to reduce the
number of chromosomes by half.
Meiosis overview
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http://www.youtube.
com/watch?v=aaNn
Gs7MmUY
Meiosis: Diploid to Haploid
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In meiosis a cell will divide twice.
The first division is meiosis I the
second is meiosis II.
Prophase I is similar to that of
mitosis with the exception of
homologous pairs matching up.
Metaphase I
The homologous pairs are next to
each other on the metaphase plate.
Anaphase I
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Anaphase I the
homologous pairs are
pulled apart, leaving
sister chromatids still
attached at the
centromeres.
Telophase I and cytokinesis are
similar to mitosis.
Meiosis II
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Meiosis II is just like mitosis with only half the chromosomes.
In Metaphase II the chromosomes line up in single file.
Anaphase II the centromeres are broken pulling sister
chromatids apart.
Meiosis produces 4 cells from one parent cell. The first division
produces genetically different daughter cells, while meiosis II
produces 2 identical daughter cells.
Mitosis vs Meiosis
Meiosis review
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http://www.youtube.
com/watch?v=aaNn
Gs7MmUY
Meiosis and Sexual reproduction produce
variation.
Homologous Chromosomes carry
different versions of the same genes.
Crossing Over can Increase Variation.
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Crossing over occurs
when the homologous
pairs match up and
exchange parts.
This recombination
produces new
combinations of
versions of genes.
Genetic Recombination
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This shows how genes on
the same chromosome can
switch with genes from
other chromsomes.
This is called
recombination.
Crossing over or
recombination occurs in
meiosis I.
Crossing over produces
new combinations of
genes on offspring
chromosomes.
Karyotyping
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Doctors can take a
picture if the nucleus or a
karyotype.
The chromosomes are
then arranged into
homologous pairs and
counted.
Extra or missing
chromosomes account
for many genetic
disorders.
Down’s Syndrome: Trisomy 21
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Down’s syndrome is caused by an
individual possessing three copies of
the 21st chromosome, Trisomy 21.
It result’s in mental retardation that
can range from mild to severe, short
stature, round face, almond shaped
eyes and palm crease.
Down’s syndrome is usually caused
by a mistake in egg development,
especially in older mothers.
Down’s syndrome occurs in 1 out of
700 children born.
Nondisjunction changes chromosome
numbers
Klinefelter’s XXY
Normal males are XY while an
individual with Klinefelter’s
syndrome possesses the XX of a
female and a Y.
 This syndrome results in mental
retardation, sterility, breast
development, and lack of facial
hair.
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Turner’s Syndrome XO
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Turner’s Syndrome
occurs when an
individual receives
only one X
chromosome.
Usually normal
intelligence, web of
skin on the neck,
sterile, constricted
aorta, short stature,
and poor breast
development.
XYY and XXX
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XYY is not a clearly defined syndrome,
though individuals are usually taller than
average, lower intelligence, weak
musculature and have social problems.
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XXX or metafemales have some fertility
problems, but are otherwise normal.
Chromosomal Alterations
Deletion a fragment is lost and the chromosome
reattaches without it.
Cri du Chat occurs with a deletion on CH 5
individuals have small heads, severe MR and
usually do not survive infancy.
Duplication if the lost fragment is reattached in the
homologous chromosome that chromosome
has two copies of the genes on the fragment.
Chromosomal Alterations
Inversion a fragment is
reinserted backwards.
Translocation occurs when the
fragment is reattached in a
different chromosome
The Philadelphia chromosome
occurs when a growth factor
gene on CH 9 is moved to CH
22, this leads CML the most
common form of leukemia.