Download File

BIO 1B
UNIT GOALS
 Identify that cells dividing for growth and repair go through mitosis.
 Identify that cells dividing to produce sex cells go through meiosis.
 Draw a diagram of mitosis and mitosis that shows the differences in







chromosome number in the daughter cells.
Compare the advantages and disadvantages of sexual and asexual
reproduction.
Describe how genetic recombination through meiosis and crossing over
increases variation.
Describe how stem cells differentiate to become the many different
cells in your body.
Identify a normal karyotype of a human cell as having 23 pairs of
chromosomes
Identify karyotypes that are not normal and locate the chromosomal
abnormality
Write how a particular type of cancer happens
Write why cancer makes people sick
CELL SIZE/ GROWTH
 Each organism starts as one cell. Organisms grow
when cells divide and make more cells. Cells use
diffusion to get materials in an out of the cell. It is
more efficient to distribute materials throughout a
smaller cell than a larger cell because smaller cells have
a larger surface area to volume ratio.
GROWTH CON’T
 When examining why multi-cellular organisms made
of many small cells instead of one large cell it is useful
to use potato cubes as a model. The following
diagrams represent potato cubes of different sizes (3
cm, 2 cm, 1 cm) that were soaked in iodine overnight.
The next day we removed the cubes from the iodine
and sliced them in half to show how far the iodine
entered the cube.
Length of
side
Surface Area Volume of
of cube
Cube
to Volume
Ratio
3cm
9*6 = 54 cm2 27 cm3
54 : 27 or 2:1
2cm
4*6 = 24 cm2 8 cm3
24:8 or 3:1
1cm
1*6 = 6 cm2
6:1
1 cm3
BIG IDEA
 The smallest cube (1cm X 1cm X 1cm) has the largest
surface area to volume ratio.
Sexual vs. Asexual reproduction
 In Asexual Reproduction a single parent produces
one or more identical offspring by dividing into two
cells. Many single celled organisms like bacteria
reproduce asexually making duplicate copies of
themselves. Most plants are also able to reproduce
asexually.
 Sexual Reproduction involves two parents giving rise
to offspring that have unique combination of genes
inherited from the two parents. This usually involves
the combination of two different forms of gametes like
eggs and sperm. In both sexual and asexual
reproduction genetic material is passed on to the
offspring.
 Asexual Reproduction Advantages
 Produce more offspring
 Only one parent is required
 All of that parent's genes are passed on to its offspring
 Do not have to waste energy or exposure to predators
by seeking mates.
 Sexual Reproduction Advantages
 Increases the rate of beneficial (helpful) mutations in a
population.
 Increases genetic variety and gene combination
increasing a population’s chance for survival.
 The increase in genetic variety increases a population’s
ability to fight off disease.
Cell Theory includes the following
tenants:
 Cell Theory
 All organisms are composed of one or more cells.
 The cell is the basic unit of structure and organization
of organisms.
 All cells come from pre-existing cells.
 Cells contain hereditary information that is passed
from cell to cell during cell division
 All cells are basically the same in chemical
composition and metabolic activities

Bell work 12.7.11
WHY IS IMPORTANT THAT CELLS STAY SMALL?
2. WHICH SURFACE AREA TO VOLUME RATIO IS
MORE BENEFICIAL TO CELLS 3:1 OR 6:5 AND
WHY?
3. WHAT ARE THE DIFFERENCES BETWEEN
ASEXUAL AND SEXUAL REPRODUCTION?
4. LIST ONE TYPE OF ORGANISM THAT
REPRODUCES ASEXUALLY.
1.
Mitosis and Meiosis
http://www.cellsalive.com/meiosis.htm
 Mitosis
 Produces the somatic, or body cells necessary for
growth
 Results in diploid cells with the same number of
chromosomes as the parent cell
 Produces 2 daughter cells with genetic material that is
identical to parent cell
 Unicellular organisms use mitosis to reproduce. They
remain unicellular, but with two organisms instead of
1.
Meiosis
 Produces the gametes or sex cells like eggs, sperm,
and spores.
 Results in haploid cells with half the number of
chromosomes as the parent cells
 Passes on half of the genetic material of the parent cell
CHROMOSOMES
 Chromosomes are contained
in the nucleus. They contain
the genetic code in the form
of genes. Genes are a unit of
heredity made of DNA. In
discussions of cell division
the genetic material is
referred to as chromosomes
when it is visible and ready to
duplicate. Otherwise it is
called chromatin.
 Chromosomes are counted based on the number of
centromeres, not the number of chromatids.
 Homologous Chromosomes are pairs of similar
chromosomes. They have the same length and
centromere location. Humans receive one
chromosome from each parent. Each chromosome
contains genes that code for the same set of traits.
However the version of the trait that you get from each
parent may be different on each chromosome so
homologous chromosomes are similar but not
identical.
Bell work 12.8.11 – Thursday
WHERE CAN CHROMOSOMES BE FOUND?
WHAT DO THEY CONTAIN?
2. WHAT IS THE CORRECT NUMBER OF
CHROMOSOMES A BODY CELL (SOMATIC)
SHOULD HAVE?
3. HOW MANY CHROMOSOMES SHOULD A
GAMETE HAVE (SPERM/ EGG)?
1.
 Diploid cells are referred to as 2n. The chromosomes
appear as homologous pairs. This is the normal
amount of chromosomes in cells. Haploid cells are
referred to as n. There is only one of each
chromosome from either the mother or the father.
This is half of the normal amount of chromosomes in
cells.
MEIOSIS
Human body cells:
 Have 46 chromosomes or 23 pairs
 This is described as n= 23 and 2n= 46
 Our somatic cells have 46 chromosomes (ex: Human
Skin Cell)
 Our gamete cells have 23 chromosomes (ex: Human
Sperm Cell)
 In Mitosis the chromosome number is conserved
throughout the process. The genetic material doubles
during the process when each chromatid replicates to
make an identical sister chromatid. Then the sister
chromatids split into two separate cells. Throughout
the process the chromosome number stays the same
since it is based on the number of centromeres not on
the number of chromatids.
 . The diagram below is based
on a fruit fly which has 8
chromosomes or 4 pairs of
chromosomes in a somatic
cell. Please note that during
Mitosis the homologous pairs
do not line up as diagrammed
below. This diagram simply
shows how the chromosome
number is determined.
CELL DIFFERENTIATION
 The cells differentiate into specific cells with
specialized functions. Following fertilization, cell
division produces a small cluster of cells. Early
embryo cells can become any cell type and are
referred to as totipotent.
 http://player.discoveryeducation.com/index.cfm?guid
AssetId=7090CF16-CDA8-4004-A13ED07E2CD59AA9&blnFromSearch=1&productcode=US
#
CELL DIFFERENTIATION
 This totipotency lasts for about 14 days
or until there are about 16 cells in the
embryo. After this, gastrulation occurs
where the embryonic cells start to
divide into germ cell layers. At this
point cells differentiate by appearance
and function.
CELL DIFFERENTIATION
 How a cell is specialized, or
differentiated, depends on its
position in the embryo.
Neighboring cells will send
chemical cues. These
chemicals signal genetic
switching on or off of genes
within the cell.
Karyotypes
 Karyotypes
 Karyotypes help geneticists to diagnose chromosomal
abnormalities. A karyotype is a picture of the paired up
chromosomes. To prepare a karyotype, scientists add colchicine,
a drug that interferes with the spindle fibers, which stops all cell
division at metaphase. Water is then added which causes the
cells to burst. The burst cells are stained and examined under a
microscope. A digital picture is taken of the chromosomes stuck
in Metaphase. Scientists use a computer to cut out the
individual chromosomes and pair them up. Chromosomes of
the same size and similar looking bands are paired according to
their centromere position. From the karyotype, certain
abnormalities, such as an extra chromosome or piece of
chromosome, can be detected.
Normal Male
copyright cmassengale
2n = 46
30
Normal Female
copyright cmassengale
2n = 46
31
Male, Trisomy 21 (Down’s)
copyright cmassengale
2n = 47
32
Female Down’s Syndrome
copyright cmassengale
2n = 47
33
Female Down’s Syndrome
copyright cmassengale
2n = 47
34
Klinefelter’s Syndrome
copyright cmassengale
2n = 47
35
Turner’s Syndrome
2n = 45
copyright cmassengale
36
Karyotype Questions
1.
2.
3.
4.
5.
What is a karyotype?
What is the difference between a females a karyotype
and a males karyotype?
What is Down’s Syndrome?
What is Kleinfelter’s Syndrome?
What is Trisomy 13 Syndrome?
Bell work 12.12.11 MONDAY
WHAT IS A KARYOTYPE?
2. WHAT ARE THE BENEFITS OF A KARYOTYPE?
3. EXPLAIN HOW YOU CAN DIFFERENTIATE A
MALE AND FEMALE BY LOOKING AT A
KARYOTYPE?
1.
CANCER
http://www.youtube.com/watch?v=WXTsxPPcTEs
 Enzymes, which are a type of protein,
control the cell division. Genes direct the
production of proteins including enzymes.
DNA Mutations can occur in genes that
produce those enzymes and control cell
division. If this happens cells can grow,
divide, and reproduced rapidly. This
uncontrolled cell division is called cancer.
HOW DO WE DIE FROM IT??
 These excess cells cause tumors that starve
the surrounding cells making a person sick.
In later stages of cancer, cancerous cells may
break away, enter the bloodstream and affect
other parts of the body (metastasis)
Causes of Cancer
 Environmental mutagens increase mutations and
therefore increase the chance of cancer.
 Viruses change cells’ DNA by integrating their genetic
material with the host cell's DNA.
 Mutations that cause uncontrolled cell division can be
inherited and passed down through the sex cells.
 Most cancers are thought to be multi-factorial and
caused by both environmental and genetic factors.
12.13.11 TUESDAY BELL WORK
WHAT IS CANCER? HOW DOES IT EFFECT
SURROUNDING CELLS?
2. WHAT DOES THE TERM METASTASIS MEAN?
3. WHAT ARE TWO WAYS SOMEONE CAN GET
CANCER?
1.
Genetic Mutations
http://www.youtube.com/watch?v=FgMKGIED4Yo
 Mutations are changes in the DNA sequence
REAL LIFE: HOUSE MUTATED TO HOOUSE,
HOUSE TO HORSE, HOUSE TO HOUE
 Mutations occur in both sex cells and body cells.
 Passing on Mutations
 An altered gene (mutation) may be passed on to every
cell that develops from it.
 EXAMPLE: OUR SKIN CELLS DIE BUT THAT TATOO
STAYS INTACT.
GENETIC MUTATIONS
 If a mutation is a sex cell, like a sperm or an egg, and if
that sex cell goes through fertilization then the
mutation will be passed on to the offspring.
 IF YOU GET A TATOO ON YOUR ARM WILL YOUR
BABY BE BORN WITH A TATOO ON IT’S ARM?
 Mutations in body cells are not passed on to offspring.
However the mutation may cause problems for the
individual.
 CELLS OF THE LUNG THAT GET CANCER FROM
CIGARETTE SMOKE- CAN EFFECT OTHER CELLS.
Causes of Mutations
 Spontaneous mutations happen as a mistake in base
pairing. (THINK OF TYPING/ TEXTING AND
MAKING MISTAKES)
 Mutagens – certain chemicals and environmental
hazards may change the structure of DNA, and
therefore may alter the proteins coded by that DNA .
 Radiation (X-rays, cosmic rays, UV light, Nuclear)
breaks apart DNA can result in deletions.
 Chemical Mutagens (asbestos, formaldehyde) usually
cause substitution mutations.