Unit 12 Mitosis and Meiosis
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Science Interactive LTD
Science Interactive LTD. PO BOX 50764 LONDON NW6 9AT email: [email protected] web: www:science-interactive.co.uk
Science Interactive LTD Copyright 2005
Science base multimedia CD-ROM forPC is a collection of38 units or tools totalling over1150
PowerPoint slides. Each unit covers a wide range of different delivery and learning styles, offering an
exciting way to involve your pupils during lessons or revision sessions. All styles of teaching and
learning are supported through use ofhigh quality images, graphics, challenging exercises andquestions. Units can be used in the classroom via an interactive whiteboard, data projector or used
during individual study via a PC orschool network.
Unit 19: The Transitional Metals
Unit 18: Metals and their Properties
Unit 17: The Alkali Metals
Unit 16: The Periodic Table and its Elements
Unit 15: Genetic Engineering
Unit 14: Evolution and Human Impact
Unit 13: Inheritance and Selection
Unit 12: Mitosis and Meiosis
Unit 11: Flow of Energy and Elements through the Environment
Unit 10: Water Transport in Plants
Unit 9: Photosynthesis in Green Plants
Unit 8: Drugs and Bad Body Maintenance
Unit 7: Hormones and the Endocrine System
Unit 6: Human Homeostasis
Unit 5: Nervous System and the Senses
Unit 4: The Respiratory System
Unit 3: Healthy Body and Immunity
Unit 2: The Circulatory System
Unit 1: The Digestive System
Unit 38: Cells, Tissue, Organs and Organs systems
Unit 37: Natural Forces
Unit 36: Sound and Hearing
Unit 35: The Alkaline Earth Metals
Unit 34: The Earth and Plate Tectonics
Unit 33: Earth and Space
Unit 32: Newton's Forces and the Effects of Forces
Unit 31: Radioactivity
Unit 30: Light and the Electromagnetic Spectrum
Unit 29: Electricity
Unit 28: Generating Electricity and its Domestic Use
Unit 27: Energy
Unit 26: Rates of Reaction
Unit 25: The Noble Gases, their Properties and Uses
Unit 24: The Halogens, their Uses and Compounds
Unit 23: Ionic and Covalent Compounds
Unit 22: Elements, Molecules and Compounds
Unit 21: Rock Cycle
Unit 20: Crude Oil and its Products
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z Unit 12
z Mitosis and Meiosis
Mitosis Meiosis
Parent cell
& replicates
2 daughter cells
4 daughter cells
DNA mixes
Parent cell
2 Daughter cells
DNA replicates
Chromosomesseparate
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Unit 12: Mitosis and MeiosisUnit 12: Mitosis and Meiosis Science Interactive LTD Copyright 2005
Understand: Keywords:
1. That lost or damaged cells need to replaced inthe human body by mitosis.
2. That mitosis is how organisms like humansgrow during pregnancy, through puberty toadult life.
3. That meiosis in humans leads to the productionof the sperm and egg cells.
4. That during meiosis, the number ofchromosomes in both the sperm and the eggcells are halved.
5. That during meiosis, random crossing ofpaternal and maternal DNA takes placeproducing genetically unique sperm and ovum.
6. That this random crossing during meiosis leadsto variation in both the genotype andphenotype of humans.
7. How the sex of an individual is determined bythe chromosomes we inherit from our parents.
Inheritance, Genes, Chromosomes, Alleles,
Mitosis, Meiosis, Sperm, Ovum, Cells,
Division, Clones, Reductive, Traits, Gametes,
Variation, Characteristics, Recessive,
Dominant, Genetic, Crosses, Diploid &
Haploid.
web: www.science-interactive.co.uk email: [email protected] Interactive LTD PO BOX 50764 LONDON NW6 9AT
Click mouse to begin
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Numbers of cellsNumbers of cells
Cells are the building blocks of all life. Unlike simple bacteria and other unicellular organisms,
living organisms contain from many millions to billions of cells. Cells can have a very wide
range of f___________ in the human body from skin cells, blood cells, muscle cells to nerve
cells. Cells can only be viewed using a light microscope. Robert Hook was the first scientist to
observe plant and animal cells using a simple light m___________ over 300 years ago.List the
cell types that you have observed under a light microscope ?
Numbers of cells in living organisms:
A small mammal, for
example a rat contains
many millions of cells
organised into ninedistinct organ system
similar to our own. List
these organ systems ?
Small mammal
A human contains many
billions of cells. Each
hour of every day of our
lives, we replace overone billion cells in our
body. During puberty we
produce even more cells.
A typical insect like a fly
or a bee contains many
hundreds of thousands of
cells. Insects have verybasic organ systems that
support life and allow
insects to reproduce.
A bacteria is a simple
single celled organism.
All the bacteria found
on the surface of thisplanet weigh more than
any other species. They
are very successful.
Notes
Diagram
Organism Bacteria Insect Human
Word bank: functions microscope
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Essential cell organellesEssential cell organellesCell organelles, like mitochondria and chloroplasts carry out important functions in plant and
animal cells. The n_________ controls the activity of the cell by building new proteins
including enzymes. It also contains DNA, the material of inheritance and is able to divide andproduce new daughter cells during cell division or mitosis. Mitochondria found in both plant
and animal cells respire glucose with o__________ releasing cellular e_________, carbon
dioxide and water. Chloroplasts found only in plant cells produce glucose and oxygen from
carbon dioxide and water !
Cell organelles in plants and animals:Word bank: nucleus oxygen energy
The cells nucleus
contains the necessary
genetic information or
genes to produce newcells, new enzymes and
new proteins. Humans
have over 31,000 genes.
Nucleus
The cell membrane
controls the passage of
substances in and out of
the cell. Movement ofmolecules happens by
passive diffusion or
active uptake.
Found only in plant cells,
chloroplast are able to
combine carbon dioxide
and water using theenergy from light to
produce glucose and
oxygen.
Mitochondria are found
in both plant and animal
cells. They respire
glucose with oxygen torelease energy for
cellular activities. They
release CO2 and water.
Function
Diagram
Organelle Mitochondria Chloroplast Cell membrane
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Specialised cells in animalsSpecialised cells in animalsCells are designed for the specific function they play in the human body as part of the billions
of cells that work to together to support life. A nerve cellfor example is long and t_____ and
conducts e__________ impulses. A red blood cell has a large surface area and no n________so it can transport the maximum amount of oxygen from the lungs to the rest of the body. A
muscle cells contains many more mitochondrial organelles than normal cells and are able to
contract producing movement. How is a sperm specialised to perform its function ...List three
things ?
Specialised cells in animals: Word bank: thin electrical nucleus
Sperm cells can propel
themselves locating the
female egg cell prior to
fertilisation as well as
carrying paternal DNA.
They also have a
streamlined head.
Sperm cell
Muscle cells contract
providing movement.
They are also rich in
mitochondria. This
allows them to respire
glucose with oxygen
producing energy.
Nerve cells form
connections with other
nerve cells, carry
impulses along a huge
neural network that
connect and coordinate
our actions and thoughts.
Red blood cells contain
haemoglobin, have a
biconcave shape and no
nucleus. They carry
oxygen from the lung
surface to the rest of the
body
Notes
Diagram
Cell Red blood cell Nerve cell Muscle cells
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py g
Specialised cells in plantsSpecialised cells in plantsAs in animals, plant cells are also designed for the function they play as part of the millions of
cells that work together to support life and produce food in green plants. A root hair cell, for
example is long and extremely thin to aid the uptake of w_______ and dissolved minerals likenitrates and phosphates from the s______. The leaf palisade cell contains many chloroplast
organelles which during photosynthesis produces glucose and o________ from carbon dioxide
and water. Which other cells have large surface areas to aid absorption ?
Specialised cells in plants:Word bank: water sun oxygen
Pollen cells, the male
gametes in plants are
normally transferred to
the female carpel by
insects. Pollen carries
the genetic information
to create a new plant.
Pollen cell
Stomata cells found on
the underside of green
leaves allows the
exchange of water,
carbon dioxide and
oxygen through the leaf
during photosynthesis.
Water moves up the
stem through the xylem
vessels. They are long
tubes reaching from the
roots to the leaf tissue.
Water moves in xylem
cells by capillary action.
Green leaves contain
many palisade cells
which are rich in
chloroplasts that enable
photosynthesis to occur.
Why do root cells not
have these cell parts ?
Notes
Diagram
Cell Palisade cells Xylem cells Stomata cell
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Cell size in plants and animalsCell size in plants and animalsCells in plants and animals vary in size. To visualize plant or animal cells we need to use a
m___________. Animal cells on average, tend to be smallerand less regular in shape, when
compared to plant cells. Both plant and animal cells grow and divide before becoming toolarge. Cells that are too large will have a reducedsurface area to volume ratio. A small surface
area to volume ratio reduces the amount of o__________ and nutrients that can be absorbed
across its surface membrane. Cells must then divide or die. This is called mitosis.
Cell size and mitosis: Word bank: microscope oxygen
Mitosis
Parent cell
2 Daughter cells
DNA replicates
Chromosomesseparate
Stage one
Stage four
Stage two
Stage three
2n
2n
4n
2n
As the cell volume increases, the ratio of surface
area to volume ratio deceases reducing the cells
ability to allow sufficient nutrients and oxygen
across the cell membrane. Cells are able to divideand clone themselves during mitosis. Over a billion
cells an hour are replaced in your body by cells
dividing.
Cell division in plants and animals
Photograph of plant
palisade cells. They are
magnified 100 times.
Find their size using thesame method. Are they
smaller or larger than
human cheek cells ?
Photograph of human
cheek cells. They are
magnified 250 times.
Use a ruler to measuretheir length. Now divide
by 250 to find their real
size.
Notes
Diagram
Cell Typical animal cells Typical plant cells
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Mitosis for replacing cellsMitosis for replacing cellsNew cells are needed for you to grow and repair. These are made by cell divisions
called mitosis. During mitosis, a cell d_________ and forms two identical clone cells.
The human body produces up to one billion cells like this every hour replacing old
worn out cells. New s______, muscle, blood, and nerve cells are all produced this
way. Some species reproduce using mitosis. Bacteria, for example multiply using
mitosis. What are the advantages of reproducing asexually ?
Replacing cells by mitosis: Word bank: division skin
Embryo grow by
cloning cells. A
single zygote leads
to the formation of
an embryos many
millions of cells
during pregnancy.
Embryo growth
Skins cells are lost
and replaced due to
normal wear and
tear by mitosis.
Every day we lose
about 100 million
skin cells.
New skin cells
Bacteria reproduce
multiply and spread
by cloning them-
selves. Each cell is
identical to the
original bacterial
cell.
Bacteria
Notes
Diagram
A human contains
many billions of
cells. Each hour
of every day, we
replace over one
billion cells in our
body.
Human
Blood cells last
only about 90
days before they
need to be
replaced by the
marrow of the
long bones.
Blood cells
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MitosisMitosis Normal cell divisionNormal cell division
Mitosis occurs during growth and repair. Mitosis leads to formation of new identical
cells. Producing c______ or identical cells has several advantages. They behave just
like the old ones and they dont require anything but the original cell. What other
advantages are there to producing identical clone cells ?
Stages in mitosis: Word bank: clone
Mitosis
Parent cell
2 Daughter cells
DNA replicates
Chromosomesseparate
Stage one
Stage four
Stage two
Stage three
2n
2n
4n
2n
Mitosis in plants
Notes
Diagram
Stage one: Chromosomes become visible and double inside the nucleus. The cell now contains 46 pairs of
chromosomes. Stage two:The chromosomes move to the centre and line up before separation. Stage three:
Each set of chromosomes separates moving to the cell poles before cell division. Stage four: The celldivides, producing two clone cells each containing 23 pairs of chromosomes. In the shoots and tips of plants
new cells are formed during mitotic cell divisions. Each daughter cell is identical to the original cell. This
picture shows several cells in various stages of mitosis.
Mitosis (normal cell division)
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MeiosisMeiosis gametes in humansgametes in humansMeiosis leads to the formation of only two types of cells. Meiosis in males forms the
s______ and in females the o______ or egg cells. Meiosis halves the number of
chromosomes, so that when the sperm and egg fuse, the fertilised zygote will have thecorrect number of chromosomes (23 chromosomal pairs). Meiosis also produces random
gene mixingleading to variation of human traits in new individuals.
Gamete production in the male and female:
sperm
egg
Word bank: sperm ovum
All of these 31,000 genes
code for all the traits and
characteristics that makehuman life unique. Cells
now divide by mitosis.
After fertilisation, all
cells of the developing
embryo now contain 23pairs of chromosomes
with over 31,000 genes.
Sperm and egg cells are
haploid with only 23
single chromosomesonly half the normal
number
Gametes cells (sperm
and egg) are produced
by the testis andovaries in the male
and female.
PregnancyEmbryoFertilisationGametes
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MeiosisMeiosis Reductive cell divisionReductive cell division
During meiosis, the number of chromosomes are halved so that the s______ and egg
carries 23 single chromosomes. During meiosis, paternal genes that code for your
characteristics randomly mix, so that we are all not the same. Name the cells in plantsthat are produces by the process of meiosis ?
Stages in meiosis: Word bank: sperm
Sperm production
Notes
Diagram
Stage 1: Chromosomes double and randomly mix inside the nucleus. The cell now contains 46 pairs of
chromosomes. Stage 2:The chromosomes move to the centre and line up before separation. Stage 3: The
cell divides, producing two new cells each containing 23 pairs of chromosomes. Stage 4: The two daughtercells divide again halving the number of chromosomes. Each gamete now contains only 23 single
chromosomes. A sperm cell carries 23 single chromosomes and fuses with an egg cell which also carries 23
single chromosomes to form a zygote, which now carries the normal diploid number of chromosomes.
Meiosis (reductive cell division)
Meiosis
Stage one
Stage four
Stage two
Stage three
2n
n
4n
2n
Parent cell
& replicates
2 daughter cells
4 daughter cells
DNA mixes
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M i iMeiosis Determining sex by chromosomesDetermining sex by chromosomes
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MeiosisMeiosis Determining sex by chromosomesDetermining sex by chromosomes
Your chromosomes also determine what sex you are at b_______. In humans there are
23pairs of chromosomes found in every cell. 22pairs are identical, butpair23 do not
match.Pair23 are called the sex chromosomes. All eggs from the female contain theX chromosome, sperm from the male contain either the X or Y chromosome. At
f_____________, the egg may join with either an X or Y sperm producing equal
numbers of males (XY) or females (XX). What are the gametes cells called in plants ?
Inheritance of the sex chromosomes:
XX
Female
XY
Male
Egg
SpermXX
Female
XY
Male
Egg
Sperm
Word bank: birth fertilisation
During fertilisation, the number of
chromosomes are restored to theirnormal diploid number (23 pairs) The
embryo now grows by normal cell
division called mitosis.
The gamete cells
(sperm and egg) carryonly 23 single
chromosomes. They
are haploid cells.
Your sex is determined at the moment
of fertilisation by the male sperm. AnX carrying sperm produces a girl, and a
Y carrying sperm produces a boy.
There is a 50: 50 chance of either sex.
Sex inheritanceGamete cellsFemaleMale
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M i iMeiosis gametes in plantsgametes in plants
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MeiosisMeiosis gametes in plantsgametes in plants
Pollination is the transfer of pollen, the male sex cells from the a_________ of the stamen by
b____ or insects to the surface of the female c_________. Once the pollen sex cells have
landed on the female carpel, pollination has been achieved. Flowering plants contain bothfemale and male reproductive organs and can either self or cross pollinate. Following
fertilisation, where the ovule and pollen cell fuse, the seed begins to develop surrounded by the
swollen ovule which forms the f_______. It is the function of the fruit to disperse the seed.
What is this organs role in the plant life cycle ?
Plant reproductive system: Word bank: anther bees carpel fruit
The stamen is the plant
male reproductive organ
which contains manymillions of microscopic
pollen cells.
Male anther
Flowering plants have
both male and female
reproductive organs.Plants can self or cross
pollinate.
The egg cells or ovules
contain the maternal
genes and are held in theovule, part of the female
carpel.
Pollen, the male sex
cells contain the paternal
genes and are held onthe anther which is part
of the male stamen.
Notes
Diagram
Pollen cells Female carpel Reproductive system
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M i iM i i Variation in humansVariation in humans oneone
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MeiosisMeiosis Variation in humansVariation in humans oneone
Humans have many of their genes which are common to us all. Over99% of our genes
in all the races are shared. Only 1% of human g_______ are unique and different.
These genes code for differences in the colour of skin, eyes, hair and other features
like the shape of our faces. Unless youre an identical twin, your genes, your traits and
you are unique amongst the other5.5billion human beings found on this planet. What
are the advantages of variation in a species like humans ?
Variation in humans:
Variation in humans (traits such as skin and eye colour) occur due to the random mixing ofDNA during meiosis ensuring that no egg or sperm carry exactly the same genes or DNA and
of course during fertilisation, when the genes from your mother and father mix to form you.
Notes
Japanese MaoriArab
Diagram
Masai warrior Aborigine
Word bank: genes
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M i iMeiosis Variation in humansVariation in humans twotwo
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MeiosisMeiosis Variation in humansVariation in humans twotwo
Variation in the human race is caused by differences in your genes, caused by the
random m______ ofDNA during the production of sperm and egg and of course when
the genes from your father and mother join during fertilisation. Your mother and
father both share exactly 50% of yourDNA and are your closest biological relatives.
Brothers and sisters can share up to 50% of theirDNA, but the figure is usually only
around 25%. Why do brothers and sisters look very similar to one another ?
Variation in humans:
Look around you in class, we all have certain similarities, but we are all unique. We belong
to the same species, can reproduce with one another but are all different. Some people are
taller or heavier or have different colour hair, skin or eyes. This is called variation. This is
because we all have different genes in our cells from our parents.
Notes
South American Europe (south)Asian
Diagram
African Europe (North)
Word bank: mixing
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Extension questions and homework
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Extension questions and homework
1: Define the following terms: Chromosome, Gene, Allele, Characteristic, Diploid, Haploid, Trait, Genotype,
Phenotype, Mutation, Recessive and Dominant.
2: Look at the three pictures below. Complete the table:
3: Answer the following:
a) Give 3 examples of human traits or characteristics
b) Give 3 examples of traits or characteristics in plants.
c) Name two cells that have a diploid number of chromosomes and two cells that have a haploid number of
chromosomes. Do any cells in humans have no chromosomes.
d) From the following, decide whether each cell is the result of mitotic or meiotic cell division.
Description
Production of sperm and egg
Plant cells dividing at shoot tip
Embryo growing during pregnancy
Mitosis/MeiosisPicture
BacteriaSpermMuscle cellPollenPlant ovumSperm cellSkin cellBlood cell
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4: The diagram below shows how the sex of a child is determined by the chromosomes inherited from both parents
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4: The diagram below shows how the sex of a child is determined by the chromosomes inherited from both parents.
(a) All human cells contain 46 chromosomes. How many chromosomes are there in
human egg or sperm cells.
(b) Explain why either a daughter or a son will share some of the characteristics
from both parents.
(c) Explain why your parents are your closest living relatives.
(d) What type of cell division leads to the formation of an embryo from a zygote
during pregnancy.
5: Chromosomes occur in pairs in all cells except gametes.
(a) What are alleles
(b) Why are there two alleles for each characteristic.
(c) Explain what is meant by dominant and recessive alleles.
(d) The characteristics of humans are either inherited, or are caused by environmental influences. [Blood group,
Weight, Eye-colour, Gender and Accidental loss of arm]
(i) Which features are controlled by environmental influences (ii) Name one that is controlled by inheritance only
(iii) One that is controlled by both.
6: A plant can either self or cross pollinate. Answer the following questions:
(a) Which process (self or cross) leads to the production of (i) Identical offspring (ii) Different offspring.
(b) List the advantages and disadvantages of asexual and sexual reproduction in plants.
XX
Female
XY
Male
Egg
Sperm XX
Female
XY
Male
Egg
Sperm
Internet:
Go to google.co.uk and find about how cloning in plants is used by commercial growers to improve the quality andyield of a particular crop. Are there any disadvantages to cloning plants for commercial reasons.