Unit 12 Mitosis and Meiosis

7/29/2019 Unit 12 Mitosis and Meiosis

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Unit 19: The Transitional Metals

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Unit 13: Inheritance and Selection

Unit 12: Mitosis and Meiosis

Unit 11: Flow of Energy and Elements through the Environment

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Unit 9: Photosynthesis in Green Plants

Unit 8: Drugs and Bad Body Maintenance

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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.

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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)

i hScience Interactive LTD Copyright 2005


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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

R d ti ll di i iR d ti ll di i iScience Interactive LTD Copyright 2005


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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


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


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


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


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


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


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.

Unit 12 Mitosis and Meiosis

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