Embed Size (px)
Citation preview
Genetics 1.1Demonstrate understanding of
biological ideas relating to genetic variation
MAH – Year 11 2011
Purpose – to gather info about what you may already know about the topic.
Quiet Independent work – What does this mean?
15minsEarly finishers exercise included
Pre – Assessment
Giants: http://www.youtube.com/watch?v=7jJq6y4pdPA&feature=channel
Genetics is the study of heredity. We share similarities with our relatives. But when someone says, you have your fathers eyes, you don’t actually have them right. So what do you have?
What gets passed on is a code in the form of DNA. This code tells your body how to make itself. You get DNA from your mum and dad.
When we talk about genetics…
GeneticsIs the study of genes and what they do, how
they are passed on from parent to offspring and how they are expressed.
VariationDescribe how all living things are different.
There is variety within the same species and between different species.
Genetics and Variation
DNA stands for Deoxyribo Nucleic Acid Is found in every cell in the body except red
blood cells
Where have you heard of DNA before?What do you think it’s role is?
DNA
Everyone of our cells (except red
blood cells) contains DNA.
DNA is stored in a structure called
the nucleus
The order of chemicals that make up DNA determine what the body makes. It is like an alphabet. By re-arranging the letters you get different
information. By re arranging the letters of the genetic code, you get different traits.
DNA is a chemical that stores information as a code.
This code is instructions for how to make life.
The end result, or what we can see based on the DNA code is called a phenotype (e.g. Tongue roller, hitchhikers thumb)
DNA carries hereditary information from one generation to the next.
Function of DNA
Based on seating plan
Temporary measure
Groups of 3
Write down who is in your group
Lab Groups
1. Sadiq, Henry, Daniel2. Owen, Matt, Jayden3. Jack, Nick, Dante4. Sam S, Liam, James5. Kahui, Sam, Steven,6. Caleb, Tyler, Danyon, 7. Calum,, Mustafa, Erekose 8. To’i, Brad, Logan9. Chris, Geoff, Ryan S10. Sam, Joshua, Liam P
Lab Groups – Year 11
Now we will isolate some DNA from some fruit cells.
Collect instruction sheet.Watch teacher model method.
What is the role of each ingredient used?What does the DNA look like?
Pages XXX workbook
Practical
Relate to Learning objective“Describe the function of DNA”
New terminologyGenetics, DNA, nucleus, inherit, code,
hereditary, phenotype
Next step: Describe the STRUCTURE of the DNA molecule
Review
Collect Homework sheet oneOne technology that involves DNA is cloning.
Your homework task relates to cloning of humans.
Homework
What are the two functions of DNA?
What was the purpose of the detergent and ethanol in yesterday’s experiment?
DO NOW
Learning objectives1) Recall the function of DNA2) Describe the structure of DNA3) Create a model of DNA
Do NowCrossword
10/02
DNA Gene Allele Mutation Genotype Phenotype Gamete Zygote Dominant Homozygous
Heterozygous Pure Breeding Punnet square Pedigree chart Natural Selection Meiosis Adaptive features Recessive
DO NOW – Set aside a whole page and write ALL of these new terms and leave two lines for a definition
Mermaid syndrome◦ http://www.youtube.com/watch?v=IAOhSUQomVg
1) DNA is a chemical that stores information as a code. This code is instructions for how to make life.
2) DNA carries hereditary information from one generation to the next.
What are the 2 functions of DNA?
Who knows?
Recall
The DNA molecule is often called a DOUBLE HELIX.
Why?
Because it is made of 2 (hence the double) strands of DNA and is in the shape of a helix.
DNA Structure
A
A A
A
T
T T
TC GT G
G
G
C
CC A
A G C G C T1
Strand
1 Strand
2 Strands
(Double)
Like a twisted ladder(Helix)
3D model – What are the parts?
Imagine each strand of DNA is made up of many single units, like a chain.
Each single unit is called a NUCLEOTIDE
A
A A
A
T
T T
TC GT G
G
G
C
CC A
A G C G C T
1 NucleotideClick me to go to a website about DNA
All nucleotides have the same structure. The only thing that changes is the base.There are 4 bases, Adenine, Thymine,
Cytosine, and Guanine
Nucleotide
Phosphate
Sugar Base
Flash DNA
DNA and base pairs
The rungs of the DNA ladder are made from pairs of bases.There are four types of bases. They have complicated names so it is easier to use their initials instead.
These bases always pair together in the same way.
How do you think the four bases pair up?
denineytosin
euanin
ehymin
e
DNA and base pairs
Base pairs hold the two strands of the DNA helix together.The rules for base pairing are…
There are millions of base pairs in a DNA molecule that always follow these rules.
A always pairs with T
C always pairs with G
Amazingly, it is the sequence of bases along a DNA molecule that forms the genetic code – it’s that simple!
http://www.youtube.com/watch?v=qy8dk5iS1f0
DNA structure - Clip
Collect and complete cloze and diagram labelling exercise
Paste it into your book
Silent, independent work
3 minutes
DNA structure
What does antiparallel mean in regard to DNA structure?
How many pairs of chromosomes do humans have?
DO NOW
Each strand of DNA is anti-parallel to the other
Strand 1
Strand 2
Students create a model of DNA double helix on whiteboard using laminated nucleotide pieces.
Now
Click me to go to DNAiThen choose “Finding
the Structure” and “Putting it Together”.
1) DNA is described as a double helix. Why?2) What is the name of the single units that
make up DNA?3) What parts make up these single units?4) What are the 4 bases?5) What are the base pair rules?6) DNA strands are anti-parallel. What does
this mean?
Lesson Review – Structure of DNA
Muddiest Point – you have 1 minute, write down one thing from today’s lesson you are most unclear about. Hand to your teacher as you
leave.
Learning Objectives1) Recall the structure and function of DNA2) Build a model of DNA
Do Now:Muddiest Point Questions
Insert date here
Lesson 3
1) What are 2 functions of DNA?2) Describe the structure of DNA?
Direct and Probe question
DNA Structure and Function
You are to work in groups of 3 to create a model of DNA from playdough.
Your model should be detailed;◦ Include at least 10 nucleotides arranged as
complimentary base pairs◦ Show each structure of the nucleotide (phosphate,
sugar, base)◦ Show the anti – parallel direction of each strand
You have the period to complete it – manage your time wisely. The last 10 minutes of the period will be spent presenting your model.
Now
What did you learn today about the structure of DNA?
How did building a model of DNA help your understanding on it’s structure?
If you were to do this again, what would you do differently?
Lesson Review
Learning objectives
1) Explain the relationship between chromosomes, genes and DNA.
2) Explain why chromosomes exist in pairs
Do now:wordfind
Insert date here
There is approx. 2 metres of DNA in each cell.
How does it all fit in??
What are they and how are they related?
If I were to say to you, what is the relationship between cars and metal, what would you say?
If I were to say to you what is the relationship between bricks and a house, what would you say?
Chromosomes, Genes and DNA
http://www.youtube.com/watch?v=eOvMNOMRRm8
23 and me
NUCLEUSCHROMOSOM
E
DNA DOUBLE HELIX
Base Pairs
Chromosomes, are the storage units of DNA. The DNA double helix is coiled tightly to form a chromosome.
A gene is a section of DNA that carries the code for ONE trait.
Below is a length of DNA from a chromosome
A gene is a section of DNA that codes for one trait
We have 2 copies of every chromosome.
Why do you think this occurs?
Chromosomes exist as pairs
One set comes from mum, the other set
comes from dad
l
l
l
Sperm carry one set of chromosomes from the father. Sperm are haploid (half
set of chromosomes)
l
l
The egg has one set of chromosomes from the mother. Eggs are haploid (half
set of chromosomes)
After fertilisation, the embryo is diploid. It has 2 sets of chromosomes.
Is a way of visually organising and arranging all the chromosomes into pairs.
Karyotype
Click me to learn more about
Karyotypes and to complete an interactive challenge
Complete the karyotype exercise.
Now
Down Syndrome
Characteristics:
Characteristic facial features, short stature; heart defects
Susceptibility to respiratory disease, shorter lifespan
Pone to developing early Alzheimer's and leukemia
Often sexually underdeveloped and sterile, usually some degree of mental delay.
Down Syndrome is correlated with age of mother but can also be the result of nondisjunction of the father's chromosome 21.
Klinefelters Syndrome
Chromo Number
Species Number of Chromos
Number of Pairs
Human 46 23Fruit Fly 8 4Rat 38 19Pea 14 7Horse 66 33
Learning Outcome: Write a scientific paragraph that defines each of the following terms DNA, genes and chromosomes and explains the relationship between them
Success is when:◦ The correct definitions for DNA, genes and chromosomes are used◦ It is stated that DNA stores information for life ◦ It is stated that chromosomes are made of DNA◦ It is stated that a gene is a segment of DNA that codes for a particular trait ◦ The relationship between DNA and its ‘packaging’ in chromosomes is
stated◦ The correct spelling and terminology is used◦ The paragraph is easy to read
You will write your own paragraph and then assess your neighbours. You will give your partner a mark for each point that is covered and write down one thing you like about your partners essay and one thing that could be improved.
Paragraph Writing – Pair Assessment
Relationship between Chromosomes, Genes and DNA
Why do chromosomes exist as pairs
Karyotype
Lesson Review
Learning objectives1) Describe what an allele is.2) Explain the role of mutations in forming
new alleles
Do now:Collect and complete cloze exercise on
chromosomes, DNA and genes.
Date
.....alternate forms of a gene....
Hitchhikers thumb or not hitchhikers thumbMid digit hair or not mid digit hairDimples or no dimplesBlood types
Alleles have a different DNA sequence
HOW DO ALLELES FORM?
Alleles
What is a Mutation?
.....A change in a DNA base sequence that can not be easily repaired
Can have varying effects based on the type of mutation
Haemoglobin is an important molecule that transports oxygen in the red blood cells and is coded by the gene HbA.
A mutation in the DNA sequence of the Haemoglobin means that in red blood cells it aggregates differently and makes the Red Blood Cells a funny shape (sickle shaped)
These misshapen blood cells obstruct blood flow
Hemoglobin and Alleles
KRT 1.2 the gene that codes for wool strength◦ Important for processing
Many different ‘versions’
Changes in DNA sequence that gets associated to different strengths of wool
KRT 1.2 Alleles
What causes Mutations? MUTAGENS: are agents that causes genes
to mutate
THEY INCLUDE:◦ High energy radiation – cosmic rays, x-rays,
ultraviolet radiation, radioactive decay
◦ Chemicals – formaldehyde, nitrogen mustards, epoxides, nitrous acid, acridine dyes and alkylating agents,
Effects of Mutations
1. Protein changes2. Changing biochemical pathways3. Changes to chromosomes4. Changes in cell division processes
Mutations lead to evolution and variation among a population
What is a mutation? What is a mutagen? Mutations lead to variation in a species –
TRUE OR FALSE?
What does complementary base pairing mean?
DO NOW
In your own words explain the relationship between alleles and mutations
You tube clips – mermaid syndrome
Mutations
The purpose of this task is for you to summarise the most important points of this lesson.
You have 2 minutes
Hand the named piece of paper to your teacher as you leave.
2 minute paper
Cell division process for growth and repair
Mitosis
This single cell is copied repeatedly to form an adult with approximately 10,000,000,000,000 cells – all with exactly the same information.
How does this copying take place?
1.Each chromosome copies its information (DNA replication) and is now called a chromatid.
2. The chromatids line up in the middle of the cell.
3. Half of each chromatid goes to each end of the cell.
4. Two new cells are formed.
MITOSIS
See an animation of
Mitosis
Mitosis!!! A continuous process Chromosomes replicate Chromosomes condense to become visible Nuclear membrane disappears Chromosomes line up in a single file across the
equator Chromosomes separate going to opposite end of the
cell Nuclear membrane reforms The parent cell starts splitting in two Two new cells are formed, each with the same
number of chromos as the parent cell
http://www.youtube.com/watch?v=jrL65nqfS0k&feature=related
If each cell has 46 chromosomes what happens when egg and sperm join together 46+46?
QUESTION??
How many chromosomes?
How many chromosomes are there in human sex cells?
How many chromosomes are there in new human body cells produced by mitosis?
46 chromosomes(23 matching pairs)
23 unpaired chromosomes
23 unpaired chromosomes
How many chromosomes?
Human sex cells have a set of 23 unpaired chromosomes - that’s half the usual number.
Sex cells in animals and plants follow the same rules.
They have half the usual number of chromosomes.
They have a complete set of single chromosomes.
Why is this important for fertilisation and reproduction?
FLASH 6 – Fertilisation
Chromosomes and fertilisation
FLASH 2 – Mitosis drag & drop
Chromosomes and fertilisation
MEIOSISMeiosis is the special type of cell division that creates gametes.
Why is it necessary to halve the amount of information passed on?
Two gametes (one from each parent) fuse to form a zygote.
A child is born
How does meiosis happen?1. Chromosomes double, just like in Mitosis to form chromatids.
2. Half of the chromatids go one way and half the other.
3. Two new cells are made.4. The chromatids divide again to
form four cells. Each with one set of information.
Haploid = 1 set of chromosomes
Diploid = 2 sets of chromosomes
Mitosis /meiosis test
Square dance
What is meiosis?
Meiosis begins with a single cell.
First the cell makes a copy of each chromosome.
Now, there are two stages of cell division…
original cell
firstdivision
seconddivision
4 new cells
How many chromosomes do the new cells have compared to the original?
What is meiosis?
Meiosis produces four new sex cells with half the original number of chromosomes.
Mitosis is also called reduction division. What does this mean?
In animals, meiosis produces ova in females and sperm cells in males.
In plants the gametes produced by meiosis are pollen grains and ovules.
http://www.cellsalive.com/meiosis.htm
Sexual Reproduction and Variation
http://www.cellsalive.com/meiosis.htm
Mitosis Meiosis
Where does it occur?
Function of cell division
Compare parent cell with daughter cells (genetically)
Number of cells produced
Complete the table
Genotypes, phenotypes, and punnet squares
Alleles Traits that you have/don’t have are called
discontinuous characteristics (e.g. Hitchhikers thumb)
Controlled by one gene with 2 alleles
Alleles are different forms of the same gene◦ Dominant (if present always expressed)◦ Recessive (if two present then will be expressed)
Alleles continued..
Inherit one allele from each parent Three ways that alleles can combine
Tongue Rolling Example: Tongue rolling (T) is dominant to non-tongue rolling (t)TTTttt
Genotype is the genetic make up of an individual◦ E.g. Tongue roll alleles are represented by T or t
What are the 3 possible genotypes?◦ TT, Tt, tt
◦ Homozygous
◦ Heterozygous
Phenotype is what the individual looks like
New words
Practise genotypes and phenotypes
6 stations for you to randomly select two alleles to create genotype
Draw insect!!
Make your own Insect!!
How we determine phenotypes and genotypes of offspring (children)
Tongue roller example◦ A homozygous tongue roller (TT) male mated
with a female who could not tongue roll◦ Draw a punnet square to determine the genotype
and phenotype ratios of their offspring
Punnet Squares
This is a monohybrid cross
All possible combinations of gametes can be shown (father can roll TT, mother can’t tt)
The genotype of all offspring can be worked out
Can work out the chances or ratio of any combination occurring in this case:
Genotype 100% Tt Phenotype 100% Can roll
Punnet Square
Mothers egg
Fathers sperm
T T
t
t TtTt
Tt Tt
What are the Genotypes of children?
What are the phenotypes?
Roller, non roller What is the ratio of
phenotypes? 3:1 How can we tell if the
genotype of a tongue roller is TT or Tt?
Punnet Square (T= tongue roller)
Mothers egg
Fathers sperm
T t
T
t ttTt
TT Tt
In humans free hanging ear lobes (F) are dominant to joined ear lobes (f)
A heterozygous male had children with a homozygous recessive female
Draw a punnet square and write the genotype and phenotype ratios
Example
GENETICS PROBLEMSIn humans, blue eyes are recessive to brown:
Dad (bb)Mum (B?) Baby (bb)
Is Mum homozygous for brown eyes? ________ How do you know? (complete the Punnett square)
MICE
In mice, albino (a) is a recessive trait
Big Momma mouse Poppa mouse Stuart Little
Complete the Punnett square to show how Stuart ended up an albino
If there were 8 babies in the litter, how many would we expect to have normal colouring? _________
Breed your insect with another
Insect Activity
THE MONK
Who is this dude?
How about this one?
Gregor Mendel. He is the father of genetics – he is the reason that we can clone sheep, cure diseases and why CSI is on telly. Sort of.
Mendel’s work:
He spent many years studying pea plants, among other things.
He found that they had a large amount of variation in their appearance, and sought to find out why.
Stick in the work sheets on Gregor Mendel and have a go at the genetic crosses
Then have a go at the monohybrid crosses pg. 45
Mrs H has extra questions for you to have a go at
We are nearly finished the content for the US so lets keep up the good work! FOCUS!!
Gregor Mendel
A kind of dominance wherein the dominant gene completely masks the effect of the recessive gene in heterozygous condition
Incomplete e.g. Snap Dragon
Co-Dominac e.g. Spots
Complete dominance
gene
allele
phenotype
genotype
Section of DNA that codes for a particular trait or characteristic.
A different form of a gene that codes for a different version of a characteristic.A description of the pair of alleles present for a characteristic.
The physical expression of the alleles.
What do these genetic terms mean?
homozygous
heterozygous
recessive
dominant
Pair of alleles that produce a characteristic that are the same, e.g. HH.
Pair of alleles that produce a characteristic that are different, e.g. Hh.
An allele that will only be expressed when both alleles are of this type, represented by a lower case letter.
An allele that will always be expressed even when there is only one of these alleles present, represented by a capital letter.
What do these genetic terms mean?
THE MONK
Who is this guy?
How about this one?
Gregor Mendel. He is the father of genetics – he is the reason that we can clone sheep, cure diseases and why CSI is on telly. Sort of.
Mendel’s work:
He spent many years studying pea plants, among other things.
He found that they had a large amount of variation in their appearance, and sought to find out why.
MENDEL AND PEASIn one of his experiments he took the anthers off a purple flower. Why?
To stop it self fertilizing!
He then took pollen from a white flower and fertilized the purple flower.
He found that 100% of the offspring were purple.
He then took two of the purple offspring and crossed them. What do you think he found?
WHAT CAUSES IT???
VARIATION
Spot the family likeness
Mum Dad
son daughter
Which parent do these children look more like?If the son grows up to have children who might they look like?
Members of the same family often look similar.
Inherited characteristics
Mum Dad
son
Humans, like all living things, inherit characteristics from their parents. How are characteristics passed on?
Why do members of the same family look similar?
daughter
Inherited characteristics
Like all babies, this little boy carries a unique set of genes, half from his mother and half from his father.
This newborn baby’s characteristics are passed in the genes it has inherited from its parents.
Causes of variation
But are your characteristics only affected by your genes?
What ELSE will influence the characteristics of this baby as he grows up?
People are different because they inherit different characteristics from their parents.
Causes of variation
Your upbringing and the environment in which you live also affect how you turn out as an adult!
When he gets older, this baby might support a different football team (like Fulham) or not even like football.
Causes of variation
Differences in some characteristics are due to a combination of both inherited and environmental factors.
Your unique characteristics are caused by:
- the unique set of genes you have inherited from your parents
- the environment in which you have developed.
Causes of variation
Variation in plants
Plants inherit characteristics through their genes just like humans and other animals.
What characteristics have these plants inherited?
Are plants also affected by their environment?
What causes variation in plants?
Plants are affected by four key environmental factors. Can you name them?
Plants are affected by their environment in a big way.
With a little more moisture, light or warmth the size of a plant can double. (Imagine if that happened to us!)
water
sunlight
temperature
nutrients in soil
What causes variation in plants?
Read the information supplied
Based on the discussion we have just had and the readings write a paragraph in your book on variation under the heading’
HERITABLE AND NON-HERITABLE VARIATION
Heritable vs non-heritable variation
Individuals which are heterozygous are called carriers, because they carry a recessive allele.
To find out whether an animal carrying a dominant is homozygous or heterozygous, the animal is mated with a homozygous recessive animal.
This is called a test cross
Test Cross
You should be able to explain the difference between variation that is heritable and variation that is non-heritable
By the end of today...
It is not an adjustment to environment, but is a heritable feature shaped by natural selection, acting on variation, because of the variation's effect on fitness
Complex sentence but we will revisit at the end of this section and you will be able to explain in your own words
Adaptive features
Adaptations are special features or behaviours that make an organism particularly suited to its environment. They are part of the evolutionary process
Ten minutes to look at the various animals/plants and determine their adaptations to the environment
Adaptations
thick fur and body fat insulate from the cold
large, wide feet spread the body’s weight and act as good paddles and snow shoes
white greasy fur repels water and acts as camouflage
How are polar bears adapted?
Other adaptations that polar bears have evolved to cope with conditions in the harsh polar environment include:
eyes have brown irises to reduce the glare from the Sun’s reflection
small ears and small body surface area to volume ratio reduces heat loss
black skin is a good absorber of heat
More polar bears adaptations
camels have three stomachs
Camels are amazing creatures! Did you know that:
Curious camel facts
some camels live to over 40 years old
some Bactrian camels can transport 450 kg
archaeological finds show that camels originated in North America
Somalia is home to over six million camels!
wide feet spread out body weight on shifting sand
How is a camel adapted to life in a very hot, dry climate?
little water is lost through sweating or urination
long, thin legs help to increase body surface area and increase heat loss
fat is stored together in the hump to reduce overheating
How is a camel adapted?
nostrils can be closed for protection during sandstorms
very varied diet, ranging from grass and bark to thorns and bones.
long eyelashes and furry ears prevent sand and dust from getting in
What other adaptations have camels evolved to cope with the harsh desert environment?
More camel adaptations
leaves are narrow spines to reduce water loss and protect from predators
water stored in a fleshy stem, and a thick, waxy surface reduces water loss
How is a cactus adapted to life in a very hot, dry climate?
roots are either very deep, or shallow and widespread to catch surface water
How is a cactus adapted?
How is this shark adapted to an aquatic environment?streamlined shape to reduce friction when moving through water
gills have a large surface area so that oxygen can be extracted from the surrounding water
silver colouring allows the fish to be camouflaged
Aquatic adaptations
fins provide stability, power and control
Living things that are well adapted to their environment survive and reproduce. Those that are not well adapted don’t survive and reproduce. An adaptation is any characteristic that increases fitness, which is defined as the ability to survive and reproduce.
Summary
Explain the theory of natural selection using words such as environment, selecting, phenotypes
Give one example of natural selection in action
You will be able to .....
...is the environment selecting FOR or AGAINST certain PHENOTYPES
phenotypes: structure, metabolism, behaviour, physiology environment factors: predators, competition, disease,
lack of food, light, water, climate factors
..possess adaptations such as ability to avoid predators or to compete strongly for food
RESULTS IN: An increase in the allele frequency of those that aid in survival
Natural Selection
Natural Selection Simulation
Read the information on natural selection and alleles and summarise the information on the paper provided
Stick into your book
Readings on Natural Selection
Explain the process of natural selection in regard to the peppered moth
Use words like: Phenotype, predators, genotypes, allele frequency
Once finished make sure all the problems in your work book are done for genetics
Then I will give you some exam ??’s to have a go with
In your own words…
What does complete dominance mean
Name three phenotypes that could be selected for in relation to natural selection
e.g. camouflage so can’t be seen by predators
What sex chromosomes do males have
What sex chromosomes do females have
DO NOW
Variation within a species becomes very important in a changing environment
Eg. If a new disease arises by mutations, then if all members of a species had the same genes then they would be wiped out
BUT
If some were more resistant then they might survive, and if the resistant phenotype was inheritable then their offspring would also be resistant.
This is how species change or evolve over time
Genetic Variation
Sexual Asexual
Use the handout to fill out the table aboveOnce finished complete the questions on page 80-81 in your work book
Compare and Contrast Sexual and Asexual Reproduction
Selective breeding http://www.youtube.com/watch?
v=rW54_vM9SF0
Genetic Engineering
Cloning
Using the information in your workbook is
Applications of genetics
Describe what selective breeding is
What does a ‘carrier’ mean in relation to complete dominance and alleles
DO NOW
Pedigree Analysis - Book
Look for ‘new’ phenotypes in the offspring of a couple as this indicates the parents are carriers of the recessive allele
Make a decision if trait is recessive/dominant and see if applies to all ‘family’ situations
Sometimes you will be unable to determine the full genotype of an individual you may know if it carries the dominant allele but not if heterozygous or homozygous
How to?
