Transcript B1 SHA - you and your genes

B1-L1, How do we vary?
LO: What makes us all different?
What are genes and what do they do?
Look at the person next to you.
Name 5 things that are different about you
Now sort them into two boxes
Things we got
or inherited
from our parents
Things that happened
as we grew up
or are changed
by the environment
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
Inherited or environmental
variation?
OK: so how do you Inherit features?
See if you can explain the following facts:
1. 50% of what makes ‘you’ comes from your dad
2. There is 50% chance of a child being male or female
3. A child with one brown haired parent is more likely to
have brown hair than blond
4. We may be able to choose what our children look like in
the future.
People are all very similar but still unique.
How does this happen?
All the information to make this baby came from
his parents.
Information from each parent is carried in their
sex cells.
All the information to develop a human being has to fit
inside the nucleus of a fertilized egg cell.
Copy me:
• There are about
30 000 pieces of
information in the
nucleus.
• Each piece of
information is called a
gene. And it tells the
body how to make
proteins
• Genes are joined up in
chains called
chromosomes.
Each chromosome in the nucleus contains thousands of genes.
• Inside a cell
• These are all the
chromosomes from
one human cell.
• 99.9% of the
information in any
fertilized egg is the
same.
• Only 0.1% of the
information they carry
makes this person
unique.
Most features are controlled by several genes and
are also affected by the environment, e.g. height.
Hair colour.
True of False
• Chromosomes are found in the nucleus.
• Sperm and egg cells have the same amount of information
as other body cells.
• When we are adults our cells stop dividing.
• Everyone in this room in unique.
• Genes are joined up into chains called chromosomes.
• The environment we grow up in causes variation.
• Our genetic information causes variation.
• Only the environment and genetics causes variation.
1 in 25 people carry the faulty gene that causes
cystic fibrosis.
B1-L2, How do we vary?
LO: To know how sex cells are made and the numbers
of chromosomes involved.
1.
2.
3.
4.
5.
Name one inherited variation you have?
Name one environmental variation you have?
What p_____ is made by the instructions on our genes?
Why are we different from each other?
Chromosome
Match up the following letters and words:
Gene
Nucleus
A
B
C
• Sometimes genes are faulty.
• How many people in this photograph do you think
have no faulty genes?
• None?
• We all have some faulty genes.
A small number of faulty
genes cause diseases.
This person has cystic
fibrosis.
• Cystic fibrosis is the most common inherited
disease in the UK.
• It affects 1 in every 2500 people.
Growth vs. Gametes
Mitosis – Growth (asexual reproduction)
Meiosis – Gametes (sex cells)
50% of what makes ‘you’ comes
from each parent
23 pairs = 46 chromosomes
In a woman each pair splits giving
an egg cell
In an man each pair splits giving a
sperm cell
Male body cell
46 Chromosomes
Sperm cell
23 Chromosomes
Baby cell
46 Chromosomes
50% Mum and
50% Dad
Female body cell
46 Chromosomes
Egg cell
23 Chromosomes
It’s true, Boys do have a little ‘y’
chromosome.
Practice Exam Questions
• For your progress folders
• EXAM CONDITIONS
B1-L3, Dominant and recessive
LO: To know how pairs of genes control features
1. chromosomes in a human body cell
2. pair of chromosomes which controls what sex a person is
3. pair of sex chromosomes a woman has
4. pair of sex chromosomes a man has
5. chromosomes in a egg or sperm cell
23
46
XY
23rd
XX
ALLELES
Dominant and Recessive
Dragons
Help! Only two dragons in the world are left.
What might their children be like??
These things all depend on
the combination of genes alleles
Breaths fire?
How many toes?
Tail spikes?
Colour?
L
D
l
d
L
D
l
d
Blue are daddy dragon genes and
Yellow are mummy dragon genes.
e
t
q
E
T
Q
e
t
q
E
T
Q
M
A
m
a
M
A
m
a
Plenary – write a definition for
these words
•
•
•
•
•
•
•
Chromosome
Gene
Alleles
Dominant
Reccesive
Genotype
Phenotype
B1-L4, Punnett squares and
Variation
LO: To know how pairs of genes control features
BB = Brown eyes and B is dominant
bb = Blue eyes
Complete these squares to show all the combinations of alleles
MUM = Brown eyes
b
b
B
B
Dad = Brown eyes
Dad = Blue eyes
B
MUM = Brown eyes
B
b
b
Eye colour
In eye colour the brown eye allele is dominant, so we call it
B, and the blue eye is recessive, so we call it b:
BB
Bb
bb
Homozygous
brown-eyed
parent
Heterozygous
brown-eyed
parent
Blue-eyed parent
What would the offspring have?
Another method
Example 1: A Homozygous brown-eyed
father and a blue-eyed mother:
Father
B
B
b
Bb
Bb
b
Bb
Bb
Mother
All offspring have brown eyes
Another method
Example 2: Two heterozygous brown-eyed
parents:
Father
B
b
B
BB
Bb
b
Bb
bb
Mother
25% chance of blue eyes
Another method
Example 3: A heterozygous brown-eyed
father and a blue-eyed mother:
Father
B
b
b
Bb
bb
b
Bb
bb
Mother
GENETIC CROSSES
The inheritance of dimples
• A person with the
genes DD will have
dimples.
• A person with the
genes dd will not
have dimples.
• A person with the
genes Dd will have
dimples.
The inheritance of dimples
• In a person with the
genes Dd only the
effect of gene D
shows.
• The effect of gene D
dominates the effect
of gene d.
• Gene D is dominant
to gene d.
• Gene d is recessive
to gene D.
D is the gene for dimples
d is the gene for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
DD
d is the gene for no dimples
dd
Body cell in mother
with a pair of genes
for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
Gametes
DD
d is the gene for no dimples
dd
Body cell in mother
with a pair of genes
for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
dd
Gametes
each sperm
has a gene for
dimples
D
D
Body cell in mother
with a pair of genes
for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
Body cell in mother
with a pair of genes
for no dimples
dd
Gametes
each sperm
has a gene for
dimples
D
D
d
d
each ovum has a
gene for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
Body cell in mother
with a pair of genes
for no dimples
dd
Gametes
each sperm
has a gene for
dimples
At fertilization
There are 4
possible ways of
joining a sperm
to an ovum
D
D
d
d
each ovum has a
gene for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
Body cell in mother
with a pair of genes
for no dimples
dd
Gametes
each sperm
has a gene for
dimples
D
d
D
At fertilization
There are 4
possible ways of
joining a sperm
to an ovum
D
D
d
each ovum has a
gene for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
Body cell in mother
with a pair of genes
for no dimples
dd
Gametes
each sperm
has a gene for
dimples
D
d
D
At fertilization
There are 4
possible ways of
joining a sperm
to an ovum
D
D
d
each ovum has a
gene for no dimples
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
Body cell in mother
with a pair of genes
for no dimples
dd
Gametes
each sperm
has a gene for
dimples
D
d
D
d
each ovum has a
gene for no dimples
At fertilization
There are 4
possible ways of
joining a sperm
to an ovum
d
D
D
d
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
Body cell in mother
with a pair of genes
for no dimples
dd
Gametes
each sperm
has a gene for
dimples
D
d
D
each ovum has a
gene for no dimples
d
At fertilization
There are 4
possible ways of
joining a sperm
to an ovum
d
D
D
Dd
Dd
d
Dd
Dd
D is the gene for dimples
Parents
Body cell in father
with a pair of
genes for dimples
d is the gene for no dimples
DD
Body cell in mother
with a pair of genes
for no dimples
dd
Gametes
each sperm
has a gene for
dimples
D
d
D
each ovum has a
gene for no dimples
d
At fertilization
There are 4
possible ways of
joining a sperm
to an ovum
d
D
D
Dd
Dd
d
Dd
Dd
All the children of this generation have genotype Dd and phenotype - dimples
Parents
father with
dimples
What would happen in this
example?
Gametes
At fertilization
Dd
Dd
mother with dimples
Answer:
Parents
father with
dimples
Dd
mother with dimples
Dd
Gametes
D
D
d
d
D
At fertilization
D
d
DD
Dd
d
Dd
dd
A child who inherits the genes DD will have dimples
A child who inherits the genes Dd will have dimples
A child who inherits the genes dd will not have dimples
In this generation the ratio of dimpled children to non-dimpled will be 3 to 1
DANGLY
ATTACHED
Continuous and Discrete variation?
• Helpful videos –
•
•
•
•
Huntingtons 1
2
3
4
Produce a poster about
•
•
•
•
Huntingtons pg 12
Cystic fibrosis pg 16 and 17
Jan – pg 19
Rhys and SCID – pg 29
B1-L5, genetic diseases
LO: To know how disease can be inherited
True or false??
1. Xx is female
2. BB is brown eyes
3. Bb is blue eyes
4. There are 23 chromosomes in a body cell
5. Chromosomes are part of a gene
6. Alleles are types of gene
7. Dd + Dd means a 50% chance of DD
8. Testosterone is a hormone that decides if you will be a
boy
write a definition for these words
• Genotype
• Phenotype
what are proteins used for???
Genetic diseases
• Can anyone name a genetic disease?
Trait
Chromosome
for Gene
Location
Genotype
Recessive or
dominant
skin cancer
1
Cc or CC
D
cystic fibrosis
7
qq
R
albinism
11
aa
R
Breast cancer
17
Nn or NN
D
Mm or MM (girls
only)
D
Hh or HH
D
Muscular
Dystrophy
X sex
chromoso
me
Huntingtons
4
Down’s Syndrome
Extra copy
of 21
HUNTINGTON’S DISORDER
1. Huntingtons disease is a dominant one.
2. Do 4 genetic crosses to determine the
chance of these couples having children
with Huntington’s disorder:
a. Hh x hh
b. HH x hh
c. HH x Hh
d. Hh x Hh
CYSTIC FIBROSIS
1. Cystic fibrosis is a recessive one.
2. Do 3 genetic crosses to determine the
chance of these couples having children
with Cystic fibrosis:
a. Ff x ff
b. Ff x Ff
c. FF x Ff
• Cystic fibrosis 1
• 2
• 3
WS Huntington’s and Cystic
fibrosis
Now what??
• You know you both carry the recessive
gene?
• What would you do??
Genetic testing
It is now possible to test individuals before they are born for
any faulty alleles. There are two main methods:
1) Amniocentesis testing:
- Done at 14-16
weeks
- 0.5% chance of
miscarriage
(5 in 1000)
- Small chance
of infection
Genetic testing
It is now possible to test individuals before they are born for
any faulty alleles. There are two main methods:
2) Maternal serum screening:
- Blood test of
mother
- 0% chance of
miscarriage
- Does not give
precise results
-High or Low risk
of having a
poorly baby . . .
DIFFERENT IDEAS ABOUT GENETIC
SCREENING FOR CYSTIC FIBROSIS
Read pages 22-23 to find out what genetic screening is.
Which opinion do you agree with?
It is very
dangerous.
People should not
have to worry
about this
information.
There’s nothing
wrong in having
an ill child.
What if my husband
and I both had the
faulty allele? Would
we have children?
We should give
people all the
information we can
about their health.
Then they can
make an informed
decision.
I want to choose
my medical
treatment – not
have any forced
on me!
For some causes of
infertility, IVF provides
a
wonderful opportunity
The financial and
emotional conflicts that
arise out of IVF can put
huge strains on a
relationship
Any society where
people can afford IVF
will be one where
overpopulation will not…
• Exam question!
You can have IVF treatment to make
sure your next baby doesn’t have
cystic fibrosis
What
should we
do, Doctor?
Decision 1
How do you
make an
ethical
decision?
Imagine you are one of the Simpletons.
You have been asked about IVF.
How will you respond?
My approach to
ethical dilemmas:
Weigh up the benefits and
costs and choose the
option that makes most
people happy.
This is the ‘utilitarian approach’
My approach
to ethical decisions:
Before I do anything,
I make sure it does
not violate other
people’s rights.
This is rights-based thinking
My approach to
ethical decisions:
Be caring and compassionate
about people and
relationships.
This is care-based thinking
My approach to
ethical decisions:
I simply choose the option
that turns out best
for me.
This is self-centred thinking
What must I decide about?
Who is
affected?
What are
the benefits
(pros) of
doing this?
What are
the
problems
(cons) of
doing this?
Utilitarian
Conclusion
My approach to ethical decisions:
Weigh up the benefits and costs and choose the
option that makes most people happy.
What must I decide about?
Who is
affected?
What rights
do we want
to protect?
(e.g. choice,
freedom, life)
Will the
decision
violate
(go against)
any rights?
How?
Rights-based
Conclusion
My approach to ethical decisions:
Before I do anything, I make sure it does not
violate other people’s rights.
What must I decide about?
Who is
affected?
How will
doing this
make their
life better?
How will
doing this
make their
life worse?
Care-based
Conclusion
My approach to ethical decisions:
Be caring and compassionate about
people and relationships.
What must I decide about?
Who is
affected?
Is this a
good thing
for me or a
bad thing
for me?
How
important is
this to me?
Self-centred
Conclusion
My approach to ethical decisions:
Simply choose the option that turns
out best for me.
Exam question starter
CAN YOU CHOOSE YOUR CHILD?
Define the following words:
1. embryo
2. implantation
3. in vitro fertilisation
4. pre-implantation genetic diagnosis
GENE THERAPY
Read page 28-29 :
Questions 1-5
And write the definitions for the following
words
Gene therapy
Genetic modification
GENE THERAPY
Gene therapy –
a treatment where a normal gene is put
into cells of someone with a genetic
disorder.
Genetic modification –
the changing of an organism’s genes. In
gene therapy this is by the addition of
normal genes.
How many things
could you use a
clone for?
Asexual reproduction in cells
Each daughter cell has
the same number of
chromosomes and genetic
information as the parent.
Natural clones
How to clone
A plant
An animal
Cloning Animals
Host mother
Clone
• Should we try to develop cloning technology?
• Should we change faulty genes? (gene therapy, preimplantation genetic diagnosis, genetic modification)
• How can we go about making this type
of decision?
Stem cell research
Stem cells are cells that have not yet specialised:
These stem cells have the
potential to develop into
any kind of cell. The rest
of the embryo is
destroyed. Most of these
embryos come from
unused IVF treatments.
Embryo
Egg and
sperm
Cloned
embryos
The ethical issue:
Should these embryos be treated as humans?
Making decisions
Some questions cannot be answered by science and need to be
considered on ethical grounds.
Factors that might influence a decision:
• Beliefs/religion
• What does “the right thing” mean?
• “Playing God”
• Risks – acceptable or unacceptable?
• Social and economic contexts
Draw a cartoon to show the cloning
process.
include science diagrams too!
Fill in the G A P S
Clones of ________ can occur when an embryo splits up
naturally.
Embryonic ________ cells are _____________ cells that can
grow into any type of cell.
These cells can be grown from ________ left over from ________
treatments.
Embryonic stem cells may be useful in the future for treating
_________.
animals
embryos
illnesses
IVF
stem
unspecialised
should we be able to clone
embryos?
Cloning with cuttings
To do
Fill a small pot with compost.
Cut the stem about 10 cm from the tip. Cut just below a leaf at an angle. Don’t cut straight across.
Take off the leaves at the bottom of your cutting.
Dip the cut end in rooting powder if you have some.
Put the cutting in your compost. Push it in gently until the compost is just below the bottom leaf.
Label your pot with your name and the date.
Put a plastic bag loosely over your plant.
In a few weeks your plants will have grown roots.