Transcript Genetics

Science Knowledge: Science 2: Life
Processes and living things
K2.4 Variation, Inheritance &
Evolution
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Download K2.4_2.0a Authored by Liz Lakin and Keith Ross,
University of Gloucestershire. accessed from
http://www.ase.org.uk/scitutors/
date created March 2006
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Slide 1
Variation, Inheritance & Evolution
Learning Objectives
• To explore the science
behind the headlines
• To establish a timeline
of events leading to
our current scientific
understanding
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• To identify the ‘big
ideas’ in this field of
biology and recognise
how they are
interlinked
• To discuss modern
applications & their
associated issues
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Slide 2
http://www.ncseweb.org/evc/EvsC-cover_400.jpg
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Slide 3
http://users.hol.gr/~dilos/prehis/Darwcar.jpg
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Slide 4
Variation
http://www.healthcastle.com/images/vegetables.jpg &
: www.picture-newsletter.com/ vegetables/index.htm
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Slide 5
Charles
Darwin
recognised the
significance of
variation in a
range of
organisms
www.nmm.ac.uk/.../ outputRegister/lowhtml
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Slide 6
The Story of the Peppered Moth
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Slide 7
Human Evolution
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Slide 8
Selection?
• What we are is
determined by our
genes and our
environment
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Slide 9
Father of Modern Genetics
• Gregor Mendel
• Austrian Monk
(1850s)
• Identified the patterns
of inheritance
• Laws of Inheritance
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Slide 10
Multiple choice questions
The questions in the slides that follow are taken from a set of
over 100 available from
www.escalate.ac.uk/1141
Percentages quoted in the slides are for a group of 100
trainee primary teachers on entry to ITE, having obtained
a ‘C’ or better at GCSE, usually two or three years
previously.
This gives secondary trainees an insight into the
misconceptions that survive a GCSE course, and all
trainees some comfort that they are not alone with their
own misconceptions about how genetics and evolution
works.
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Slide 11
Recessive Genes
If you and your partner both carry the
disease for cystic fibrosis (but are not
sufferers), what would be the probability
that your children will then inherit
the actual disease?
a. 25% (1 in 4)
5%
b. 33.3% (1 in 3)
19%
c. 50% (1 in 2)
35%
d. 100% (1 in 1 - certainty)
39%
(% are for a survey of post GCSE students – see notes)
Mendelian Cross
Both parents carry the
recessive gene for
cystic fibrosis (c) they
also carry the ordinary
gene (C). The cross
can be summarised as
follows:
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Father
c
Mother
CC
C
C
CC
Cc
CF carrier
c
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Cc
cc
CF carrier
CF
sufferer
Slide 13
Eye Colour
In eye colour the allele
for brown eyes is
dominant (B) and the
allele for blue eyes is
recessive (b). Try
some different crosses
with homozygous
parents (BB or bb) and
heterozygous parents
(Bb):
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Father
B
b
b
Bb
bb
b
Bb
bb
Mother
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Slide 14
So what are Genetics?
Look at the person
next to you
identify
Our• common
inheritance
asand
humans
as many external similarities between the
two of you, as you can.
Now identify
as many
differencesin
as our
The• tiny
amount
of variation
possible.
genes
We share half our genes with bananas
and 99% with the chimpanzee
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Slide 15
One fertilised cell to an
organism!
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Slide 16
Development of an egg
What will happen to the weight of a fertilised
bird's egg from time of laying to just before
the chick hatches?
• It gets lighter
6%
• It gets heavier
54%
• It stays much the same 35%
(% are for a survey of post GCSE students – see notes)
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Slide 17
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Slide 18
Genes
• What are your genes?
• Do bacteria have genes?
• Is the genetic information in the sex cells
the same as in other cells?
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Slide 19
Let’s look at cells …
• Several types
• 75 billion in a human
being
• Capable of carrying
out many different
functions e.g. …
– Protection
– Movement
– Excretion
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Slide 20
Importance of Proteins
Click on the one statement you most agree with about why
proteins are so important to living things.
a. They are a nutritious food
8%
b. They are the enzymes in our bodies which enable our cells
to work.
37%
c. When combined with oxygen, lots of energy is given off
6%
d. Protein provides the structural material in all living things
45%
(% are for a survey of post GCSE students – see notes)
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Slide 21
Material of Inheritance …
• What are the requirements of hereditary
material?
– Store information
– Permanence
– Ability to change (mutate)
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Slide 22
Unique function of DNA
• Stores information for protein synthesis
• Makes copies of itself ~ self replication
• Able to change/vary/mutate
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Slide 23
DNA
• Deoxyribonucleic Acid
• Molecular language ~ 4 different
letters
• Codon – three letter word – most
code for an amino acid
• GENE ~ sentence of many words
(amino acids) which enables it to
build PROTEINS
• Proteins are enzymes that enable
reactions to take place in cells
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Slide 24
… base, nucleotide, gene,
chromosome
The following terms all relate to the DNA
molecule. List them in relation to their size,
starting with the smallest
a
gene
b nucleotide
http://en.wikipedia.org/wiki/Nucleotide
c
chromosome
d bases
(4% of the BEd Students got it right)
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Slide 25
DNA
Click on the four sentences about human DNA that are
true.
a. It carries the code to make proteins.
50%
b. It can pass from one generation to the next.
83%
c. It can make copies of itself.
68%
d. It is a single stranded molecule.
26%
e. It is made of protein.
51%
f. It is identical in almost every cell of our body. 66%
(% are for a survey of post GCSE students – see notes)
Protein Synthesis
• A simulation …
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Slide 27
Link to HOME Quiz
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Slide 28
Variation from mutation
Which two of the following processes leads to
'variation' in the offspring:
a. Cell cloning.
4%
b. Gamete formation.
34%
c. Mitosis (normal cell division). 51%
d. Meiosis (sex cell formation) 55%
(% are for a survey of post GCSE students – see notes)
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Slide 29
Tracing your ancestry
A mutation of which of the following could be
inherited from both your parents?
a. Messenger RNA
20
b. Nuclear DNA
29
c. Ribosomal RNA
13
d. Mitochondrial DNA
35
(% are for a survey of post GCSE students – see notes)
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Slide 30
Artificial Selection
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Slide 31
Manipulation of genes …
• Genotype
• Phenotype &
selective breeding
• Manipulation of
genes
• Biotechnology
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Slide 32
How genes work …
• Inheritance
• Mutations
• Stem cells
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Slide 33
Genetic Engineering
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Slide 34
What do we need to do to
genetically engineer something?
• Location of genes
• Transfer of genes
• Isolation of genes
• Removal of genes
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• Cultivation of
genes
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Slide 35
Where do we go from here …?
• Dolly ~ cloned from a mature cell by
nuclear transfer
• Polly ~ cloned from an embryo cell, but
contains a human gene which produces the
human protein in the sheep’s milk
• Why are they scientifically significant?
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Slide 36
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Slide 37
What are the issues … ?
• Monsanto monopoly
• 1998 Government moratorium on the
growth of GM crops
• Media hype and scare mongering
• Human cloning & designer babies
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Slide 38
So what do you think?
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Slide 39
So what do you really think?
• Should scientist be
• Should scientists be
allowed to alter
allowed to alter
animal genes:
Human genes:
– For medical
– For medical
reasons?
reasons?
– For healthier or
– For commercial
more efficient
reasons?
food production?
– For commercial
reasons?
Slide 40
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Recap …
• What do genes do?
• Where do we find genes?
• What makes DNA so good as hereditary
material?
• What information does DNA store?
• How does it store it?
• What happens next …
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Slide 41
Protein (enzyme) Synthesis
• Key points:
– Copy DNA
– Messenger RNA copy to site of synthesis
– Collect (Transfer RNA) selection of amino
acids and arrange amino acids in correct
sequence
– Builds a polypeptide chain (= protein)
– Several produced at one time
– Allows chemical reactions to take place in cell.
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Slide 42
Gene Expression
• Switching genes on and off …
• Stem cells and mature differentiated cells
• Growth = cell division and cell
differentiation
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Slide 43
Gene Therapy
• Treatment of diseases by the introduction of
powders containing working copies of the
defective gene ~ saturation approach
• Cystic Fibrosis
• Problems:
– Disease is rare in the population
– Expensive to treat
– Research pressure into common ailments
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Slide 44
Genetic Engineering
• Transfer of genes from one species to
another.
• How is it done?
• Gene Splicing
• Limitations ~ can only add genes
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Slide 45
• http://www.food.gov.uk/gmdebate/aboutgm/?view=GM%20Microsite
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Slide 46
Countries which are already growing some GM crops
Concept map
•
•
•
•
•
•
•
Compare building a house and cell?
DNA, genes and enzymes
Mitosis (cell division) and meiosis (sex)
Phenotype and genotype – recessive genes
Growth = cell division & differentiation
Mutation - natural and artificial
GM debate and other issues
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Slide 47
Learning log
• Look at the questions – where were your
conceptual misunderstandings?
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Slide 48