DNA and Genetics

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DNA and Genetics
Dr André van Wyk UFS
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• Somatic cells
• Cells of the Soma Body cells
• Complete number of chromosomes 2n
• Diploid

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2n
2n
2n
Growth 2n 2n Mitosis
2n

• Somatic cells
• Cells of the Soma Body cells
• Complete number of chromosomes
• Diploid

Mitosis 2n 2n or n n this correct?
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n
n
mitosis
n
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n
2n
2n
2n n Meiosis
Sex cells Half of the chromosome number n
haploid cells Reduction of the chromosome number
a must for the survival of the species
2n
n n 2n Haploid Haploid Diploid
FERTILISATION
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The importance of Meiosis

• The process of meiosis reduces the number of
  
• chromosomes by half.
• Meiosis is the process through which somatic
  cells (2n)
• are changed into sex cells (n).
• Meiosis ensures that the number of chromosomes
  in
• the species stays the same over generations
• Meiosis is important to introduce genetic
  variation.

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http//www.cellsalive.com/cell_cycle.htm
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http//www.cellsalive.com/mitosis.htm
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Http//genetics.gsk.com/overview.htm
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DNA Position in the cell
DNA double helix
Nucleus
Chromosomes
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In the nucleus of almost every cell in your body
is the collection of DNA needed to make you.
DNA in the nucleus is grouped into 23 sets
(pairs) of chromosomes that are called your
"genome."

• In each chromosome, the DNA is grouped into
• "genes."
• Your genome contains about 35,000 genes.

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Instructions to make your whole body and keep it
working is contained in DNA

• Instructions is called genetic code
• The DNA in your genes tells the cell which
• amino acids (protein building blocks) must
• combine to make a protein. It also gives
• instructions in which sequence the amino
• acids must combine.
• Thus, DNA provides the blueprint of all life in
• a living body.
• Let us investigate how that this happens.

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DNA STRUCTURE

• DNA molecule double helix (ladder)
• String of repeating molecules units called
  nucleotides
• Each nucleotide consist out of
• - Deoxyribose sugar
• - One phosphate group
• - One nitrogen containing base (A,G,C and T)
• Adenine and Guanine purine bases
• Thymine and Cytosine pyrimidine bases

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Remember
Did you know The total length of DNA in mammal
cells is 2 metres in your body 10 billion km
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Structure of DNA
Phosphate
A
T
C
G
Deoxyribose Sugar
Britannica video
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It's hard to believe that an alphabet with only
four letters can make something as wonderful and
complex as a person
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DNA Replication

• With cell division -chromosome split in two
  (mitoses and meiosis )
• DNA must divide
• DNA must make exact copies of itself
• DNA molecule unzip
• New bases attached themselves in correct place of
  each strand
• Each strand becomes a double helix
• Sometimes mistakes happens mutation
• Mutations is important in evolution

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DNA Replication
Unzip into two single strands
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DNA replication continue
New bases attached themselves in the correct
place of each strand
Free nucleotides in nucleoplasm
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Two identical strands are formed Each strand now
becomes a double helix.
Strand 1
Strand 2
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Activity 1

• DNA structure and DNA replication
• Group work.
• Instructions
• - Use the package marked DNA and
• place the pieces together in order to
• Know the structure of DNA
• Use the pieces and demonstrate the DNA
  replication process.

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Significance of DNA replication

• Important for growth, reproduction
• Mutations can cause variation
• The main enzyme that catalyze the process is DNA
  polymerases
• Forms building block for amino acids that forms
  proteins
• Three bases provides more than the 20
  combinations needed to code amino acids (p23)
• The sequence of the three bases is called a codon.

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Activity 2Extraction of DNA (LO1)

• Instructions Use Worksheet 1
• Step 1
• Place ½ teaspoon of ground wheat in a spice jar.
  Add 10 teaspoons of tap water to the ground wheat
  and mix non-stop with a wooden stick for 3
  minutes
• Step 2
• Add ¼ teaspoon of dishwashing liquid to the cells
  that have been suspended in water in step 1. Mix
  gently with a wooden stick every ½ minutes for 5
  minutes.

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• Step 3
• Remove all foam that may have formed on top of
  the mixture with a paper towel.
• Step 4
• Tilt the jar and slowly add an estimated equal
  volume of methylated spirit to the mixture and
  carefully pouring it down the side of the jar.
• Step 5
• Use the wooden sticks to fish these white slimy
  threads out of the spice jar and transfer it to
  a 10ml pill vial.

Rubric
You have extracted DNA
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Assessment of DNA

• Draw and label a diagram of DNA (LO1AS2)
• (manipulate data)
• Make a model of DNA (LO1AS3)
• ( Communicate data/findings)
• Extraction of DNA out of wheat (LO1AS2)
• http//rubistar.4teachers.org (example rubric 1)

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Questions on the DNA Molecule
1
G
2
3
T
4
5

• Identify the above molecule.
• Give labels for parts numbered 1to 5
• 3. Describe how the above molecule
• replicates itself.
• Why is it of significance that this molecule can
  
• replicate itself?

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Bacterial DNA - Manufacturing of insulin

• Diabetics need insulin to live
• Diabetes use insulin from pigs and cattle. This
  is not the same as human insulin and sometimes
  produces side effects. With genetic engineering,
  bacteria are used to produce some human insulin

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1. A string of DNA is taken from a bacterium
6. The insulin is collected and purified ready
for use

• The bacteria
• reproduce, making clones of themselves

• A piece is cut out using enzymes
• as chemical scissors

3. A cell is taken from a human pancreas. The
gene for insulin is cut from the chromosome
4. The insulin gene is put into the string of
bacteria DNA
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Structure of RNA

• Single strand
• Sugar is ribose
• Four nitrogen bases
• Adenine and Uracil
• Guanine and Cytosine

Assessment Make a stick drawing of RNA
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AssessmentTabulate the Differences between DNA
and RNA
DNA RNA
Double strand Single strand
Deoxyribose sugar Ribose sugar
Thymine and Adenine Thymine and Uracil
Nucleoplasm Nucleoplasm and cytoplasm
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Three types of RNA and their functions
1. Messenger RNA (mRNA) 2. Transfer RNA (tRNA) 3.
Ribosomal RNA (rRNA)

• 1. Messenger RNA (mRNA) which acts as a template
  for protein synthesis and has the same sequence
  of bases as the DNA strand that has the gene
  sequence.

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2. Transfer RNA (tRNA), one for each triplet
codon that codes for a pecific amino-acid (the
building blocks of proteins). tRNA molecules are
covalently attached to the corresponding
amino-acid at one end, and at the other end they
have a triplet sequence (called the anti-codon)
that is complementary to the triplet codon on the
mRNA.
3. Ribosomal RNA (rRNA) which make up an
integral part of the ribosome, the protein
synthesis machinery in the cell.
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RNA Transcription

• DNA is the template
• DNA manufactures mRNA in nucleus
• Transported out from the DNA of nucleus
• into the cytoplasm
• Transcription similar to DNA replication

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mRNA structure
RNA bases pairing
TRANSCRIPTION
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Crystal structure of tRNA molecules.
The single-stranded chain is folded in a
'clover-leaf
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The process of translation and protein synthesis
TRANSLATION
TRANSCRIPTION
mRNA moves to ribosome r RNA
Amino acids linked up to form protein molecule
tRNA carries amino acid to ribosome
DNA unzip to expose a gene
mRNA copies the gene
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Protein synthesis in the cell
Free amino acids
tRNA brings amino acid to ribosome
Ribosome incorporating amino acid in protein
chain
mRNA being translated
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Assessment of RNA (LO2)

• Describe the role of DNA and RNA in the following
  
• 1.1 Formation of mRNA by transcription
• 1.2 Movement of mRNA from the nucleus to
  cytoplasm
• 1.3 Translation of mRNA (codon) to form
  protein using tRNA (anticodon)

1. Determine the sequence of bases in mRNA from DNA
   molecule.

GTA ATG TGG TTT
3. Give the mRNA sequence that matched the
anticodons of the tRNA
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Activity 2

• Transcription and translation.
• Group work.
• Instructions
• - Use the package marked Protein synthesis
  and imitate the processes of transcription and
  translation with the pieces in the pack.

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Protein synthesis (assessment)
1.
2
3
4
6
5
7

1. Give labels for number 1 to 7
2. Describe the processes that occur at numbers
   2,3,5

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Part 2 Chromosomes, meiosis and sex cells
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Mitoses
Mitoses

• Revision
• Group work
• Using the clay provided and build a model of the
  process of mitoses. The clay must represent the
  chromosomes.
• Cut pieces of paper to represents the cell
  structures/stages.
• Especially pay attention to the structure of the
  chromosomes.

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Meiosis
First meiotic division
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Meiosis I
Interphase Duplication of each chromosome
Prophase I Paring of homologous Chromosomes -
chiasmata crossing over
Metaphase I Organisation of two tetrads in the
equatorial plane
Anaphase I Separation of homologous chromosomes
Completion of Meiotic division Two daughter
cells each with two dyads
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Crossing over
Significance of crossing over Genetic material
is exchanged cause variation
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Second meiotic division
Metaphase II
Anaphase II
Four haploid cells, each with two chromosomes
known as reproductive cells. (ovum or sperm)
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Second meiotic division
Metaphase II Each daughter cell from the
previous division has two dyads
Anaphase IIMitotic separation of chromatids of
each chromosome
Completion of second meiotic division four
haploid cells, each with two chromosomes known as
reproductive cells. (ovum or sperm)
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Sex cells
Sperm and Ovum
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Activity 3 (LO1)
Each group use the clay and build the process of
meiosis
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The importance of Meiosis

• The process of meiosis reduces the number of
• chromosomes by half
• One cell divides into four cells with each the
  haploid (n)
• number of chromosomes
• The first meiotic division reduces the number of
  chromosomes
• The second meiotic division is actually mitosis
  which
• increases the number of cells
• Meiosis is the process through which gametes are
  prepared for
• fertilisation.
• Meiosis ensures that the number of chromosomes
  in the species stays the same over
  generations
• Meiosis is important to introduce genetic
  variation.

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Assessment

• Use diagrams to identify the different phases
• Use one word to describe the paired chromosomes
• What would the chromosome number in each cell be
  at the end of meiosis?
• Describe the importance of crossing over
• Describe the importance of meiosis
• Explain why the four cells at the end of meiosis
  is not identical

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Chromosomes
(p43)
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Chromosomes
Homologous pair
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Karyogram and karyotype

• Diagram of arrangement of chromosomes
• Chromosomes are paired according to size
• Arrangement is called karyogram
• Set of chromosomes is called a karyotype
• Human karyogram shows the 23 pairs of chromosomes
• Chromosome set 23 indicate the sex of the
  individual

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Karyogram
Normal Male
Normal Female
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Down syndrome

• Down's syndrome is caused by the presence of
  three copies of the 21st chromosome.
• This chromosomal defect is known as Trisomy-21.
• Down's syndrome almost always results in mental
  retardation, though the severity of the
  retardation varies.

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Characteristics of Down syndrome
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Assessment

• Identify on the karyogram if the individual is
  female or male?
• Does this individual has an abnormal number of
  chromosomes?
• Name the genetic disease that the individual
  suffer from.

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Assessment (LO1)
Use the table below and draw a graph to show the
relation of maternal age to Down syndrome
Relation of Maternal Age to Down Syndrome Relation of Maternal Age to Down Syndrome
Mothers age (Years) Risk of Occurrence
20 - 29 1 in 2 000
30 - 34 1 in 750
40 - 44 1 in 100
45 - 49 1 in 40
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Hutchinson-Gilford progeria syndrome
This is a rare condition of premature ageing that
begins in childhood or early adult life and leads
to death within a few years
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Albinism
A person or animal whose melanocytes in the skin
do not contain any melanin (pigment) is called an
albino. This results in a characteristic
appearance with snow-white hair, pink or blue
eyes, and pinkish-white skin that is very
sensitive to sunlight
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?Carrier A a
?Carrier A a
Albinism is inherited
½ a
½ A
½ a
½ A
¼ aa
¼ aA
¼ AA
¼ Aa
carriers ½
albino
normal phenotype ¾
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Part 3Genetics
Genetics is the scientific study of how physical,
biochemical, and behavioural traits are
transmitted from parents to their offspring
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Terminology

• Genes - small portions of DNA and protein
• Alleles - genes controlling same characteristic
  example eye colour
• Haploid half the number of chromosomes
• Diploid full set of chromosomes
• Somatic/body cells (containing genes in pairs)
• Sex cells/gametes (containing unpaired genes)
• Homozygous has similar genes for specific
  characteristic
• Heterozygous- unlike genes for a specific
  characteristic
• Human genome - the entire genetic blueprint of a
  human beings

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Father of Genetics
Father of Genetics
Gregor Mendel developed the principles of
heredity while studying seven pairs of inherited
characteristics in pea plants. Although the
significance of his work was not recognized
during his lifetime, it has become the basis for
the present-day field of genetics.
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Mendel Monohybrid crosses
Parents
YY
yy
P1
Generation 1
Smooth or dented seeds
F1
Yy
Yy
x
Generation 2
Green or yellow seeds
F2
YY
Yy
yy
Yy
Green or yellow pods
Punnet square
White or purple flowers
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Father of Genetics
Genetics Assessment
Question Determines the Genotype and the
Phenotype, by means of a Punnet diagramme, the F1
and F2 generations when a homozygote yellow
coloured plant (Dominant - Y) is crossed with a
white one Resssive - y).
male female P1 zygotes YY x yy Meiosis Gamet
es Y Y y y Fertilisation
Female Male Male Male
Female Punnet Y Y
Female y Yy Yy
Female y Yy Yy
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F1 Genotype Heterozygous 100 Yy Phenotype
100 Yellow
F2 generation male female
female male male
female Punnet Y y
female Y YY Yy
female y Yy yy
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F2 Genotype Homozygous 25 YY
Heterozygous 50 Yy Homozygous 25
yy Phenotype 75 Yellow 25 White
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Assessment (LO1)
The following histograms represent the percentage
of various genotypes that occur in the F1
generation in several monohybrid crosses. For
each, predict the genotypes of the parents (P1).
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Inheritance and variation
Father
Mother
Off spring
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Human traits
Recessive traits
Dominant traits
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Inherited traits



Bent little finger
Dimples
Hitch-hikers thumb
Mid-digit hair

Widows peak
Rolled tongue
Earlobes Free and Attached




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Activity 4

• Complete the tabel on human traits in your group
• Study the project handed out to you
• Discuss in your group how this project covers
  LO1, LO2 and LO3 (SAG)
• How can this project help you with assessment.

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Sex determination
Is it a boy or a girl?
XX girl XY boy
Hallo here am I
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Blood types

• The method of classifying human blood on the
  basis of the inherited properties of red blood
  cells (erythrocytes) as determined by their
  possession or lack of the so-called antigens A
  and B.
• Thus, persons may have type A, type B, type O, or
  type AB blood. The A, B, and O blood groups were
  first identified by the Austrian immunologist
  Karl Landsteiner in 1901.

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Blood multiple alleles

• Four phenotypes A,B,AB and O
• Are determined by presence of two out of three
  possible alleles namely A,B and O

Phenotype Possible genotype
A AA, AO
B BB, BO
AB AB
O OO
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Assessment
In the TV series Days of Our Lives, two good
friends, namely, Hope and Lexie each gave birth
to a son. These babies were deliberately switched
in the hospital. From the following blood types,
determine which baby belongs to which
parents Baby 1 Type O Baby 2 Type
A Hope Type B Hopes Husband Type
AB Lexie Type B Lexies Husband Type B
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Human Pedigrees (p73)
Shows the line of ancestors the line of
ancestors of an individual animal or person.
Haemophilia
Affected male
Female carrier

• Used to trace diseases like Haemophilia, Muscular
  dystrophy, Cystic fibrosis

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Assessment of LO 3 Ethical dilemmas

• Discuss whether insurance companies should have
  the right to refuse cover for a child if prenatal
  tests results indicate that the child will suffer
  a severe genetic disorder?
• Using the technology available today, suppose
  that you could learn with certainty, that by the
  age of 60 you would suffer from a genetic
  disease. Would you like to know?
• Makae and Sipho want to marry. Show, in a
  family tree form, all the possible genotypes of a
  child they intend to have. (Gg xGg) gg cystic
  fibrosis.

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Genetic counseling

• Genetic counseling, a process where information
  and advice is given about inherited disorders.
  Often it is given to a couple who are planning to
  have a child but who suspect that there is a
  greater than normal risk of the child being
  affected by a genetic disorder

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Genetic modification
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• In genetic modification, scientists use
  restriction enzymes to isolate a segment of DNA
  that contains a particular gene of interest (1).
• In this instance, it is a human gene. A plasmid
  extracted from its bacteria and treated with the
  same restriction enzyme can hybridize with this
  fragments sticky ends of complementary DNA
  (2).
• The hybrid plasmid is reincorporated into the
  bacterial cell, where it replicates as part of
  the cells DNA (3).
• A large number of daughter cells can be cultured
  and studied, and their gene products may be
  extracted for further use (4).

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Examples of Genetic modification
A scorpion venom gene, engineered into a virus,
is used as a spray to kill insects
Poultry with modified genes are resistant to
salmonella food poisoning bacteria, and lay
bigger eggs more often
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Salmon eggs have genes inserted into them which
make them grow ten times faster than normal
Genetically modified pigs grow faster, have less
fat, and produced cholesterol-free meat
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Assessment (LO3)
These tomatoes have been given genes from fish
which make them frost resistant and fresh for
longer. Would you eat them?
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Do a survey on the following two questions Do
people know what genetic modified foods
are? Will they eat genetically modified food?

• Design a questionnaire
• Use two groups of people
• Group 1 15 - 30
• Group 2 30 50 years old
• Draw bar graph on the results obtained in the two
  questions plot both sets of data on the same
  graph
• Draw a Pie chart with the results
• Write down a hypothesis for your investigation
• Write down your independent and dependant factors
• Write down your conclusion for this investigation

LO1 assessment
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Extinct zebra
Etienne
Tracy
Interbreeding
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The story of the extinct zebra

• Baby of the thought extinct zebra is in the Cape
  museum since 1858 stuffed by taxidermist
• Later Mr Rau curator of the museum decided to
  send it to be re-stuffed
• They discovered some muscle tissue left on the
  inside of the skin
• DNA testing show this zebra is related to Equus
  burchelli (still alive today)
• Special inbreeding programme was started and
  today we have back the original species