Download Inheritance-Act-1-3

Genetics & Inheritance
• SCN 4-14c: I can use my understanding of how
characteristics are inherited to solve simple genetics
problems and relate this to my understanding of
DNA, genes and chromosomes.
Activity 1
1. I will be able to define the terms
fertilisation, species, variation and
chromosome and gene.
2. I will be able to relate my
understanding of the process of
fertilisation to the passing on of
chromosomes.
GLOW Science Videos Genetics
Watch Inheritance 1
Definition
“If organisms belong to the same species
they can interbreed to produce fertile
offspring.”
Horse
Donkey
Horses and donkeys can
mate to produce a mule –
but mules are not fertile
so horses and donkeys
are separate species.
This is a HYBRID.
Tuesday, May 23, 2017
Mule
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The Liger
• In the wild tigers and lions are enemies
likely to kill each other.
• Most lions are in Africa and most tigers
are in Asia.
• These types of cross occur in captivity
A Beefalo
23/05/2017
Variation
“Variation” is the name given to differences between
individuals of the SAME species.
Variation is due to GENETIC or ENVIRONMENTAL causes.
For example, consider identical twins:
1) Ways in which Patty and
Selma are the same (caused
by genes):
Selma
Bouvier
2) Ways in which Patty and
Selma are different (caused
by environment):
Patty
Bouvier
Variation
Human examples – height, pulse, blood
type, hand span, etc..
This variation within a species can either be
CONTINUOUS or DISCONTINUOUS.
•
•
•
•
If the variation in a characteristic…
can not be put into distinct groups
has a continuous range of values
it shows a wide range of values between
the maximum and minimum
measurements
• = CONTINUOUS VARIATION.
Continuous Variation
Continuous Variation
e.g. weight
Continuous Variation
e.g. Height
• If the variation in a characteristic….
• -allows individuals to be placed into
distinct groups
• -does not show a range of values
• -has clear cut differences between
individuals
• = DISCONTINUOUS VARIATION.
Dicontinuous Variation
Discontinuous Variation
e.g. ear lobes
Attached lobe
Unattached lobe
23/05/2017
Where is this information stored?
Section of a chromosome:
Genes for
blood group:
Genes for
eye colour
Genes for
hair colour
Different species have different
numbers of chromosomes. Humans
have 46 (23 pairs) in every cell.
Variation in Humans
• Human species have 23 pairs of
chromosomes in every cell except the
gametes.
• There is an enormously large number of
combinations of chromosomes to form
zygotes because fertilisation is random.
• This means that all zygotes are
different. (It depends on which gamete
does the fertilising!)
Tuesday, May 23, 2017
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Fertilisation
• All of our cells contain one set of chromosomes from
the mother and one set of chromosomes from the
father – this make the 2n!
• This means there is one set of genes from the mother
and one set of genes from the father.
Karyogram –shows the Chromosomes found in a male and
female human. What do you notice about them?
Activity 2
I can define the term allele and give
examples of alleles for different
characteristics.
Alleles
• Genes control the
characteristics of an
organism, e.g. flower colour
in peas.
• Alleles are different forms of
the same gene.
Flickr.com
chestofbooks.com
– An allele is a different form of
that gene, e.g. red flower or
white flower.
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Examples of alleles
Organism
Gene
Different Alleles
Pea plant
Height
Tall or dwarf
Humans
Blood type
A or B or O
Fruit fly
Wing type
Normal or vestigial
Maize
Seed colour
Purple or yellow
Labrador Dog
Coat colour
Golden or black
Budgerigar
Feather colour
Blue or green
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E.g. Pea Flower Colour
E.g. Human Characteristics
rothamsted.ac.uk
Think & Discuss:
• So for each of your characteristics there are 2 genes
controlling it – one from your mother and one from
your father.
• If these lists show the genes in a sperm and in an egg,
what genes would you expect to find in the new
human?
GENES IN EGG
Brown hair gene
Tall gene
Tongue rolling gene
Blue eye colour
GENES IN SPERM
Blond hair gene
Short gene
Non-tongue rolling gene
Blue eye colour
Answer:
They would have all of them!
GENES IN EGG
Brown hair gene
Tall gene
Tongue rolling gene
Blue eye colour
GENES IN SPERM
Blond hair gene
Short gene
Non-tongue rolling gene
Blue eye colour
So what would they look like?
Activity 3
• I can define the terms genotype,
phenotype, dominant and recessive.
Genotype V Phenotype
• Genotype is the sum of all the genes you
possess (represented by letters).
• Phenotype is the actual physical
characteristics you have because of
those genes (represented in words).
• Not all the genes in your genotype can
or will show up in your phenotype – why
not?
Genotype and Phenotype
seniorapbiologyreview.wikispaces.com
Dominant V Recessive
GENES IN EGG
Brown hair gene
Tall gene
Tongue rolling gene
Blue eye colour
GENES IN SPERM
Blond hair gene
Short gene
Non-tongue rolling gene
Blue eye colour
• The gene in each pair which is dominant always shows
through. Imagine the following scenario:
• The tall gene is dominant to the short gene so the
person would be?
• Tongue rolling is dominant to non-tongue rolling so the
person would be?
• The persons eye colour would be?
• A dominant allele will always show up
in the appearance of an organism.
• A recessive allele will only show up if
it is paired with another recessive
allele.
• When describing an allele, for
convenience, we usually give it a symbol,
generally the first letter of the
dominant allele.
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dj003.k12.sd.us
• If it is dominant it gets the capital letter
and if it is recessive it gets the lower case
of the same letter.
• E.g. in pea plants tall is dominant over dwarf,
and so the tall allele is given the letter T, and
the dwarf allele the letter t.
• The genotype of the organism is the alleles
it carries for that particular
T
characteristic.
t
Complete the
“Symbols for Alleles” sheet
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• TT is a genotype and the plant phenotype will be
tall.
• Tt is a genotype and the plant phenotype will be tall,
because the T is dominant over the t. Recessive
genes have no effect when paired with dominant
genes.
• tt is a genotype and the plant phenotype will be
dwarf.
• The outward appearance of one of its characteristics
i.e.What the plant actually looks like (how the genes
are expressed) is called its phenotype.
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abagond.wordpress.com
GLOW Science Videos Genetics
Watch Inheritance 2
Definition Board
• Work in a pair and try to write a definition for each
word on a sticky note:
1. Gene
2. Chromosome
3. Genotype
4. Phenotype
5. Dominant
6. Recessive
7. Allele
8. Continuous
9. Discontinuous
GLOW Science Videos Genetics
You could go back to the
Inheritance 1 and 2 Videos and
try the Quizzes!