GENETICS…
Aim for the day:
Understand that genes have different versions or ‘flavours’ called alleles.
Understand that our genotype is the genes or alleles that a person has, and a phenotype is the set of observable characterisitcs of an individual resulting from the interaction of their genotype and environment
GENETICS…
Aim for the day:
Genes
Alleles
Genotype
Phenotype
GENETICS…
DAD
Half of our chromosomes come from our
and the other half comes from
MUM
WE’RE A MIXTURE!
WE’RE A MIXTURE!
WE’RE A MIXTURE!
WE’RE GOING ON A MISSION
INSIDE A CELL
ON MY NOSE…
*Note: My skin cells are not actually pink.
This is a microscope slide and it’s been STAINED so you can see the cells...
Can you see the darker nucleus in each cell?
There it is ☺
Recognise these??
Humans have 23 pairs of
Chromosomes.
What are we dealing with?
One Chromosome
A homologous pair
of chromosomes
A homologous pair
of chromosomes
Homologous chromosomes are a pair of chromosomes that have the SAME genes, each derived from one parent.
Chromosomes are made up
of LOTS of different genes
Gene for
eye colour
Chromosomes are made up
of LOTS of different genes
Gene for
hair colour
are alternative
forms of genes that are
located at specific
locations on chromosomes
ALLELES
For example…
Allele for
blue eyes
Allele for
brown eyes
B
b
b
B
B
b
b
B
The blue and the brown
are different ALLELES
of the same GENE
What is a homologous pair or chromosomes?
If alleles are located on a specific site on a chromosome, and you have one of each chromosome from each parent... How many alleles do YOU have for a gene?
b
B
2 alleles
What is a homologous pair or chromosomes?
If alleles are located on a specific site on a chromosome, and you have one of each chromosome from each parent... How many alleles do YOU have for a gene?
b
B
2 alleles
Where are genes located?
Where are genes located?
What is a homologous pair or chromosomes?
What is an allele?
If alleles are located on a specific site on a chromosome, and you have one of each chromosome from each parent... How many alleles do YOU have for a gene?
b
B
2 alleles
Let’s look at DOMINANT and RECESSIVE alleles
Now we know that alleles are different versions of the same genes...
What does dominant mean
in everyday language??
Having the most influence or control.
This guy is dominant!
Dominant
Watch this (slightly odd) video about dominant and recessive alleles
If there is even ONE copy
of the dominant allele
then it will show up
In the phenotype…
b
B
Dominant!
Combinations of
alleles
B
B
b
b
Homozygous
Homozygous
Homo means SAME
Homozygous
RECESSIVE
B
B
b
b
Identical copies of the dominant allele
Identical copies of the recessive allele
Homozygous
DOMINANT
Genotype and
phenotype
BB and bb are the
GENES. They are the
GENOTYPE.
Brown and blue eyes are the
PHENOTYPE.
The phenotype is what you can
actually see when the genes are expressed.
What is a genotype? Can you give an example?
What is a genotype? Can you give an example?
Do you think R or r is dominant?
What is a genotype? Can you give an example?
Do you think R or r is dominant?
Which is homozygous dominant? RR, Rr, or rr?
What is a genotype? Can you give an example?
Do you think R or r is dominant?
Which is homozygous dominant? RR, Rr, or rr?
Which is homozygous recessive? RR, Rr, or rr?
What is a genotype? Can you give an example?
Do you think R or r is dominant?
Which is homozygous dominant? RR, Rr, or rr?
Which is homozygous recessive? RR, Rr, or rr?
What is a phenotype?
What is a genotype? Can you give an example?
Do you think R or r is dominant?
Which is homozygous dominant? RR, Rr, or rr?
Which is homozygous recessive? RR, Rr, or rr?
What is a phenotype?
Give an example of a phenotype for someone in your group.
If RR is homozygous dominant
and
rr is homozygous recessive...
Which genotype is heterozygous?
b
B
Hetero means DIFFERENT
Heterozygous
b
B
Heterozygous
In this case, the allele that causes BROWN eyes is dominant over the one for BLUE.
So, if someone has the genotype Bb, their phenotype will still be Brown.
b
B
Test your knowledge:
Where can you find a gene?
Test your knowledge:
Where can you find a gene?
What is a gene?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Where can you find alleles?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Where can you find alleles?
The difference between dominant and recessive alleles?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Where can you find alleles?
The difference between dominant and recessive alleles?
What is homozygous dominant?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Where can you find alleles?
The difference between dominant and recessive alleles?
What is homozygous dominant?
What is homozygous recessive?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Where can you find alleles?
The difference between dominant and recessive alleles?
What is homozygous dominant?
What is homozygous recessive?
What is heterozygous?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Where can you find alleles?
The difference between dominant and recessive alleles?
What is homozygous dominant?
What is homozygous recessive?
What is heterozygous?
What is a genotype?
Test your knowledge:
Where can you find a gene?
What is a gene?
What is a gene for?
What is an allele?
Where can you find alleles?
The difference between dominant and recessive alleles?
What is homozygous dominant?
What is homozygous recessive?
What is heterozygous?
What is a genotype?
What is a phenotype?
Alleles in action…
You have genes for immunity.
There are different alleles for each immunity gene.
You want to find a partner with DIFFERENT alleles for immunity, so that your children have lots of different alleles.
If your children inherit different alleles from you and your partner, they will have high immunity!
If your children inherit the same alleles from you and your partner, they will not be as immune.
We have evolved to use our sense of smell to pick a partner that will help us have the healthiest children!
Help me find out
what my genotype is!
My Mum has brown eyes.
Her genotype could be
____ OR ____
My Dad has blue eyes.
His genotype must be ____
BB or Bb?
bb
bb
My brother has blue eyes
Brown eyes
My phenotype is
My genotype is ??
Brown eyes
b
B
My phenotype is
My genotype is
All of these boys have dark hair.
B = Brown
b = Blonde
Write the two genotypes they could possibly all have.
Regular thumbs are dominant = R
Hitchhikers thumbs are recessive = r
Write the genotype for people who have hitchhikers thumbs.
?
What is the ? pointing at?
75% of the world has detached earlobes.
25% of the world has attached earlobes.
Which is the dominant allele for earlobes?
Write a genotype for attached earlobes (the recessive trait):