Traits and Inheritance Lesson 5

Students will be able to observe there own phenotype to a range of traits and determine potential genotypes.

Success Criteria

Students will be able to distinguish between genotype and phenotype and understand the concept of dominance and reccessive.

​Learning Intention

​Recap - Chromosomes

Last lesson we learnt that humans have 46 chromosomes and that we inherit 23 from mum and 23 from dad.

This is why we share some traits with our parents, but also why we are different from them.

Our parents DNA came from their parents and so on.

​Recap - Chromosomes Continued

Chromosomes is how the long DNA molecule is stored within the cell.

In Humans the DNA is stored in 46 segments (23 pairs) of chromosomes.

DNA is wrapped around proteins after being supercoiled.

​Recap - Genes

Genes are sections of DNA that code for protein.

Proteins allow our boides to function, but they also determine our traits / characteristics.

Therefore Genes determine our characteristics.

Introducing Alleles

We have 23 pairs of chromosomes.

Each pair of genes has the same genes in the same location, however because we inherited one from our dad and one from our mum, the code from each gene on each chromosome may be different.

An Allele is a version or a copy of the gene.

Dominant and Recessive

Some Alleles are Dominant and some are Recessive.

A dominant allele means you only need one copy to inherit the trait.

A recessive allele means you need two copies to inherit the trait.

​In this example:
A is the allele for brown eyes and it is dominant.

a is the allele for blue eyes and it is recessive.

Genotype and Phenotype

An Individuals Genotype is their genetic code.
An Individuals Phenotype is the trait that is expressed.

​Therefore, in the example earlier:
The genotype AA and Aa will result in the Brown eye phenotype.

The genotype aa will result in the blue eye phenotype.

Lets play Genetic Wheel!

1. Divide up into groups of 2
   

2. Each person will obtain 1x genetic wheel sheet 1x human trait sheet
   

3. We will plot toghether one by one each trait.
   

4. After you and your partner are done plotting, we will confer toghether as a class and see our similarities and differences.

   
   These traits are controlled by one gene. Many traits however are controlled by multiple genes

Laugh Dimples Trait

Dimples are indentations that occur near our mouths when we laugh or smile.

Record on your genetic wheel if you have this trait. (Do this by colouring in your corrresponding letter)

ll no dimples (homozygous recessive) L dimples (heterozygous or homozygous dominant)

Tongue Roll Trait

Can you roll your tongue?

Record on your genetic wheel if you have this trait. (Do this by colouring in your corrresponding letter)


tt can’t roll tongue into “U” shape (homozygous recessive)
T can roll tongue into “U” shape (heterozygous or homozygous dominant )

Note: In regards to tongue rolling weve now found that multiple genes contribute to this trait.

Crossing thumbs

Unconciously, when you cross your thumbs, what thumb is on top?

Record on your genetic wheel if you have this trait. (Do this by colouring in your corrresponding letter)

cc right thumb on top of clasped hands (homozygous recessive)
C left thumb on top of clasped hands (heterozygous or homozygous dominant )

Straight or Bent pinkes?

When you line your pinkies up, are they straight or bent?

Record on your genetic wheel if you have this trait. (Do this by colouring in your corrresponding letter)

pp pinkies are straight when pressed side by side (homozygous recessive)
P pinkies bend away from each other, toward the ring fingers, when pressed side by side (heterozygous or homozygous dominant)

Earlobe Trait

Are your earlobes attached or free?

Record on your genetic wheel if you have this trait. (Do this by colouring in your corrresponding letter)

ee attached ear lobe (homozygous recessive) E free ear lobe (heterozygous or homozygous dominant)

Widows Peak Trait

Do you have a widows peak?

Record on your genetic wheel if you have this trait. (Do this by colouring in your corrresponding letter)

ww no widow’s peak (homozygous recessive)
W has a widow’s peak (heterozygous or homozygous dominant)

​Bending thumbs trait

Bending thumb, also known as hitchikers thumb is a trait that causes the thumb to bend.

Record on your genetic wheel if you have this trait. (Do this by colouring in your corrresponding letter)

Bending thumbs (Hitch-hiker’s thumb) bb thumb bends at 90 degree angle (homozygous recessive) B thumb is straight (heterozygous or homozygous dominant)

​Lets now plot it as a class

Each person would have landed on a number on the genetic wheel.

One by one lets go around and see if anyone lands on the same number.

Key Points

In your genetic notebook please add the following points:

An Allele is a version or a copy of the gene.

Some Alleles are Dominant and some are Recessive.

A dominant allele means you only need one copy to inherit the trait.

A recessive allele means you need two copies to inherit the trait.

An Individuals Genotype is their genetic code.
An Individuals Phenotype is the trait that is expressed.