- One parent is heterozygous dominant in earlobe
- The other parent is homozygous recessive in earlobe
- Crossing a heterozygous dominant organism with a homozygous recessive organism causes their offspring to be homozygous recessive of 50% probability
- Therefore, the offspring will have a 50% probability to be homozygous recessive

- An attached earlobe is a recessive trait in human
- If both recessive genes are present , then the recessive trait will be visible / expressed
- Hence, to have an attached earlobe requires the human to have both recessive genes

- To have an attached earlobe requires the human to have both recessive genes
- A homozygous recessive organism contains only recessive genes
- So, to have an attached earlobe requires the human to be homozygous recessive

- The offspring will have a 50% probability to be homozygous recessive
- To have an attached earlobe requires the human to be homozygous recessive
- So, the offspring will have a 50% probability to have an attached earlobe

So, the offspring will have a 50% probability to have an attached earlobe
In humans, the gene for a free earlobe [E] is dominant over the gene for an attached earlobe [e]. If one parent has a free earlobe [ Ee ] and the other parent has an attached earlobe ( ee ), what is the probability that their offspring will have an attached earlobe?
- One parent is heterozygous dominant in earlobe 
- The other parent is homozygous recessive in earlobe 
- An attached earlobe is a recessive trait in human 
- A homozygous recessive organism contains only recessive genes 
- Crossing a heterozygous dominant organism with a homozygous recessive organism causes their offspring to be homozygous recessive of 50% probability 
- If both recessive genes are present , then the recessive trait will be visible / expressed