1. B2.7 Cell division and inheritance

2. B2.7 Cell division and inheritance
Characteristics are passed on from one generation to
the next in both plants and animals.
Simple genetic diagrams can be used to show this.
There are ethical considerations in treating genetic
disorders.

3. Key words
Cell
Nucleus
Chromosomes
DNA
Characteristics
Generation
Gene
Genetic diagrams
Inherited
Dominant
Recessive
Alleles
You are the result of two things...
and

4. Inside each cell is a nucleus.
Inside the nucleus are 46 chromosomes.
Each chromosome contains thousands of genes.
Chromosomes are made of a chemical called DNA.
largest
smallest

6. You have 46 chromosomes.
There are 23 pairs of chromosomes.
23 of your chromosomes come from your mother.
23 of your chromosomes come from your father.

7. You have 46 chromosomes.
There are 23 pairs of chromosomes.
The 23rd pair = the sex chromosomes.
23 of your chromosomes come from your mother.
23 of your chromosomes come from your father.
XX = female
XY = male

8. You have 46 chromosomes.
There are 23 pairs of chromosomes.
The 23rd pair = the sex chromosomes.
23 of your chromosomes come from your mother.
23 of your chromosomes come from your father.
XX = female
XY = male
A gene found on the Y
chromosome causes embryos to
develop as male

9. So - chromosomes come in pairs, and you have 23 pairs of
chromosomes.
Your genes also come in pairs.

10. Different versions of genes are known as alleles.
The gene for ear lobe attachment is shown here.
E = unattached
e = attached.
Which allele is dominant?
Will this person have attached or unattached ear lobes?

11. genetic cross
Mother = Ee
unattached Earlobes
Father = Ee
unattached Earlobes

12. genetic cross
Mother = Ee
unattached Earlobes
Father = Ee
unattached Earlobes

13. genetic cross
Mother = Ee
unattached Earlobes
What percentage
of their offspring
are likely to have
attached earlobes?
Father = Ee
unattached Earlobes
EE
Ee
Ee
ee

14. genetic cross
Mother = Ee
unattached Earlobes
What percentage
of their offspring
are likely to have
attached earlobes?
As e is recessive and E
dominant then only 1 out of
4 will have unattached
earlobes: 25%
Father = Ee
unattached Earlobes
EE
Ee
Ee
ee