b2.7 intro

B2.7 Cell division and inheritance

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.

You are the result of two things...

and

Key words

CellNucleusChromosomesDNACharacteristicsGenerationGeneGenetic diagramsInheritedDominant RecessiveAlleles

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

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.

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 = femaleXY = male

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 = femaleXY = male

A gene found on the Y chromosome causes embryos to develop as male

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

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?

Different versions of genes are known as alleles.

genetic cross Mother = Eeunattached Earlobes

Father = Eeunattached Earlobes

genetic cross Mother = Eeunattached Earlobes

Father = Eeunattached Earlobes

genetic cross Mother = Eeunattached Earlobes

Father = Eeunattached Earlobes

What percentage of their offspring are likely to have attached earlobes?

EE

Ee

Ee

ee

genetic cross Mother = Eeunattached Earlobes

Father = Eeunattached Earlobes

What percentage of their offspring are likely to have attached earlobes?

EE

Ee

Ee

eeAs e is recessive and E dominant then only 1 out of 4 will have unattached earlobes: 25%