1. So why do you look like that??

2. Phenotype
The physical appearance of individuals within a species varies
The genes that are inherited from parents control the phenotype of each individual

3. Genotype
The different genes that each individual has is their genotype
Every body cell carries pairs of genes on the paired chromosomes
Genes can be dominant or recessive

4. What have you learnt from this section?
Test yourself here
Or go back and look at this section again
Or select a new topic from the menu
Link to ‘about variation’ match up
Link to Hot potatoes ‘About DNA’

5. So how do your genes work?

6. Gene competitions?
This rabbit’s genotype is BB – the black fur gene is dominant
This rabbit’s genotype is bb – the white fur gene is recessive

7. How do the genes work? Homozygous - two genes the same BB?
Heterozygous - two different alleles
Homozygous
BB?
Bb?
bb?

8. How do they work? Dominant genes are ‘stronger’
They are written as capital letters -‘B’
Recessive genes are ‘weaker’
They are written as small letters – ‘b’
This rabbit may have a genotype of either Bb or BB

9. Genes in conflict? B + B =BB B + b = Bb b + b = bb
Phenotype - Black fur
Genotype BB
Phenotype - Black fur
Genotype - Bb
Phenotype - White fur
Genotype - bb

10. Now work it out….. B B B B B B B b b B b b b b b B b B b b parent
gametes
offspring

11. What are the off spring like?
All the offspring have the same genotype
They all have one dominant gene
They all have one recessive gene
The dominant gene ‘wins’ so the offspring all have black fur! B b B b

12. What is their genotype? B b
Offspring have a mixture of their parents’ genes:
They are heterozygous
They each have one allele for white fur and one allele for black fur B b

13. What about the next generation?
parents
gametes
3 : 1
offspring

14. What are their genotypes?
heterozygous B b B B
homozygous b b
homozygous

15. Teachers can use the extra resource Punnet Squares on an IWB
Got it?
Test your self here
Or go back and have another look at the facts first!
Link for teachers to smartboard exercise – ‘practise punnet squares’
Link for students to ‘genetics shootout’
Or back to the main menu.
Teachers can use the extra resource Punnet Squares on an IWB
but you may need to download Smartbook software [free of charge] to use the file –