Inheritance of two characteristics
Introduction
A cross between two organisms where the heritance patterns of two genes are studied is
call Dihybrid cross. In this experiment the corn cob represents an offspring from two other
corn cobs. The shape and colour of the kernels represents a gene that are passed down
from the parents.
Aim
Our aim is to study the corn cob and the difference of the kernels and with the information
given to us, we need to work out the genotype of the parents and the pattern of the
inheritance involved.
Hypothesis
The two parents are heterozygous with the ‘BbSs’ which means the offspring will have the
same ratio of 9:3 : 3:1
Materials and Methods
refer to prac handout: “Inheritance of two characteristic’s”
Results:
From the results determined the black kernels is dominant and the yellow is recessive.
Colour: Black wrinkled, Black smooth
Shape: Yellow smooth, Yellow wrinkled
Columns on the
top of the cob
1
2
3
4
5
6
7
Total:
Brown smooth
Brown wrinkled
Yellow smooth
Yellow wrinkled
6
9
5
12
10
4
6
52
0
4
5
0
3
3
3
18
2
5
7
12
8
12
8
52
29
18
22
16
22
19
15
141
Ratio:
2:8
1
3
7:8
Determine the colour
From the data collected we found that ‘Black kernels’ is dominant and the ‘ Yellow kernel’ is
recessive.
Determine the shape
‘Smooth is dominant’ and the ‘Yellow wrinkled’ is recessive’
In question one, I chose dominant because you see a lot more ‘dominant’ which are ‘ Black
kernels’ then ‘recessive kernels’.
If parents are heterozygous for two characteristic’s, Their genotype would be ‘BbLl’
because there is only one type of gamete from each parent, therefore only one kind of
offspring produced in the first generation.
What phenotypes would I expect in the offspring?
G
g
G GG
Gg
G Gg
gg
The genotypes of the Gametes from two parents show only one kind of gamete, because
each parent is homozygous for both traits.
Expected ratio in the offspring’s phenotype’s?
The offspring phenotype ration would be 9:3:3:1
Expected ratio and Actual ratio
Expected ratio: 2:8:1:3:7:8
Actual ratio: 9:3:3:1
Conclusion
My final results support my hypothesis which was correct. I found out that the two parents
were heterozygous. In the end the parent are heterozygous because they pass on the gene
to the off spring giving the ratio of 9:3:31.
Dakota McKenna.