a. Explain briefly the following terms: i. gene; ii. Hybrid; iii. Trait. (b) Two heterozygous yellow flowers are crossed. Using a genetic diagram, state the...
Question 1 Report
a. Explain briefly the following terms:
i. gene;
ii. Hybrid;
iii. Trait.
(b) Two heterozygous yellow flowers are crossed. Using a genetic diagram, state the phenotypic and genotypic ratios of the first filial generation.
(c) State four transmitted characters in plants.
Answer Details
(a) Explanation of terms
- (i) Gene: a unit of hereditary material, a length of DNA on a chromosome, that carries the code for a particular characteristic and is passed from parent to offspring.
- (ii) Hybrid: the offspring produced from a cross between two genetically different (unlike) parents; in genetics a heterozygote carrying two different alleles of a gene.
- (iii) Trait: an observable inherited characteristic or feature of an organism, such as flower colour or height.
(b) Cross between two heterozygous yellow flowers
Let \(Y\) = allele for yellow (dominant) and \(y\) = allele for the recessive colour. Each heterozygous parent is \(Yy\).
Parental genotypes: \(Yy \times Yy\)
Gametes: \(Y\) and \(y\) from each parent.
| Gametes | Y | y |
|---|---|---|
| Y | YY | Yy |
| y | Yy | yy |
Genotypic ratio of F1: \(1\,YY : 2\,Yy : 1\,yy\).
Phenotypic ratio of F1: 3 yellow : 1 recessive (non-yellow), i.e. \(3:1\).
(c) Four transmitted (inherited) characters in plants
- Flower colour.
- Seed shape (round or wrinkled).
- Height of the plant (tall or short).
- Fruit or seed colour. Leaf shape is also acceptable.
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