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Genotype 1:2:1 1:2:1:2:4:2:1:2:1
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Phenotype 3:1 9:3:3:1
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Ratio cross -1:1 -1:1:1:1
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HOW DO TRAITS GET EXPRESSED?
 Cellular DNA is the information source for making proteins in the cell. A section of
DNA that provides information for one protein is called the gene for that protein.
 Let us take the example of tallness as a characteristic. We know that plants have
hormones that can trigger growth. Plant height can thus depend on the amount of a
particular plant hormone. The amount of the plant hormone made will depend on the
efficiency of the process for making it. Consider now an enzyme that is important for
this process. If this enzyme works efficiently, a lot of hormone will be made, and the
plant will be tall. If the gene for that enzyme has an alteration that makes the enzyme
less efficient, the amount of hormone will be less, and the plant will be short. Thus,
genes control characteristics, or traits.
 The chromosomes carry the genes for various characters. Through different
processes the information carried on the genes are converted into proteins. These
proteins in turn control the various characteristics in the body. Enzymes and
hormones are important proteins which control the body functions and express the
various traits.

 If both parents can help determine the trait in the progeny, both parents must be
contributing a copy of the same gene. This means that each pea plant must have
two sets of all genes, one inherited from each parent. For this mechanism to
work, each germ cell must have only one gene set.

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