<span>Answers;
1.Breeding of individuals that have genes for two different characteristics; Dihybrid cross
2.A grid system used to predict possible combinations of genes due to random fertilization; Punnet square
3 A condition in which both alleles are dominant; Codominance
4.when more than two alternatives exist for a gene; multiple alleles
5.A condition in which neither pair of alleles is dominant or recessive, so the traits blend in the phenotype ;Incomplete dominance;
Explanation;
</span>Dihybrid cross;
<span>It involves the breeding of individuals that have genes for two different characteristics. It involves the cross of individuals that are both heterozygous for two different traits. For example two different traits in a pea plant; color and shape; for color we have; Y-allele for yellow seeds and y- allele for green seeds, For Shape trait; R-allele for round seeds and r-allele for wrinkled seeds. So the dihydbrid cross would be (RrYy </span>× RrYy).
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Punnet square;
</span><span>This a grid system or a square diagram that is used to predict possible combinations of genes due to random fertilization. It is used by biologists determine the probability of an offspring having a particular genotype.
</span><span>The letters on the outside of a Punnett Square stand for the parent allele.
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Codominance;
<span>This is a condition in heterozygotes in which both members of an allelic pair are dominant and both contribute to the phenotype.
A good example of codominance is the ABO blood group; A person with blood group AB, it means that both the A allele and B allele are equally expressed.
Multiple alleles
</span><span>This is when more than two alternatives for a gene exist.
Examples of multiple allelism in human;The genes of the ABO blood group system. The human ABO system is controled by three alleles, namely; A-allele, B-allele and O-allele.
Incomplete dominance;
</span><span>This is condition in heterozygotes in which both members of an allelic pair are neither dominant nor recessive to other alleles, so the two traits blend in the phenotype of the individual.
An example; is a snapdragon flower that is pink as a result of cross-pollination between a red flower and a white flower. Which means neither the white allele or the red allele are dominant. </span>
In his experiment mendel first crossed tall and short peas plant and noticed that the F1 plants were all tall. in the second experiment he crossed the the F1 plants and noticed that short plants reappeared in the rate of 25% in F2 generation. in his third experiment he crossed he crossed F2 plants and noticed that when he crossed some tall plants with the shot plants the F3 generation contained short plant in frequency of 50%. after this observations mendel concluded that there were genes that could be only expressed in homozygous state but not in heterozygous state. these genes were later referred to as recessive alleles wheres the genes that prevented the expression of recessive genes were later referred to as dominant genes.
