Genetic Code

1.Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other allele. This results in a third phenotype in which the expressed physical trait is a combination of the dominant and recessive phenotypes.

Incomplete dominance is similar to, but different from co-dominance. In co-dominance, an additional phenotype is produced, however both alleles are expressed completely. Co-dominance is exemplified in AB blood type inheritance.

2.Allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. These DNA codings determine distinct traits that can be passed on from parents to offspring. The process by which alleles are transmitted was discovered by Gregor Mendel and formulated in what is known as Mendel's law of segregation.

3.Codominance is a condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other.

4.Independent assortment is a basic principle of genetics developed by a monk named Gregor Mendel in the 1860's. Mendel formulated this principle after discovering another principle now known as Mendel's law of segregation. This principle states that the alleles for a trait separate when gametes are formed. These allele pairs are then randomly united atfertilization. Mendel arrived at this conclusion by performing monohybrid crosses. These were cross-pollination experiments with pea plants that differed in one trait, for example pod color.

5. Nondisjunction is the failure of paired chromosomes to separate (to disjoin) during cell division, so that both chromosomes go to one daughter cell and none go to the other. Nondisjunction causes errors in chromosome number, such as trisomy 21 (Down syndrome) and monosomy X (Turner syndrome). It is also a common cause of early spontaneous abortions.

6.Syndromes due to changes in sex...