Describe various chromosomal disorders found in human beings.

Chromosomal abnormalities are the type of genetic disorders caused due to the change in one or many chromosomes or the abnormal arrangement of the chromosomes. There are different types of chromosomal abnormalities as follows: Aneuploidy – It is a condition in which there is a loss or gain of chromosomes due to abnormal segregation of genes during cell division. For example a human cell having 45 or 47 chromosomes instead of the usual 46. It does not include a difference of one or more complete sets of chromosomes. Polyploidy – It is a condition in which the count of the entire set of chromosomes increases due to the failure of cytokinesis in cell division. It is mostly observed in plants. In humans, when there is an extra copy of a chromosome in one of the pairs, it is called trisomy and when one of the chromosome from pair is lacking, it is called monosomy.

What is Co-dominance? Explain with an example.

Codominance is a heterozygous condition in which both alleles at a gene locus are fully expressed in the phenotype. Alleles which show an independent effect are called as Codominant alleles. In codominance, neither phenotype is completely dominant. In co-dominance both dominant alleles of a gene express themselves equally in F 1 hybrids. The phenotypic ratio matches with genotypic ratio i.e., 1:2:1 in F 2 generation of offspring. In codominance, it does not matter whether the alleles in the homologous chromosomes are dominant or recessive. If the homologous chromosome consists of two alleles that can produce proteins, then both will be produced and forms a different phenotype or characteristics to that of a homozygote. Example of co-dominance can be seen in coat colour in cattle.