Meiosis involves pairing of homologous chromosomes. When paired chromosomes come close they cross-over at certain point or points leading to the formation of "chiasma". Here exchange of genetic material takes place. This is one of the biggest reasons that although we bear the genes of our parents and even our siblings also bear the genes of the same parents but they are different. Since crossing-over varies in different cell division and hence there is a variation in the genetic makeup of the siblings and also between the parents and siblings.
Karyotyping is related to the number of chromosomes present in an organism. It is concerned with the appearance of chromosomes in the nucleus of eukaryotic cells. It is important to find out the presence of any genetic abnormality.
For example- An individual having Downs Syndrome will have three copies of the 21st chromosome which could be detected with the help of karyotyping when chromosomes will be arranged. This is the reason why Down Syndrome is also known as Trisomy (three copies) of 21st chromosome. The total number of chromosomes in case of human is 46 but in case of patient with Trisomy, the number is 47.
Every organism possess specific set of chromosomes. A diploid cell has two set of chromosome, one called the maternal set of chromosome (obtained from mother) the other called paternal chromosome (obtained from father).
1. A true breeding brown mouse is mated with a true-breeding white mouse and all their offspring are brown. If two of these brown offspring are mated, what percentage of the F1 and F2 generations will be brown?
The true breeding brown mouse has dominant gene for the color (BB) while the true breeding white mouse has recessive genes for color (bb). As per the Mendels Law of Dominance, only the dominant character is expressed, when these two mouse are crossed then the first filial generation or the F1 generation is Brown with the ...