Cell Cycle and Chromosomes

Oogonia divides by repeated mitotic divisions.

Primary oocyte increases in size during the growth phase.

There are 3 polar bodies produced in the process of oogenesis.

Meiosis takes place in ootidogenesis.

Egg contains 2X chromosomes.

Human males have XY sex chromosomes, while females have XX. The Y chromosome carries the SRY gene that triggers male development. YY is not viable in humans, XO causes Turner syndrome, and XX is the female karyotype.

C. B. Bridges (1925) reported his balance theory of sex determination in Drosophila.

Gametes are haploid (n) and contain half the DNA content of somatic cells which are diploid (2n). This 1:2 ratio results from meiosis which reduces chromosome number by half.

Binary fission is a form of asexual reproduction that occurs primarily during favorable conditions when resources are abundant. During unfavorable conditions, many single-celled organisms form cysts or spores to survive rather than reproducing actively. The process requires energy and optimal conditions for successful division and growth of daughter cells.

All of the above cause chromosomal mutation.

It involves change in chromosome number that is an exact multiple of monoploid. Thus, it involves addition or deletion of one set of chromosomes.

Individuals with three sets of chromosomes; 2n + n = 3n

Loss of a pair of chromosome from a diploid set

As the genes get rotated within a chromosome by 180 degrees, the position of genes gets changed.

Addition or deletion alters the reading frame of all base triplets in the gene distal to the mutation.