Cell Cycle and Chromosomes

Human females have two X chromosomes (XX), while males have one X and one Y (XY). An unfertilized egg (ovum) always contains one X chromosome from the mother. Sperm can carry either X or Y chromosome, determining the baby's sex.

Robertsonian translocation is a type of reciprocal translocation caused by breaks at or near the centromeres of two acrocentric chromosomes. The reciprocal exchange of parts gives rise to one large metacentric chromosome and one extremely small chromosome that may be lost from the organism with little effect because it contains so few genes.

It is the structure in the chromosome which gives it shapes like I, V, L, etc.

Total number of chromosomes in the gamete of fruit fly is 4.

Ophioglossum has 1260 chromosomes.

An unfertilised egg always has an X chromosome.

A Robertsonian translocation in balanced form results in no excess or deficit of genetic material and causes no health difficulties. In unbalanced forms, Robertsonian translocations cause chromosomal deletions or addition and result in syndromes of multiple malformations, including trisomy 13 (Patau syndrome) and trisomy 21 (Down syndrome).

In squamous cell carcinoma, a protein from the epidermal growth factor receptor (EGFR) gene is often overexpressed in conjunction with polysomy of chromosome 7, so chromosome 7 can be used to predict the presence of EGFR in squamous cell carcinoma.

Turner syndrome 45, X encompasses several conditions in human females, of which monosomy X (absence of an entire sex chromosome, the Barr body) is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent or has other abnormalities.

The exchange of chromosomes segments between non-homologous chromosomes is called translocation.

The chromosome which carry the least number of genes (i.e. only 231) is Y-Chromosome.

Monosomy refers to lack of one chromosome of the normal complement. Partial monosomy can occur in unbalanced translocations or deletions, in which only a portion of the chromosome is present in a single copy. Monosomy of the sex chromosomes (45X) causes Turner syndrome.

In genetics, a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes. A gene fusion may be created when the translocation joins two otherwise separated genes, the occurrence of which is common in cancer.

It has a short generation time (about 10 days at room temperature) so several generations can be studied within a few weeks.

A gene is a unit of heredity in a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living things depend on genes, as they specify all proteins and functional RNA chains.