SciTech – Current Affairs

Bubble boy syndrome #

It is also called severe combined immunodeficiency, it is a rare genetic disorder that results in a defective immune system in baby boys.
How is it caused?
It results from a genetic defect in the X-Chromosome and therefore called X-linked SCID
The defective X-chromosome lacks in the gene that forms the immune system.
The absence of gene prevents the bone marrow from producing healthy stem cells that form the immune system.
Since the baby is born with extremely weak immune system, it is protected from infectious germs by enclosing it in a sterile environment like a plastic pod (a bubble)
Further since it affects almost only baby boys; it is called as bubble boy syndrome.
The bubble baby boys with SCID die within 1 or 2 years in the absence of treatment.

X-linked genetic disorders in males #
X-linked genetic disorders mostly affect males. (eg. Haemophilia)
They are caused by a gene alteration on the X chromosome.
Males have XY chromosomes and Females have XX chromosomes.
Since males have only one X chromosome, if they have a gene alteration on their X chromosome they will develop the condition.
Since females have a second unaltered copy of the gene on their other X chromosome to compensate for an altered gene they do not develop the condition.
However a female who has a gene alteration on one of her X chromosomes is said to be a carrier for the X-linked genetic disorders.

Global Genome sequencing projects: Human Genome Project #

An international project to decode the 3 billion base pairs in the human genome, completed in 2003.
Key results
It discovered that the number of genes in human genetic material is around 20,000 to 25,000.
Further the amount of DNA an organism carries is not related to the organism’s complexity.
Also there is no relationship between the number of genes an organism has and its complexity.
UK was the 1st to launch a whole genome sequencing project called Genomics England
Australia is working on the 100,000 Genomes Project.
GenomeAsia100K is a genome sequencing project representing populations from South and South-East Asia including 50000 Indians.
Japan and China also have started their own genome sequencing projects.