Download Learnerz IAS app from the Play Store now! Download



Sex Chromosomes UPSC NOTE




  • In humans, each cell nucleus contains 23 pairs of chromosomes, a total of 46 chromosomes.

  • The first 22 pairs are called autosomes.

  • Autosomes are homologous chromosomes i.e. chromosomes which contain the same genes (regions of DNA) in the same order along their chromosomal arms. 

  • The 23rd pair of chromosomes are called allosomes.

  • These consist of two X chromosomes in most females, and an X chromosome and a Y chromosome in most males. 


  • Females therefore have 23 homologous chromosome pairs, while males have 22. 

  • The X and Y chromosomes have small regions of homology called pseudoautosomal regions.


What are sex chromosomes?

  • A sex chromosome is a type of chromosome involved in sex determination. 

  • Humans and most other mammals have two sex chromosomes, X and Y, that in combination determine the sex of an individual. 

  • Females have two X chromosomes in their cells, while males have one X and one Y.

X chromosome:

  • Females have two X chromosomes, while males have one X and one Y chromosome. 

  • The chromosome X represents about 5% of a cell's total DNA and likely contains about 900 genes.


  • An X chromosome is always present as the 23rd chromosome in the ovum.

Y chromosome:

  • The Y chromosome is very small. 

  • It likely contains 50 to 60 genes and represents 2% of a cell's total DNA. 

  • Either an X or Y chromosome may be present in an individual sperm.

  • Because only males have the Y chromosome, the genes on this chromosome tend to be involved in male sex determination and development.


  • The Y chromosome, often referred to as the “master of maleness”.

  • Sex linked diseases are passed down through families through one of the X or Y chromosomes.



Amritsar,1,April 2024,301,Art & Culture,1,August 2023,251,Courses,7,Daily Current Affairs,48,December 2023,189,Disaster Management,2,Environment and Ecology,145,February 2024,228,Foundation Course,1,GDP,1,GEMS Club,1,GEMS Plus,1,Geography,151,Govt Schemes,2,GS 2,1,GS1,6,GS2,31,GS3,15,GST,1,History,7,Home,3,IAS Booklist,1,Important News,71,Indian Economy,112,Indian History,2,Indian Polity,129,International Organisation,12,International Relations,93,Invasive Plant,1,January 2024,240,July 2023,281,June 2022,6,June 2023,268,June 2024,140,March 2024,238,May 2022,17,May 2024,330,Mentorship,2,November 2023,169,October 2023,203,Places in News,2,Science & Technology,66,Science and Technology,86,September 2023,205,UPSC CSE,111,
Learnerz IAS | Concept oriented UPSC Classes in Malayalam: Sex Chromosomes UPSC NOTE
Sex Chromosomes UPSC NOTE
Learnerz IAS | Concept oriented UPSC Classes in Malayalam
Loaded All Posts Not found any posts VIEW ALL Readmore Reply Cancel reply Delete By Home PAGES POSTS View All RECOMMENDED FOR YOU LABEL ARCHIVE SEARCH ALL POSTS Not found any post match with your request Back Home Sunday Monday Tuesday Wednesday Thursday Friday Saturday Sun Mon Tue Wed Thu Fri Sat January February March April May June July August September October November December Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec just now 1 minute ago $$1$$ minutes ago 1 hour ago $$1$$ hours ago Yesterday $$1$$ days ago $$1$$ weeks ago more than 5 weeks ago Followers Follow THIS PREMIUM CONTENT IS LOCKED STEP 1: Share to a social network STEP 2: Click the link on your social network Copy All Code Select All Code All codes were copied to your clipboard Can not copy the codes / texts, please press [CTRL]+[C] (or CMD+C with Mac) to copy Table of Content