Introduction to Chromosomes in Human Cells
A Look at the Functions, Types, Centromeres and Telomeres
Feb 28, 2009
Most human cells have a functioning structure (or organelle) called a nucleus. This is where 23 pairs of chromosomes, structures of tightly coiled DNA and proteins (called histones) reside. People have traits in common with their biological parents because they inherit a set of chromosomes from both the mother and father.
What are the Functions of Chromosomes?
DNA is very long, and being packed into chromosomes allows it to fit inside the cell. Chromosomes also offer protection for the genetic information contained since their structures allow for easy copying. This is especially important in reproductive cells, as problems with chromosomes can lead to problems for a fetus.
Different Types of Chromosomes
Chromosomes are linear in some organisms, and round in others. The 23 pairs of chromosomes found in human nuclear DNA are linear in shape. A round chromosome can also be found in other human organelles called mitochondria, which are responsible for energy production in the cell.
The majority of chromosomes, numbered 1 to 22, are called autosomes or autosomal chromosomes. They are numbered in size order, from largest to smallest. The remaining pair are the sex chromosomes, X and Y. They determine a human’s biological sex – a female has two X chromosomes, whereas a male has one X and one Y chromosome.
The genetic material for the Y chromosome always comes from the father, and this chromosome’s only known function is to provide the inherited material for being male.
Centromeres and Telomeres in Chromosomes
Linear chromosomes have a constriction in their structure called “centromeres”. The article Chromosomes on the NHGRI’s website offers a good definition: “Centromeres help to keep chromosomes properly aligned during the complex process of cell division. As chromosomes are copied in preparation for production of a new cell, the centromere serves as an attachment site for the two halves of each replicated chromosome, known as sister chromatids.”
Telomeres are the ends of the chromosomes, and their job is to seal the structure from potential damage. Because of this, they are sometimes compared to the ends of shoelaces. Many cells lose a bit of their telomeres every time they divide, and consequently telomeres are considered to be relevant to the genetics of aging.
For more information on cells, DNA and genes, read Basic Cell Biology for Understanding Genetics and Basic Genetics Terms for Beginners.
Sources
Chromosomes, National Human Genome Research Institute website, accessed: 26th February 2009, no author specified.
How do scientists read chromosomes?, Genetic Science Learning Center website, accessed: 28th February 2009, no author specified.
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