Chromosomes are made of long aggregates of genes formed from condensed chromatin. Chromatin is made up of DNA, proteins, RNA and other macromolecules. It is located in the nucleus of a cell and becomes a chromosome during the prophase stage of mitosis in eukaryotic cell division.
One of the main functions of chromatin is to reduce the size of DNA so it can fit in the cell. It does this by wrapping a DNA molecule tightly around proteins called histones. The histones are there to maintain the structure of the chromosome. Other functions of chromatin include reinforcing DNA molecules for mitosis, preventing DNA damage, and helping to control DNA replication.
A fully formed chromosome is made up of two chromatin sections that join together at a central point called the centromere. One of the chromatin sections, or arms, is generally shorter than the other. The shorter section is referred to as the "p arm" of the chromosome, and the longer section is called the "q arm."
Before cell division occurs, chromosomes cannot be seen inside the nucleus, even with the help of a microscope. It is only during cell division that the DNA becomes compact enough to be observed, so most of what scientists know about chromosomes comes from observing cell division.Learn More
Each chromosome in the cell nucleus contains DNA compressed to over 10,000 times shorter than it would be if it were to be stretched out. Despite this compression, each chromosome is capable of rapidly unwinding, taking up new complementary nucleotides and reforming during each cycle of mitosis.Full Answer >
Translocation mutations take place when a portion of a chromosome is relocated. The genes from one chromosome can move to another position on the same chromosome; alternatively, they can become incorporated into a different chromosome.Full Answer >
Genes that occur at the same place on the chromosome but occur in different forms are called alleles. Alleles are essentially different versions of a gene, and they can cause dissimilarities in an organism's function or structure. An example is the gene responsible for melanin production in most animals. One version of this gene causes the organism to produce adequate melanin, while the other allele prevents melanin from being produced.Full Answer >
A gene is a specific location on a chromosome that codes for a particular protein. Alleles are variants of a gene that determine how the protein looks.Full Answer >