Autosomes vs Sex Chromosomes
The most important structures in a cell during division are the chromosomes, which contain DNA. This is because they are responsible for the transmission of the hereditary information from one generation to the next. There are two types of chromosomes. Those are autosomes and sex chromosomes. Sex chromosomes are important in sex determination.
Humans have 23 pairs of chromosomes. One of them is known as sex chromosomes. Other 22 are autosomes. Sex chromosomes are of 2 types; X and Y. Y is smaller, and X and Y are partially homologous. However, they pair and segregate into daughter cells during meiosis. Males have X and Y combinations. Females have X and X combination. All female gametes carry only one X chromosome. Male gametes may carry X or Y. The number carrying X is equal to the number carrying Y. If an ovum is fertilized by a sperm carrying X, the result is a female XX. If an ovum is fertilized by a sperm carrying Y, the result is a male XY.
Sex linked characters show deviations from Mendel’s laws. All the genes carried by X chromosomes do not determine sexuality. Many of the genes have other functions similar to genes carried in autosomes. Sex linked inheritance shown by genes carried with X chromosomes is not represented in Y chromosomes. These genes normally have recessive alleles and are shown by recessive mutations. These defective alleles are very rare in human population. Therefore, they are not expressed in females as they carry 2X chromosomes. Heterozygous females are carriers, and they may pass the gene on to their sons. They are expressed in males because they have only one X chromosome.
Any chromosome, which is not a sex chromosome, is an autosome. There are 22 pairs of autosomes in humans. Each autosome contains a large number of genes arranges in a definite sequence. In these homologous pairs, the 2 chromosomes are of the same length. The position of the centromere is the same. Mitosis is the process by which all these chromosomes duplicate and give one copy of each chromosome to each of the daughter cells. This ensures that all somatic cells of an organism’s body carry an identical set of genes.
What is the difference between Autosomes and Sex Chromosomes?
• Autosomes are homologous chromosomal pairs and sex chromosomes are partially homologous chromosomal pairs.
• Sex chromosomes involve in sex determination and autosomes do not involve in sex determination.
• In sex chromosomes, Y chromosome is shorter and in autosomal pairs both the chromosomes are of the same height.
• In sex chromosomal pair, the position of the centromere may not be the same and, in autosomal pairs, the position of the centromere is the same.