There are two main properties of homologous chromosomes: 1) the length of chromosomal arms and 2) the placement of the centromere. Homologous chromosomes are chromosomes which contain the same genes in the same order along their chromosomal arms. This proved interchromosomal genetic recombination. Creighton and McClintock discovered that the new allele combinations present in the offspring and the event of crossing over were directly related. Later on during the 1930s Harriet Creighton and Barbara McClintock were studying meiosis in corn cells and examining gene loci on corn chromosomes. Using this logic he concluded that the two genes he was studying were located on homologous chromosomes. Using test cross experiments, he revealed that, for a single parent, the alleles of genes near to one another along the length of the chromosome move together. That data and information was further explored by Thomas Morgan. History Įarly in the 1900s William Bateson and Reginald Punnett were studying genetic inheritance and they noted that some combinations of alleles appeared more frequently than others. This mixing of maternal and paternal traits is enhanced by crossing over during meiosis, wherein lengths of chromosomal arms and the DNA they contain within a homologous chromosome pair are exchanged with one another. The alleles on the homologous chromosomes may be different, resulting in different phenotypes of the same genes. In diploid (2n) organisms, the genome is composed of one set of each homologous chromosome pair, as compared to tetraploid organisms which may have two sets of each homologous chromosome pair. After mitosis occurs within the daughter cells, they have the correct number of genes which are a mix of the two parents' genes. One homologous chromosome is inherited from the organism's mother the other is inherited from the organism's father. Homologous chromosomes are made up of chromosome pairs of approximately the same length, centromere position, and staining pattern, for genes with the same corresponding loci. Overview Ĭhromosomes are linear arrangements of condensed deoxyribonucleic acid (DNA) and histone proteins, which form a complex called chromatin. This is the basis for Mendelian inheritance which characterizes inheritance patterns of genetic material from an organism to its offspring parent developmental cell at the given time and area. Homologs have the same genes in the same loci where they provide points along each chromosome which enable a pair of chromosomes to align correctly with each other before separating during meiosis. A couple of homologous chromosomes, or homologs, are a set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization.
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