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Chromosomal crossover, or crossing over, is the exchange of genetic material during sexual reproduction between two homologous chromosomes ' non-sister chromatids that results in recombinant chromosomes. It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a process called ...
Most recombination occurs naturally and can be classified into two types: (1) interchromosomal recombination, occurring through independent assortment of alleles whose loci are on different but homologous chromosomes (random orientation of pairs of homologous chromosomes in meiosis I); & (2) intrachromosomal recombination, occurring through ...
A gene family is a set of several similar genes, formed by duplication of a single original gene, and generally with similar biochemical functions. One such family are the genes for human hemoglobin subunits; the ten genes are in two clusters on different chromosomes, called the α-globin and β-globin loci. These two gene clusters are thought ...
Crossing over during meiosis, with chiasma shown. In genetics, a chiasma (pl.: chiasmata) is the point of contact, the physical link, between two (non-sister) chromatids belonging to homologous chromosomes. At a given chiasma, an exchange of genetic material can occur between both chromatids, what is called a chromosomal crossover, but this is ...
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. One homologous chromosome is inherited from the organism's mother; the other is inherited from the organism's father. After mitosis occurs within the daughter cells, they ...
The basic number of chromosomes in the somatic cells of an individual or a species is called the somatic number and is designated 2n. In the germ-line (the sex cells) the chromosome number is n (humans: n = 23). [4] [5] p28 Thus, in humans 2n = 46. So, in normal diploid organisms, autosomal chromosomes are present in two copies.
Allele. An allele[1], or allelomorph, is a variant of the sequence of nucleotides at a particular location, or locus, on a DNA molecule. [2] Alleles can differ at a single position through single nucleotide polymorphisms (SNP), [3] but they can also have insertions and deletions of up to several thousand base pairs. [4]
During meiosis, homologous recombination can produce new combinations of genes as shown here between similar but not identical copies of human chromosome 1. Homologous recombination is a type of genetic recombination in which genetic information is exchanged between two similar or identical molecules of double-stranded or single-stranded ...