Chromosomal crossover

... occurs when two chromosomes , normally two homologous instances of the same chromosome, break and then ... chromosome being lost during cell division . If homologous chromosome are not perfectly aligned an unequal ... can create duplicate genes. Any pair of homologous chromosomes may be expected to cross over three ...

Meiosis

... of chromosomes for prophase is different. homologous chromosomes join into tetrads (so called ... the chromosomal material is tightly coiled. homologous chromosomes derived from maternal and paternal ... the structures and then "zip up". The paired homologous chromosomes, now known as bivalents, shorten and ...

Y chromosome

... are fixed by following the template on the homologous chromosome . This repair technique is called ... Y chromosome (and one X chromosome.) Without a homologous chromosome, the Y chromosome cannot utilize this ... exchanging information with matching genes on the homologous chromosome, a process called "crossing over." But ...

Bioinformatics

... of a gene: if the sequence of gene A , whose function is known, is homologous to the sequence of gene B, whose function is unknown, one could infer ... is used to predict the structure of a protein once the structure of a homologous protein is known. This currently remains the only way to predict protein ...

Bioinformatics

... of a gene: if the sequence of gene A , whose function is known, is homologous to the sequence of gene B, whose function is unknown, one could infer ... is used to predict the structure of a protein once the structure of a homologous protein is known. This currently remains the only way to predict protein ...

Flagellum

... bacterial (or eubacterial) flagellum; in the 1980s they were thought to be homologous on the basis of gross morphology and behavior (Cavalier-Smith, 1987). Both ... one basic kind of prokaryotic flagellum, and that archaeal flagella are homologous to it (an example is Cavalier-Smith (2002), who is aware of the ...

Genetic recombination

... crossing over . In analog fashion exchange of alleles is possible between homologous sites within one DNA molecule. If the structure of genes is changed in ... chromatids are in tight formation with one another. During this time, homologous sites on two chromatids can mesh with one another, and may exchange ...

Trait

... . The nucleus of a diploid cell contains two of each chromosome, with homologous (mostly identical) pairs of chromosomes having the same genes at the same ... the information flow charted above. For example, if the alleles on homologous chromosomes exhibit a "simple dominance " relationship, the trait of the ...

Allele

... gene. One version might result in red petals, while another might result in white petals. Some organisms are diploid - that is, they have paired homologous chromosomes in their somatic cells , and thus contain two copies of each gene. An organism in which both copies of the gene are identical - that ...

Apoptosis

... which they called Apaf-1 (apoptotic protease activating factor). The team published their results in an article titled "Apaf-1, a human protein homologous to C. elegans CED-4, participates in cytochrome c-dependent activation of caspase-3 [21] . Wang and his team identified and reconstituted the ...

Charles Darwin

... into an innovative study of how their beautiful flowers served to control insect pollination and ensure cross fertilisation. As with the barnacles, homologous parts served different functions in different species. Lying on his sickbed, his rooms became filled with experiments on climbing plants. He was ...

Convergent evolution

... ). Structures that are the result of convergent evolution are called analogous structures or homoplasies ; they should be contrasted with homologous structures which have a common origin. Another example is the aerial rootlets found in English ivy ( Hedera helix ) and wintercreeper ( ...

Evolution

... has revealed that structures with similar internal organization may perform divergent functions. Vertebrate limbs are a common example of such homologous structures . A vestigial organ or structure may exist with little or no purpose in one organism, though they have a clear purpose in others. The ...

Heterozygote

... Heterozygote cells are diploid or polyploid and have different alleles at a locus (position) on homologous chromosomes . When an organism is referred to as a heterozygote, or being heterozygous for a specific gene , it means that the organism carries ...

Convergent evolution

... ). Structures that are the result of convergent evolution are called analogous structures or homoplasies ; they should be contrasted with homologous structures which have a common origin. Another example is the aerial rootlets found in English ivy ( Hedera helix ) and wintercreeper ( ...

Homozygote

... Homozygote cells are diploid or polyploid and have the same alleles at a locus (position) on homologous chromosomes . When an organism is referred to as being homozygous for a specific gene, it means that it carries two identical copies of that gene ...

Hormone

... cortex and the gonads are primary sources. Examples of steroid hormones are testosterone and cortisol . Sterol hormones such as calcitriol are a homologous system. Lipid and phospholipid hormones are derived from lipids such as linoleic acid and phospholipids such as arachidonic acid . The main ...

Isozyme

... Isozymes , (or isoenzymes ) are isoforms (closely related variants) of enzymes . In many cases, they are coded for by homologous genes that have diverged over time. Although, strictly speaking, allozymes represent different alleles of the same gene , and isozymes ...

Lung

... supply by diffusion across the moist outer skin of their bodies. Evolutionary origins The lungs of vertebrates are closely related (i.e. homologous ) to the gas bladders of fish (but not to their gills ). The evolutionary origin of both are thought to be outpocketings of the upper ....

Major histocompatibility complex

... may be referred to collectively as "antigen-presenting cells" (APCs). Class II molecules are also heterodimers , but in this case consist of two homologous peptides, an α and β chain, both of which are encoded in the MHC. The peptides presented by class II molecules are derived from ...

Modern evolutionary synthesis

... arises by chance through mutation (this is now known to be due to mistakes in DNA replication ) and recombination (crossing over of homologous chromosomes during meiosis ). Evolution consists primarily of changes in the frequencies of alleles between one generation and another as a ...