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A tetrad is the association of a pair of homologous chromosomes (4 sister chromatids) physically held together by at least one DNA crossover. This physical attachment allows for alignment and segregation of the homologous chromosomes in the first meiotic division. In most organisms, each replicated chromosome (composed of two identical sisters ...
A pair of homologous chromosomes, or homologs, is a set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization. Homologs have the same genes in the same loci , where they provide points along each chromosome that enable a pair of chromosomes to align correctly with each other before ...
The vierbein field, , has two kinds of indices: labels the general spacetime coordinate and labels the local Lorentz spacetime or local laboratory coordinates. The vierbein field or frame fields can be regarded as the "matrix square root" of the metric tensor , g μ ν {\displaystyle g^{\mu \nu }\,} , since in a coordinate basis,
This image shows haploid (single), diploid (double), triploid (triple), and tetraploid (quadruple) sets of chromosomes. Triploid and tetraploid chromosomes are examples of polyploidy. Polyploidy is a condition in which the cells of an organism have more than two paired sets of ( homologous ) chromosomes .
Gene conversion is the process by which one DNA sequence replaces a homologous sequence such that the sequences become identical after the conversion. [1] Gene conversion can be either allelic, meaning that one allele of the same gene replaces another allele, or ectopic, meaning that one paralogous DNA sequence converts another.
This is an accepted version of this page This is the latest accepted revision, reviewed on 11 February 2025. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
The crucial new idea, for Einstein, was the introduction of a tetrad field, i.e., a set {X 1, X 2, X 3, X 4} of four vector fields defined on all of M such that for every p ∈ M the set {X 1 (p), X 2 (p), X 3 (p), X 4 (p)} is a basis of T p M, where T p M denotes the fiber over p of the tangent vector bundle TM.
Calculations in the Newman–Penrose (NP) formalism of general relativity normally begin with the construction of a complex null tetrad {,,, ¯}, where {,} is a pair of real null vectors and {, ¯} is a pair of complex null vectors. These tetrad vectors respect the following normalization and metric conditions assuming the spacetime signature