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Normally, homologous chromosomes pair up in bivalents during meiosis and separate into different daughter cells. However, when multiple copies of similar chromosomes are present in the nucleus, homeologous chromosomes can also pair with homologous chromosomes resulting in the formation of trivalents or multivalents. [3]
The haploid gametes produced by most organisms combine to form a zygote with n pairs of chromosomes, i.e. 2n chromosomes in total. The chromosomes in each pair, one of which comes from the sperm and one from the egg, are said to be homologous. Cells and organisms with pairs of homologous chromosomes are called diploid.
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms.This number, along with the visual appearance of the chromosome, is known as the karyotype, [1] [2] [3] and can be found by looking at the chromosomes through a microscope.
G-banding, G banding or Giemsa banding is a technique used in cytogenetics to produce a visible karyotype by staining condensed chromosomes. It is the most common chromosome banding method. [1] It is useful for identifying genetic diseases (mainly chromosomal abnormalities) through the photographic representation of the entire chromosome ...
Polyploidy is a condition in which the cells of an organism have more than two paired sets of chromosomes. Most species whose cells have nuclei are diploid, meaning they have two complete sets of chromosomes, one from each of two parents; each set contains the same number of chromosomes, and the chromosomes are joined in pairs of homologous ...
In a diploid cell there are two sets of homologous chromosomes of different parental origin (e.g. a paternal and a maternal set). During the phase of meiosis labeled “interphase s” in the meiosis diagram there is a round of DNA replication, so that each of the chromosomes initially present is now composed of two copies called chromatids .
Two single-celled haploid gametes, each containing n unpaired chromosomes, fuse to form a single-celled diploid zygote, which now contains n pairs of chromosomes, i.e. 2n chromosomes in total. [17] The single-celled diploid zygote germinates, dividing by the normal process , which maintains the number of chromosomes at 2n.
The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes is collectively known as atDNA or auDNA. [2] For example, humans have a diploid genome that usually contains 22 pairs of autosomes and one allosome pair (46 ...