A report on Chromosome

Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch. (3) Short arm (p). (4) Long arm (q).
Organization of DNA in a eukaryotic cell
The major structures in DNA compaction: DNA, the nucleosome, the 10 nm "beads-on-a-string" fibre, the 30 nm fibre and the metaphase chromosome.
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Human chromosomes during metaphase
Stages of early mitosis in a vertebrate cell with micrographs of chromatids
The 23 human chromosome territories during prometaphase in fibroblast cells
Karyogram of a human male
In Down syndrome, there are three copies of chromosome 21.

Long DNA molecule with part or all of the genetic material of an organism.

- Chromosome
Diagram of a replicated and condensed metaphase eukaryotic chromosome. (1) Chromatid – one of the two identical parts of the chromosome after S phase. (2) Centromere – the point where the two chromatids touch. (3) Short arm (p). (4) Long arm (q).

76 related topics with Alpha

Overall

In meiosis, the chromosome or chromosomes duplicate (during interphase) and homologous chromosomes exchange genetic information (chromosomal crossover) during the first division, called meiosis I. The daughter cells divide again in meiosis II, splitting up sister chromatids to form haploid gametes. Two gametes fuse during fertilization, forming a diploid cell with a complete set of paired chromosomes.

Meiosis

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Special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells.

Special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, such as sperm or egg cells.

In meiosis, the chromosome or chromosomes duplicate (during interphase) and homologous chromosomes exchange genetic information (chromosomal crossover) during the first division, called meiosis I. The daughter cells divide again in meiosis II, splitting up sister chromatids to form haploid gametes. Two gametes fuse during fertilization, forming a diploid cell with a complete set of paired chromosomes.
Meiosis Prophase I in mice. In Leptotene (L) the axial elements (stained by SYCP3) begin to form. In Zygotene (Z) the transverse elements (SYCP1) and central elements of the synaptonemal complex are partially installed (appearing as yellow as they overlap with SYCP3). In Pachytene (P) it's fully installed except on the sex chromosomes. In Diplotene (D) it disassembles revealing chiasmata. CREST marks the centromeres.
Schematic of the synaptonemal complex at different stages of prophase I and the chromosomes arranged as a linear array of loops.
Diplontic life cycle
Haplontic life cycle.
Overview of chromatides' and chromosomes' distribution within the mitotic and meiotic cycle of a male human cell

It involves two rounds of division that ultimately result in four cells with only one copy of each chromosome (haploid).

The structure of the DNA double helix. The atoms in the structure are colour-coded by element and the detailed structures of two base pairs are shown in the bottom right.

DNA

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Polymer composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.

Polymer composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning, growth and reproduction of all known organisms and many viruses.

The structure of the DNA double helix. The atoms in the structure are colour-coded by element and the detailed structures of two base pairs are shown in the bottom right.
Chemical structure of DNA; hydrogen bonds shown as dotted lines. Each end of the double helix has an exposed 5' phosphate on one strand and an exposed 3' hydroxyl group (—OH) on the other.
A section of DNA. The bases lie horizontally between the two spiraling strands ([[:File:DNA orbit animated.gif|animated version]]).
DNA major and minor grooves. The latter is a binding site for the Hoechst stain dye 33258.
From left to right, the structures of A, B and Z DNA
DNA quadruplex formed by telomere repeats. The looped conformation of the DNA backbone is very different from the typical DNA helix. The green spheres in the center represent potassium ions.
A covalent adduct between a metabolically activated form of benzo[a]pyrene, the major mutagen in tobacco smoke, and DNA
Location of eukaryote nuclear DNA within the chromosomes
T7 RNA polymerase (blue) producing an mRNA (green) from a DNA template (orange)
DNA replication: The double helix is unwound by a helicase and topo­iso­merase. Next, one DNA polymerase produces the leading strand copy. Another DNA polymerase binds to the lagging strand. This enzyme makes discontinuous segments (called Okazaki fragments) before DNA ligase joins them together.
Interaction of DNA (in orange) with histones (in blue). These proteins' basic amino acids bind to the acidic phosphate groups on DNA.
The lambda repressor helix-turn-helix transcription factor bound to its DNA target
The restriction enzyme EcoRV (green) in a complex with its substrate DNA
Recombination involves the breaking and rejoining of two chromosomes (M and F) to produce two rearranged chromosomes (C1 and C2).
The DNA structure at left (schematic shown) will self-assemble into the structure visualized by atomic force microscopy at right. DNA nanotechnology is the field that seeks to design nanoscale structures using the molecular recognition properties of DNA molecules.
Maclyn McCarty (left) shakes hands with Francis Crick and James Watson, co-originators of the double-helix model.
Pencil sketch of the DNA double helix by Francis Crick in 1953
A blue plaque outside The Eagle pub commemorating Crick and Watson
Impure DNA extracted from an orange

Within eukaryotic cells, DNA is organized into long structures called chromosomes.

Mitosis in an animal cell (phases ordered counter-clockwise).

Mitosis

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Mitosis in an animal cell (phases ordered counter-clockwise).
Mitosis divides the chromosomes in a cell nucleus.
Label-free live cell imaging of Mesenchymal Stem Cells undergoing mitosis
Onion (Allium) cells in different phases of the cell cycle enlarged 800 diameters.
a. non-dividing cells
b. nuclei preparing for division (spireme-stage)
c. dividing cells showing mitotic figures
e. pair of daughter-cells shortly after division
Stages of early mitosis in a vertebrate cell with micrographs of chromatids
Condensing chromosomes. Interphase nucleus (left), condensing chromosomes (middle) and condensed chromosomes (right).
Prophase during mitosis
A cell in late metaphase. All chromosomes (blue) but one have arrived at the metaphase plate.
Metaphase during Mitosis
Anaphase during Mitosis
Telophase during mitosis
Cytokinesis illustration
Cilliate undergoing cytokinesis, with the cleavage furrow being clearly visible
An abnormal (tripolar) mitosis (12 o'clock position) in a precancerous lesion of the stomach (H&E stain)
Mitosis appearances in breast cancer
Cell shape changes through mitosis for a typical animal cell cultured on a flat surface. The cell undergoes mitotic cell rounding during spindle assembly and then divides via cytokinesis. The actomyosin cortex is depicted in red, DNA/chromosomes purple, microtubules green, and membrane and retraction fibers in black. Rounding also occurs in live tissue, as described in the text.
Some types of cell division in prokaryotes and eukaryotes
closed intranuclear pleuromitosis
closed extranuclear pleuromitosis
closed orthomitosis
semiopen pleuromitosis
semiopen orthomitosis
open orthomitosis
Normal and atypical forms of mitosis in cancer cells. A, normal mitosis; B, chromatin bridge; C, multipolar mitosis; D, ring mitosis; E, dispersed mitosis; F, asymmetrical mitosis; G, lag-type mitosis; and H, micronuclei. H&E stain.

In cell biology, mitosis is a part of the cell cycle in which replicated chromosomes are separated into two new nuclei.

Eukaryote

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Eukaryotes are organisms whose cells have a nucleus enclosed within a nuclear envelope.

Eukaryotes are organisms whose cells have a nucleus enclosed within a nuclear envelope.

The endomembrane system and its components
Simplified structure of a mitochondrion
Longitudinal section through the flagellum of Chlamydomonas reinhardtii
Structure of a typical animal cell
Structure of a typical plant cell
Fungal Hyphae cells: 1 – hyphal wall, 2 – septum, 3 – mitochondrion, 4 – vacuole, 5 – ergosterol crystal, 6 – ribosome, 7 – nucleus, 8 – endoplasmic reticulum, 9 – lipid body, 10 – plasma membrane, 11 – spitzenkörper, 12 – Golgi apparatus
This diagram illustrates the twofold cost of sex. If each individual were to contribute the same number of offspring (two), (a) the sexual population remains the same size each generation, where the (b) asexual population doubles in size each generation.
Phylogenetic and symbiogenetic tree of living organisms, showing a view of the origins of eukaryotes and prokaryotes
One hypothesis of eukaryotic relationships – the Opisthokonta group includes both animals (Metazoa) and fungi, plants (Plantae) are placed in Archaeplastida.
A pie chart of described eukaryote species (except for Excavata), together with a tree showing possible relationships between the groups
The three-domains tree and the Eocyte hypothesis
Phylogenetic tree showing a possible relationship between the eukaryotes and other forms of life; eukaryotes are colored red, archaea green and bacteria blue
Eocyte tree.
Diagram of the origin of life with the Eukaryotes appearing early, not derived from Prokaryotes, as proposed by Richard Egel in 2012. This view implies that the UCA was relatively large and complex.

Each gamete has just one set of chromosomes, each a unique mix of the corresponding pair of parental chromosomes resulting from genetic recombination during meiosis.

A haploid set that consists of a single complete set of chromosomes (equal to the monoploid set), as shown in the picture above, must belong to a diploid species. If a haploid set consists of two sets, it must be of a tetraploid (four sets) species.

Ploidy

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A haploid set that consists of a single complete set of chromosomes (equal to the monoploid set), as shown in the picture above, must belong to a diploid species. If a haploid set consists of two sets, it must be of a tetraploid (four sets) species.

Ploidy is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes.

In the first stage of sexual reproduction, "meiosis", the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During "fertilisation", haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.

Sexual reproduction

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In the first stage of sexual reproduction, "meiosis", the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During "fertilisation", haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.
An Australian emperor dragonfly laying eggs, guarded by a male
Flowers contain the sexual organs of flowering plants.
Puffballs emitting spores

Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete (such as a sperm or egg cell) with a single set of chromosomes (haploid) combines with another to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid).

A label diagram explaining the different parts of a prokaryotic genome

Genome

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All genetic information of an organism.

All genetic information of an organism.

A label diagram explaining the different parts of a prokaryotic genome
An image of the 46 chromosomes making up the diploid genome of a human male. (The mitochondrial chromosome is not shown.)
Part of DNA sequence - prototypification of complete genome of virus
Composition of the human genome
Log-log plot of the total number of annotated proteins in genomes submitted to GenBank as a function of genome size.

The Oxford Dictionary suggests the name is a blend of the words gene and chromosome.

Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis)

Cell division

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Process by which a parent cell divides, when a mother cell divides into two or more daughter cells.

Process by which a parent cell divides, when a mother cell divides into two or more daughter cells.

Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis)
Divisome and elongasome complexes responsible for peptidoglycan synthesis during lateral cell-wall growth and division.
Image of the mitotic spindle in a human cell showing microtubules in green, chromosomes (DNA) in blue, and kinetochores in red
Cell division over 42. The cells were directly imaged in the cell culture vessel, using non-invasive quantitative phase contrast time-lapse microscopy.
Kurt Michel with his phase-contrast microscope

In eukaryotes, there are two distinct types of cell division; a vegetative division, whereby each daughter cell is genetically identical to the parent cell (mitosis), and a reproductive cell division, whereby the number of chromosomes in the daughter cells is reduced by half to produce haploid gametes (meiosis).

The major structures in DNA compaction: DNA, the nucleosome, the 10 nm beads on a string chromatin fibre and the metaphase chromosome.

Chromatin

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Complex of DNA and protein found in eukaryotic cells.

Complex of DNA and protein found in eukaryotic cells.

The major structures in DNA compaction: DNA, the nucleosome, the 10 nm beads on a string chromatin fibre and the metaphase chromosome.
Basic units of chromatin structure
The structures of A-, B-, and Z-DNA.
Fig. 2: Alternative structural forms of DNA influencing chromatin structure
Fig. 3: Structure of DNA with two B-Z DNA junctions: It encompasses 1. breakage of a hydrogen-bond, where a Guanine rotates around its glycosyl-bond and the sugar thereby transforms into its syn-conformation. 2. Rotation of the corresponding second base (Cytosine) involving rotation of the sugar around the sugar-phosphate-bond. 3. At the B-Z junction hydrogen-bonds remain broken and bases are extruded.
A cartoon representation of the nucleosome structure. From.
Two proposed structures of the 30 nm chromatin filament.
Left: 1 start helix "solenoid" structure.
Right: 2 start loose helix structure.
Note: the histones are omitted in this diagram - only the DNA is shown.
Karyogram of human male using Giemsa staining, showing the classic metaphase chromatin structure.
Condensation and resolution of human sister chromatids in early mitosis
Microscopy of heterochromatic versus euchromatic nuclei (H&E stain).

During mitosis and meiosis, chromatin facilitates proper segregation of the chromosomes in anaphase; the characteristic shapes of chromosomes visible during this stage are the result of DNA being coiled into highly condensed chromatin.

This file demonstrates the basic knowledge needed to read a karyotype

Karyotype

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This file demonstrates the basic knowledge needed to read a karyotype
Karyogram of human male using Giemsa staining
Fusion of ancestral chromosomes left distinctive remnants of telomeres, and a vestigial centromere
human karyotype (male)
Karyogram from a human female lymphocyte probed for the Alu sequence using FISH.
Spectral karyogram of a human female
Spectral human karyotype

A karyotype is a preparation of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, sorted by length, centromere location and other features and for a test that detects this complement or counts the number of chromosomes.