What are chromosomes?

Question

this has to with mitosis

Answer 1

chromosomes are what makes you they carry your genetic information eg hair colour eye colour, you have 46 chromosomes in each cell or 23 pairs, but in sex cells the egg and the sperm u have only 23 as they join up with the opposite sex cell to make 46. thats meitosis, miosis is the development of ordinary body cells, this is done so if for example you cut your self you body is able to repair itself, hope you understand this and it was useful for you :)

Answer 2

The chromosome has an x shape that seperates to make two and it contains genetic information of that organism.
Each chromosome located in the DNA copies its entire genome by duplication. After replication each chromosome consists of two sister chromatids each a collection of the same genes present in single copy before replication. The centromere holds the two chromatids together. Then in mitosis the sister chromatids are pulled apart and repackaged as complete chromosome sets in two nuclei, one at each end of the cell. Mitosis, the division of the nucleus is followed by cytokinesis the division of the cytoplasm.

Answer 3

Chromosomes carry your DNA. They begin to replicate during interphase and later on become visible. They line up across the middle of the cell and then are pulled apart by the spindles. Once cytokensis (sp?) is completed the two new cells both have genetic info.

Answer 4

A chromosome is a large macromolecule into which DNA is normally packaged in a cell. Minimally, it is a very long, continuous piece of DNA (a single DNA molecule), which contains many genes, regulatory elements and other intervening nucleotide sequences.

The word chromosome comes from the Greek χρώμα (chroma, color) and σώμα (soma, body).

In the chromosomes of eukaryotes, the uncondensed DNA exists in a quasi-ordered structure inside the cell nucleus, where it wraps around histones (structural proteins, Fig. 1), forming a composite material called chromatin. Each chromosome has two arms, the shorter one called p arm (from the French petit, small) and the longer one q arm (q follows p in the Latin alphabet). During mitosis (cell division), the chromosomes are condensed and a spindle composed of microtubules is formed. Microtubules self-assemble from dimers of alpha and beta tubulin. They attach to chromosomes at specialized structures called kinetochores, one of which is present on each sister chromatid. Sister chromatids are attached at an area called the centromere (not necessarily at the center of the chromosome). A special DNA base sequence in the region of the kinetochores provides, along with special proteins, longer-lasting attachment in this region. This is the only natural context in which individual chromosomes are visible with an optical microscope.

Prokaryotes do not possess histones or nuclei. In its relaxed state, the DNA can be accessed for transcription, regulation, and replication.

History
Chromosomes were first observed in plant cells by Swiss botanist Karl Wilhelm von Nägeli in 1842, and independently in Ascaris worms by Belgian scientist Edouard Van Beneden (1846-1910). The use of basophilic aniline dyes was a fundamentally new technique for effectively staining the chromatin material in the nucleus. Their behavior in animal (salamander) cells was later described in detail by German anatomist Walther Flemming, the discoverer of mitosis, in 1882. The name was invented later by another German anatomist, Heinrich von Waldeyer.


Chromosomes in plants, yeast and animals
Eukaryotes (cells with nuclei such as plants, yeast, and animals) possess multiple linear chromosomes contained in the cell's nucleus. Each chromosome has one centromere, with one or two arms projecting from the centromere.


Chromosomes in bacteria
Bacteria have a single circular chromosome. Bacterial DNA also exists as plasmids which are circular pieces of DNA that can be transmitted between bacteria. Antibiotic resistance genes are often carried on plasmids and can thus spread between different bacteria. The distinction between plasmids and chromosomes is poorly defined, though size and necessity are generally taken into the account. Bacterial chromosomes initiate replication and one origin of replication.

Bacterial chromosomes tend to be tethered to the plasma membrane of the bacteria. In molecular biology application, this allows for its isolation from plasmid DNA by centrifugation of lysed bacteria and pelleting of membranes (and the attached DNA).


Chromatin
Two types of chromatin can be distinguished:

Euchromatin, which consists of DNA that is active, e.g., expressed as protein.
Heterochromatin, which consists of mostly inactive DNA. It seems to serve structural purposes during the chromosomal stages. Heterochromatin can be further distinguished into two types:
Constitutive heterochromatin, which is never expressed. It is located around the centromere and usually contains repetitive sequences.
Facultative heterochromatin, which is sometimes expressedIn the very early stages of mitosis, the chromatin strands become more and more condensed. They cease to function as accessible genetic material and become a compact transport form. Eventually, the two matching chromatids (condensed chromatin strands) become visible as a chromosome, linked at the centromere. Long microtubules are attached at the centromere and two opposite ends of the cell. During mitosis, the microtubules pull the chromatids apart, so that each daughter cell inherits one set of chromatids. Once the cells have divided, the chromatids are uncoiled and can function again as chromatin. In spite of their appearance, chromosomes are highly structured which enables these giant DNA structures to be contained within a cell nucleus

Answer 5

They're the structures in the cell that contain genes. In eukaryotic cells, they're not visible except at the time of mitosis when they become visible during prophase and separate during anaphase.