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Introduction
The small threadlike portion of the cell that contains genetic information in genes is known as the chromosome. The compactness of any chromosome is a specific property. The 46 chromosomes contained in human cells, for example, have a total length of 200 nm (1 nm = 10 9 meters); if the chromosomes were unwound, the genetic information they contain would be nearly 2 meters (6.5 ft) long. The compactness of the xx chromosome aids in organizing genetic material during cell division. It allows it to fit inside structures such as the nucleus of a cell, which has an average diameter of about 5 to 10 m (1 m = 0.00l mm, or 0.000039 inches), or the polygonal head of a virus particle, which can have a diameter of only 20 to 30 nm. A chromosome is a well-organized DNA bundle located in the cell nucleus. Each creature has a different number of chromosomes. Humans contain 23 chromosomal pairs, including 22 pairs of numbered autosomes and one pair of sex chromosomes, X and Y. Each parent contributes one chromosome to each pair, giving kids half of their mother’s chromosomes and half of their father’s.
Significance and Formation of Chromosomes
One of the most significant distinctions between viruses, prokaryotes, and eukaryotes is the shape and position of chromosomes. The chromosomes of non-living viruses are either DNA (deoxyribonucleic acid) or RNA (ribonucleic acid), which are firmly packed inside the viral head. Chromosomes are made solely of DNA in prokaryotic organisms (bacteria and blue-green algae). A nuclear membrane does not protect a prokaryotic cell’s single chromosome. The chromosomes are housed in a membrane-bound cell nucleus in eukaryotes. A eukaryotic cell’s chromosomes are essentially DNA coupled to a protein core. They also have RNA in them. Each eukaryotic species has its number of xx chromosomes (chromosome number). In asexually reproducing organisms, the chromosome number is the same in all of the organism’s cells. The set of chromosomes within body (somatic) cells are diploid (2n; each chromosome has two copies), that’s double the haploid (1n) amount observed in sexually reproducing animals’ sex cells or gametes. This haploid number is generated during meiosis. During fertilization, two gametes join to form a zygote, a single cell with a diploid set of chromosomes.
Mitosis is the process through which somatic cells divide and proliferate. The chromosomes uncoil between cell divisions, culminating in chromatin, a scattered mass containing genetic material. When xx chromosomes are uncoiling, DNA synthesis may commence. DNA repeats itself in preparation for cell division during this phase. The DNA compresses into chromosomes after replication. Each chromosome at this point is made up of a collection of duplicate chromatids kept together by the centromere. The centromere is where the kinetochore, a protein structure that connects the spindle fibres, attaches (part of a structure that pulls the chromatids to opposite ends of the cell). The centromere replicates, and the chromatid pair splits during the middle stage of cell division; each chromatid becomes a distinct chromosome at this time. The cell splits, and both daughter cells contain a complete set of chromosomes (diploid). In the new cells, the chromosomes uncoil, generating a diffuse web of chromatin once more.
Types of Chromosomes
In many organisms with separate sexes, there are two types of chromosomes: sex chromosomes & autosomes. Except for sex-linked features, which are governed by sex chromosomes, autosomes control the overall inheritance of all attributes. Humans contain 22 sets of autosomes and one couple of sex chromosomes. During cell division, they all behave in the same way. See linkage group for information on sex-related features.
The physical breakdown of chromosomal subunits is known as chromosome breakage. It’s generally followed by a get-together (frequently at a foreign site, resulting in a chromosome unlike the original). The standard model of crossing over is based on the breakage and reunion of homologous chromosomes, which results in unanticipated offspring after mating.
Molecular vs. chromosomal sites
One approach to characterizing the placement of a gene on a chromosome is chromosomal location, also known as cytogenetic location. The molecular location is another method for determining a gene’s location. The base pair sequence identifies the gene’s molecular location on a chromosome. The molecular location is more accurate; nonetheless, slight changes in the address may occur between study groups due to different genome sequencing technologies.
In humans, the EGFR gene is located on chromosome 7p12, whereas the molecular location is Chromosome 7, NC 000007.14 (base pairs 55,019,032 to 55,207,338).
Conclusion
Chromosomes are thread-like structures that exist within the nucleus of animal and plant cells. Each chromosome is composed of protein and one molecule of deoxyribonucleic acid (DNA). DNA, which is passed down from parents to children, includes the precise instructions that distinguish each type of living species. The number of chromosomes is unique to each species and can vary greatly between them. The genotypic ratios of a cross are determined by the distribution of two copies of a gene to equal numbers of gametes and the fact that gametes mix at random during fertilization.
