Chromosomes in Humans
The correct diploid number of chromosomes in humans is 46, out of which 44 are somatic ones and remaining 2 are sex determining chromosomes. Any abnormalities in the chromosomal number or structure are expressed as genetic disorders. Read on to know more...
Chromosomes are threadlike structures of DNA present in the cell nucleus, which are responsible for carrying genetic information. The word chromosome is derived from the Greek words for color (chroma) and body (soma). In laboratory studies, chromosomes are stained easily with specific dyes, hence the name. Studying chromosomes in humans is an important aspect in genetics, as the phenotypic expression of an individual entirely depends on them. Also, genetic disorders are caused due to abnormalities in the chromosomes.
Chromosomes in Humans: An overview
The human genome is diploid, meaning it contains 2 sets of chromosomes. As per researches in human genetics, it is found that more than 3 billion DNA base pairs are present in a single haploid human genome. In addition to these, chromosomes contain non-coding genes, regulatory elements and proteins. Together, they are arranged in an organized manner as chromosomes. Following are some points concerning facts about human chromosomes, which you may find interesting.
Number of Chromosomes in Humans
The total chromosomes can be expressed in diploid and haploid number. While the diploid number of chromosomes in humans is 46, the haploid number is 23. All normal human cells are diploid and the gametic cells (male gametes and female gametes) are haploid. In short, the number of chromosomes in humans differs, based on whether you are referring to a diploid cell or a haploid cell.
Sex Chromosomes in Humans
When we say sex chromosomes, they are used for determining the gender of an individual. Out of the 23 pairs of chromosomes, 22 are autosomal and 1 pair is the pair known as sex chromosomes. Males have one 'X' and one 'Y' chromosome, represented as (XY); whereas females have two copies of the same chromosome 'X' (represented as XX). Besides humans, this XY sex-determination system is observed in many sexually reproducing organisms, like ginkgo biloba tree and Drosophila insect.
Chromosomes and Reproduction
In the process of fertilization, the male gamete that contains 22 autosomes and 1 sex chromosome (either X or Y) fuses with the female gamete that contains 22 autosomes and 1 sex chromosome (X) to form a diploid zygote. Thus, the resulting zygote has 44 autosomes and 2 sex chromosomes (may be XX or XY). Precisely speaking, two haploid cells or gametes fertilize to form a diploid cell during the reproduction process, thus retaining the typical chromosome number in humans.
Chromosome Abnormalities in Humans
Abnormalities in chromosomes are usually due to alterations in the chromosome number or structure. An example of genetic disorder due to extra chromosomes in humans is Down syndrome. In this condition, three copies of one chromosome is present in an individual, a condition known as trisomy. On the other hand, lack of one chromosome leads to an abnormality called monosomy. An example of this is Turner syndrome, a disease in females in which there is only one X chromosome.
Speaking about structural abnormalities of chromosomes in humans, they are caused either due to the presence of additional chromosomal parts (duplication) or lack of the same (deletion). In some conditions, sections of the chromosomes get exchanged between two chromosomes during cell division (translocation), resulting in a structural abnormality. In majority of the cases, abnormalities in the chromosomes of an offspring are inherited from its biological parents.
On a concluding note, presence of typical number of chromosomes in humans is imperative to express normal phenotype characteristics. Any major changes in the numerical value or structure is a cause for medical condition. For ease in studies, similar looking chromosome pairs are lined up in a proper fashion, along with their respective numbers, which is referred to as karyotype. Various researches in human genetics are ongoing to find out the solutions for chromosome related medical conditions.
The correct diploid number of chromosomes in humans is 46, out of which 44 are somatic ones and remaining 2 are sex determining chromosomes. Any abnormalities in the chromosomal number or structure are expressed as genetic disorders. Read on to know more...
Chromosomes are threadlike structures of DNA present in the cell nucleus, which are responsible for carrying genetic information. The word chromosome is derived from the Greek words for color (chroma) and body (soma). In laboratory studies, chromosomes are stained easily with specific dyes, hence the name. Studying chromosomes in humans is an important aspect in genetics, as the phenotypic expression of an individual entirely depends on them. Also, genetic disorders are caused due to abnormalities in the chromosomes.
Chromosomes in Humans: An overview
The human genome is diploid, meaning it contains 2 sets of chromosomes. As per researches in human genetics, it is found that more than 3 billion DNA base pairs are present in a single haploid human genome. In addition to these, chromosomes contain non-coding genes, regulatory elements and proteins. Together, they are arranged in an organized manner as chromosomes. Following are some points concerning facts about human chromosomes, which you may find interesting.
Number of Chromosomes in Humans
The total chromosomes can be expressed in diploid and haploid number. While the diploid number of chromosomes in humans is 46, the haploid number is 23. All normal human cells are diploid and the gametic cells (male gametes and female gametes) are haploid. In short, the number of chromosomes in humans differs, based on whether you are referring to a diploid cell or a haploid cell.
Sex Chromosomes in Humans
When we say sex chromosomes, they are used for determining the gender of an individual. Out of the 23 pairs of chromosomes, 22 are autosomal and 1 pair is the pair known as sex chromosomes. Males have one 'X' and one 'Y' chromosome, represented as (XY); whereas females have two copies of the same chromosome 'X' (represented as XX). Besides humans, this XY sex-determination system is observed in many sexually reproducing organisms, like ginkgo biloba tree and Drosophila insect.
Chromosomes and Reproduction
In the process of fertilization, the male gamete that contains 22 autosomes and 1 sex chromosome (either X or Y) fuses with the female gamete that contains 22 autosomes and 1 sex chromosome (X) to form a diploid zygote. Thus, the resulting zygote has 44 autosomes and 2 sex chromosomes (may be XX or XY). Precisely speaking, two haploid cells or gametes fertilize to form a diploid cell during the reproduction process, thus retaining the typical chromosome number in humans.
Chromosome Abnormalities in Humans
Abnormalities in chromosomes are usually due to alterations in the chromosome number or structure. An example of genetic disorder due to extra chromosomes in humans is Down syndrome. In this condition, three copies of one chromosome is present in an individual, a condition known as trisomy. On the other hand, lack of one chromosome leads to an abnormality called monosomy. An example of this is Turner syndrome, a disease in females in which there is only one X chromosome.
Speaking about structural abnormalities of chromosomes in humans, they are caused either due to the presence of additional chromosomal parts (duplication) or lack of the same (deletion). In some conditions, sections of the chromosomes get exchanged between two chromosomes during cell division (translocation), resulting in a structural abnormality. In majority of the cases, abnormalities in the chromosomes of an offspring are inherited from its biological parents.
On a concluding note, presence of typical number of chromosomes in humans is imperative to express normal phenotype characteristics. Any major changes in the numerical value or structure is a cause for medical condition. For ease in studies, similar looking chromosome pairs are lined up in a proper fashion, along with their respective numbers, which is referred to as karyotype. Various researches in human genetics are ongoing to find out the solutions for chromosome related medical conditions.
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