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प्रश्न
Describe the structure of sex chromosomes with the help of labelled diagram.
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उत्तर
Structure of X and Y chromosomes:
- The x chromosome is straight, rod-like, and longer than the Y chromosome.
- The x chromosome is metacentric, while the Y chromosome is acrocentric.
- The x chromosome has a large amount of euchromatin (extended region) and a small amount of heterochromatin (highly condensed region).
- Euchromatin has a large amount of DNA material, hence the X chromosome is genetically more active.
- The y chromosome has a small amount of euchromatin and a large amount of heterochromatin, hence it is genetically less active or inert.
- Both X and Y chromosomes show homologous and non-homologous regions.
- Homologous regions show similar genes while non-homologous regions show dissimilar genes.
- Crossing over occurs only between homologous regions of X and Y chromosomes.
- The non-homologous region of the X chromosome is longer and contains more genes than that of a non-homologous region of the Y chromosome.
- X-linked genes are present on the non-homologous region of the X-chromosome while Y-linked genes are present on the non-homologous region of the Y-chromosome.
संबंधित प्रश्न
State the exact location of the Centromere
Name the following:
The number of chromosomes present in a nerve cell of a human being.
Enumerate the various changes that occur in the nucleus of the cell during prophase.
Give Technical Terms
The stage at which the formation of chiasmata occurs.
Column ‘II’ is a list of items related to ideas in Column ‘I’. Match the term in Column ‘II’ with a suitable idea given in Column ‘I’.
| Column I | Column II |
| Genetics | Chromosomes are similar in size and shape. |
| Autosomes | The alternative forms of a gene. |
| Recessive gene | Study of laws of inheritance of characters |
| Allele | A gene that can express only when in a similar pair. |
| Homologous chromosomes | Chromosomes are other than the pair of sex chromosomes. |
In humans, the sex chromosome complement is
The centromere is found at the centre of the ______ chromosome.
Explain the structure of a chromosome.
______ is a sudden permanent heritable change that can occur in the gene, in the chromosome or chromosome number.
Normally, genes occur in a pair of chromosome, but genes of X and Y chromosomes shows different gene loci indicating ______.
