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Question
Explain the structure of chromosomes with labelled diagram.
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Solution
Structure of chromosome:
- A typical chromosome consists of two chromatids joined together at the centromere also known as primary constriction.
- Primary constriction consists of a disk shape plate called the kinetochore. During cell division, spindle fibers get attached to the kinetochore.
- Apart from primary constriction, a few chromosomes possess an additional one or two constrictions called secondary constriction.
- At secondary constriction I (nucleolar organizer), nucleolus becomes organized during interphase.
- A satellite body (SAT body) is attached at secondary constriction II, in very few chromosomes.
- Each chromatid in turn contains a long, unbranched, slender, highly coiled double-stranded DNA thread, called chromonema, extending through the length of the chromatid.
- The ends of chromosomes (i.e. chromatids) are known as telomeres.
A: Parts of chromosomes
B: Showing secondary constrictions and details
Structure of Chromosome
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Answer the following question in your own words.
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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. |
Identify the TRUE statements with respect to aneuploidy.
- When the chromosome number is not the exact multiple of the haploid set, it is described as aneuploidy.
- Aneuploidy is only addition of one or more chromosome(s) to the total number of chromosomes in a cell.
- Aneuploidy is further classified as hypoploidy and hyperploidy.
In higher unisexual animals, one pair of chromosomes is not identical in two sexes. It is called as ______.
After a mitotic cell division, a human female cell will have ______.
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