sci_bio
Cell Division
Chapter summary, hard words and model exam answers for ICSE Class 10 Hindi.
Free online summary and notes (ICSE Class 10 Hindi). Read it here, no PDF download needed.
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Biology · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
Mitosis makes identical copies for growth and repair. Meiosis makes gametes for sexual reproduction.
Each chromosome becomes two identical chromatids joined at the centromere, so each daughter cell can get a full set.
Chromosomes condense (Prophase), line up (Metaphase), separate to the poles (Anaphase), and form two nuclei (Telophase).
Crossing over and random assortment shuffle the genes, so every gamete is different. This is the basis of variation.
Hard words & meanings
| chromosome | a thread-like structure of DNA and protein carrying genes, found in the nucleus |
| chromatid | one of the two identical copies of a chromosome joined at the centromere after replication |
| centromere | the point where two sister chromatids are joined and where spindle fibres attach |
| diploid (2n) | a cell with two sets of chromosomes; human body cells have 46 |
| haploid (n) | a cell with one set of chromosomes; human gametes have 23 |
| gamete | a sex cell (sperm, egg or pollen) that is haploid |
| crossing over | the exchange of DNA segments between homologous chromosomes in meiosis I |
| cytokinesis | the division of the cytoplasm that splits one cell into two |
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