sci_bio
Variation & Mutations
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.
About the author
Biology · CBSE 10 · ICSE 10 · GCSE (AQA, Edexcel, OCR)
Summary
Variation can be genetic (from our DNA) or environmental (from our surroundings). Only genetic variation is passed to children.
Height is continuous and polygenic. Blood group is discontinuous, set by one gene with little environmental effect.
Substitution swaps one base; deletion or insertion shifts every codon after it (a frameshift), usually wrecking the protein. Mutagens like UV light raise the rate.
Without variation a species cannot adapt. Farmers also exploit it through selective breeding.
Hard words & meanings
| variation | the differences in characteristics between individuals of the same species |
| continuous variation | variation showing a full range of values with no gaps, plotted as a bell curve (e.g. height) |
| discontinuous variation | variation falling into distinct separate categories with no in-betweens (e.g. blood group) |
| mutation | a change in the DNA base sequence of a gene, or in chromosome number or structure |
| substitution | a mutation where one base is replaced by a different one |
| deletion | a mutation where one or more bases are removed, causing a frameshift |
| frameshift | the shift in the reading of all codons after an insertion or deletion |
| mutagen | a physical or chemical agent that raises the mutation rate, e.g. UV light or tobacco chemicals |
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