Heredity and Variation — Maharashtra (SSC) Class 9 Science Solutions (Free)
Free step-by-step Maharashtra (SSC) Class 9 Science solutions for "Heredity and Variation" — important questions with detailed answers, download PDF for board exam preparation.
TL;DR: Free step-by-step Maharashtra (SSC) Class 9 Science solutions for "Heredity and Variation" — important questions with detailed answers, download PDF f…
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Q1: Define heredity and variation. Why is variation important?
Heredity is the transmission of traits from parents to offspring through genes. Variation is differences in traits among organisms in a population. Variation is important for evolution, adaptation, and survival - populations with variation can adapt to environmental changes better.
Q2: What is a chromosome? How many chromosomes are found in human cells?
A chromosome is a structure in the cell nucleus containing DNA and proteins. It carries genes responsible for hereditary traits. Human cells have 46 chromosomes (23 pairs), with 44 autosomes and 2 sex chromosomes (XX in females, XY in males).
Q3: Explain Mendel's law of segregation.
Mendel's law of segregation states that during gamete formation, paired alleles separate so that each gamete receives only one allele for a trait. During fertilization, alleles from parents combine, restoring the pair in offspring. This explains how traits skip generations.
Q4: What is a gene? What is the relationship between genes and traits?
A gene is a segment of DNA that codes for a specific protein and determines a particular trait. Each gene occupies a specific position (locus) on a chromosome. Traits result from the expression of genes - different alleles of a gene produce different variations of a trait.
Q5: Define dominant and recessive traits with an example.
Dominant trait is expressed when at least one dominant allele is present. Recessive trait is expressed only when two recessive alleles are present. Example: In pea plants, tall (T) is dominant over short (t). TT and Tt are tall; tt is short.
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