Heredity - Class 10 - Science
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Back Questions - Heredity | NCERT | Science | Class 10
How do Mendel’s experiments show that traits may be dominant or recessive?
Mendel's experiments, particularly his work with pea plants, demonstrated the concepts of dominant and recessive traits clearly. By cross-breeding pea plants with different characteristics (such as flower color and seed shape), he observed patterns in the offspring's traits. For example, when he crossed a plant with purple flowers (a dominant trait) with one with white flowers (a recessive trait), the first generation (F1) consistently showed purple flowers. Only when these F1 plants were self-pollinated did the recessive white flower trait reappear in the second generation (F2), but in a predictable 3:1 ratio (three purple to one white). Through this and similar experiments, Mendel showed that traits are inherited as discrete units (genes), with dominant ones masking recessive ones in heterozygous combinations.
How do Mendel’s experiments show that traits are inherited independently?
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Sign up nowA man with blood group A marries a woman with blood group O and their daughter has blood group O. Is this information enough to tell you which of the traits – blood group A or O – is dominant? Why or why not?
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Sign up nowA Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw
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Sign up nowA study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
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Sign up nowOutline a project which aims to find the dominant coat colour in dogs.
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Sign up nowExtra Questions - Heredity | NCERT | Science | Class 10
A homozygous purple flower variety of pea plant [PP] is crossed with a white flower variety of pea [pp]. Answer the following questions by using Punnett square:
i) Mention the phenotype and genotype of the F1 generation offspring.
ii) If the offspring of the F1 generation are crossed, what will be the phenotypic and genotypic ratios of the F2 generation?
iii) State Mendel's Law of Dominance.
iv) What is the scientific name of the pea plant? v) Name two genetic diseases in humans.
Find the solution with detailed analysis below:
Phenotype and Genotype of F1 Generation
When a homozygous purple flower (PP) is crossed with a homozygous white flower (pp), all the offspring in F1 generation are heterozygous purple flowers (Pp). Here, the phenotype (observable physical traits) of all F1 offspring is purple. Since they receive one allele for purple (P) and one for white (p), their genotype is heterozygous (Pp).
Here is the Punnett square:
P | P | |
p | Pp | Pp |
p | Pp | Pp |
Phenotypic and Genotypic Ratios of the F2 Generation
If we cross the F1 generation (all heterozygous, Pp) offspring with each other, the genotype in the next generation (F2) can be represented by the following Punnett square:
P | p | |
P | PP | Pp |
p | Pp | pp |
The Phenotypic Ratio for F2 is 3 purple : 1 white. The Genotypic Ratio is 1 homozygous purple (PP) : 2 heterozygous purple (Pp) : 1 homozygous white (pp), or 1:2:1.
Mendel’s Law of Dominance
Mendel's Law of Dominance states that in a heterozygote, the dominant allele manifests itself in the phenotype, completely masking the effect of the recessive allele. The allele that expresses itself is termed as dominant while the one which does not is termed as recessive.
Scientific Name of the Pea Plant
The scientific name of the garden pea is Pisum sativum.
Two Genetic Diseases in Humans
Thalassemia: This genetic disorder impairs the body's ability to produce hemoglobin, affecting the flow of oxygen.
Down's Syndrome: Caused by a trisomy of chromosome 21, leading to a total of 47 chromosomes instead of the usual 46.
This detailed analysis explains the concepts and answers for each part as requested.
The genetic composition of an organism is known as:
A) genotype
B) physiotype
C) phenotype
D) morphotype
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