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CBSE NOTES ⇒ Class 10th ⇒ Science ⇒ 9. Heredity and Evolution

9. Heredity and Evolution

Inherited Traits


Inherited Traits


Dominant Traits : Those inherited traits of parents which are visible in the offspring, called dominant traits. 

Recessive Traits : Those inherited traits of parents which are hiden in the offspring are called recessive traits. 

Example: short plant (t) in Mendel's experiment.

Genotype: Gynotype is a group of genes which is responsible for a special characteristic. It is a genetic information present in cells and It is not visible directly in the indivisual.

Examples of genotypes: 

(a) The gene responsible for colour of eyes. 

(b) The gene responsible for colour of hair. 

(c) The gene responsible for height.

(d) The gene responsible for the heridetory(genetic) diseases.

How to make genotype changes. 

(a) Changing in gene and chromosome. 

(b) Recombination of gene. 

(c) Hybriding of gene.    

Phenotypes: Those visible traits which are seen in the organism and depends on genotype is called phenotype traits. 

But it can be influenced by the envirmental factors. This is the manifestation of the informations of gene. It can be found by simple observation. 

Examples: colour of eyes, colour of hair, height, voice, some diseases and some fixed behavior. 

Differences Between Inherited Traits: 

Acquired Traits: 

1. These are the traits which are developed in an individual due to special conditions
2. They cannot be transferred to the progeny(offspring).
3. They are helpful in evolution
eg. Low weight of starving beetles.

Inherited Traits: 

1. These are the traits which are passed from one generation to the next.
2. They get transferred to the progeny(offspring).
3. They are helpful in evolution.
eg. Colour of eyes and hair

Monohybrid cross in Mendel's Experiment : 

In this experiment Mendel's had taken two pea plants of single character of tall and short plant as parent plants. All plants are tall as tall as parent. Mendelian experiments test this by getting both the parental plants and these F1 tall plants to reproduce by self-pollination. The second-generation, or F2, progeny of the F1 tall plants are not all tall. Instead, one quarter of them are short. This indicates that both the tallness and shortness traits were inherited in the F1 plants, but only the tallness trait was expressed. 

Ratio of characters in Mendelian experiment: 

There are following ratios of characters of plants grown in F2 generation on the basis of genotype and phenotype in Mendel's monohybrid cross test.

Phenotype : Tt Tt Tt tt (3 : 1) 

3 tall and 1 short plant

Genotype: Tt Tt Tt tt (1: 2 : 1) 

Genetically 1 tall (TT) : 2 tall (Tt) : 1 short (tt)  

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Study Materials List:

CBSE NOTES ⇒ Class 10th ⇒ Science
1. Chemical Reactions and Equations
2. Acids, Bases and Salts
3. Metals and Non-metals
4. Carbon and its Compounds
5. Periodic Classification of Elements
6. Life Processes
7. Control and Coordination
8. How do Organisms Reproduce
9. Heredity and Evolution
10. Light-Reflection and Refraction
11. Human Eye and Colourful World
12. Electricity
13. Magnetic Effects of Electric Current
14. Sources of Energy
15. Our Environment
16. Management of Natural Resources

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