Heredity

Q1. What are genes?  

Ans. A gene is the basic physical and functional unit of heredity. It is made up of DNA.

Q2. In the case of round yellow and green wrinkled, which is the dominant trait set?

Ans. The round shape of seed and Yellow colour of the seed.

Q3. The sex of a child is determined by what they inherit from their father and not their mother.” Justify. 

Ans. Because the Y sex chromosome is inherited only from the father.

Q4. Name the scientist who established the laws of inheritance. 

Ans. Gregor Johann Mendel. 

Q4. Name the scientist who established the laws of inheritance. 

Ans. Gregor Johann Mendel. 

Q5. Where genes are located? 

Ans. Genes are located over the chromosomes/DNA as linear segments. 

Q6. Why did Mendel select the Pea plant for his experiment? 

Ans. Availability of pure line plant, clearly visible observable characters, contrast characters of same features, easily pollinated (self and cross), etc.

Q7. Describe genotype and phenotype with one example of each. 

Ans. The genotype of an organism is its complete set of genetic material, E.g.- TT, Tt, tt. The phenotype is an observable feature. E.g.- tall, dwarf. 

Q8. What is the significance of variation? 

Ans. Variation enables organisms to adjust and adapt better according to the changing conditions of the environment (Survival advantage).

Q9. Mention the difference between the inherited and the acquired characters. Give one example of each of the characters that are inherited and the ones that are acquired in humans.  

Ans. 

1. Inherited trait: 

• Obtained from parents (since the time of his birth and passed on from one generation to another.

• Attached ear lobe, baldness. 

2. Acquired trait: 

• Gain after birth (person develops during his lifetime). 

• Obesity, reading skill. 

Q10.
(a) Write the full form of DNA
(b) Why are variations essential for the species?  

Ans. 

(a) Deoxyribonucleic acid

(b) Genetic variation in a group of organisms enables some organisms to survive better than others in the environment in which they live.

Q11. Make a representation of a Dihybrid cross showing a phenotypic ratio of 9:3:3:1.   

Ans. 

(Fig. 8.5.)

Q12. Describe the law of dominance, law of segregation and law of segregation. 

Ans. 

Law of dominance: When parents having pure contrasting characters are crossed then only one character expresses itself in the F1 generation. This character is the dominant character and the character/factor which cannot express itself is called the recessive character. 

Law of segregation: The phenomenon of separation of the two alternating factors of one character, during gamete formation, so that one gamete receives only one factor of a character is called as ‘Law of Segregation'. 

Law of independent assortment: the alleles of two (or more) different genes get sorted into gametes independently of one another.

Q15. State the importance of the chromosomal difference between sperm and eggs of humans. Also, mention the criteria of sex determination. 

Ans. 

Human sperm: 22 + XY

Human egg: 22 + XX

Sex of the child will be determined by which sperm type fuses with the egg. The sex of the child will be male if 22+Y sperm fuses with the egg. It will be female if 22+X sperm fuses with the ovum.