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1. Haemophilia is caused due to X-linked recessive gene. Females have double X chromosomes. 

2. Even if she has haemophilic gene on one of her X-chromosome, the dominant gene on other Xchromosome, suppresses its expression. Female therefore, does not become haemophilic. 

3. If she inherits haemophilic gene on both of her X-chromosomes, this combination becomes lethal. Such embryo is aborted. If born, she dies soon. This makes the possibility of female becoming a haemophilic extremely rare.

Coat colour in cattle

Red female RR × White male WW 

P₁ generation : RR × WW 

Gametes : R and W 

F₁ generation all RW Roan coloured 

P₂ generation RW × RW

Genotypic ratio : 1 RR : 2 RW : 1 WW 

Phenotypic ratio : 1 Red : 2 Roan : 1 White

1. Linkage is the tendency of genes to be inherited together because they are present in the same chromosome. 

2. All the genes on a chromosome are linked to one another. In the linkage group some of the genes are included. 

3. The number of linkage groups of a particular species corresponds to its haploid number of chromosomes present in the organism. 

4. In human beings, there are 23 linkage groups which correspond to the pairs of chromosomes found in each cell. 

5. Linkage groups can be separated only at the time of crossing over during meiosis. The linkage group can form a new combination of genes after crossing over. 

6. Linkages Eire of two types, viz, complete linkage and incomplete linkage. 

7. Morgan discovered linkage in animals while Bateson and Punnett discovered it in plants.

Human female is referred to as carrier of colour blindness because of the following reasons:

1. Females possess double Xchromosomes in her gametes.

2. If one X-chromosome is carrying recessive gene for colour blindness, her other dominant X hides the expression of colour blindness and hence she does not become a patient. 

3. But such female can carry the defective gene to her progeny. Thus she is called carrier of colour-blindness. 

4. A female having one recessive gene on X-chromosome is a carrier female, while a female possessing both recessive genes on both the Xchromosomes will be colour blind which is very rare.

Down’s syndrome is an example of chromosomal disorder caused due to nondisjunction of autosomes.

Thalassemia is an example of autosomal recessive disorder.

The substances are made up of many tiny particles which cannot be seen by naked eye. Even though we cannot see the tiny particles of sugar in sugar solution, we can understand that tiny particles of sugar is dissolved in the solution while we taste it.

All the substances are made up of tiny particles which cannot be seen by naked eye and these tiny particles bear all the properties of the substances.

Strainer is a kind of sieve which is used to separate a liquid from solid.

The materials which have very small range of plastic extension are called brittle materials. Such materials break as soon as the stress is increased beyond the elastic limit. 

Examples: Cast iron, glass, ceramics, etc.

Condensation.

When two or more than two substances are mixed together in any ratio then it is called a mixture.

1. camphor

2. naphthalene balls becomes smaller

1. Filtration

2. Vaporisation.

Separation method process is a to separate two substances, that once formed a mixture.

For making panner, a few drops of lemon juice are added to milk as it boils, This gives a mixture of particles of solid paneer and liquid The paneer is then separated by filtering the mixture through a fine cloth or strainer.

a. Salt is obtained from seawater by the process of Evaporation. 

b. Impurities settled at the bottom when muddy water was kept overnight in a bucket, The clear water was then poured off from the top. The process of separation used in this example is called Sedimentation and decantation.

(a) Mixture of milk and sugar

(i) happy
(ii) Sun
(iii) threshed
(iv) winnowed
(v) handpicked
(vi) sieved
They got a good price as they used appropriate methods of separation to get good quality of flour.

Hand picking, threshing and winnowing.

1. Decantation is used to separate insoluble solid or liquid Rain water is a mixture of mud and water. It is purified by decantation 

2. Oil and water also get separated by this method because oil floats over water

Filter paper is used Filtration

1. (b)

2. (c)

3. (a)

4. (d)

It was a joke, especially among young people in the Ashram, that if you wanted to see Gandhiji everyday and talked to him and hear him crack jokes, you had only to be ill and get into bed.

Gandhiji arranged the care of the sick in person at the Ashram.

By alum, dirt settles at the bottom and clean water at the top.

Sedimentation and decantation.

Lagoon is an area of relatively shallow, quiet water situated in a coastal environment and having access to the sea but separated from the open marine conditions by a barrier.

Dissolved impurities from water can be removed by distillation.

Gandhiji visited the sick every day and spent a few minutes at every bed-side. He also saw to things carefully and never failed to crack a joke
or two with the patient.

A homogeneous mixture is a solid, liquid or gaseous mixture that has the same proportions of its components throughout a given sample.

Example: air, salt solution, squash etc.

The young lad was fond of coffee. He did not get his favourite drink in the Ashram because it was not allowed there.

(b) Condensation

Sieving is the process of filtering components of a mixture of different sizes. Sieving allows fine particles to pass through the holes of the sieve, while the bigger impurities remain on the sieve.
Sieving is used in flour mills to separate broken particles of grains from flour. It is also used at construction sites to separate lumps, smaller stones from the mixture of sand and cement.

a. False

b. False

a. Sublimation. A solid directly changes into gas

b. Camphor, iodine, naphthalene.

a. False

b.  False

We should add sugar before adding ice. Sugar dissolves in warm water more quickly than in cold water. We can dissolve more sugar before mixing ice in water.

d. Condensation

We should add ice after dissolving sugar because the dissolving power of water decreases with decrease in temperature, so if we add ice Before dissolving sugar, less amount of sugar will be get dissolved.

The element X is oxygen. The atomic number is 8, and its electronic configuration is 2,6. Oxygen is used for respiration by the living beings.

False

Carbon in its allotropic forms under suitable conditions, burns in oxygen to produce carbon monoxide or carbon dioxide depending on the extent of combustion. Incomplete combustion results in the evolution of carbon monoxide, whereas complete combustion would result in the formation of carbon dioxide.