Heredity and Types of Inheritance for Class 5 Science
- Every human being has particular characteristics or traits, which are passed from one generation to another because of the transfer of genetic material. This transmission is called inheritance.
- Genes present in the nucleus of our cells play a vital role in types of inheritance. The study of genes is called genetics.
- The passage of characters leads to gradual changes in generations, which is called evolution. It is studied to understand the development and continuity of life on Earth over the years.
Transfer of a Physical Trait
What Do You Understand by the Term Physical Traits? Can Two People Have the Same Physical Traits?
The features that we can see with the eyes are called physical traits. For example, the type of hair, skin colour, and colour of the eyes.
Yes, two people can have the same physical traits, but that does not imply the same genetic makeup.
Do Twins Have the Same Genetic Makeup?
No, twins do not have the same genetic makeup. No two people share the same genetic makeup, either twin or not.
What Do You Understand by Identical Twins and Non-Identical Twins?
- Identical twins are born when a single fertilised egg in the female body segregates and develops into two different babies.
- Non-identical twins are born when two different fertilised eggs grow into two separate babies.
Difference Between Acquired and Inherited Traits
What Are Sex Chromosomes?
- The chromosomes which are responsible for the determination of the sex of a person are called sex chromosomes.
- In humans, X and Y are sex chromosomes.
- The combination of XX chromosomes leads to a female child, whereas XY chromosomes lead to a male child.
How Are Genetic Disorders Transferred in a Family for Generations?
- Genetic disorders are transferred along with the passage of genes from one generation to another.
- It is not necessary that every member of the future generation would suffer from the same disease.
- In some cases, the disease stays hidden due to different combinations of genes.
- It may again express itself in the future generation when the combination or pairing of genes changes.
People Living in the Mountains Have High Levels of Haemoglobin in Their Blood. Why? Do You Think It Is a Genetic Trait?People Living in the Mountains Have High Levels of Haemoglobin in Their Blood. Why? Do You Think It Is a Genetic Trait?
- Haemoglobin plays a vital role in the transfer of oxygen in our bodies.
- As we go to height or ascend on mountains, the air becomes thinner, which leads to a fall in oxygen level in the air.
- The body compensates for the same by building a large number of red blood cells so that they can work to transport more amount of oxygen.
- The rise in red blood cells leads to an increase in haemoglobin.
- It is a change which occurs due to external factors. Hence, it is an acquired trait.
How the Combination of Genes Plays a Role in the Expression of Dominant and Recessive Traits?
- Genes occur in pairs.
- Out of the pair, one gene represents a dominant trait and the other a recessive trait.
- The expression of traits depends on their combination. There are the following possibilities—
|One gene of dominant trait, and the other of a recessive trait||Dominant|
|Both the genes of a dominant trait||Dominant|
|Both the genes of recessive traits||Recessive|
Why Do Acquired Traits Not Pass From One Generation to Another?
- Acquired traits do not alter the genetic make-up of an individual.
- For example, the building of muscles is because of exercise, not because of any genetic alteration. Similarly, the piercing of ears has nothing to do with genes.
- Hence, acquired traits do not pass from one generation to another.
The Chromosomes Are Divided Into Halves at the Time of Formation of Gametes in Individuals. Why Do You Think This Happens?
- The gametes from two different individuals combine to form a zygote which develops into a new individual.
- If the chromosomes were not halved at the time of formation of gametes, then the number of chromosomes would be doubled in the new individual.
- It may lead to genetic mutations, which may result in genetic disorders or the expression of any unknown trait.
- Hence, nature has made a mechanism for the continuity of the basic gene pattern of a species.
Why Can Only a Pea Plant Be Crossed With Another Pea Plant, Not a Gram Plant?
- The crossing can be done only between individuals of similar species.
- The reason is that gametes of individuals belonging to different species are not compatible. Hence, they would not lead to the formation of a zygote or a new individual.
- The same theory applies to animals too.The same theory applies to animals too.
A group of individuals with the same characteristics that can be crossed together to form fertile offspring is called a species.
What Do You Understand by the Term Hybrid?
An individual produced due to the crossing of two genetically different individuals is called a hybrid.
For example, a mule is obtained by the cross between a donkey and a horse.
What Is a Gene? State the Essential Characteristics of a Gene?
- Gene is the structural and functional unit of inheritance.
- It should possess the following characteristics—
- It should be located in the cells of an individual.
- It should be able to store genetic information.
- It should be physically ad chemically stable.
- It should be able to express itself in an individual.
- It should be able to undergo gradual changes which would bring necessary changes in a species for its survival.