33 Science -- Heredity

Differentiate between:a. Genotype and Phenotype.b. Dominant characteristics and Recessive characteristics.c. F1 generations and F2 generations.d. Monohybrid cross and Dihybrid cross.

Differentiate between:
a.    Genotype and Phenotype.
b.    Dominant characteristics and Recessive characteristics.
c.   F₁ generations and F₂ generations.
d.    Monohybrid cross and Dihybrid cross.

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a. Genotype and Phenotype.

Genotype	Phenotype
The internal genetic makeup or appearance of an organism is called genotype.	The external appearance of an organism for a contrasting characteristic is called phenotype.
Parental characteristics can be found in genotype.	Parental characteristics cannot be found 100% in phenotype.
It is expressed in letters.	It is expressed in words.

b. Dominant characteristics and Recessive characteristics.

Dominant characteristics	Recessive characteristics
The characteristics which are prominent and appear in successive generations are called dominant characteristics.	The suppressed characteristics which cannot be expressed in successive generations are called recessive characteristics.
Dominant characteristics are seen over recessive.	Recessive characteristics remains hidden.

c. F1 generations and F2 generations.

F1 generations	F2 generations
The generation obtained by crossing two parental stocks is called F1 generations.	The generation obtained by crossing two parental stocks of F1 generations is F2 generations.
The parents of F1 generation have pure genotype.	The parents of F2 generation does not have pure genotype.
It is also first filial generation.	It is also second filial generation.

d. Monohybrid cross and Dihybrid cross.

Monohybrid cross	Dihybrid cross
The cross involving only one pair of constracting characteristics is called monohybrid cross.	The cross involving two pair of constracting characteristics is called Dihybrid cross.
Here, off springs having phenotypic ratio of 3:1 are produced in F₂ generation.	Here, off springs having phenotypic ratio of 9:3:3:1 are produced in F₂ generation.

What is genetics? Who is considered as father of genetics? Why?

The branch of biological science of inheritance which deals with the study of heredity and variation is called genetics. Gregor Johann Mendel is considered as father of genetics because the first scientific study of genetics was carried by him and introduced the concept of genes as the basic unit of heredity.

What's heredity? What are heredity characteristics? Give two examples.

Heredity is the phenomenon by which Living organisms transmit parental characteristics to their off springs.
Heredity characteristicsare the characteristicsof the parents which are transmitted to their off springs.
Any too examples are:
- Type of hair in Human beings.
- Color of the eyes.

What are genes? Write short note on gene concept?

The tiny units of heredity located in the chromosomes is called genes.
The concept of 'gene' was introduced by sulten and the term 'gene' was introduced by Johannsom. It is located in chrosomes and arranged in linearfashion. It determine the physical, anatomical andphysiologicalcharacteristicsof organism. These characteristics are transmitted from one generation to other.

Define allelomorph.

Allelomorph is one of a gene or pair of matchinggenes. It contains a pair of identical alleles.

Define homozygous.

When the both alleles of a particular gene areidentical, it is called homozygous.

Define heterozygous.

When two alleles of a particular gene arenot identical, it is calledheterozygous.

What are hybrid? How are hybrid produced?

The organism produced after cross fertilization between two genetically different organisms iscalled hybrids.
Hybrids are produced by crossing between organismshaving two contrasting characteristics. This process is called hybridization.

What did Mendel selected pea plant for his study? Give your reasons.

Mendel selected pea plant for his study because of following reasons:
- Pea plant can be cultivated easily and have a short life cycle.
- Breeding controlled easily.
- Pea plant produce large number of off springs after fertilization.
- The flower of pea plants are adequate in size and easy to handle.
- Pea plant are found in various species.

State and explain the Mendel's law of dominance?

Mendel's law of dominance states that, "In a crossingbetween pure organism for constrasting characteristicsof a pair, only onecharacteristicsof a pairappears in thefirst filialgeneration.
Let us consider a pure tall pea plants (TT) anda pure dwarf pea plant (tt). When a pure tall peaplant is cross pollinatedwith the puredwarfone, allthe off springs will be tall in firstfilial generation. Here, tallness appears by suppressing the dwarfness.In this cross, tall is the dominant characteristicsasit...

State and explain the law of segregation with one example.

Law of segregation states that, "The hybrid obtained in F₁generation contains two contrasting characteristics of dominant and ressive in nature. Those characteristics remain together for long time in hybrids but don't mix with each other and separates at the time of gametes gets only a pure characteristics."
The monohybrid cross between a pure red floweredpea plant and pure white floweredpea plant up to the2nd filial generation. In F₁ generation all pea plantsproduced hybrid red (Rr) with...

what is dihybrid cross? Give one example.

Dihybrid cross is the crossin which to pairs of constracting characteristics are taken into consideration.
For example: Cross between red-flowered tall pea plant and white flowered dwarf pea plant.

Does Mendel's law apply the human beings too? State any two difficulties Mendel would have faced if he had carried out his experiment on human beings instead of pea plants?

Yes, Mendel's law applies the human beings also.
Any two difficulties that Mendel would have faced if he had carried his experiments on human beings instead of pea plants are:
- Human beings have long term life cycle. It is impossible to observe many generations.
- It is impossible to cross between siblings.
- Human being have many contrasting characters which makes difficult to study them.
- It is easier to handle pea plant than human as fertilization and reproduction process is easier and...

Differentiate between mutation and variation.

The difference between mutation and variation are:

Mutation	Variation
A sudden heritable changein the genetic material of an organism is called mutation.	The structural difference that provides individualityto each member of a species is called variation.
Various factors likeuv rays, x-rays, etc. are responsible for mutation.	Structural and functionaldifference of gene, environmentfactors are responsibleforvariation.
It is rarely seen dueto genetical disorder.	It I usuallyseen...

A tall (T) per plant and a dwarf (t) pea plant were first cross pollinated and then self pollinated. The given table shows the result of the experiment. Answer the following questions with the help...

a. Which filial generation does this result belongs to?
-This result belongs to 2nd filial generation.
b. What is the percentage of pea plant having hybrid characteristics?
-50 percentage of pea plant have hybrid characteristics.
c. Which pair of genes indicate pure tall plant?
-(IT) indicates pure tall pea plant.

Draw a phylogenetic chart to show the result in 1st and 2nd filial generation after crossing a round seeded tall pea plant with a wrinkled seed seeded pea plant.

For mice black (B) is dominant phenotype and white (b) is recessive. In certain experiment, a black male mouse of genotype Bb is crossed with a white female of genotype bb. Show with the help of a ...

Here,

Here,
Bb is a black mice because B is dominant character and bb is a pure white mice.
So,
Total black mice (Bb) = 2
And total white mice (bb) = 2
So, phenotype ratio = 2 : 2
= 1 : 1

State the significance of Mendelism.

The significance of Mendelism are
- Diseases resistantand high yielding varieties of plantsand animals can be produced by application of Mendelism.
-Hybrids with desired characteristics can be produced.
-The genotypes and phenotypes likely to be produced insuccessive generations can be predicted before the cross is made.
-Dominant and recessive characteristics oforganismcan be known.

What is meant by genetic variation? State the factors that bring out genetic variations.

The structural differences that provide individualityto each member of a species is called variation.
The factors that bring out geneticvariation are:
- Structural and functional differences of a gene.
- Environmental factors like food, light, temperature, etc.

In humans, the gene of black skin color gene (B) is dominant over the gene of white color (b). Study the given pedigree chart and answer the following questions:

a. Write down the genotype and phenotype of mother.
-Genotype: bb
-Phenotype: Pure white
b. What is the phenotypic and genotyperatio of blackand white complexion in F₂generation.
- Phenotype: 2:2 or1:1
-Genotype:2:2 or1:1

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