Tag: mendel's law of inheritance

Questions Related to mendel's law of inheritance

A breeding experiment studying a single trait is 

  1. Monozygous

  2. Dizygous

  3. Dihybrid

  4. Monohybrid


Correct Option: D
Explanation:

Monohybrid cross refers to inheritance of a single contrasting trait by two parents at a time. For example, a cross of tall (T) and dwarf (t) pea plants (TT xtt). Dihybrid cross refers to inheritance of two pairs of contrasting characters by two parents at the same time. For example, a cross of two pea plants, one with yellow and round seeds (YYRR) and other with green and wrinkled seeds (yyrr). The term “monozygous” represents twins being developed from a single zygote. The first division in zygote produces two identical cells that independently develop into two embryos; monozygotic twins are produced. The term “dizygous” represent twins being developed from individual zygotes. Fertilization of two eggs by separate sperms produces two zygotes that independently develop into two embryos. Thus, the correct answer is the option D.

A husband and wife have normal vision but fathers of both of them were colour blind. Probability of their first daughter to be colour blind is

  1. 25%

  2. 50%

  3. 75%

  4. 0%


Correct Option: D
Explanation:

Probability of their first (or any) daughter being colourblind is nil as the daughter of normal father can never be colourblind.

Biological unit controlling heredity is ___________.

  1. Genome

  2. Chromosome

  3. Genotype

  4. Gene.


Correct Option: D
Explanation:

A.Genome – a set of chromosome in an organism in a body.

B.Chromosome – Dark coloured, small rod like structures, appear in the dividing nucleus is called Chromosome.

C.Genotype – It is the representation of an individual’s genetic constitution with respect to a single character or set of characters.

D.Gene - A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. However, many genes do not code for proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.

So, the correct option is ‘Gene’.

According to modern concept, Mendel's factor is called as_____________

  1. Chromosome

  2. Gene

  3. DNA

  4. Chromatid


Correct Option: B
Explanation:
  • According to the modern concept, Mendel's factor is called a gene. Mendel believed that heredity is the result of discrete units of inheritance, and every single unit (or gene) was independent in its actions in an individual’s genome. According to this Mendelian concept, inheritance of a trait depends on the passing-on of these units. For any given trait, an individual inherits one gene from each parent so that the individual has a pairing of two genes.

What is the correct sequence from least complex to most complex in terms of the amount of information they carry?

I. Chromosomes
II. Base pair
III. Codon
IV. Gene

  1. I $\rightarrow $ II$\rightarrow $ III $\rightarrow $ IV

  2. II $\rightarrow $ III$\rightarrow $ I $\rightarrow $ IV

  3. III $\rightarrow $ II $\rightarrow $ I $\rightarrow $ IV

  4. II $\rightarrow $ III $\rightarrow $ IV $\rightarrow $ I

  5. II $\rightarrow $ IV $\rightarrow $ II $\rightarrow $ I


Correct Option: D
Explanation:

A base pair (II) carries least information as at least three bases together (base triplet) make a codon (III) which in turn code for an amino acid. Genes (IV) are the stretch of DNA and each gene codes for a particular protein. Many genes are linearly arranged on a chromosome which means that chromosomes carry information for many proteins.

Therefore, the correct answer is option D.

When a cross is made between a tall plant with yellow seeds (Tt Yy) and a tall plant with green seeds (Tt yy), what is true regarding the proportions of phenotypes of the offsprings in F1 generation?
Proportion of Tall and Green         Proportion of Dwarf and Green 

  1. $\dfrac{3}{8}$ $\dfrac{1}{8}$

  2. $\dfrac{2}{8}$ $\dfrac{1}{8}$

  3. $\dfrac{1}{8}$ $\dfrac{3}{8}$

  4. $\dfrac{2}{8}$ $\dfrac{2}{8}$


Correct Option: A

A tall plant was grown in nutrient deficient soil and remained dwarf. When it is crossed with dwarf plant then

  1. all hybrid plants are dwarf

  2. all hybrid plants are tall

  3. depend upon genotype of a tall plant

  4. 75% tall and 25% dwarf


Correct Option: B
Explanation:

A tall plant was grown in nutrient deficient soil and remained dwarf .So , after crossed with dwarf plant then all hybrid plants are tall. Hybrid genotype is Tt.

Hence, correct option is B. 

In Drosophila, the allele for a normal grey body colour G is dominant to ebony body g. The following table summarises the results of several crosses.


S. No. Cross Result
1. strain 1*gg all wild-type
2. strain 2*gg 1 wild type: 1 ebony
3. strain 3*gg all ebony
4. strain 4*Gg 3 wild type:1 ebony


Which strain both have the genotype Gg?

  1. 1 and 3

  2. 1 and 4

  3. 2 and 3

  4. 2 and 4


Correct Option: D
Explanation:

The first cross between strain 1 and gg result in all wild-type offspring, it must have genotype GG. As in that case, all offspring will have Gg genotype hence showing wild-type character. Similarly, strain 3 must have genotype gg resulting in all ebony bodied offspring.


While, strain 2 and 4 have genotype Gg. 

Cross for strain 4*Gg can be shown as:-

 Gamete type  G  g
 G  GG  Gg
 g  Gg  gg

Here, it can be seen that offspring have 3 wild type:1 ebony as grey body ( wild type ) colour G is dominant. 


Cross for strain 2*gg can be shown as:-
| Gamete type |  g |  g | | --- | --- | --- | |  G |  Gg |  Gg | |  g |  gg |  gg | Here, it can be seen that offspring have 1 wild type: 1 ebony as grey body ( wild type ) colour G is dominant. So, the correct option is '2 and 4'.

It is said that Mendel proposed that the factor controlling any character is discrete and independent. His proposition was based on the

  1. Results of $F _3$ generation of a cross

  2. Observations that the offspring of a cross made between the plants having two contrasting characters shows only one character without any blending

  3. Self pollination of $F _1$ offsprings

  4. Cross pollination of $F _1$ generation with recessive parent


Correct Option: B
Explanation:

Mendel crossed two parent plants having contrasting characters. He found that in the first filial generation, F1 generation, the dominant of the two expressed while the recessive is suppressed. Apart from this,  When the f1 generation is self crossed, in the F2 generation, these recessive characters appear again. Therefore, it is not that they have disappeared. 

So, option B is the correct answer.

Which of these is not a part of Mendel's laws

  1. Law of independent assortment

  2. Law of segregation

  3. Law of dominance

  4. Law of linkage


Correct Option: D
Explanation:

Linkage is the tendency of two or more genes to inherit together as a pair and not to sort out independently.
Thus, linkage is not applicable according to Mendelian principles.
Linkgae is strictly against Law of independent assortment where Mendel explains that the characters are sorted out independently while forming gametes.