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Laws of inheritance - class-XII

Description: laws of inheritance
Number of Questions: 17
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Tags: heredity biology genetics - some basic fundamentals mendel's law of inheritance
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How many different types of phenotypes would be produced in $F _{1}$ progeny in the following cross that obeys Mendel's law of independent assortment $AABBCC\times aabbcc$.

  1. $1$

  2. $8$

  3. $27$

  4. $64$


Correct Option: A

Discovery Of Mendels law of segregation required the use of:

  1. dihybrid parental and F1 crosses

  2. plants showing incomplete dominance

  3. test crosses

  4. parental crosses with true-breeding plants followed by crosses with F1 heterozygous plants


Correct Option: D
Explanation:

Discovery of mendels law of segregation required the use of parental crosses with true breeding plants followed by crosses with f1 heterozygous plants.

So, the correct option is 'parental crosses with true-breeding plants followed by crosses with F1 heterozygous plants'

Mendel proposed his 'laws' on the basis of his researches on seven contrasting characters in garden pea which has $14$ chromosomes per somatic cell. If, instead of garden pea, Mendel had chosen to work on seven characters in a plant species having only four chromosomes per somatic cell, then the most likely outcome would have been that.

  1. He would have discovered blending inheritance

  2. He could not have proposed that genes are located on the chromosomes

  3. He might not have discovered the law of independent assortment

  4. He might not have discovered the law of segregation


Correct Option: A

If individuals of genotype Aa Bb Cc are intercrossed, how many different phenotypes can appear in their offspring?

  1. 3

  2. 6

  3. 8

  4. 16


Correct Option: B
Explanation:

In the given question the number of the heterozygous gene pair is 3 so the number of phenotypes will also be 3.

So, the correct option is '6'.

Which of the following explains how progeny can possess combinations of traits that neither parent possessed?

  1. Polygenic inheritance

  2. Law of independent assortment

  3. Law of independent segregation

  4. Chromosome theory


Correct Option: B
Explanation:

Mendel's law of independent assortment states that allele pairs separate and segregate independently of one another during the formation of gametes. So, traits are transmitted to offspring independently of one another and recombinants are seen along with the parental types in the genotype of the next generation. So, progeny can have a new combination of traits that are not seen in either parent. So, the correct option is 'Law of independent assortment'.

Which of the following is not considered as a law?

  1. Law of dominance

  2. Law of independent assortment

  3. Law of segregation

  4. None of the above


Correct Option: A
Explanation:

The law of dominance is significant and true but is not universally applicable. Only Law of independent assortment and Law of segregation are considered to be laws. The third one is considered as a basic principle but not a genetic law of Mendel. Therefore, (a) is the correct answer.

Choose the correct answer from the alternatives given.
Mendels law of independent assortment does not hold true for the genes that are located closely on ______________________.

  1. Same chrormosome

  2. Non-homologous chromosomes

  3. X-chromosome

  4. Autosomes


Correct Option: A
Explanation:

As per linkage experiments carried out by Morgan, the two linked genes do not always segregate independently of each other and $F _2$ ratio deviated very significantly from 9:3:3:1 ratio (expected when two genes are independent). Hence, if linkage was known at the time of Mendel, he would riot have been able to explain law of independent assortment. 

Choose the correct answers from the alternatives given.
The mechanisms of .................have been referred to as life's defenses against disorder.

  1. respiration

  2. homeostasis

  3. adaptation

  4. metabolism


Correct Option: B
Explanation:

Homeostasis is any self-regulating process by which an organism trying to maintain stability while adjusting to conditions that are best for its survival. If homeostasis is successful, life continues, if it's unsuccessful, it results in a disaster or death of the organism.

So the correct answer is B, homeostasis.

According to the concept of dominance, the modified allele is equivalent to the unmodified allele when?

  1. It produces normal/less efficient enzyme

  2. It produces the same phenotype/trait

  3. It results in the transformation of substrate

  4. More than one option is correct


Correct Option: A
Explanation:
A gene is responsible for the appearance of a specific trait. In diploid organisms, a gene is represented by a pair of alleles. When these two alleles are not identical, one of alleles is different with modified information. Normal allele will form normal enzyme. Changed or modified allele can form three types of enzymes i.e. normal enzyme, non-functional enzyme, no enzyme at all. Enzyme is always required for the formation of substrate say ‘S’. Modified allele is almost similar to normal allele and forms the same enzyme and produces same phenotypic trait i.e., leads to the formation of substrate ‘S’. But sometimes allele formed are non­functional enzyme or no enzyme and phenotypic trait depends on functioning of un-modified allele. Functioning or unmodified allele will form the original normal phenotypic trait (due to dominant allele) and modified allele will be known as recessive allele.
So the correct option is 'it produces normal/less efficient enzyme'.

The effect of dominant allele is studied under ______________

  1. Law of independent assortment

  2. Law of dominance

  3. Law of segregation

  4. None of the above


Correct Option: B
Explanation:

Some alleles are dominant while others are recessive. Organism with at least one dominant allele will display the effect of the dominant allele, which is studied under Law of dominance. Therefore, (b) is the correct answer.

Assume that flower colour is controlled by a single gene. In a given plant, red flower colour is dominant over white flower colour. Two red flower bearing plants were crossed and the progeny consists of 45 plants bearing red flowers and 4 plants bearing white flowers this indicates that

  1. Both the parents are heterozygous for the gene controlling flower colour

  2. One parent is true breeding for red flowers on the other heterozygous

  3. A mutation must have occurred in the progeny which (mutation) caused the appearance of white flowers

  4. The results are not consistent with the expected ratio 3 Red : 1 White. Hence both the parents cannot be heterozygous


Correct Option: C
Explanation:

Ratio is totally deviated from 3(red) : 1 (white), Hence this is a case of mutation which is resulting into this outcome.

Mendel's law of segregation states that?

  1. The alleles do not show any blending and that both the characters are recovered as such in $F _2$ generation

  2. The factors or alleles of a pair segregate from each other such that a gamete receives only one of the two factors

  3. Homozygous parent produces all gametes that are similar while heterozygous produces two kinds of gametes each having one allele with equal proportion

  4. All of the above


Correct Option: A

Find which options are correct. According to Mendel's law of purity of gametes.
A) In $F1$ hybrid, the dominant and recessive character though remain together for long time but do not contaminate or mixed with each other.
B) The inheritance of one character is always independent to the inheritance of other character within the same individual.
C) The gamete formed contains the factors, which determines single trait pertaining to a particular character.
D) Two genes of allelomorphic pair are not related as dominant or recessive but each of them expresses itself partly.

  1. A, B and C are correct

  2. A and B are correct

  3. B and D are correct

  4. A and C are correct


Correct Option: A

Independent segregation of genes is seen in case of _____________

  1. Law of dominance

  2. Law of segregation

  3. Law of independent assortment

  4. Both (A) and (C)


Correct Option: C
Explanation:

Genes for different traits can segregate independently during the formation of gametes. This is the result of Law of independent assortment which was studied Mendel. Therefore, (C) is the correct answer.

Each gamete carries only one allele. This is proposed in which law?

  1. Law of dominance

  2. Law of segregation

  3. Law of independent assortment

  4. None of the above


Correct Option: B
Explanation:

During gamete formation, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene. This was proposed in the Law of segregation. Therefore, (b) is the correct answer.

Which of the following follows Mendel's law of segregation?

  1. Genetic material is equally distributed during mitosis.

  2. Each gamete receives one gene for an allele.

  3. Genetic material enters only one gamete.

  4. All of the above.


Correct Option: B
Explanation:

Mendel's law of Segregation: The principle of segregation describes how pairs of gene variants are separated into reproductive cells. The segregation of gene variants, called alleles, and their corresponding traits was first observed by Gregor Mendel in 1865. Mendel was studying genetics by performing mating crosses in pea plants.
Each gamete receives one gene for an allele and thus, is haploid in nature. Both male and female gametes, which are haploid will fuse and forms a diploid zygote.

So, the correct answer is 'Each gamete receives one gene for an allele.'

How was Mendel's work ultimately reconciled with Darwin's theory of natural selection during the evolutionary synthesis in the 1930s and 1940s?

  1. Scientists recognized that once one thinks about species as populations, rather than individuals, there is no incompatibility between them.

  2. Mendel's theory was replaced by the mutation theory.

  3. It was recognized much of the variation we observe in nature is due to recombination, rather than mutation.

  4. a and c.


Correct Option: D
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