Biology

Genetics and Plant Breeding

1,240 Questions

Genetics and Plant Breeding explores the principles of heredity, chromosomal inheritance, and hybridization techniques. It includes key concepts like Mendelian genetics, gene linkage, and polygenic inheritance. This topic is essential for students tackling advanced biology or botany sections in competitive examinations.

Mendelian InheritanceChromosome TheoryGene LinkagePolygenic InheritancePlant HybridizationPopulation Genetics Equilibrium

Genetics and Plant Breeding Questions

Multiple choice bio-chemistry inborn errors of metabolism haemophilia and colour blindness non infectious diseases keeping diseases away

The possibility of a female becoming haemophilic is extremely rare because the mother of such a female has to be at least (i) and father should be (ii). 

  1. (i) Haemophilic, (ii) Carrier

  2. (i) Carrier, (ii) Haemophilic

  3. (i) Haemophilic, (ii) Normal

  4. (i) Haemophilic, (ii) Haemophilic
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • Haemophilia is genetically due to the presence of a $recessive$ sex-linked gene h, carried by the X chromosome. 
  • A female becomes haemophilic only when both Its X chromosomes carry the gene $(XhXh)$. However, such females (mothers) generally die before birth because the combination of these two recessive alleles is lethal. A female having only one allele for haemophilia $(XX^h)$ appears normal because of the allele for normal blood clotting present on the other X-chromosome is dominant. Such females are known as carriers. 
  • In the case of males, a single gene for the defect is able to express itself as the Y-chromosome is devoid of any corresponding allele $(Xh^Y)$.
  • Thus, the possibility of a human female becoming haemophilic is extremely rare because she has to be homozygous recessive for the trait, i.e., her father must be a haemophilic and mother must be at least a carrier.

Multiple choice self pollination asexual and sexual reproduction in plants botany

In a homozygous plant self-pollination

  1. Is never possible

  2. Yields progeny which are highly gentically variable

  3. Yields progeny which are not genetically variable

  4. Is generally overcome by various adaptations
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

self-pollination causes an increase in homozygosity in progeny in every generation of selfing up to approximately 96% in the F5, and selfing of homozygous line produce genetically similar progeny with negligible or little variability. So, the correct option is C. ( Yields progeny which are not genetically variable )

Multiple choice self pollination asexual and sexual reproduction in plants botany

A tobacco plant which is heterozygous for albinism (a recessive character) is self pollinated if 1200 seeds are subsequently germinated, how many of the seedlings would have the parental genotype

  1. 300

  2. 600

  3. 900

  4. 1200
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

XX X Xx ...      Parents

I

XX Xx Xx xx ...     Fl hybrid

In Fl generation half of the total offsprings represent 
parental genotype i.e., Xx. Therefore out of 1200 seedling 600 will have parental genotype.

Multiple choice biology for the continuity of generation reproductive systems different stages of growth reproductive system in humans

Assertion:  In humans, the gamete contributed by the male determines whether the child produced will be male or female.

Reason:  Sex in humans is a polygenic trait depending upon a cumulative effect of some genes on X-chromosome and some on Y-chromosome

  1. If both the assertion and the reason are true and the reason

    is a correct explanation of the assertion

  2. If both the assertion and reason are true but the reason is not a correct explanation of the assertion

  3. If the assertion is true but the reason is false

  4. If both the assertion and reason are false

  5. If the assertion is false but reason is true
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The assertion is true because human sex determination is based on the sperm carrying either an X or a Y chromosome. The reason is false because sex determination in humans is chromosomal (XX/XY), not polygenic.

Multiple choice biology mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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. $64$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a cross AABBCC x aabbcc, all F1 progeny will be AaBbCc. Since all individuals have the same genotype, they will all express the same phenotype.

Multiple choice biology mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
D Correct answer
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'

Multiple choice biology mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice biology mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
B Correct answer
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'.

Multiple choice biology mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

Multiple choice biology mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
A Correct answer
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'.
Multiple choice mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
B Correct answer
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.

Multiple choice mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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

Multiple choice mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice mendel's law of inheritance mendel's laws laws of inheritance mendel's laws of inheritance

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
Reveal answer Fill a bubble to check yourself
A Correct answer