Biology

Genetics and Plant Breeding

1,177 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 biology reproduction in humans twins reproduction and modern technology post fertilization events

Concordant type of twins are

  1. Free martins

  2. Dizygotic twins

  3. Monozygotic twins

  4. Both B and C
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Monozygotic or identical twins are those twins which are formed by the splitting of one zygote into two embryos. They have almost the same characteristics both phenotypically and genotypically. Dizygotic or fraternal twins are formed when two different eggs are fertilized by two different sperms.
so, the correct option is ' Monozygotic twins'.
Multiple choice bio-chemistry inborn errors of metabolism haemophilia and colour blindness non infectious diseases keeping diseases away

Select the incorrect statement from the following :

  1. Baldness is a sex limited trait

  2. Linkage is an exception to the principle of independent assortment in heredity.

  3. Galactosemia is an inborn error of metabolism

  4. Small population size results in random genetic drift in a population
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Baldness is a sex-influenced trait, not a sex-limited trait. Sex-influenced traits are expressed in both sexes but are more common in one (like male pattern baldness).

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 self pollination asexual and sexual reproduction in plants botany

Effect of pollen on character of pericarp and seed coat is?

  1. Xenia

  2. Metaxenia

  3. Ruminate endosperm

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

Metaxenia refers to the effect of pollen on maternal tissues like the pericarp and seed coat, which are outside the embryo and endosperm. Xenia refers to the effect of pollen on the endosperm itself.

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
C Correct answer
Explanation

Mendel worked with the garden pea, which has 14 chromosomes and 7 linkage groups, corresponding to the 7 traits he studied. If he had used a species with only 4 chromosomes, the number of linkage groups would be fewer than the 7 characters studied, meaning some characters would show linkage and fail to assort independently.

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.