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 trihybrid cross classical genetics botany

In humans, pointed eyebrows (B) are dominant over smooth eyebrows (b). Seemas father has pointed eyebrows, but she and her mother have smooth. What is the genotype of the father?

  1. BB

  2. Bb

  3. bb

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

Since pointed eyebrow (B) is dominant over smooth eyebrows (b). So, Seema can have smooth eyebrows only if her father is heterozygous for the dominant character. If her father has the genotype Bb and her mother is bb (smooth eyebrows) then her genotype will be either Bb (pointed) or bb(smooth eyebrows). If however, her father is homozygous for the trait the gamete being transferred from him will have the allele B and hence the progeny will only show the genotype Bb for pointed eyebrows. So, the correct option is 'Bb'.

Multiple choice trihybrid cross classical genetics botany

On selfing a plant of ${F} _{1}$ generation with genotype "AABbCC", the genotypic ratio in ${F} _{2}$-generation will be

  1. $1:2:1$
  2. $1:1$
  3. $9:3:3:1$
  4. $27:9:9:9:3:3:3:1$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The possible gametes from the given genotype AABbCC are ABC and AbC.

The various possibilities of their their selfing would be :
1.  ABC × ABC = AABBCC
2. ABC × AbC = AABbCC
3. AbC × ABC = AABbCC
4. AbC × AbC = AAbbCC
It is evident from the above crosses that the genotypic ratio of F2 generation will be 1:2:1.
So, the correct option is '1:2:1'.

Multiple choice trihybrid cross classical genetics botany

In trihybrid, when all gene show complete linkage then what is the ratio of test cross?

  1. 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1

  2. 1 : 1

  3. 1 : 1 : 1 : 1

  4. 9 : 3 : 3 : 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A trihybrid cross is between two individuals that are heterozygous for three different traits. For example, RrYyCc x RrYyCc is a trihybrid cross where, 

RR = round, Rr = round, rr = wrinkled
YY = green, Yy = green, yy = yellow

CC = smooth, Cc = smooth, cc = constricted
The complete linkage is when genes are so closely associated that they are always trans­mitted together, and that does not undergo crossing over. 
So, in this case, the ratio of test cross for trihybrid with complete linkage will be 1:1. 
Thus, the correct answer is '1:1'.

Multiple choice trihybrid cross classical genetics botany

If a quantitative character is influenced by the additive effect of four genes how many phenotypic categories are expected in the progeny of a tetrahybrid cross

  1. $5$
  2. $7$
  3. $9$
  4. $11$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For quantitative inheritance by four genes, we have a total of 8 alleles that will determine the phenotypes of the individual. Those offspring with all 8 dominant alleles ( Let's assume it as AABBCCDD ) will show the highest additive effect. Gradually as we keep decreasing the number of dominant alleles, additive effect will become less prominent. Hence, offspring with 7,6,5,4,3,2 and 1 dominant alleles will show different phenotypes. Finally, those individuals with no dominant alleles i.e. all recessive ( aabbccdd ) will show the least additive effect of characters. If we count all of them we have a total of 09 types of phenotypes possible. 

So, the correct option is '9'.

Multiple choice trihybrid cross classical genetics botany

When a hybrid (AaBbCcDd) is selfed then the genotypes AABbCCDd, AaBBCcDd, AaBbCcDd, aabbccdd would be in a proportion of?

  1. $2 : 4 : 8 : 21$
  2. $4 : 8 : 16 : 1$
  3. $4 : 8 : 16 : 27$
  4. $8 : 4 : 16 : 81$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The tetrahybrid cross of AaBbCcDd can be easily calculated by assuming their independent assortment.

The probability of both the alleles same is 1/4
The probability of both alleles different is 1/2
Hence when we calculate this for all the conditions AABbCCDd, AaBBCcDd, AaBbCcDd, aabbccdd is 4:8:16:1

So the correct answer is ' 4  : 8 : 16 : 1'.

Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

Choose the correct answer from the alternatives given.


In a monohybrid cross between two heterozygous individuals, percentage of  re homozygous individuals obtained in $F 1$ generation will be ________.

  1. 25%

  2. 50%

  3. 75%

  4. 100%
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a monohybrid cross between two heterozygotes (Tt x Tt), the F1 genotypes are 1 TT, 2 Tt, and 1 tt. The homozygous individuals are TT and tt (1+1=2 out of 4), which is 50 percent.

Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

Mendel formulated the law of purity of gametes on the basis of

  1. monohybrid cross

  2. dihybrid cross

  3. test cross

  4. back cross
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A gamete may carry either the dominant or the recessive factor but not both as we find in F1 individuals. This is why it is called either as 'principle of segregation' or as 'law of purity of gametes'. This concept of segregation is often called Mendel's first principle. The alleles of contrasting characters selected in the monohybrid cross will show exact Dominance and Recessive relationships. Monohybrid cross refers to  mating between two organisms with different variations at one genetic chromosome of interest. The character(s) being studied in a monohybrid cross are governed by two or multiple variations for a single locus.

So, the correct answer is 'monohybrid cross'.

Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

Which of the following term was used by Mendel for hereditary units?

  1. Factor (determiner)

  2. Genome

  3. Genetic particle

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gregor Mendel is the father of genetics. When he explained about heredity for the first time ever, the term "Gene" which is now being used, was not given. After his demise only, most of his research studies came to lime light. According to his explanations, he called them as 'Factor' or determiner which was otherwise known as heredity units.

Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

For green coloured pod and rounded seed, which is the functional unit of inheritance?

  1. Cistron

  2. Gene

  3. Chromosome

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

Genes are the functional hereditary units.  Gene is also defined as the functional unit of DNA which codes for a character. Genes are located on chromosomes, which are then carried to the next generation and thus plays a great role in heredity.

Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

Which of the following is true regarding genes?

  1. Gene is a unit of heredity which is transferred from a parent to offspring

  2. Gene is a distinct sequence of nucleotides forming part of a chromosome

  3. Gene is the order which determines the order of monomers in a polypeptide

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Genes are basic unit of heredity present on the chromosome.
  • They are made up of DNA hence they are sequence of nucleotides.
  • These orders of nucleotides in DNA later determine the sequence of polypeptide chain formed from them during translation. 
  • So, the correct option is 'All of the above'.
Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

In pea plants, the long-stem trait $(L)$ is dominant and the short-stern trait $(I)$ is recessive. Two pea plants were crossed, producing seeds that yielded 165 long-stem plants and 54 short-stem plants. The genotypes of the parent plants were most likely

  1. $LI$ and $LL$
  2. $LI$ and $LI$
  3. $II$ and $II$
  4. $LL$ and $II$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

  • The ratio of long stem plants to short stem plants among the progeny is 165:54 which means it has a ratio of 3:1. This ratio is possible if the parents are heterozygous in nature which after the cross will produce homozygous tall, heterozygous tall and homozygous dwarf offsprings. 
  • As the heterozygous offspring expresses the dominant allele, they will also be tall. This is a classic example of the monohybrid ratio that produces a ratio of 3:1 in the F2 generation of pure line parents.

So, the correct option is 'LI and LI'.

Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

When a cross is made between two parents with respect to a single character, it is called as

  1. Dihybrid

  2. Monohybrid

  3. Trihybrid

  4. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • A monohybrid cross is a type of cross between two individuals with different alleles at one genetic locus of interest. 
  • The character(s) being studied in a monohybrid cross are governed by two or multiple alleles for a single locus.
  • A dihybrid cross is a cross between two pure lines (varieties, strains) that differ in two observed traits. In Mendelian sense, between the alleles of both these loci, there is a relationship of complete dominance - recessive.
  • Trihybrid cross is the mating of two individuals, organisms, or strains that have different gene pairs that determine three specific traits or in which three particular characteristics or gene loci are being followed.
Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

A cross in which a single pair of contrasting characters is studied at a time is called as_____________

  1. Monohybrid cross

  2. Dihybrid cross

  3. Trihybrid cross

  4. Tetrahybrid cross
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • A monohybrid cross is a mating between two individuals with different alleles at one genetic locus of interest. The cross involves a single pair of contrasting characters.

So, the correct answer is option A.
Multiple choice botany mendel's law of inheritance genetics terminology similarities and dissimilarities in organisms introduction to genetics features of human body and sign language

A breeding experiment studying a single trait is 

  1. Monozygous

  2. Dizygous

  3. Dihybrid

  4. Monohybrid
Reveal answer Fill a bubble to check yourself
D Correct answer
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.