Tag: inheritance

Questions Related to inheritance

In Mirabilis jalapa, if the $F _1$ pink flowered plants are crossed with white-flowered plants, the progeny will be

botany classical genetics incomplete dominance deviation from mendelism inheritance

  1. All pink flowered plants

  2. 1 pink : 2 red : 1 white

  3. 1 pink : 1 white

  4. 3 red : 1 white

Show answer
Correct Option: C
Explanation:
   R  r
 r  Rr (pink)  rr (white)
 r  Rr (pink)  rr (white)

Crossing between F$ _1$ generation and the recessive parent is called a test cross. 

After crossing of pink flowered plants with white-flowered plants, progeny obtained was in a ratio = 2: 2 (pink: white) i.e. 1: 1.
So, the correct option is '1 pink: 1 white'.

Which of the following is a deviation from Mendelian principle ?

botany classical genetics incomplete dominance deviation from mendelism inheritance

  1. Inheritance of AB blood groups in man

  2. Inheritance of flower colour in Mirabilis jalapa

  3. Inheritance of cotyledon colour in Pisum sativum

  4. Inheritance of AB blood group in man and flower colour in Mirabilis jalapa

Show answer
Correct Option: D
Explanation:
 Co-dominance A  B 
 A  AA  AB
 B  AB  BB
 Incompletedominance  R  r
 R  RR  Rr
 r  Rr  rr

Inheritance of AB blood group in human follows co-dominance while inheritance of flower colour in Mirabilis jalapa follows incomplete dominance. 

Co-dominance is a form of dominance where alleles of a gene pair in a heterozygote are fully expressed. In AB  blood group, both A and B alleles are fully expressed. Therefore, an individual has neither A nor B blood group but AB blood group.
Incomplete dominance is a form of inheritance in which one allele for a specific trait is not completely expressed over its paired allele. In Mirabilis jalapa, plants with Rr genotype are not red (dominant allele) but pink (a third phenotype produced as a result of a combination of other two phenotypes).
So, the correct option is 'Inheritance of AB blood group in man and flower colour in Mirabilis jalapa'.

Read the passage and answer the following question.
A certain species of bird has two feather variations displayed by males: a dull-colored one that blends into their preferred habitat and a brightly colored one that is very obvious. The adult females are dull colored. The predation rate for brightly colored adults is three times higher than for the dull-colored adults. In spite of this, the brightly colored plumage persists in the population. 
Which of the following is the correct explanation?
botany classical genetics incomplete dominance deviation from mendelism inheritance

  1. Females prefer the brighter plumage and so mate with this phenotype more often.

  2. The dull plumage provides a selection advantage over the bright plumage.

  3. The adults with dull plumage require less energy investment to ensure their survival.

  4. Those brightly colored birds that do survive have more highly developed survival skills than those that do not survive.

  5. Dull-colored adult males are more lethargic than the brightly colored birds.

Show answer
Correct Option: A
Explanation:

Dull plumage confers a survival advantage to birds by protecting them against predators while those having brighter plumage are easily spotted. However, brighter plumage helps male birds to attract female birds for mating and confers reproductive advantage. This leads to persistence of brighter plumage population despite its more chances to get captured by a predator. Thus, the correct answer is option A.

A pea plant with round seeds having large starch grains is crossed with another pure pea plant with wrinkled seeds having small starch grains. The $F _1$ heterozygotes formed are self pollinated. What is the phenotypic ratio of plants with round seeds and intermediate starch grains to plants with wrinkled seeds and larger starch grains expected in $F _2$ generation

botany classical genetics incomplete dominance deviation from mendelism inheritance

  1. 5 : 6

  2. 2 : 3

  3. 3 : 4

  4. 6 : 1

Show answer
Correct Option: D
Explanation:

A pea plant with round seeds having large starch grains is crossed with another pea plant with wrinkled seeds having small starch grains. The F1 heterozygotes formed self-pollinated. The phenotypic ratio of plants with round seeds and intermediate starch grains to plants with wrinkled seeds and larger starch grains in F2 generation are 6:1.

So, the correct option is ‘6:1’

The inheritance of flower color in Antirrhinum (dog flower) is an example of

botany classical genetics incomplete dominance deviation from mendelism inheritance

  1. incomplete dominance

  2. co-dominance

  3. multiple alleles

  4. linkage

Show answer
Correct Option: A
Explanation:

In the dog flower Antirrhinum there are two types of flower color in pure state: red and white. When the two types of plants are crossed, the hybrid or plants of generation have pink flowers. This is due to a phenomenon called the incomplete dominance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles ( in this case the red and white color and incompletely dominant and hence the third color pink is observed when they mix).

So, the correct answer is 'Incomplete dominance'.

What percentage of progenies would have broad leaves and pink flower in F2 generation of Snapdragon if the first trait follows the law of dominance and the other shows incomplete dominance?

botany classical genetics incomplete dominance deviation from mendelism inheritance

  1. 37.5%

  2. 56.25%

  3. 62.5%

  4. 12.5%

Show answer
Correct Option: A
Explanation:

Assume that the broad shape of leaves is governed by alleles B,b where 'B' represents dominant allele for broad leaves. Similarly, 'R' and 'r' are alleles for the colour of the flower. 'RR' progenies show red colour,' rr' progenies show white colour and 'Rr' progenies show pink colour due to incomplete domination.


Dihybrid cross for F2 generation in Snapdragon can be shown as below - 

 Gamete type  BR  Br  bR  br
 BR  BBRR  BBRr  BbRR   BbRr
 Br  BBRr BBrr   BbRr  Bbrr
 bR  BbRR   BbRr bbRR   bbRr
 br   BbRr  Bbrr  bbRr  bbrr
We can see, 6 out of 16 ( Genotypes BbRr and BBRr ) progenies will have broad leaves and pink flower which is equal to 37.5%.
So, the correct option is '37.5%'.