Tag: botany

Questions Related to botany

A beaker is filled with water and twigs of Hydrilla are inserted in the funnel so that the cut ends are in the tube of the funnel and the funnel is put in the water. Then a test tube full of water is inverted over the inverted funnel. Air bubbles from the plant collect at the tip of the tube. This experiment demonstrates that oxygen is evolved during photosynthesis. But, if boiled water is used instead of pond water in which Hydrilla grows, then?

botany how plants grow experiments on photosynthesis - light importance of light for photosynthesis photosynthesis necessities- experiments various experiments on photosynthesis experiments on photosynthesis - gases

  1. Air bubbles are not produced

  2. Air bubbles are produced in large numbers

  3. Only a few air bubbles are produced

  4. Only one air bubble is produced

Show answer
Correct Option: A
Explanation:

If boiled water is used in the test tube, there will be no air bubbles. This is hydrilla cannot survive the high temperature of boiled water. 

So, option A is the correct answer.

What phenotypic ratio is obtained by selfing of a trihybrid in which two gene pair are completely linked?

trihybrid cross classical genetics botany

  1. $3:6:3:2:1$

  2. $3:1$

  3. $1:1:1:1$

  4. $9:3:3:1$

Show answer
Correct Option: A

What would be the sum of phenotypes and genotypes obtained from a trihybrid test cross?

trihybrid cross classical genetics botany

  1. $35$

  2. $8$

  3. $16$

  4. $24$

Show answer
Correct Option: A

A plant with genotype  AaBbCC produce $40millon$ pollen grains. Then calculate how many pollen grains will be with at least two dominant alleles?

trihybrid cross classical genetics botany

  1. $10millon$

  2. $20millon$

  3. $30millon$

  4. $40millon$

Show answer
Correct Option: A

In a cross in Drosophila, the heterozygous animal with grey body $(b+)$ and long wing $(vg+)$ with black body and vestigial wings, the progeny has the animals in the following ratio -grey vestigial 24 : grey long 126 : blck long 26 : black vestigial 124. What is the frequency of recombinants in the population?

trihybrid cross classical genetics botany

  1. 14.5

  2. 17.5

  3. 16.7

  4. 15.8

Show answer
Correct Option: A

A polygenic trait is controlled by $3$ genes $A, B$ and $C$. In a cross $AaBbCc \times AaBbCc$, the phenotypic ratio of the offsprings was observed as
$1 : 6 : x : 20 : x : 6 : 1$ What is the possible value of $x$?

trihybrid cross classical genetics botany

  1. $3$

  2. $9$

  3. $15$

  4. $25$

Show answer
Correct Option: C
Explanation:

In polygenic inheritance, a particular trait is controlled by 3 different genes. The given problem is of polygenic inheritance. In this, phenotypic ratio is 1:6:15:20:15:6:1 instead of 27:9:9:9:3:3:3:1 in F$ _2$ generation. In the given example, the genotype of parents is AaBbCc and AaBbCc. They will produce gametes ABC, ABc, Abc, abc, aBC, aBc, abC, AbC. The phenotypic ratio will be 1:6:15:20:`15:6:1.

Thus, the correct answer is '15.'

Frequency of a perfect heterozygous cross between AABBCC and AaBbCc is

trihybrid cross classical genetics botany

  1. 1/8

  2. 2/8

  3. 3/8

  4. 4/8

Show answer
Correct Option: A
Explanation:

Genotype AABBCC can produce only one type of gamete, i.e., ABC. The frequency for production of ABC gamete is 1.
Genotype AaBbCc can produce 8 types of gametes, i.e., ABC, Abc, ABc, AbC, abc, aBC, aBc and abC.
The frequency of production of one of these gametes is 1/8.
According to the question, a perfect heterozygous cross will occur only when abc gamete from AaBbCc parent fertilises with ABC gamete from AABBCC parent.
Thus, the frequency for this = 1/8X1 = 1/8.

A typical dihybrid and trihybrid test-cross ratio are respectively:

trihybrid cross classical genetics botany

  1. $1:1$ and $1:1:1:1$

  2. $1:1:1:1:1:1:1:1$ and $1:1:1:1$

  3. $1:1:1:1$ and $1:1$

  4. $1:1:1:1$ and $1:1:1:1:1:1:1:1$

Show answer
Correct Option: D
Explanation:
Dihybrid Test ratio: $1:1:1:1$
Trihybrid Test ratio : $1:1:1:1:1:1:1:1$
Test cross $\Rightarrow F _1$ generation $X$ recessive parent 
for dihybrid test cross- $RrYy\times rryy$
for Trihybrid test cross- $yyrrtt\times YyRyTt$

Number of genotypes produced when individuals of genotype 'YyRrTt' are crossed with each other

trihybrid cross classical genetics botany

  1. 4

  2. 45

  3. 28

  4. 27.

Show answer
Correct Option: D
Explanation:

A trihybrid plant YyRrTt during fertilization produces 27 types of genotypes.

It is calculated as 3n , n= number of contrasting pairs of characters/traits.

In YyRrTt, 3 contrasting pairs of characters are present. So 33 = 27.

So, the correct option is ‘27’.

Trihybrid ratio is

trihybrid cross classical genetics botany

  1. 27 : 9 : 9 : 9 : 3 : 3 : 3 : 1

  2. 27 : 9 : 9 : 6 : 6 : 3 : 3 : 1

  3. 1 : 6 : 15 : 20 : 15 : 6 : 1

  4. 36 : 6 : 6 : 6 : 3 : 3 : 3 : 1.

Show answer
Correct Option: A
Explanation:

A cross is made between the two parents on the basis of 3 contrasting characters is called Trihybrid cross. Mendel conducted trihybrid cross by three characters height of the stem, form of seed, and colour of the cotyledons. In the F2 generation, he obtained, 27:9:9:9:3:3:3:1.

So, the correct option is ‘27:9:9:9:3:3:3:1’.