Tag: genetics

Quizzes (32) Questions (37)

Questions Related to genetics

Multiple choice botany classical genetics non mendelian inheritance deviation from mendelism genetics

In Mirabilis jalapa , the percentage of plants having pink and red flowers would be ________ when pink flower plant is test crossed.

  1. 25% pink and 25% red

  2. 50% pink and 50% red

  3. 50% pink and 0% red

  4. 0% pink and 50% red
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
 Gamete  R r 
 r Rr- Pink flower  rr- White flower 

Mirabilis jalapa is a plant showing incomplete dominance which means that when in F$ _1$ generation intermediate phenotype appears instead of the two parent phenotypes. 

While, the test cross is defined as a cross between an F$ _1$ plant and the homozygous recessive parent.
So, for plants to be pink in Mirabilis jalapa the plant has to be Rr in genotype. (where R is dominant on r while RR gives Red color and rr gives white color flowers in a plant).
Desired cross: Rr x rr 
So, the phenotype ratio is: 1:1::Pink flower:White flower
So, the correct answer is '50% pink and 50% red'.

Multiple choice botany classical genetics non mendelian inheritance deviation from mendelism genetics

Different forms of a gene are called

  1. Heterozygotes

  2. Alleles

  3. Complementary genes

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

A.Heterozygotes – Organisms with a pairs of contrasting characters are called Heterozygotes.

B.Alleles - An alternative form of a character in a pair, controlled by a single gene is called Allele. It is dominant either in homozygous or heterozygous state.

C.Complementary gene – Two genes present on separate loci that interact together to produce a dominant phenotype is called Complementary gene. In the F2 generation 9:7 ratio.

D.Supplementary gene – genes which include two pairs of non-allelic genes. Both of them are involved in affecting the same character. Out of the non-allelic genes, one gene is dominant and can express by itself. Second gene is also dominant but expresses only when it is supported by the presence of the first gene. In the F2 geneartion 9:3:4 ratio.

So, the correct option is ‘Alleles’. 

Multiple choice botany classical genetics non mendelian inheritance deviation from mendelism genetics

A cross between yellow flowered and round fruit (both dominant) bearing plant and white flowered elongated fruit (both recessive) bearing plant yielded 20 plants in $F _1$ progeny which formed 960 plants in $F _2$ generation. The number of plants with yellow flowers and round fruits in $F _1$ and $F _2$ generations would be

  1. 20, 960

  2. 20, 540

  3. 10, 180

  4. 10, 60.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

class=A cross is made between pure yellow flowered  and round fruit(YYRR) with white flowered elongated fruit(yyrr). In the F1 generation 20 progeny with yellow flowered and round fruits(YyRr) are formed. When they are subjected to self pollination followed by self fertilization, in the F2 generation, 960 progeny are formed. In these 540 plants are yellow flowered round fruits, plants are yellow flowered elongated fruits, 180 fruits are white flowered round fruits and 60 plants are white flowered elongated fruits the correct option is 20, 540

Multiple choice botany classical genetics non mendelian inheritance deviation from mendelism genetics

Two plants of Summer Squash both having circular fruits are crossed. $F _1$ plants had discoid fruits. $F _2$ generation has 3 types of fruits, discoid, circular and long in the ratio of

  1. 9 : 3 : 4

  2. 9 : 6 : 1

  3. 12 : 3 : 1

  4. 7 : 6 : 3
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is a classic example of duplicate recessive epistasis in Summer Squash fruit shape. The F2 ratio for this type of interaction is 9:6:1, where 9 are discoid, 6 are circular, and 1 is long.

Multiple choice botany classical genetics non mendelian inheritance deviation from mendelism genetics

A modified dihybrid mendelian ratio of 9 : 3 : 4 indicates

  1. Supplementary genes

  2. Complementary genes

  3. Lethal genes

  4. Epistalic genes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A.Supplementary genes – A pair of non allelic genes, one of which produces its effect independently in the dominant state while the dominant allele of the second gene is without any independent effect but is able to modify the effect of the former to produce to a new trait are called Supplemetary genes. Due to these genes in the F2 generation, 9:3:4 ratio of progeny are obtained. It is a modified Mendel dihybrid ratio.

B.Complementary genes – Two genes present on separate loci that interact

together to produce dominant phenotypic character; neither of them if present alone can express itself are called complementary genes. Due to these genes in the F2 generation, 9:7 ratio of progeny are obtained. It is a modified Mendel dihybrid ratio.

C.Lethal genes – A pair of genes present in the homozygous conditions, causes the death of the individual are called Lethal genes. Due to the genes, in F2 generation 2:1 ratio of progeny are obtained.

D.Epistatic genes – A gene which masks the action of another gene is termed as epistatic gene and process is called epistasis. Due to these genes in the F2 generation, either 9:3:4  or 12.3.1 ratio of progeny are obtained. It is a modified Mendel dihybrid ratio.

So, the correct option is ‘supplementary genes’.     

Multiple choice pleiotropy genetics zoology

Teacher asks the student to give the best example to explain pleiotropy. The correct answer is

  1. Flower colour in snapdragon

  2. Seed coat colour of garden pea

  3. ABO blood group system of human

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

Pleiotropy occurs when one gene will code and control the phenotype or expression of several different and unrelated traits. Phenylketonuria is an autosomal recessive disorder controlled by a mutant gene present on the 12th chromosome. This mutant gene fails to code for the enzyme phenylalanine hydroxylase required for normal metabolism of amino acid phenylalanine to tyrosine. Due to this, there is an accumulation of phenylalanine in body fluids such as blood, sweat, CSF. An abnormal breakdown product phenyl ketone is found in urine A higher level of phenylalanine and pheylketone cause severe brain damage leading to mental retardation. Thus phenylketonuria is the best example to explain pleiotropy.

So, the correct answer is 'Phenylketonuria'

Multiple choice pleiotropy genetics zoology

A pleiotropic in Drosophila is that of

  1. Red-white eye

  2. Bar eye

  3. Vestigial gene

  4. Forked bristles.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In Drosophila, the vestigial gene is a classic example of pleiotropy, affecting not only wing size but also haltere size, bristle orientation, and reproductive fitness.

Multiple choice pleiotropy genetics zoology

A $15: 1F _2 $ ratio of a cross between a wheat variety with red kernels (homozygous for two dominant genes) and another with white kernels shows 

  1. Polygenic inheritance

  2. That the two genes are complementary

  3. Single factor inheritance

  4. That it is a tes cross
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

E.Nilsson – Ehle crossed red kernelled variety with white kernelled variety of wheat. The grains of F1 were self crossed among themselves, five different phenotypic classes appeared in F2 showing the ratio of 1:6:15:20:15:6:1.

These scientist found that the kernel colour in wheat is determined by two pairs of genes A and B. It is called polygenic inheritance.

So, the correct option is ‘polygenic inheritance’.

Multiple choice pleiotropy genetics zoology

A pleiotropic gene in humans is

  1. Marfan's syndrome

  2. Colour blindness

  3. Eye colour

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

Mutations in the human gene for fibrillin-1 (FBN1) in the Marfan syndrome and related disorders. Mutations in FBN1 produce Marfan syndrome, a pleiotropic autosomal dominant connective tissue disorder with prominent manifestations in the skeleton, eye and cardiovascular system.

So, the correct information is 'Marfan's syndrome.'

Multiple choice pleiotropy genetics zoology

Occasionally, a single gene may express more than one effect. The phenomenon is called

  1. multiple allelism

  2. mosaicism

  3. pleiotropy

  4. polygeny.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When there are three or more alternative forms of a gene, it is called multiple allelism. Polygeny suggests that humans evolved from several different ancestors. When a single gene has more than one effects, it is called pleiotropy.

So, option C is the correct answer.