A cross in which two contrasting characters are studied is called _________.

• Monohybrid cross

• Bihybrid cross

• Dihybrid cross

• Two hybrid cross

Answer explanation

A cross in which two contrasting characters are studied is called dihybrid cross.

When two pairs of contrasting characters are taken in a dihybrid cross, the inheritance of one pair is independent of the other. This law is:

• Law of dominance

• Law of segregation

• Law of independent assortment

• Both option 1 and option 2

Answer explanation

When two pairs of contrasting characters are taken in a dihybrid cross, the inheritance of one pair is independent of the other. This is the law of independent assortment.

How many different types of gametes will be produced by a plant having the genotype GgYYRR?

• 2

• 3

• 4

• 9

Answer explanation

The plant having the genotype GgYYRR is heterozygous for only one character that is G and g. We know that in gametes only one allele is present for one character. Hence in plant having the genotype GgYYRR only two types of gametes will be produced. That will have genotype GYR and gYR.

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NGSS.HS-LS3-2

Pea plant having inflated yellow pod (IIgg) is crossed with the pea plant having constricted green pod (iiGG). What will the phenotype of the plant of F₁ generation?

• Inflated and green pod

• Inflated and yellow pod

• Constricted and green pod

• Constricted and yellow pod

Answer explanation

Here inflated pod shape is dominant over constricted pod shape. Similarly green pod colour is dominant over yellow pod colour. Both parents are homozygous for 2 different characters and its phenotype are IIgg and iiGG. Therefore the genotype of F₁ hybrid will be IiGg. So the phenotype of the plant of F₁ generation will be inflated and green pod

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NGSS.HS-LS3-1

NGSS.HS-LS3-2

In Mendel's experiment with garden pea, round seed shape (RR) was dominant over wrinkled seed shape (rr) and yellow seed colour (YY) was dominant over green seed colour (yy). What are the expected phenotypes in the F₂ generation of the cross RRYY X rryy?

• Only round yellow seed

• Only round green seed

• Only wrinkled green seed

• Round yellow seed, wrinkled yellow seed, round green seed, wrinkled green seed.

Answer explanation

A cross is made between RRYY X rryy i.e. round and yellow seed, and wrinkled and green seed. So in F₁ generation the genotype of plant will be RrYy. We know that F₂ generation is produced by self pollination. By the Punnett square we can find the genotype of offsprings, from which we can know the phenotype of offsprings. So in F₂ generation, expected phenotypes are 9 round yellow seeds, 3 wrinkled yellow seeds, 3 round green seed and 1 wrinkled green seed. Thus, option 4 corresponds with expected phenotypes.

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NGSS.HS-LS3-1

NGSS.HS-LS3-2

In F₂ generation of Mendelian dihybrid cross of green and inflated garden pea plant with yellow and constricted garden pea plant, the number of phenotypes obtained will be ____.

• 1

• 2

• 3

• 4

Answer explanation

In the mendelian dihybrid cross of garden pea plant, F₂ generation has 4 phenotypes. They are - Green and inflated pod, Green and constricted pod, Yellow and inflated pod, Yellow and constricted pod. The phenotypic ratio is 9:3:3:1

The following Punnett square represents the pattern of inheritance in a dihybrid cross in which yellow (Y) and round (R) seed condition is dominant over green (g) and wrinkled (r) seed condition. Then plant of type 'I' will produce seeds with genotype that will be identical to seeds produced by the plant of:

• Type N

• Type C

• Type B

• Type K

Answer explanation

We can draw the Punnett square for the given genotypes like this. In this we can see that the genotype of plant type 'I' is identical to the genotype of plant type 'C'.

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NGSS.HS-LS3-1

NGSS.HS-LS3-2