Case study (4 Marks)

Question 14 Marks

Distinguish Between: Turner’s syndrome and Klinefelter’s syndrome.

Answer

Turner’s syndrome	Klinefelter’s syndrome
1. Individual with Turner’s syndrome has total 45 chromosomes in each of her cell.	1. Individual with Klinefelter’s syndrome has total 47 chromosomes in each of his cell.
2. Turner’s syndrome is XO female, caused due to monosomy of X-chromosome.	2. Klinefelter’s syndrome is XXY male, caused due to trisomy of X chromosome.
3. The external phenotype is of female.	3. The external phenotype is of male.
4. The stature is short.	4. The stature is tall and thin.
5. Secondary sexual characteristics are not developed in Turner’s syndrome.	5. Secondary sexual characteristics are poorly developed in Klinefelter’s syndrome.

Question 24 Marks

Distinguish Between: Incomplete dominance and Co$-$dominance.

Answer

Incomplete dominance	Co-dominance
$1.$ Incomplete dominance is seen when the phenotypes of the two parents blend together to create a new phenotype for their offspring.	$1.$ Co$-$dominance is seen when the two parent phenotypes are expressed together in the offspring.
$2.$ Both the genes of an allelomorphic pair express themselves partially in $F_1$ hybrids.	$2.$ Both the genes of an allelomorphic pair express themselves equally in $F_1$ hybrids.
$3.$ In incomplete dominance, a mixture of the alleles in the genotype is seen in the phenotype.	$3.$ In co$-$dominance, both alleles in the genotype are seen in the phenotype.
$4.$ The phenotypic effect of one allele is more prominent than the other.	$4.$ The phenotypic effect of both the alleles is equally prominent.
$5.$ Blending or intermixing of two alleles can be observed. A white flower and a red flower alleles mix and produce pink flowers.Example : Pink flowers in Mirabilis jalapa.	$5.$ No intermixing or blending effect of two alleles is observed. The colours don’t mix but are seen in patches.Example : Roan colour in cattle.

Question 34 Marks

Distinguish Between: Phenotype and Genotype.

Answer

Phenotype	Genotype
$1.$ Phenotype refers to the outward appearance of an individual such as shape, colour, sex, etc.	$1.$ Genotype refers to the genetic composition of an individual.
$2.$ Phenotype can be observed directly in an individual.	$2.$ Genotype cannot be seen, but can be found out by modern techniques like $\text{DNA}$ fingerprinting.
$3.$ Individuals resembling each other may or may not have the same genotype.	$3.$ Individuals possessing the same genotype usually have the same phenotypic expression.
$4.$ The phenotypic ratio obtained in the $F_2$ generation of a monohybrid cross is $3 : 1.$	$4.$ The genotypic ratio obtained in the $F_2$ generation of a monohybrid cross is $1 : 2 : 1.$

Question 44 Marks

Distinguish Between: Dominant characters and Recessive characters.

Answer

Dominant characters	Recessive characters
$1.$ The characters that are expressed in the $F_1$ generation are called dominant characters.	$1.$ The characters that are not expressed in the $F_1$ generation are called recessive characters. They are prevented from expressing themselves, due to presence of dominant allele.
$2.$ Dominant character is expressed either in homozygous or heterozygous combination.	$2.$ Recessive characters are expressed only when they are in homozygous combination.
$3.$ Dominant characters cannot be masked by recessive characters. E.g. Round seed and yellow seed are dominant characters in pea plant.	$3.$ Recessive characters are masked by dominant characters.E.g. Wrinkled seed and green seed are recessive characters in pea plant.

Question 54 Marks

Distinguish Between: Monohybrid cross and Dihybrid cross.

Answer

Monohybrid cross	Dihybrid cross
$1.$ Crosses involving a single pair of alleles are called monohybrid crosses.	$1.$ Crosses involving two pairs of alleles are called dihybrid crosses.
$2.$ Monohybrid crosses yield a phenotypic ratio of $3 : 1$ in the $F_2$ generation.	$2.$ Dihybrid crosses yield a $9 : 3 : 3 : 1$ ratio in $F_2$ generation.
$3.$ Monohybrid crosses yield $1 : 2 : 1$ genotypic ratio in $F_2$ generation.	$3.$ Dihybrid crosses yield $1 : 1 : 2 : 2 : 4 : 2 : 2 : 1 : 1$ genotypic ratio in $F_2$ generation.
$4.$ Application of the law of independent assortment is not applicable in monohybrid crosses.	$4.$ Application of the law of independent assortment is applicable in dihybrid crosses.

Question 64 Marks

Distinguish Between: Homozygous and Heterozygous.

Answer

Homozygous	Heterozygous
1. Individuals with similar gene pairs are called homozygous.	1. Individuals with different gene pairs are called heterozygous.
2. Homozygous individuals form only one type of gametes.	2. Heterozygous individuals form more than one type of gametes.
3. Individuals with similar gene pairs TT, tt, RR and rr are homozygous.	3. Individuals with dissimilar gene pairs Tt and Rr are heterozygous.
4. Homozygous are also called pure breed.	4. Heterozygous are referred to as hybrids.

Question 74 Marks

Answer

1-c , 2-a , 3-d , 4-b

BIOLOGY Case study (4 Marks)