Question 1

Question 2State the three Mendel's laws of inheritance.

Accepted Answer

Mendel's law of inheritance are as follows —Law of Dominance — Out of a pair of contrasting characters present together, only one is able to express itself while the other remains suppressed. The one that expresses is the dominant character and the one that is unexpressed is the recessive one.Law of Segregation (also called the law of purity of gametes) — The two members of a pair of factors separate during the formation of gametes. They do not blend but segregate or separate into different gametes. The gametes combine together by random fusion at the time of zygote formation.Law of Independent Assortment — When there are two pairs of contrasting characters, the distribution of the members of one pair into the gametes is independent of the distribution of the other pair.

Question 2

Question 4Distinguish between the following pairs:(a) Karyotype and Karyokinesis(b) Autosomes and Sex chromosomes(c) Homozygous and Heterozygous chromosomes

Accepted Answer

(a) Difference between karyotype and karyokinesis —KaryotypeKaryokinesisThe complete set of chromosomes in the cells of an organism is its karyotype.The division of the nucleus during mitosis is called karyokinesis.(b) Difference between autosomes and sex chromosomesAutosomesSex chromosomesThey determine the somatic traits.They determine the sex of an organism.They are numbered as 1 to 22.They are recognized by the letters XO, XY, ZO, ZW.They show Mendelian inheritance.They do not show Mendelian inheritance.Human show 22 pairs of autosomes.Humans show only 1 pair of sex chromosome.(c) Difference between homozygous and heterozygous chromosomesHomozygous chromosomesHeterozygous chromosomesIt has two same copies of the same allele coding for a particular trait.It contains two different copies of alleles coding for a particular trait.

Question 3

Question 6The physical expression of a character is called :GenotypeAllelesPhenotypeTraits

Accepted Answer

PhenotypeReason — Phenotype are the observable characteristics that are genetically controlled.

Question 4

Question 7Purity of gametes is linked to :Law of dominanceLaw of independent assortmentLaw of segregationLaw of limiting factor

Accepted Answer

Law of segregationReason — Two alleles of a character are independent and separate during formation of gametes. They do not mix with each other or lose their identity.

Question 5

Question 8The phenotypic dihybrid ratio of F2 generation is9:3:1:19:1:3:19:1:3:39:3:3:1

Accepted Answer

9:3:3:1Reason — The phenotypic dihybrid ratio of F2 generation is 9:3:3:1 due to the law of independent assortment.

Question 6

Question 9In the human male, a sperm contains autosomes and :X and Y chromosomesOnly X chromosomeX or Y chromosomeOnly Y chromosome

Accepted Answer

X or Y chromosomeReason — In the human male, a sperm contains autosomes and either an X chromosome or a Y chromosome.

Question 7

Question 10If the mother is normal and the father is haemophilic, then their two daughters will be :NormalHaemophilicCarrierNone

Accepted Answer

CarrierReason — Since mother is normal, one of the X chromosome in daughters will be normal. Hence they will be carrier due to X chromosome received from father.

Question 8

Question 11Susheel, a colourblind man, is married to Susheela, a woman with normal vision. Which of the following combinations would be possible in their children?Colourblind daughters and colourblind sonsNormal daughters and normal sonsCarrier daughters and normal sonsCarrier daughters and colourblind sons

Accepted Answer

Carrier daughters and normal sonsReason — Since the mother is normal so the daughters will be carrier due to the X chromosome received from father but sons will be normal. Colour-blind father (X°Y) X°YNormal Mother(XX)XX°Carrier daughterXYNormal sonXX°Carrier daughterXYNormal son

Question 9

Question 3Distinguish between the following pairs:(i) Monohybrid and Dihybrid cross(ii) Genotype and Phenotype(iii) Character and Trait(iv) Dominant and Recessive Allele(v) Autosomes and Sex chromosomes

Accepted Answer

(i) Difference between Monohybrid and Dihybrid cross:Monohybrid CrossDihybrid crossSingle feature is taken into considerationTwo features are taken into consideration.Phenotypic ratio in second generation is 3:1Phenotypic ratio in second generation is 9:3:3:1Genotypic ratio is 1:2:1Genotypic ratio obtained is very complex(ii) Difference between Genotype and Phenotype:GenotypePhenotypeSet of genes present in any organism is known as its genotype.Characters expressed or physical appearance of characters is called phenotype.Can be determined by genotyping method.Can be determined by observation.It is formed by expressed and unexpressed genes.It consists of only expressed genes.(iii) Difference between Character and Trait:CharacterTraitAny inheritable feature of an organism is a character.The alternative forms of a character are called traits.For example, flower colour is a character.For example, within the character of flower colour, specific traits will be red, blue, or white flower colour.(iv) Difference between Dominant and Recessive Allele:Dominant AlleleRecessive AlleleThe gene that expresses itself phenotypically.The gene that remains unexpressed in presence of dominant allele.Expresses in homozygous as well as heterozygous condition.Expresses only in homozygous condition.Represented by capital letters.Represented by small letters.(v) Difference between Autosomes and Sex chromosomes:AutosomesSex chromosomesAutosomes are chromosomes that determine the general body features.Sex chromosomes determine the sex of an organism.Humans have 22 pairs of autosomes.Humans have 1 pair sex chromosomes.

Question 10

Question 1In a certain species of animals, black fur (B) is dominant over brown fur (b). Predict the genotype and phenotype of the offspring, when both parents are 'Bb' or have heterozygous black fur.

Accepted Answer

BbBBBBbbBbbbIn the question it is given that B refers to black fur and b refers to brown fur. So the genotype and phenotype of the offspring will be:Genotype — 1 (Homozygous Black Fur) : 2 (Heterozygous Black Fur) : 1 (Homozygous Brown Fur)Phenotype — 3 (Black Fur): 1 (Brown Fur)

Question 11

Question 5A homozygous plant having round (R) and yellow (Y) seed is crossed with another homozygous plant having wrinkled (r) and green (y) seeds. Answer the following questions :(a) Give the genotype of the F1 generation.(b) Mention the phenotype of the F1 offsprings.(c) Give the possible combinations of gametes that can be obtained from F1 hybrids.(d) Give the dihybrid phenotypic ratio and the phenotype of the offsprings of the F2 generation when two plants of F1 generation are crossed.(e) Name and state the law which explains the dihybrid phenotypic ratio.

Accepted Answer

(a) Genotype : RrYy(b) All Round and yellow seeds(c) RY, Ry, rY, ry(d) 9:3:3:1(e) Law of Independent Assortment, which states that the distribution of the alleles of one character into the gametes is independent of the distribution of the alleles of the other character.

Genetics — Some Basic Fundamentals

Descriptive Type

Multiple Choice Type

Progress Check 4

Structured Application Skill Type