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The CORRECT option is (d) Coiling of SHELLS

To explain I would say: The coiling of shells is not an example of organelle inheritance. It is evidence of maternal inheritance. Examples of organelle inheritance include plastid inheritance in Mirabilis JALAPA, iojap inheritance in maize, and inheritance of POKY.

The correct choice is (a) WIDOW’s peak

The BEST EXPLANATION: Widow’s peak is an example of a dominant trait. Other dominant traits include tongue ROLLERS, morphan syndrome, free ear lobes, etc. Some recessive traits are tongue non-roller’s, Duchenne muscular DYSTROPHY, Lesch-Nyhan syndrome, fused ear lobes, Tay- Sachs disease, etc.

The correct answer is (b) Blue eyes

To EXPLAIN: Blue eyes are the representation of a recessive trait. Some other recessive TRAITS include albinism, alkaptonuria, and cystic fibrosis. Some dominant traits are achondroplasia, BROWN eyes, BRACHYDACTYLY, Huntington disease, etc.

The correct answer is (a) Short stature

The explanation is: Short stature is not a character of the person SUFFERING from Klinefelter’s syndrome. The person’s height who is suffering from Klinefelter’s syndrome is taller than the average HUMAN height. Other characteristic features include BREAST DEVELOPMENT (gynecomastia), small testes (testicular atrophy), and female type pubic HAIR pattern.

The correct choice is (C) Well developed ovaries

To EXPLAIN: FEMALES suffering from Turner’s syndrome do not have well-developed ovaries. Instead, they have rudimentary ovaries. Other CHARACTERISTIC features of this disease are short stature, poor BREAST development, and no menstruation.

Right answer is (b) False

To explain I WOULD say: It is not true that there are no loops on the finger-tips of the PEOPLE SUFFERING from Down’s syndrome. Instead, their finger-tips have MANY loops as compared to the finger-tips of normal human beings.

Correct ANSWER is (c) The fusion of a normal egg with a normal sperm

The explanation: The fusion of a normal egg with a normal sperm leads to the formation of a healthy baby. KLINEFELTER’s syndrome APPEARS due to the union of an ABNORMAL egg (two X-chromosomes + autosomes) with a normal sperm (Y-chromosome+ autosomes) or a normal egg (X-chromosome + autosomes) with abnormal sperm (XY chromosomes+ autosomes).

The CORRECT answer is (c) 44+ XXY

The explanation is: The GENOTYPE of the PERSON suffering from Klinefelter’s syndrome is 44+ XXY. This DEVIATION from a normal person’s genotype is due to the additional copy of the X-chromosome.

The CORRECT ANSWER is (d) Straight tongue

To explain I would SAY: The tongue of the person suffering from Down’s syndrome is not straight. It is WRINKLED and is comparatively bigger than a normal human tongue. The tongue is also FURROWED. These features help in the diagnosis of Down’s syndrome.

Correct CHOICE is (a) Very tall

The explanation: Tallness is not a characteristic feature of Down’s SYNDROME. Some characteristic FEATURES INCLUDE- Short STATURE, small round head, partially open mouth, furrowed tongue, etc.

Correct answer is (B) False

The best I can explain: It is not true that only mental health is retarded in the case of Down’s syndrome. Physical and psychomotor skills are also not developed. They have underdeveloped GONADS and GENITALS. Their JOINTS are also loose.

The correct option is (a) 1866

The best EXPLANATION: In 1866, Down’s syndrome was first described by Langdon Down. This DISORDER is a result of the trisomy of chromosome number 21. SHORT stature, small ROUND head, etc. are some of the EFFECTS of this disorder.

Right option is (c) Broad PALM with palm crease

For explanation: Congenital heart disease, short STATURE, and underdeveloped gonads are some features of Down’s syndrome which also occur in other people. But, broad palm with a palm crease is the CHARACTERISTIC feature of someone with Down’s syndrome.

The correct choice is (B) IMBALANCE in chromosome number and chromosome arrangement

Explanation: The chromosomal DISORDERS are the disorders that are based on the imbalance in chromosome number and chromosomal arrangement. The disorders which are due to the mutant allele and their DEFECTIVE products are known as Mendelian disorders.

Right answer is (c) 11

To elaborate: The mutation in the HBB gene on chromosome NUMBER 11 LEADS to the disorder beta-thalassemia. It is inherited as an AUTOSOMAL recessive trait. The severity of beta-thalassemia DEPENDS upon the nature of the mutation.

Correct option is (a) DEFECTS in RBCs

For explanation: The defect in the synthesis of globin POLYPEPTIDE in RBC causes a group of disorders known as THALASSEMIA. Absence or REDUCED synthesis of ONE of the globin chains leads to the excess of other chains which accumulate in our body to causes different diseases.

The correct choice is (c) THREE

Best EXPLANATION: Three TYPES of genotypes of sickle CELL anaemia are possible in a population. These are:

i. Hb^A Hb^A: Normal individuals

ii. Hb^A Hb^S: Normal individuals but act as a CARRIER in spreading the disease

iii. Hb^S Hb^S: Diseased individuals and they die before attaining maturity

The correct option is (a) 25%

Easiest explanation: The percentage of CHILDREN being a carrier of haemophilia if their mother is a carrier and their father is a normal MAN is 25% because the GAMETES formed by mother are X and X^h while the gametes formed by father are X and Y. The genotype of the offspring obtained would be XY, XX, XX^h and X^hY. Thus 50% of children are normal, 25% are carriers of haemophilia and 25% are haemophilic (only SON).

The CORRECT answer is (a) False

The best I can explain: No, heterozygous individuals of SICKLE cell anaemia are not severely AFFECTED by the DISEASE. Apparently, they appear to be unaffected by the disease. But, there is a 50% PROBABILITY of transmission of the mutant gene to the progeny.

Correct OPTION is (a) Anti haemophilic GLOBULIN

The explanation is: AHG stands for Anti haemophilic globulin. It is a type of BLOOD protein which is required for normal blood CLOTTING. The person suffering from haemophilia A cannot synthesise this protein and even a small cut may lead to CONTINUOUS bleeding for a long time.

Correct choice is (B) Mother is a CARRIER and FATHER is haemophilic

The best EXPLANATION: A female can only be haemophilic if her mother is at least a carrier of this disease and her father is haemophilic. But the possibility of a female becoming haemophilic is extremely rare because being haemophilic for the parents at the later STAGE of life is unviable.

Right option is (b) False

To explain: No, haemophilia is not an AUTOSOMAL recessive trait. It is X-linked recessive trait and shows transmission from normal carrier female to a male progeny. In this disease, the exposed blood of affected individuals cannot coagulate DUE to the PRESENCE of defective blood clotting FACTORS.

Correct choice is (b) 50%

Best explanation: The percentage of children which are colour BLIND if their father is colour blind and the mother is a CARRIER for colour blindness is 50% because the father will produce Xc and Y chromosome and the mother will produce Xc and X chromosomes. Their children will have the genotypes- XcY, XY, XcXc and XcX. Therefore, 50% of children are colour blind, 25% have normal vision and 25% are the carriers of the disease.

The correct OPTION is (a) 0%

For explanation I would say: The percentage of sons having normal vision, if the FATHER has normal vision and mother is colour blind is 0% because as colour blindness is a sex-linked TRAIT, it MEANS that the trait only transmits through X-chromosome. As the mother is colour blind, both her gametes will carry the gene for colour blindness, so none of their sons will have a normal vision.

The correct option is (d) FATHER is COLOUR blind and MOTHER is a carrier

The EXPLANATION is: A female can be a colour blind only in two conditions:

i. When her father is colour blind and her mother is the carrier of this disease

ii. When both her father and her mother are colour blind

Therefore, for a female to be colour blind, her father must ALSO have colour blindness.

Correct OPTION is (a) RED and GREEN

To EXPLAIN I would say: People who are colour BLIND fail to distinguish between red and green colours. Colour blindness is a sex-linked recessive trait in which the normal gene and its recessive allele are carried by X-chromosome.

The correct OPTION is (d) It does not lead to cancer

Explanation: Ionizing RADIATIONS are responsible for different TYPES of cancer as ionizing radiations CAUSE the breaks in the chromosomes. The cells which become IONIZED show abnormal cellular division. The frequency of induced mutations is also directly proportional to the doses of the radiations.

Correct answer is (b) Nitrous acid

The explanation: Nitrous acid is the chemical mutagen that is both mutagenic to replicating and non-replicating DNA. Acridines are very POWERFUL mutagens and they INDUCE frame shift-mutation or GIBBERISH mutation.

Right OPTION is (a) H.J Muller

The best explanation: H.J Muller is considered as the FATHER of Actinobiology. He used X-rays to increase the rate of MUTATION in Drosophila. He opened an entirely NEW field in inducing mutations.

The correct choice is (C) A decrease in the number of sets of chromosomes

To elaborate: Decrease in the number of sets of chromosomes is not known as polyploidy. In polyploidy conditions, after the telophase stage of cell division, cytokinesis FAILS to occur which results in an INCREASE in a WHOLE set of chromosomes in an organism. Polyploidy is often seen in plants and it results in sterility in ANIMALS.

Correct option is (b) False

Easiest explanation: It is not true that diploids are better for mutation experimental studies. Instead, haploids are taken for mutation experimental studies because all the mutations, WHETHER DOMINANT or recessive can get expressed IMMEDIATELY in haploids, as there is only ONE allele of each gene present in every CELL.

Right answer is (B) 2n-2

The best EXPLANATION: 2n-2 REPRESENTS nullisomic condition which is a TYPE of aneuploidy. 2n-1, 2n+1, and 2n+2 represent the monosomic condition, trisomic condition, and tetrasomic condition respectively.

Correct option is (C) Phenylketonuria

For EXPLANATION: Phenylketonuria is not an example of aneuploidy. The examples of aneuploidy are Down’s syndrome, Klinefelter’s syndrome, and TURNER’s syndrome where down’s and Klinefelter’s syndrome SHOW trisomy CONDITION while turner’s syndrome show monosomic condition.

The correct choice is (a) Drosophila

For explanation: INVERSION occurs frequently in Drosophila as a result of X-ray radiation. Inversion is TECHNICALLY a type of chromosomal aberration where the linear order of GENES changes by 180° through the ROTATION.

Right option is (b) Translocation

Easy explanation: An important class of translocation having evolutionary significance is known as SEGMENTAL changes or RECIPROCAL translocation. It involves the mutual exchange of chromosome segments between TWO non-homologous CHROMOSOMES.

Right answer is (b) False

The BEST I can explain: Paracentric is not a type of INVERSION involving CENTROMERE. Instead, it is an inversion without involving centromere. PERICENTRIC is a type of inversion which INVOLVES centromere.

Correct answer is (b) Chronic myelogenous leukaemia

The EXPLANATION is: CML stands for Chronic myelogenous leukaemia. CML occurs due to the translocation of a segment of the long ARM from CHROMOSOME 22 to chromosome 9. Chromosome 22 is ALSO known as the PHILADELPHIA chromosome.

Right choice is (d) Shifting of a PART of a CHROMOSOME to another non-homologous chromosome

For EXPLANATION: TRANSLOCATION is the shifting of a part of a chromosome to another non-homologous chromosome. It results in the formation of new recombinant chromosomes as this INDUCES faulty pairing of chromosomes during meiosis.

The correct CHOICE is (c) When a PART of a CHROMOSOME is lost

The best I can EXPLAIN: Deletions are a type of chromosomal aberrations where a part of a chromosome is lost. It is of two types-terminal and INTERCALARY deletions. When the terminal segment of the chromosome is lost then it is known as terminal deletions and when an intercalary segment is lost then it is known as intercalary deletions.

Correct answer is (b) False

The best I can explain: No, CHANGE in more than one NUCLEOTIDE pair is not called a spontaneous mutation, INSTEAD it is known as gross mutation. When gene mutations OCCUR naturally and automatically DUE to any internal reasons, then it is called as spontaneous mutations.