A change in a single base pair of DNA, such as causing sickle cell anemia, is known as a _______ mutation.
Mutation due to change in a single base pair of DNA is known as point mutation.
Question 292 of 519
📘 CLASS XII
The analysis of traits in several generations of a family, used to trace the inheritance of a specific trait or disease, is called the _______.
Analysis of traits in several generations of a family, used to trace the inheritance of a specific trait, abnormality or disease, is called the pedigree analysis.
Question 293 of 519
📘 CLASS XII
Down's syndrome is a chromosomal disorder caused due to the presence of an additional copy of chromosome number _______ (trisomy).
Down’s Syndrome is caused by the presence of an additional copy of the chromosome number 21 (trisomy of 21).
Question 294 of 519
📘 CLASS XII
Match List-I (Mendelian Concepts) with List-II (Explanation/Example):
List-I
List-II
A. Law of Dominance
I. F1 generation resembles only one parent
B. Law of Segregation
II. Alleles do not show blending and segregate during gamete formation
C. Co-dominance
III. F1 generation resembles both parents
D. Incomplete Dominance
IV. F1 phenotype is in between the two parents
Choose the correct answer from the options given below:
The Law of Dominance explains the F1 resembling one parent. The Law of Segregation ensures alleles do not blend. Co-dominance results in the F1 resembling both parents (e.g., ABO blood group IA IB). Incomplete dominance produces an intermediate phenotype (e.g., pink Snapdragon flowers).
Question 295 of 519
📘 CLASS XII
Match List-I (Genetic Terms) with List-II (Definition):
List-I
List-II
A. Alleles
I. Slightly different forms of the same gene
B. Genotype
II. Allelic composition of an organism (e.g., Tt)
C. Phenotype
III. Descriptive appearance (e.g., Tall)
D. Homozygous
IV. Allelic pair of genes are identical (e.g., TT or tt)
Choose the correct answer from the options given below:
Alleles are slightly different forms of the same gene. Genotype refers to the composition like TT or tt. Phenotype refers to the descriptive appearance like tall or dwarf. Homozygous refers to identical allelic pairs.
Question 296 of 519
📘 CLASS XII
Match List-I (Sex Determination Organism) with List-II (Mechanism/Feature):
List-I
List-II
A. Grasshopper
I. XO type of sex determination
B. Birds
II. Female heterogamety (ZW)
C. Humans/Drosophila
III. XY type of sex determination
D. Male Heterogamety
IV. Males produce two different types of gametes
Choose the correct answer from the options given below:
Grasshopper is an example of XO type sex determination. In birds, females are heterogametic (ZW). Humans and Drosophila show XY type sex determination. Male heterogamety involves males producing two different types of gametes (X/O or X/Y).
Question 297 of 519
📘 CLASS XII
Match List-I (Genetic Disorder) with List-II (Key Feature):
List-I
List-II
A. Haemophilia
I. X-linked recessive disease resulting in non-stop bleeding
B. Sickle-cell anaemia
II. Caused by single base substitution (GAG to GUG)
C. Colour Blindness
III. Due to mutation in genes present on the X chromosome, affecting red/green cones
D. Phenylketonuria
IV. Autosomal recessive trait leading to mental retardation and metabolic error
Choose the correct answer from the options given below:
Haemophilia is an X-linked recessive disease affecting blood clotting. Sickle-cell anaemia is caused by a point mutation (single base substitution GAG to GUG). Colour blindness is an X-linked recessive disorder due to defects in cone cells. Phenylketonuria is an inborn error of metabolism (autosomal recessive) resulting in mental retardation.
Question 298 of 519
📘 CLASS XII
Match List-I (Chromosomal Disorder) with List-II (Karyotype/Cause):
List-I
List-II
A. Down’s Syndrome
I. Trisomy of chromosome 21
B. Klinefelter’s Syndrome
II. Karyotype 47, XXY
C. Turner’s Syndrome
III. Karyotype 45, X0
D. Polyploidy
IV. Increase in a whole set of chromosomes (often seen in plants)
Choose the correct answer from the options given below:
Down’s Syndrome is caused by trisomy of chromosome 21. Klinefelter’s Syndrome is 47, XXY. Turner’s Syndrome is 45, X0. Polyploidy is the increase in a whole set of chromosomes, typically due to failure of cytokinesis.
Question 299 of 519
📘 CLASS XII
Match List-I (Scientist) with List-II (Key Contribution):
List-I
List-II
A. T.H. Morgan
I. Experimental verification of Chromosomal Theory using Drosophila
B. Sutton & Boveri
II. Proposed the Chromosomal Theory of Inheritance
C. Alfred Sturtevant
III. Used recombination frequency to map gene distance
D. Henking
IV. Discovered the 'X body' during spermatogenesis in insects
Choose the correct answer from the options given below:
T.H. Morgan provided experimental verification of the chromosomal theory. Sutton and Boveri formulated the chromosomal theory of inheritance. Sturtevant used recombination frequency to map gene positions. Henking discovered the X body (later X-chromosome) in insects.
Question 300 of 519
📘 CLASS XII
Match List-I (Type of Mutation/Variation) with List-II (Description):
List-I
List-II
A. Mutation
I. Phenomenon resulting in alteration of DNA sequences
B. Point Mutation
II. Change in a single base pair of DNA
C. Aneuploidy
III. Gain or loss of a chromosome(s) due to failure of segregation
D. Chromosomal Aberrations
IV. Loss (deletions) or gain (duplication/insertion) of a segment of DNA
Choose the correct answer from the options given below:
Mutation is the alteration of DNA sequences. Point mutation is a change in a single base pair (e.g., sickle cell anemia). Aneuploidy is the gain or loss of a chromosome. Chromosomal aberrations involve alteration in chromosomes due to loss or gain of DNA segments.
