True or False
- Genes which code for a pair of contrasting traits are known
as alleles.
- Recessive allele is able to express itself in the presence of
dominant allele.
- A new grouping of genes or a new combination of
characters which is different from the parental types is
called recombination.
- Frequency of crossing over between the two genes
decreases if they are placed close to each other.
- Down’s syndrome occurs due to sex-chromosomal
aneuploidy.
- Allosomes or sex chromosomes in birds are XX-XY.
- Linked genes are located on different chromosomes and
undergo independent assortment.
- Polygenes produce continuous variation in the expression
of traits.
- Albinism is an autosomal, recessive genetic disorder caused
due to the absence of enzyme tyrosinase.
- The phenomenon of expression of both the alleles in a
heterozygote is called codominance.
Match The columns
- Match Column I with Column II.
Column I Column II
A. Test cross (i) 2N + 1
B. Walter Sutton (ii) Tt × tt
C. Thomas Hunt Morgan (iii) Chromosomal Theory
of Inheritance
D. Trisomy (iv) 2N – 2
E. Nullisomy (v) Father of Experimental
Genetics
- Match Column I with Column II. (There can be more than
one match for items in Column I)
Column I Column II
A. Autosomal chromosomal (i) Human
disorder
B. Allosomal chromosomal (ii) Down’s syndrome
abnormality
C. Male heterogamety (iii) Turner’s syndrome
D. Polygenic Inheritance (iv) Drosophila
E. Mendelian disorder (v) Edward’s syndrome
(vi) Klinefelter’s
syndrome
(vii) Haemophilia
(viii) Skin colour in
human beings
(ix) Sickle-cell anaemia
(x) Kernel colour in
wheat
passage Based Questions
23.(A) Complete the given passage with appropriate words or
phrases.
Phenylketonuria is an inborn, (i) , (ii) metabolic disorder
in which the (iii) lacks the enzyme (iv) needed to
change (v) to (vi) in (vii). It results in (viii). This is
caused due to presence of abnormal gene on (ix). This
defective gene is due to (x).
(B) Read the given passage and correct the errors, wherever
present.
In a pedigree chart, a square represents the female, a
circle represents the male, solid (blackened) symbol shows
the trait under study or affected individual; unaffected or
normal individuals are shown by crossed or shaded symbol
and open or clear symbol signifies the carrier individual.
Parents are shown by vertical line while their offsprings are
connected to it by a horizontal line. The offsprings are then
shown in the form of a horizontal line above the parents
and numbered with roman numerals. Each generation is
given an arabic numeral and a separate row or horizontal
line.
Assertion & reason
In each of the following questions, a statement of Assertion
(A) is given and a corresponding statement of Reason (R)
is given just below it. Of the statements, mark the correct
answer as :
(a) if both A and R are true and R is the correct explanation
of A
(b) if both A and R are true but R is not the correct explanation
of A
(c) if A is true but R is false
(d) if both A and R are false.
- Assertion : In human beings, females are homogametic
and males are heterogametic.
Reason : In humans, females have XX sex chromosomes
whereas males have XY sex chromosomes.
- Assertion : Incomplete linkage produces more of parental
types alongwith few recombinants in the progeny.
Reason : Genes in an incomplete linkage are present
distantly on the same chromosome and have a tendency
to occasionally separate.
- Assertion : Frequency of crossing over may be higher
than the frequency of observed recombinations.
Reason : Sometimes two or even more crossing
overs may occur simultaneously in the same non sister
chromatids of the non-homologous chromosomes, and
alters the frequency of recombinations.
