Short Answer Type Questions
- How many phenotypes of human skin colour are possible if
two individuals of intermediate skin colour (aa bb Cc)
marry? - In shorthorn cattle, coat colour may be red, white, or roan. roan
is an intermediate phenotype expressed as a mixture of red
and white hair. The following data were obtained from various
crosses: - red × red → all red
- white × white → all white
- red × white → all roan
- roan × roan → 1/4 red : 1/2 roan : 1/4 white
(i) What is the inheritance pattern for coat colour in shorthorn
cattle?
(ii) What are the genotypes of parents and offspring for each
cross?- Mention one difference between complete linkage and
incomplete linkage. - read the given passage and fill up the blank spaces.
(i) inheritance is a type of inheritance controlled by one or
more genes in which the dominant alleles have (ii) effect
with each dominant allele expressing a part or unit of the
trait, the full trait being shown only when all the (iii) alleles
are present. This type of inheritance is also called as (iv)
inheritance and its examples are (v) and (vi).
ANSWER KEY
New MCQs- (a) 2. (b) 3. (d) 4. (a) 5. (a)
- (d) 7. (b) 8. (c) 9. (a) 10. (b)
- (a) 12. (c) 13. (a) 14. (c) 15. (c)
- (c) 17. (a) 18. (d) 19. (d) 20. (d)
Exam Section - (b) 2. (d) 3. (a) 4. (b) 5. (b)
- (e) 7. (a) 8. (a) 9. (c) 10. (b)
Assertion & Reason- (b) 2. (a) 3. (c) 4. (a) 5. (b)
Short Answer Type Questions- When two individuals of intermediate skin colour (aa bb
Cc) marry the phenotypes of skin colour will vary from very
dark (or black) to very light (or white). a total of eight allelic
combinations is possible in the gametes forming 27 distinct
genotypes distributed into seven phenotypes (black, dark,
fairly dark, intermediate, fairly light, light, white). - (i) The inheritance pattern is incomplete dominance in which
none of two contrasting alleles is completely dominant and
the expression of the character in f 1 hybrid is intermediate
or a fine mixture of the expression of the two contrasting
alleles.
(ii) Genotypes of parents Genotypes of offspring - rr × rr → rr
- WW × WW → WW
- rr × WW → rW
- rW × rW → 1rr : 2rW : 1WW
- Complete linkage is the grouping of genes on a chromosome
which is not altered and is inherited as such from generation
to generation without any cross over. It produces only parental
types and no recombinants.
Incomplete linkage is the phenomenon of an occasional
crossing over between two homologous chromosomes so that
one or more alleles present in a linkage group are replaced
by other alleles. It produces both parental and recombinant
individuals. - (i) - Quantitative
(ii) - cumulative
(iii) - dominant
(iv) - polygenic
(v) - kernel colour in wheat
(vi) - skin colour in humans