DAV
Public School, Kailash Hills
Holiday
Homework (2017-18)
Class
XII (Biology)
HOTS
1. If a branch “dasheri mango” is grafted on a
tree producing “desi mangoes” what type
of mangoes will be borne on grafted
branch& other branches of the plant? 1
2. Most
sugarcane varieties cultivated today are aneuploids and are sterile. But they
grow
and perform extremely well. Sterility in
sugarcane is not of any disadvantage. Why? 1
3. Why
do organisms like algae and fungi which normally adopt asexual reproduction
switch over to sexual method of reproduction
just before the onset of adverse conditions?
1
4. If a
certain plant when introduced into a new environment neither produces seeds nor
it
responds to vegetative propagation. How can
more plants be produced? 2
5. Even though each pollen grain has two male gametes. Why are at least 10
pollen grains and
not 5 pollen grains required to fertilise 10
ovules present in a particular carpel? 2
6.
“Apomictic genes are trying to be inserted in hybrid varieties” –Explain 3
7. a)
“Dehydration of seed increases their shelf life” – Explain 2
b) Cleistogamous flowers are strictly self
pollinating,” Explain. What is the disadvantage
of this phenomenon?
2
c) Even after killing the generative cell
with a laser beam, the pollen grain of a flowering
plant germinates and produces normal
pollen tube. How does it happen? 1
8.
Suppose the acrosome of mammalian spermatozoa does not function normally, how
would
it affect fertilization? Give reasons.
2
9. Fill
the blank spaces a, b, c, and d given in the following table.
S. No. Organism Organ Gamete
(i) a Testes Spermatozoa 2
(ii) Human female b Ovum
(iii) Plant (Angiosperm) c Pollen grains
(iv) Plant (pteridophytes) antheridium d
10. a)
In which part of human female reproductive system do the following events take
place? 1x5
i. Release of 1st polar body
ii. Release of 2nd polar body
iii. Fertilization
iv. Implantation
b) From where do the signals for parturition
originate and what does maternal pituitary release
for simulating uterine contraction for child
birth?
11. A
woman who was pregnant (8 weeks), on clinical examination was found to have
conceived
a defective foetus with a serious genetic
defect.
1) With what test would the doctor have
confirmed the genetic defect.
2) What suggestive measure would you
recommend? 2
12.
Study the following diagram and answer the following questions:
a)
Label the parts A,B,C,D,E and F
3
b) How
does D differ from F?
1
13.
State which law of Mendelian inheritance is expressed in the following
diagram?
To different gamete 
To different gamete 1
To different gamete 1
14.
Assume that no new mutations have arisen in the family. 2
Answer each question with either ‘Yes’ or ‘No’
i)
Could this be inherited as recessive trait?
ii)
Could this be inherited as dominant trait?
15. The
map distance between A & B genes is 18 unit; between B & C is 20 2
unit and C & A is 2 unit.(a)What is the
order of genes on a linkage group?(b)
Write the unit of map distance.
16 .
Colour blindness is a recessive trait. A couple with normal vision has two
sons, 2
one colour blind and one with normal
vision. If the couple also has daughters what
proportion of them will have normal vision?
18. From
the given monohybrid ratio identify the type of inheritance and give one 3
example each.
i) Both phenotypic and genotypic ratio is
1:2:1
ii) Phenotypic ratio is 3:1 and genotypic
ratio is 1:2:1
17.
Mention the steps involved in the following Pea plant cross
3
Removal of anthers---------------------- A
Transfer of Pollen------------------------ B
|
Raising the next generation-------------C
19.
Mention whether the male individuals of the following organisms are homozygous/
heterozygous.
1x5
i) Human = XY-XX
ii) Hen = ZW-ZZ
iii) Drosophila = XY-XX
iv) Grasshopper = XO-XX
v) Birds = ZZ-ZW
20.
Mention the type of error in the following diseases:
1. Sickle cell anaemia
2. Haemophilia
3. Phenylketonuria
4. Down’s syndrome
5. Klinefelter’s syndrome
