Which one of the flowing pairs of plants structures has haploid number of chromosomes?
Megaspore mother cell and antipodal cells
Egg cell and antipodal cells
Nucellus and antipodal cells
Nucellus and antipodal cells
B.
Egg cell and antipodal cells
In angiosperms, a single diploid megaspore mother cell matures within the ovule. Through meiosis, it gives rise to four megaspores (haploid). In most plant, only one of these megaspore divides three times by mitosis and produces eight haploid nuclei enclosed with a 7 celled embryo sac. One nucleus is located near the opening of embryo space in the middle of embryo sac and is called polar nuclei, two nuclei are contained in cells called antipodals, located at the end of the embryo sac, opposite the egg cell.
Nucellus is centrally located mass of thin-walled parenchymatous cells covered by integuments in ovule.
A lake near a village suffered heavy mortality of fishes within a few days. Consider the following reasons for this
(1) lost of urea and phosphate fertiliser were used in the crops in the vicinity.
(2) The area was sprayed with DDT by an aircraft.
(3) The lake water turned green and stinky/
(4) Phytoplankton populations in the lake declined initially thereby greatly reducing photosynthesis.
Which were two of above the main causes of fish mortality in the lake?
2, 3
3, 4
1,3
1,3
Gel electrophoresis is used for
cutting of DNA into fragments
separation of DNA fragments according to their size
construction of recombinant DNA by joining with cloning vectors
construction of recombinant DNA by joining with cloning vectors
The fruit is chambered, developed from inferior ovary and has seeds with succulent testa in
pomegranate
orange
guava
guava
A transgenic food crop, which may help in solving the problem of night blindness in developing countries is
Flavr savr tomatoes
Starlink maize
Bt soybean
Bt soybean
In humans, at the end of the first meiotic division, the male germ cells differentiate into the
Primary spermatocytes
Secondary spermatocytes
spermatids
spermatids
In human adult females, oxytocin
is secreted by the anterior pituitary
stimulates the growth of mammary glands
stimulates pituitary to secrete vasopressin
stimulates pituitary to secrete vasopressin
Polymase is formed by
several ribosomes attached to a single mRNA
many ribosomes attached to a strand of endoplasmic reticulum
a ribosome with several subunits
a ribosome with several subunits
In the DNA molecule
the total amount of purine nucleotides and pyrimidine nucleotides is not always equal
there are two strands, which run parallel in the 5' →3' direction
the proportion of adenine in relation to thymine varies with organism
the proportion of adenine in relation to thymine varies with organism
Given below four methods (A - D) and their modes of action (1-4) in achieving contraception. Select their correct matching from the four options that follows
|
|
Method |
|
Mode of action |
|
A |
The Pill |
1 |
Prevents sperms reaching cervix |
|
B |
Condom |
2 |
Prevents implantation |
|
C |
Vasectomy |
3 |
Prevents ovulation |
|
D |
Copper – T |
4 |
Semen contains no sperms |
|
A |
B |
C |
D |
|
3 |
1 |
4 |
2 |
|
A |
B |
C |
D |
|
4 |
1 | 2 | 3 |
|
A |
B |
C |
D |
|
3 |
4 | 1 | 2 |
|
A |
B |
C |
D |
|
3 |
4 | 1 | 2 |
