The pollen tube usually enters the embryo sac
through one of the synergids
by directly penetrating the egg
between one synergid and central cell
by knocking off the antipodal cells.
A.
through one of the synergids
The pollen tube arrives in the micropyle of the integument of the ovule, and enters the embryo sac.
The synergids of the embryo sac literally put their energies together to burst the end of the pollen tube. Meanwhile, the generative cell has followed the pathway digested by the tube cell. Along the way it has divided to produce two sperm cells. The two sperm cells exit the pollen tube through the burst end.
One sperm cell unites with the egg. This process is called syngamy (union of gametes) or [gag] fertilization. I much prefer syngamy to fertilization (see below). The product of the union of egg and sperm is called a zygote, and it has two sets of master plans, one from each gamete. The zygote will divide and grow and differentiate to become a new embryonic plant with root, stem, and leaf. Ultimately it will become an adult plant.
A lake with an inflow of domestic sewage rich in organic waste may result in
drying of the lake very soon due to algal bloom
an increased production of fish due to lot of nutrients
death of fish due to lack of oxygen
increased population of aquatic food web organisms.
Minamata disease was caused due to the consumption of
sea food containing lot of cadmium
fish contaminated with mercury
oysters with lot of pesticide
sea food contaminated with selenium.
An artificial pacemaker is implanted subcutaneously and connected to the heart in patients
having 90% blockage of the three main coronary arteries
having a very high blood pressure
with irregularity in the heart rhythm
suffering from arteriosclerosis.
An example of gene therapy is
production of injectable hepatitis B vaccine
production of vaccines in food crops like potatoes which can be eaten
introduction of gene for adenosine deaminase in persons suffering from Severe Combined Immuno-deficiency (SCID)
production of test tube babies by artificial insemination and implantation of fertilized eggs
What is the first step in the Southern Blot technique
Denaturation of DNA on the gel for hybridization with specific probe
Production of a group of genetically identical cells
Digestion of DNA by restriction enzyme
Isolation of DNA from a nucleated cell such as the one from the scene of crime
Women who consumed the drug thalidomide for relief from vomiting during early months of pregnancy gave birth to children with
no spleen
hare-lip
extra fingers and toes
underdeveloped limbs.
Given below is a pedigree chart of a family with five children. It shows the inheritance of attached ear-lobes as opposed to the free ones. The squares represent the male individuals and circles the female individuals. Which one of the following conclusions drawn is correct
The parents are homozygous recessive.
The trait is Y-linked.
The parents are homozygous dominant.
The parents are heterozygous.
Given below is a representation of a kind of chromosomal mutation. What is the kind of mutation represented
Deletion
Duplication
Inversion
Reciprocal translocation
Which one of the following pairs is correctly matched with regard to the codon and the amino acid coded by it
UUA - valine
AUG - cysteine
AAA - lysine
CCC - alanine
