<span>Until about 200 million years ago, Earth's continents were joined as a single land mass called Pangaea.</span>
Answer:
a. two sperm enter the ovule; one fertilizes the egg, one fuses with 2 polar nuclei
Explanation:
Double fertilization is the characteristic feature of the angiospermic plants. After pollination, pollen grains deposited on the stigma of the pistil or carpel. The pollen grain on the stigma germinates forming a pollen tube. The pollen tube carrying two male gametes grows down through the style of the pistil and enters into the embryosac formed within the ovule and releases two male gametes.
One of the gametes fuses or fertilizes with the egg forming zygote. The other male gamete fuses with the two polar nuclei of the embryo sac. The fertilization between two polar nuclei and one male gamete is called the triple fusion. The triple fusion results in triploid primary endosperm cell (3n).
Thus, in angiosperms, there are two fertilizations called double fertilization resulting in the zygote (2n) and primary endosperm cell (3n).
Answer:C
Explanation:
During termination of transcription a section of DNA contains about 20 basepair GC nucleotides. This GC rich sequence that marks the end of a gene during transcription.
In the Rho-independent transcription termination mechanisms, the formation hairpin rich in GC nucleotides causes RNA polymerase to stall,
It is difficult for RNA polymerase can to work pass through GC rich hairpin, because GC basepair is made of 3 hydrogen bonds.
This causes the RNA polymerase to stall
Yea I think it's c but I'm not completely sure but yea it might be c
Answer: 18 chromosomes
Explanation: Gametes have half the number of chromosomes as normal body cells. 36/2=18.