Answer:
the 3rd one is the correct option.
Answer:
False
Explanation:
Approximately 200 out of 200 million sperms ejaculated during intercourse reach the general vicinity of the egg. They sperms must undergo capacitation during which dilute inhibitory factors fluids of the female reproductive tract weaken the membrane of the sperm head so that head of the sperm can be broken easily when it came in contact with the egg.
The first sperm to reach an egg isn’t the one to fertilize it because the egg is surrounded by a gelatinous membrane called the zona pellucida. Outside this layer, a layer of small granulosa cells also present.
Therefore, it requires numerous sperm to clear a path through these barriers before one of them can penetrate the egg and fertilize it.
Answer:
D. They block communication between enhancers and non-targeted promoters
Explanation:
Insulator sequences are the group of DNA sequences that protect the protein-coding regions of the DNA from the surrounding regulatory sequences. Some insulator sequences are present between the enhancers and promoters of a gene. These insulator sequences do now allow these enhancers to regulate the expression of genes by sending inappropriate signals.
However, if the insulator sequences are not present between the enhancers and promoters of certain genes but are located somewhere else, enhancers can upregulate the expression of these genes.
