Which of the following is a change in the sequence that leads to formation of a stop codon?
missense mutation
nonsense mutation
silent mutation
deletion mutation

-nonsense mutation

Explanation:

Non-sense mutations can be described as mutations that to formation of a non-sense or stop codon in mRNA made from mutated gene. There are a  total of 64 codons, out of which 61 code for specific amino acids and 3 codons act as stop codon or non-sense codons.

As these codons provide signal for termination of transcription, non-sense mutations lead to formation of a incomplete or truncated proteins due to premature termination of translation.

Thus, the correct answer is  'second option.'

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."