Answer:
The correct answer is option B, that is, promoter, operator, gene.
Explanation:
In a prokaryote, just in front of the operator, the promoter is located, and just in front of the structural genes, the operator is located. All these in combination give rise to an operon.
Any gene, which codes for an enzyme or a structural protein is termed as a structural gene, in the lac operon, a structural gene codes for three distinct kinds of enzymes. A short sequence of DNA is situated just in front of the structural gene, which is known as the operator. An operator functions as a switch for transcription, that is, it monitors whether the process of transcription will take place or not.
Just in front of an operator, a sequence of a promoter is present, and for the transcription and translation of all the structural genes, the RNA polymerase needs to combine first with the promoter. In case, if no transcription is to take place, then the operator allows the repressor to bind with it and prevent the attachment of RNA polymerase with the promoter. Hence, the correct sequence of a prokaryotic operon is a promoter, operator, and gene.
Answer:
(B) Reduce his calorie intake to achieve a healthy weight
Explanation:
Research has shown that excess body fat or obesity increases the risk of cancer, since timothy is overweight, he needs to reduce his calorie intake to achieve a healthy weight
The correct answer is B. Vitamin A.
Vitamin A (retinol, retinoic acid) is a fat-soluble vitamin important for vision, growth, cell division, reproduction and immunity. It also has antioxidant properties.
Vitamin A is present in many foods, such as spinach, dairy products and liver. Other sources are foods rich in beta-carotene, such as leafy vegetables, carrots and cantaloupe. Your body transforms beta-carotene into vitamin A.
There are two dofferent types of vitamin A. The first type, preformed vitamin A, it is found in beef, poultry, fish and dairy products. The second type, provitamin A, is found in fruits,vegetables and other products of vegetable origin. The most common type of provitamin A present in foods and dietary supplements is beta-carotene.
Not consuming enough vitamin A, can cause diseases (which can be avioded with a good diet). Vitamin A plays a very important role in vision. On the one hand, it is essential for the production of the pigment consumed by photoreceptors responsible for vision in darkness. Therefore, low levels of vitamin A lead to night blindness.
