The main molecule found in nucleus is called DNA(deoxyribonucleic acid). This molecule is made of subunits called nucleotides. A nucleotide is made of a nitrogenous base that can be adenine, thymine, guanine or cytosine; a five carbon sugar called deoxyribose and a phosphate group. This molecule controns protein synthesis. Proteins are crucial to the cell's function.
Answer:

Explanation:
Straight wings are dominant over curved wings
Let Straight wings : H
curved wings : t
smooth eyes are dominant to sparkling eyes
let smooth eyes = H
spark ling eyes = t
tan body is dominant to ebony body color.
Again; Let tan body color be H
Let ebony color be t
If flies that are heterozygous for all three traits are crossed;
we have HtHtHt × HtHtHt
Then the selected trihybrid traits for the cross will be (HHH,HHt, HtH, Htt, tHH, tHt, ttH, ttt)
We will realize that from the punnet square in the diagram below, the proportion of the offspring would you expect to be heterozygous for all three traits (i.e HtHtHt) is asterisk in the punnet square and will be 
= 
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the Cell Theory was give by German scientists, Schleiden and T.Shwan in 1839. It stated that,
- All organism are composed of one or more cells
- The cell is the structural and functional unit of life
- It is a de novo structure, that means it COULD arise from non living thing which was incorrect.
It was corrected by the German pathologist Rudolf Virchow in 1855. He made a convincing case, corrected and added the third point of the cell theory. It is,
- Cells can arise only by a division of pre-existing cell. It is <u>NOT</u> a de novo structure.
Cell theory brought a great evolution in the field of biology which established the function of organism is the result of activities and interaction of the cell units.
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- <u>Flask 1</u>: It is observed that there are no micro-organism, this is because the meat is sealed and no micro-organism could enter through it.
- <u>Flask 2</u>: It is observed that there are micro-organism present because meat is not sealed but open.
- <u>Flask 3</u>: As the S tube is used, the micro-organism are not able to reach the meat because of the curvy path
These observations support the point that<u> cells could arise only by a division of pre-existing alive cells</u> because in Flask 1 when there were no micro-organism present so there was no organisms found so no micro-organism arised, In flask 3 the S tube was used so no micro-organism could reach the meat thus there were no organism there which could divide to reproduce. The flask 2 was open, so the micro organisms reached the meat so they divided which means Cells can only arise by a division of pre-existing cells.
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