In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Chromosomes are not visible in the cell’s nucleus—not even under a microscope—when the cell is not dividing. However, the DNA that makes up chromosomes becomes more tightly packed during cell division and is then visible under a microscope. Most of what researchers know about chromosomes was learned by observing chromosomes during cell division.
Answer: D.) This gene sequence ensures transcription of arabinose genes only
when arabinose is available, saving the cell from expending energy
unnecessarily
The answer choices are not provided, so I cannot select the correct one. However, I may provide you examples and guidance on how to choose the correct one.
As mentioned in the explanation, a scientific question must have a variable that is changed, the independent variable, and a variable on which the effect of the change is measured. This is the dependent variable. Examples of such questions include:
How will the amount of water given to a plant affect its rate of growth?
What will be the amount of sugar that can be dissolved in water at a given temperature?
At what temperature will a balloon filled with air pop?
All of these questions may be tested using experiments.
Answer:
Explanation:
An antimicrobial agent is a natural or synthetic chemical that kills or inhibits the growth of microorganisms. Bacteria have a mechanism of transferring genomic material called <em>horizontal gene transfer</em><em>, the movement of genes between cells that are not direct descendants of one another</em>. Horizontal gene transfer allows cells to quickly acquire new characteristics and drives metabolic diversity. <u>One of the characteristics usually acquired is the resistance to antibiotics</u>.
Three mechanisms of genetic exchange are known in prokaryotes:
(1) transformation, in which free DNA released from one cell is taken up by another; (2) transduction, in which DNA transfer is mediated by a virus; and (3) conjugation, in which DNA transfer requires cell-to-cell contact and a conjugative plasmid in the donor cell.
Examples of genes transferred by transducing bacteriophages include multiple antibiotic resistance genes among strains of <em>Salmonella enterica </em>serovar <em>Typhimurium</em>, Shiga-like toxin genes in <em>Escherichia coli</em>, virulence factors in <em>Vibrio cholerae</em>, and genes encoding photosynthetic proteins in cyanobacteria.
Conjugative plasmids use a mechanism to transfer copies of themselves and the genes they encode, such as those for antibiotic resistance, to new host cells.
Answer:
Water can hydrogen bond.
Explanation:
Liquids become gases once they are heated to a certain temperature. Heat is a form of energy. This change occurs when the intermolecular forces between the liquid molecules are energized enough to break. This breakage is necessary because gaseous molecules exist individually and do not interact with one another. That being said, it takes more heat to boil water because its intermolecular forces are stronger than methanes.
Intermolecular forces (IMF) are a result of partial charges on the molecular atoms that cause temporary bonds to form between molecules.
Methane is a nonpolar molecule, meaning each atom can only have slight partial charges. The strongest IMF methane participates in are London Dispersion Forces.
Water, however, is a polar molecule, with the hydrogens having strong partial positive charges and the oxygens having strong partial negative charges. This allows water to participate in a very strong IMF called hydrogen bonding. Again, because these partial charges are so strong, the water molecules can form stronger IMFs.
<u>*When molecules have stronger IMFs, they require more energy(heat) to overcome them.*</u>
