Genetics : Properties of Nucleic Acids
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Example Questions
Example Question #53 : Genetics
An unknown sample of organic residue is analyzed and found to contain carbon, oxygen, hydrogen, nitrogen, and phosphorous.
Researchers concluded that the sample was composed of nucleic acids.
The presence of which element allowed the researchers to reach that conclusion?
oxygen
phosphorous
carbon
nitrogen
phosphorous
Of the major types of macromolecules — lipids, proteins, nucleic acids, and carbohydrates — only nucleic acids contain phosphorous.
Example Question #54 : Genetics
The two nucleic acids in a base pair are connected by what type of bond?
disulfide bridges
hydrogen bonds
covalent bonds
phosphodiester bonds
hydrogen bonds
Base pairs connect across the center of the double Helix using multiple hydrogen bonds. A-T pairs use 2 hydrogen bonds and C-G pairs use 3 hydrogen bonds.
Phosphodiester bonds do connect nucleotides, but they connect them along the backbone of DNA and do not connect the base pairs. Disulfide bridges connect sulfur containing R groups in proteins. Covalent bonds is a large category of chemical bonds, but base paired nucleotides are connected through intermolecular forces (H-Bonds) rather than bona fide chemical bonds.
Example Question #55 : Genetics
The 5' end of a DNA strand contains what functional group?
poly A tail
deoxyribose sugar
nitrogenous base
phosphate group
phosphate group
The 5' end of a DNA strand is defined by the presence of the 5' carbon on the deoxyribose sugar towards that end. At the 5' carbon, there is a phosphate group which allows it to be added to the growing nucleotide chain.
A deoxyribose sugar is a major component of DNA, but it is not the functional group located at the 5' end of the DNA strand. The nitrogenous bases are attached to the 1' carbon. The poly A tail is a post transcriptional modification of mRNA.
Example Question #56 : Genetics
What property of the nitrogenous bases leads to them pointing toward the inside of the double helix of DNA?
aromaticity
hydrophobicity
inflexible bonds
steric effects
hydrophobicity
Other than the sites of hydrogen bonding, the nitrogenous rings are hydrophobic in nature. This property leads them to stick toward the center of the helix and away from the polar solvents around them. Once they are correctly base paired, their hydrophilic sites are mitigated by the hydrogen bonding leading to increased stability.
Example Question #61 : Genetics
What characteristics define a nucleotide?
5-carbon sugar
phosphate group, nitrogen-containing base
phosphate group, 5-carbon sugar & nitrogen-containing base
phosphate group
nitrogen-containing base
phosphate group, 5-carbon sugar & nitrogen-containing base
A nucleotide is the building block of nucleic acids, such as DNA & RNA. They contain a phosphate group, 5-carbon sugar & nitrogen-containing base all covalently bound together.
Example Question #62 : Genetics
What is the difference between pyrimidine and purine bases?
Pyrimidine bases are monocyclic, while purine bases are bicyclic.
Pyrimidine bases are less pure.
Purine bases are only seen in DNA models.
Pyrimidine bases have more conjugated bonds.
Purine bases have less double bonds.
Pyrimidine bases are monocyclic, while purine bases are bicyclic.
Pyrimidine bases include cytosine, thymine, and uracil (RNA), and are monocyclic. Purine bases include adenine and guanine, and are bicylic with two rings in the molecular structure.
Example Question #63 : Genetics
What replaces thyamine in RNA production?
uracil
adenine
guanine
cytosine
uracil
The correct answer here is uracil. Remember that in DNA replication, the nucleic acids present are TCGA. When we switch over to RNA production, the thyamine is replaced by uracil to form UCGA. If you chose any of the other options, remember that each one has a pair (AT and CG) and in RNA it switches over to UA and CG. If you remember that, you will always recall that uracil replaces thyamine in RNA sequencing
Example Question #64 : Genetics
Which of the following sub units of organic compounds is characterized as a lipid?
proteins
carbohydrates
fatty acids
sugars
fatty acids
The correct answer here is fatty acids because lipids are fats. If you look to the other options, we can eliminate nucleic acids because those are what characterize DNA and RNA (thyamine, uracil, guanine, adenine, and cytosine). Proteins are characterized as amino acids, not lipids. You can easily eliminate sugar and carbohydrates because those are the same thing, both characterized as -saccharides.
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