MCAT Biology : DNA Replication and Repair
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Example Questions
Example Question #1161 : Biology
Which base pair requires the most amount of energy to break?
G-T
G-C
T-G
T-C
A-T
G-C
The guanine and cytosine base pairing forms 3 hydrogen bonds. Both adenine and thymine form only 2 hydrogen bonds. Thus the G-C base pair has the strongest interactions, and requires the most amount of energy to break.
Example Question #11 : Dna Replication And Repair
Which of the following choices represents the structure of DNA from least organized to most organized?
Deoxyribose, nucleoside, nucleotide, DNA double helix, nucleosome, chromatin
Deoxyribose, nucleoside, chromatin, DNA double helix, nucleotide, nucleosome
Nucleotide, deoxyribose, nucleotide, DNA double helix, chromatin, nucleosome
Deoxyribose, nucleoside, nucleotide, DNA double helix, chromatin, nucleosome
None of these
Deoxyribose, nucleoside, nucleotide, DNA double helix, nucleosome, chromatin
Deoxyribose is the sugar in the backbone of DNA. Next, a nitrogenous base is attached to the deoxyribose, which together, is called a nucleoside. A nucleoside with one or more phosphate groups attached is called a nucleotide. The double stranded DNA coils around histone proteins; this complex is called a nucleosome. Lastly the DNA gets further packaged and condensed into chromatin.
Example Question #12 : Dna Replication And Repair
The central nervous system consists of the brain and the spinal cord. In general, tracts allow for the brain to communicate up and down with the spinal cord. The commissures allow for the two hemispheres of the brain to communicate with each other. One of the most important commissures is the corpus callosum. The association fibers allow for the anterior regions of the brain to communicate with the posterior regions. One of the evolved routes from the spinal cord to the brain is via the dorsal column pathway. This route allows for fine touch, vibration, proprioception and 2 points discrimination. This pathway is much faster than the pain route. From the lower limbs, the signal ascends to the brain via a region called the gracile fasciculus. From the upper limbs, the signal ascends via the cuneate fasciculus region in the spinal cord.
The dorsal column pathway is a fast and advanced signaling system. Some researchers believe that this pathway evolved not to long ago. If this transformation required the change in the DNA, how might this have occurred?
I. Point mutation
II. Frame shift
III. Nonsense mutation
I, II, and III
III only
II only
I and II
I only
I, II, and III
All of these choices may cause a change in the DNA. A point mutation involves a single base pair change in the DNA or the RNA. A frameshift mutation involves a deletion or insertion, in which any number of base pairs are inserted or deleted, which causes a shift in the reading frame of the DNA (not RNA). A nonsense mutation involves the change in DNA that results in a premature stop codon in the mRNA.
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