AP Biology › Understanding Differences Between DNA and RNA
In DNA adenine (A) bonds to thymine (T) and guanine (G) bonds to cytosine (C). What is the bonding scheme in RNA?
A-U and C-G
A-C and G-U
A-G and C-U
A-T and C-G
None of these
In RNA, thymine is substituted by uracil. So adenine will bond to uracil instead of thymine when RNA interacts with DNA and when RNA folds with itself to make a 3-dimensional structure.
All of the following bases are found in RNA except __________.
thymine
uracil
guanine
cytosine
adenine
Uracil is only found in RNA under normal conditions. It replaces thymine, which is only found in DNA. Therefore, thymine, adenine, cytosine, and guanine are the bases found in DNA, and uracil, adenine, cytosine, and guanine are the bases found in RNA.
Which of the following molecules is not present in DNA?
Uracil
Thymine
Phosphate
Deoxyribose sugar
All of these
Uracil is a nitrogenous base that is only found in single-stranded RNA—it is not found in DNA. Thymine pairs with adenine in DNA, whereas in RNA, uracil pairs with adenine.
Which of the following is not a true characteristic of an RNA molecule?
It contains deoxyribose sugar
It contains the nucleotide uracil
It can be single stranded
It can be double stranded
RNA molecules are most commonly found in a single stranded form (e.g. mRNA), but they can also be found in a double stranded form (e.g. viruses). It has four base pairs—uracil, adenine, guanine, and cytosine—and a ribose sugar-phosphate backbone. DNA molecules contin a deoxyribose sugar in their sugar-phosphate backbone; thus, this answer is incorrect.
DNA with its associated protein scaffold forms a complex called __________.
chromatin
chromatid
centromere
chromosome
nucleotide
Chromatin is the DNA-protein complex and is organized as a long, thin fiber. Chromosomes are densely-packed chromatin, wrapped around proteins called histones. The centromere is the region of a condensed chromosome that connects sister chromatids to each other, and is the site at which the spindle fibers attach during mitosis in order to move them about the cytoplasm.
Which of the following RNA molecules transports amino acids to ribosomes to be used to assemble the protein molecule?
tRNA
mRNA
snRNA
pre-mRNA
rRNA
mRNA is messenger RNA, it carries the genetic code that determines the protein. snRNA directs splicing of pre-mRNA. tRNA transports the amino acids used for assembling proteins. rRNA is a component of ribosomes (the other component is protein). pre-mRNA- single strand of RNA processed to form mRNA.
Which of the following are correct regarding the central dogma of biology?
DNA directs the synthesis of mRNA, which in turn directs the production of polypeptides
RNA assists with the replication of DNA which encodes information for proteins
RNA encodes the information for the assembly of ribosomes, which are the sites of protein production
RNA signals DNA to activate protein production
DNA encodes information for the production of messenger RNA which then interacts with the cell's protein-synthesizing machinery to produce proteins. Ribosomes are the sites of polypeptide synthesis but are not coded for by RNA. The central dogma of biology is DNA RNA
protein
The entire collection of DNA in a cell is called the __________.
genome
nucleus
chromosome
DNA ladder
chromatin
The genome is defined as the total genetic library of a cell. It is estimate that in humans, the genome codes for about 25,000 different genes.
Which of the following types of RNA is double stranded?
Viral RNA
mRNA
tRNA
rRNA
Many types of RNA exist within cells, some are single stranded and others are double stranded. The following are among the types of single stranded RNA: mRNA (messenger RNA), tRNA (transfer RNA), and rRNA (ribosomal RNA). Messenger or mRNA carries genetic information from DNA to ribosomes for protein synthesis. Transfer or tRNA carries amino acids to ribosomes that match with mRNA codons. Last, ribosomal or rRNA codes for ribosomes, which are necessary for protein synthesis. An example of a double stranded RNA molecule is viral RNA. Viral RNA is the genetic material of many viruses and has a structure of two complementary strands.
Which of the following statements is false?
DNA is a polyanion, while RNA is a not
DNA uses thymine, while RNA uses uracil
DNA is typically double-stranded, while RNA is typically single-stranded
DNA and RNA utilize different sugars in their sugar-phosphate backbones
Both DNA and RNA are polyanions. This is just a fancy way of saying that they are polymers of negatively charged molecules. The phosphate groups in the sugar-phosphate backbone account for this, as phosphate groups generally carry a charge of negative three.
DNA uses thymine and deoxyribose sugar, while RNA uses uracil and ribose sugar. While DNA is usually molded into a double-stranded helix, RNA is usually single-stranded, which allows for the binding of anticodons during translation.