HESI A2 Exam: DNA and RNA
•What are the four nitrogenous bases of DNA?
•What is DNA replication?
•What is a codon?
•What is messenger RNA?
•What is transcription?
DNA is the hereditary material in humans and almost all other organisms.
Genes are factors that control traits. Genes are the units of heredity and are a locus (or region) of DNA. They determine what traits are expressed in individuals.
DNA controls the cell’s production of proteins. DNA is shaped as a double helix, which looks like a twisted ladder. Each rung of the ladder is made up of a pair of nitrogen bases. There are four bases (adenine, guanine, thymine, and cytosine). Adenine always pairs with thymine and guanine always pairs with cytosine. The sides of the ladder are made up of a pentose sugar and phosphate. This combination- a pentose sugar, a phosphate group, and the nitrogen base make a nucleotide.
DNA replication is the biological process of producing two identical replicas of DNA from one original DNA molecule. This process occurs in all living organisms and is the basis for biological inheritance.
Nucleotides bind together in specific patterns to form the genetic code that defines a given trait.
RNA is essential in various biological roles in coding, decoding, regulation, and expression of genes.
In order for a protein to be expressed, it first needs to be transcribed to mRNA. This mRNA is translated into protein by ribosomes. Messenger RNA is a large family of RNA molecules that convey genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression.
A transfer RNA is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length, that serves as the physical link between the mRNA and the amino acid sequence of proteins.
A codon codes for an amino acid. The amino acids are linked together as translation takes place. A group of three DNA letters makes up one codon.
Transcription is the first of several steps of DNA based gene expression in which a particular segment of DNA is copied into RNA (especially mRNA) by the enzyme RNA polymerase. Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During transcription, a DNA sequence is read by an RNA polymerase, which produces a complementary, antiparallel RNA strand called a primary transcript.
In molecular biology and genetics, translation is the process in which ribosomes in the cytoplasm or endoplasmic reticulum synthesize proteins after the process of transcription of DNA to RNA in the cell's nucleus. The entire process is called gene expression. In translation, messenger RNA (mRNA) is decoded in a ribosome, outside the nucleus, to produce a specific amino acid chain, or polypeptide.
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