Replication, Transcription, Translation

Terms in this set (55)

Deoxyribonucleic acid, a self-replicating material present in nearly all living organisms as the main constituent of chromosomes. It is the carrier of genetic information.

Griffith Experiment

It was one of the first experiments showing that bacteria can get DNA through a process called transformation.

A virus that infects and replicates within a bacterium. Bacteriophages are composed of proteins that encapsulate a DNA or RNA genome, and may have relatively simple or elaborate structures.

Hershey-Chase Experiment

Alfred Hershey and Martha Chase that helped to confirm that DNA is genetic material. In their experiments, Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not.

In DNA replication each strand of the duplex acts as a template for the synthesis of a new double helix.

Nitrogenous Base

A nitrogenous base is simply a nitrogen containing molecule that has the same chemical properties as a base. They are particularly important since they make up the building blocks of DNA and RNA: adenine, guanine, cytosine, thymine and uracil.

Chargaff's Rule

Chargaff's rules states that DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases and, more specifically, that the amount of guanine is equal to cytosine and the amount of adenine is equal to thymine.

X-Ray Diffraction

X-ray powder diffraction (XRD) is a rapid analytical technique primarily used for phase identification of a crystalline material and can provide information on unit cell dimensions. The analyzed material is finely ground, homogenized, and average bulk composition is determined.

Watson and Crick showed that each strand of the DNA molecule was a template for the other. During cell division the two strands separate and on each strand a new "other half" is built, just like the one before. This way DNA can reproduce itself without changing its structure -- except for occasional errors, or mutations.

Rosalind Franklin

Rosalind Elsie Franklin was an English chemist and X-ray crystallographer who made contributions to the understanding of the molecular structures of DNA (deoxyribonucleic acid), RNA (ribonucleic acid), viruses, coal, and graphite.

The process of making an identical copy of a section of duplex (double-stranded) DNA, using existing DNA as a template for the synthesis of new DNA strands. In humans and other eukaryotes, replication occurs in the cell nucleus.

Meselson-Stahl Experiment

The Meselson-Stahl experiment was an experiment by Matthew Meselson and Franklin Stahl in 1958 which supported the hypothesis that DNA replication was semiconservative.

Density Gradient Separation

Density gradient is a spatial variation in density over an area. The term is used in the natural sciences to describe varying density of matter, but can apply to any quantity whose density can be measured.

Conservative vs. Semiconservative Replication

Conservative Model
In this model the two parental DNA strands are back together after replication has occurred. That is, one daughter molecule contains both parental DNA strands, and the other daughter molecule contains DNA strands of all newly-synthesized material.

Semiconservative Model
In this model the two parental DNA strands separate and each of those strands then serves as a template for the synthesis of a new DNA strand. The result is two DNA double helices, both of which consist of one parental and one new strand.

Dispersive Model
In this model the parental double helix is broken into double-stranded DNA segments that, as for the Conservative Model, act as templates for the synthesis of new double helix molecules. The segments then reassemble into complete DNA double helices, each with parental and progeny DNA segments interspersed.

Replication Fork

The replication fork is a structure that forms within the nucleus during DNA replication. It is created by helicases, which break the hydrogen bonds holding the two DNA strands together. The resulting structure has two branching "prongs", each one made up of a single strand of DNA. These two strands serve as the template for the leading and lagging strands, which will be created as DNA polymerase matches complementary nucleotides to the templates; the templates may be properly referred to as the leading strand template and the lagging strand template.

Single-stranded Binding Protiens

Single-strand binding protein is attached to post-replication fork single strands of DNA, preventing their "reannealing" that is, reforming the double-stranded, double helix state.

DNA topoisomerases are ubiquitous enzymes found in all cell types from viruses to man. These enzymes act to regulate DNA supercoiling by catalysing the winding and unwinding of DNA strands. They do this by making an incision that breaks the DNA backbone, so they can then pass the DNA strands through one another, swivelling and relaxing/coiling the DNA before resealing the breaks. DNA topoisomerases can be divided into two groups based on the number of strands that they break.

Helicases are enzymes that bind and may even remodel nucleic acid or nucleic acid protein complexes. There are DNA and RNA helicases. DNA helicases are essential during DNA replication because they separate double-stranded DNA into single strands allowing each strand to be copied.

DNA Polymerase I

DNA polymerase I participates in the DNA replication of prokaryotes. DNA chain growth is in the 5' to 3' direction with addition at the 3' hydroxyl end. The new chain is base-paired with the template, and the new chain and template are antiparallel. DNA polymerase I is the most abundant polymerase and functions to fill gaps in DNA that arise during DNA replication, repair, and recombination.

DNA Polymerase III

DNA polymerase III holoenzyme is the primary enzyme complex involved in prokaryotic DNA replication. It was discovered by Thomas Kornberg (son of Arthur Kornberg) and Malcolm Gefter in 1970

In molecular biology, DNA ligase is a specific type of enzyme, a ligase, that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

DNA primases are enzymes whose continual activity is required at the DNA replication fork. They catalyze the synthesis of short RNA molecules used as primers for DNA polymerases. Primers are synthesized from ribonucleoside triphosphates and are four to fifteen nucleotides long. Most DNA primases can be divided into two classes. The first class contains bacterial and bacteriophage enzymes found associated with replicative DNA helicases.

The leading strand is the strand of nascent DNA which is being synthesized in the same direction as the growing replication fork. A polymerase "reads" the leading strand template and adds complementary nucleotides to the nascent leading strand on a continuous basis. The polymerase involved in leading strand synthesis is DNA polymerase III (DNA Pol III) in prokaryotes.

The lagging strand is the strand of nascent DNA whose direction of synthesis is opposite to the direction of the growing replication fork. Because of its orientation, replication of the lagging strand is more complicated as compared to that of the leading strand. The lagging strand is synthesized in short, separated segments. On the lagging strand template, a primase "reads" the template DNA and initiates synthesis of a short complementary RNA primer. A DNA polymerase extends the primed segments, forming Okazaki fragments. The RNA primers are then removed and replaced with DNA, and the fragments of DNA are joined together by DNA ligase. DNA polymerase III (in prokaryotes) or Pol δ (in eukaryotes) is responsible for extension of the primers added during replication of the lagging strand

Okazaki Fragments

Okazaki fragments are short, newly synthesized DNA fragments that are formed on the lagging template strand during DNA replication. They are complementary to the lagging template strand, together forming short double-stranded DNA sections.

A telomere is a region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes.

Apoptosis is a process of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death.

Beadle and Tatum

From Beadle and Tatum's work arose a basic hypothesis: One gene specifies the production of one enzyme.

One Gene - One Protein Hypothesis

The one gene-one enzyme hypothesis is the idea that genes act through the production of enzymes, with each gene responsible for producing a single enzyme that in turn affects a single step in a metabolic pathway.

Messenger RNA (mRNA) 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.

Transfer ribonucleic acid (tRNA) is a type of RNA molecule that helps decode a messenger RNA (mRNA) sequence into a protein. tRNAs function at specific sites in the ribosome during translation, which is a process that synthesizes a protein from an mRNA molecule.

Ribosomal RNAs (rRNA) perform critical functions in the ribosome that allow protein synthesis to occur.
The genes that encode rRNAs evolve (i.e. change sequence over time) in a very unique manner that makes them excellent "markers" to trace evolutionary history and powerful tools to identifying species from sequence data.

Transcription is the first step of gene expression, in which a particular segment of DNA is copied into RNA (mRNA) by the enzyme RNA polymerase. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language.

In molecular biology and genetics, translation is the process in which cellular ribosomes create proteins. In translation, messenger RNA (mRNA)—produced by transcription from DNA—is decoded by a ribosome to produce a specific amino acid chain, or polypeptide.

A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis. DNA and RNA molecules are written in a language of four nucleotides; meanwhile, the language of proteins includes 20 amino acids.

The anticodon region of a transfer RNA is a sequence of three bases that are complementary to a codon in the messenger RNA. During translation , the bases of the anticodon form complementary base pairs witht the bases of the codon by forming the appropriate hydrogen bonds.

The ribosome is a complex of over 50 proteins plus its own complement of RNA, often denoted rRNA. There are free ribosomes that are suspended in the cytoplasm of the cell, but many of them are attached to the rough endoplasmic reticulum associated with the nuclear envelope of the cell.

In a single strand of DNA or RNA, the chemical convention of naming carbon atoms in the nucleotide sugar-ring means that there will be a 5′-end, which frequently contains a phosphate group attached to the 5′ carbon of the ribose ring, and a 3′-end (usually pronounced "five prime end" and "three prime end"), which typically is unmodified from the ribose -OH substituent. In a DNA double helix, the strands run in opposite directions to permit base pairing between them, which is essential for replication or transcription of the encoded information.

A term used to describe the opposite orientations of the two strands of a DNA double helix; the 5' end of one strand aligns with the 3' end of the other strand.

Promotor Region

In genetics, a promoter is a region of DNA that initiates transcription of a particular gene. Promoters are located near the transcription start sites of genes, on the same strand and upstream on the DNA (towards the 5' region of the sense strand).

The coding region of a gene, also known as the coding sequence or CDS (from coding DNA sequence), is that portion of a gene's DNA or RNA, composed of exons, that codes for protein. The region is bounded nearer the 5' end by a start codon and nearer the 3' end with a stop codon.

Termination Sequence

In genetics, a transcription terminator is a section of nucleic acid sequence that marks the end of a gene or operon in genomic DNA during transcription.

RNA polymerase, also known as DNA-dependent RNA polymerase, is an enzyme that produces primary transcript RNA. In cells, RNAP is necessary for constructing RNA chains using DNA genes as templates, a process called transcription. RNA polymerase enzymes are essential to life and are found in all organisms and many viruses. In chemical terms, RNAP is a nucleotidyl transferase that polymerizes ribonucleotides at the 3' end of an RNA transcript.

snRNPs (pronounced snurps), or small nuclear ribonucleoproteins, are RNA-protein complexes that combine with unmodified pre-mRNA and various other proteins to form a spliceosome, a large RNA-protein molecular complex upon which splicing of pre-mRNA occurs

Introns are noncoding sections of an RNA transcript, or the DNA encoding it, that are spliced out before the RNA molecule is translated into a protein. The sections of DNA (or RNA) that code for proteins are called exons

An exon is any part of a gene that will become a part of the final mature RNA produced by that gene after introns have been removed by RNA splicing. The term exon refers to both the DNA sequence within a gene and to the corresponding sequence in RNA transcripts.

The E-site is the third and final binding site for t-RNA in the ribosome during protein synthesis. The "E" stands for exit, and is accompanied by the P-site (for peptidyl) which is the second binding site, and the A-site (aminoacyl), which is the first binding site.

The P-site (for peptidyl) is the second binding site for t-RNA in the ribosome. The other two sites are the A-site (aminoacyl), which is the first binding site in the ribosome, and the E-site (exit), which is the third and final binding site in the ribosome. L27 is located at the P-site as shown by affinity labeling. The P-site during translation holds the t-RNA which is linked to the growing polypeptide chain. When a stop codon is reached ending translation, the peptidyl-tRNA bond of the t-RNA located in the P-site is cleaved releasing the newly synthesized protein.

The A-site (A for aminoacyl) of a ribosome is a binding site for charged t-RNA molecules during protein synthesis. One of three such binding sites, the A-site is the first location the t-RNA binds during the protein synthesis process, the other two sites being P-site (peptidyl) and E-site (exit).

Elongation: The tRNA transfers an amino acid to the tRNA corresponding to the next codon. Translocation: The ribosome then moves (translocates) to the next mRNA codon to continue the process, creating an amino acid chain. Termination: When a stop codon is reached, the ribosome releases the polypeptide.

A polyribosome (or polysome) is a complex of an mRNA molecule and two or more ribosomes that is formed during active translation.

According to the genetic code, the cell would need tRNAs with 61 different anticodons to complement the available 61 codons. However, due to the degeneracy of the genetic code, the third base is less discriminatory for the amino acid than the other two bases. This third position in the codon is referred to as the wobble position. At this position Us and Cs may be read by a G in the anticodon. Similarly, As and Gs may be read by a U or y (pseudouridine) in the anticodon.

In biology, a mutation is a permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.

A mutation affecting only one or very few nucleotides in a gene sequence.

Frame Shift Mutation

A frameshift mutation (also called a framing error or a reading frame shift) is a genetic mutation caused by indels (insertions or deletions) of a number of nucleotides in a DNA sequence that is not divisible by three.

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