Molecular Genetics Flashcards
Histone
A special protein molecule that is the core around which the DNA strand wraps
Genome
The complete set of an organism’s hereditary information
Transformation
A change in a genotype or phenotype caused by the direct uptake of genetic material by a cell
Bacteriophage
A virus that infects bacteria
Purine
A class of nitrogenous bases with a double-ring structure; adenine and guanine are purines
Pyrimidine
A class of nitrogenous bases with a single-ring structure; thymine and cytosine are pyrimidines
Complementary base pairing
The chemical tendency of adenine to form hydrogen bonds with thymine, and cytosine to form hydrogen bonds with guanine
Semiconservative replication
A mechanism of DNA replication in which each of the two strands of parent DNA is incorporated into a new double-stranded DNA molecule
Replication origin
A specific sequence of DNA that acts as a starting point for replication
Helicase
A replication enzyme that separates and unwinds the DNA strands
Replication fork
The point of separation of the two parent DNA strands during replication
Topoisomerases
A class of enzymes that relieve tension caused by the unwinding of parent DNA; they cleave one or two of the DNA strands, allow the strand(s) to untwist, and then rejoin the strand(s)
Single-strand binding protein (SSB)
A replication enzyme that prevents parent DNA strands from annealing to each other once they have been separated by helicase
Replication bubble
The separating of DNA in both directions during replication
Nucleoside triphosphate
A building block and energy source for replicating DNA
RNA primase
A replication enzyme that produces RNA primers
RNA primer
A replication molecule that acts as a starting point for replication
DNA polymerase III
A prokaryotic replication enzyme that builds new DNA strands from nucleotides
Leading strand
The DNA strand that is copied in the direction toward the replication fork
Lagging strand
The DNA strand that is copied in the direction away from the replication fork
Okazaki fragment
The piece of new DNA on the lagging strand
DNA polymerase I
A prokaryotic replication enzyme that fills in gaps in the lagging strand between Okazaki fragments; also proofreads the final strands
DNA ligase
An enzyme that catalyzes the formation of a phosphodiester bond between two DNA strands, as well as between Okazaki fragments
DNA polymerase II
A prokaryotic replication enzyme that repairs damage to DNA, including damage that occurs between replication events
Nucleosome
A unit of DNA storage, consisting of eight histones with DNA strands wrapped around them; the DNA around each nucleosome is about 147 nucleotides in length
Solenoid
A group of six nucleosomes
Telomere
A repeating sequence of DNA at the end of a chromosome that protects coding regions from being lost during replication
Supercoiling
The continuous twisting of prokaryotic DNA that reduces the volume of the DNA
Cell senescence
The period in a cell’s lifespan when it loses the ability to divide and grow; often referred to as cell aging
Hayflick limit
The total number of times that a normal cell can divide
Telomerase
An enzyme that adds new telomere sequences to the ends of chromosomes
One gene-one enzyme hypothesis
The hypothesis, proposed by Beadle and Tatum, that each gene is unique and codes for the synthesis of a single enzyme
One gene-one polypeptide hypothesis
The hypothesis that each gene is unique and codes for the synthesis of a single polypeptide; the restated version of the non gene-one enzyme hypothesis
Central dogma
The fundamental principle of molecular genetics, which states that genetic information flows from DNA to RNA to proteins
Transcription
Mechanism by which the information coded in nucleic acids of DNA is copied into nucleic acids of RNA; something rewritten in the same language
Translation
Mechanism by which the information coded in the nucleic acids of RNA is copied into the amino acids of proteins
Messenger RNA (mRNA)
The end product of the transcription of a gene; mRNA is translated by ribosomes into a protein
Transfer RNA (tRNA)
A carrier molecule that binds to a specific amino acid and adds the amino acid to the growing polypeptide chain
Ribosomal RNA (rRNA)
An RNA molecule within the ribosome that bonds the correct amino acid to the polypeptide chain
RNA polymerase
An enzyme that reads a DNA strand and creates a complementary strand of RNA
Template strand
The DNA strand that is copied into an mRNA molecule during gene transcription
Precursor mRNA (pre-mRNA)
The initial RNA transcription product
Genetic code
The specific coding relationship between bases and the amino acids they specify; the genetic code can be expressed in terms of either DNA or RNA bases
Codon
A group of three base pairs that code for an individual amino acid
Start codon (initiator codon)
The codon that signals the start of a polypeptide chain and initiates translation
Ex. AUG
Stop codon
A codon that signals the end of a polypeptide chain and causes the ribosome to terminate translation
Ex. UAA, UAG, UGA
Promotor
A nucleotide sequence that lies just before a gene and allows for the binding of RNA polymerase
TATA box
A region of the promoter that enables the binding of RNA polymerase
Coding strand
The DNA strand that is not being copied but contains the same sequence as the new RNA molecule
Termination sequence
A sequence of bases at the end of a gene that signals the RNA polymerase to stop transcribing
Poly A tail
A chain of adenine nucleotides that are added to the 3’ end of the pre-mRNA molecule to protect it from the enzymes in the cytosol
5’ cap
A sequence of seven Gs that is added to the start of a pre-mRNA molecule; ribosomes recognize this site and use it as the site of initial attachment
Exon
A sequence of DNA or RNA that codes for part of a gene
Intron
A non-coding sequence of DNA or RNA
Spliceosome
An enzyme-protein complex that removes introns from the mRNA
Small ribonucleoproteins (smRNP)
A protein that binds to introns and signals them for removal
Alternative splicing
A process that produces different mRNAs from pre-mRNA (exons and introns), allowing more than one possible polypeptide to be made from a single gene
Anticodon
The complementary sequence of base pairs on a tRNA that corresponds to a codon on an mRNA
Aminoacylation
The process by which a tRNA molecule is bound to its corresponding amino acid
aminoacyl-tRNA
A molecule of transfer RNA bound to its associated amino acid
Reading frame
A particular system for separating a base pair sequence into readable codons
Polysome
A complex that is formed when multiple ribosomes attach to the same mRNA molecule in order to facilitate rapid translation
Insulin
A hormone produced in the pancreas that lowers the blood glucose level by promoting the uptake of glucose by the body cells
Lac operon
A cluster of genes that contains the DNA sequences to regulate the metabolism of lactose
Operator
The region in the operon that regulatory factors bind to
Repressor protein
A protein that binds to the operator to repress gene transcription
Inducer
A signal molecule that triggers the expression of an operon’s genes
Ex. lactose
Corepressor
A signal molecule that binds to a regulatory protein to reduce the expression of an operon’s genes
Ex. tryptophan
Point mutation
A change in a single nucleotide within a gene
Substitution
The replacement if one base pair in a DNA sequence by another base pair
Insertion
The addition of a base pair (small-scale mutation) or larger region (large-scale mutation) to a DNA sequence
Deletion
The removal of a base pair (small-scale mutation) or larger coding region (large-scale mutation) form a DNA sequence
Inversion
Two adjacent bases trading places (small-scale mutations) or the reversal of a sequence of DNA (large-scale mutations)
Single nucleotide polymorphism (SNP)
A difference in the DNA between individuals caused by point mutations
Missense mutation
A mutation that changes a single amino acid in the coding sequence
Nonsense mutation
A mutation that results in a premature stop codon
Silent mutation
A mutation that doesn’t alter the resulting sequence of amino acids
Frameshift mutation
A shift in the reading frame resulting in multiple missense and/or nonsense effects
Translocation
The movement of entire genes or sequences of DNA from one chromosome to another
Mutagen
An environmental agent that directly alters the DNA within a cell
Ex. radiation or chemicals
Spontaneous mutation
A mutation that is caused by an error in DNA replication
Ex. sickle cell anemia
Induced mutation
A mutation that is caused by an environmental agent
Ex. ultraviolet rays from the sun (skin cancer - radiation)