Unit 2 Flashcards
Nucleotides
The repeating unit of nucleic acids; composed of a sugar group, a phosphate group, and a nitrogenous base.
Chargaff’s rule
In DNA, the percent composition of adenine is the same as thymine, and the percent composition of cytosine is the same as guanine.
Complementary Base Pairing
In DNA, the interaction of bases of nucleotides on opposite strands through the formation of hydrogen bonds.
Antiparallel
The directionality of the two strands in a DNA molecule; the strands run in opposite directions, with each end of a DNA molecule containing the 3’ end of one strand and the 5’ end of the other strand.
Genome
The complete genetic makeup of an organism; an organism’s total DNA sequence.
Gene
The basic unit of heredity that determines, in whole or part, a genetic trait; a specific sequence of DNA that encodes for proteins and RNA molecules and can contain sequences that influence these molecules.
Nucleoid
A structure in bacteria that contains the chromosomal DNA.
DNA supercoiling
The formation of additional coils in the DNA structure due to twisting forces on the molecule.
Regulatory Sequence
A DNA sequence that regulates a gene’s activity.
Histone
A member of a family of proteins that associate with DNA in eukaryotic cells, which acts to help compact the DNA.
Chromatin
The non-condensed form of genetic material that predominates for most of the eukaryotic cell cycle; consists of a complex of DNA and proteins.
DNA replication
The process of producing two identical DNA molecules from an original, parent DNA molecule.
Semi-Conservative Replication
The mechanism of DNA replication in which each newly synthesized DNA molecule is composed of one strand from the original DNA molecule and one new strand.
Origin of Replication
The DNA sequence where replication begins.
Helicase
A group of enzymes that aid in unwinding DNA.
DNA Polymerase 3
An enzyme that adds nucleotides to the 3’ end of a growing polynucleotide strand.
Okazaki Fragments
Short DNA fragments that are generated during the synthesis of the lagging strand in DNA replication.
Primer
In DNA replication, a short segment of RNA that is complementary to a part of the 3’ to 5’ DNA template strand and serves as a starting point for addition of nucleotides.
DNA Polymerase 1
An enzyme that removes RNA primer and fills gaps between Okazaki fragments on the lagging strand with DNA nucleotides; proofreads newly synthesized DNA.
DNA Ligase
An enzyme that catalyzes the joining of Okazaki fragments.
DNA Polymerase 2
An enzyme that proofreads newly synthesized DNA.
Mismatched Repair
A mechanism got repairing errors made during DNA replication, whereby a group of proteins recognize a mispaired nucleotide on the newly synthesized strand and replace it with a correctly paired nucleotide.
Telomere
A repetitive section of DNA near each end of a chromosome; the presence of this sequence helps to protect from loss of important genetic information during replication of the linear DNA in eukaryotic cells.
One-gene/one-polypeptide Hypothesis
A proposal that one gene codes for one polypeptide (or protein)
Messenger RNA (mRNA)
RNA that contains the genetic information of a gene and carries it to the protein synthesis machinery; it provides the information that determines the protein’s amino acid sequence.
Genetic Code
A Set of rules for determining how genetic information in the form of the nucleotide sequence is converted to an amino acid sequence is converted to an amino acid sequence of a protein; a code specifying the relationship between a nucleotide codon and an amino acid.
Triplet Hypothesis
A proposal that the genetic code is read three nucleotide bases at a time.
Gene Expression
The transfer of genetic information from DNA to RNA to protein.
Transcription
The synthesis of protein from an mRNA template.
RNA polymerase
The main enzyme that catalyzes the formation of RNA from a DNA template.
Promoter Region
A sequence of nucleotides in DNA that indicates where the RNA polymerase complex should bind to initiate transcription.
Precursor mRNA (pre-mRNA)
mRNA that has not undergone processing
Mature mRNA
mRNA that has undergone processing.
5’ cap
The modified form of a G nucleotide; added to the 5’ end of an mRNA.
3’ Poly-A Tail
A series of A nucleotides added to the 3’ end of mRNA.
Splicing
In mRNA, a process of excising out the introns and combining in the exons.
Transfer RNA (tRNA)
An RNA molecule that links the codons on mRNA to the corresponding amino acid for protein synthesis.
Anticodon Loop
A triplet of bases positioned at one end of a tRNA that recognizes and base-pairs with a codon on mRNA during protein synthesis.
Acceptor Stem
The 3’ end of a tRNA molecule that is the site of attachment for a particular amino acid, based on the anticodon.
Aminoacyl-tRNA synthetase
An enzyme responsible for attaching an amino acid to a tRNA.
Ribosome
A cell structure composed of proteins and rRNA provides the state where protein synthesis occurs.
Polyribosome
A structure composed of multiple ribosomes along an mRNA strand.
Mutation
A permanent change in the nucleotide sequence of a cell’s DNA.
Single-gene mutation
A mutation that involves changes in the nucleotide sequence of one gen.
Chromosome Mutation
A mutation involving chromosome changes may involve many genes.
Point mutation
A mutation involving a single base pair substitution, insertion, or deletion.
Start codon
A triple of three bases that specifies the first amino acid of a protein.
Reading Frame
Collectively, the codons of mRNA that are read to produce an amino acid sequence; it is set by the start codon
Peptide Bond
A covalent bond formed between two amino acids during protein synthesis.
Frameshift Mutation
A mutation caused by the addition or deletion of a number of nucleotides not divisible by three, resulting in a change in the reading frame
Silent mutation
A mutation that does not change the amino acid sequence of a protein.
Missense Mutation
A mutation that changes the amino acid sequence of a protein
Nonsense Mutation
A mutation that shortens a protein by introducing a stop codon
Mutagen
An event or substance that increases the rate of changes to the DNA sequence of an organism’s genome.
