Unit 5 Flashcards
Deoxyribonucleic acid (DNA)
A double-stranded polymer of nucleotides (each consisting of a deoxyribose sugar, a phosphate, and four nitrogenous bases) that carries the genetic information of an organism.
Bacteriophage
Any bacteria-infecting virus
Isotope
Différent atoms of the same element containing the same number of protons but a different number of neutrons
Radioisotopes
Unstable isotopes that decay spontaneously by emitting radiation
Deoxyribose sugar
Sugar molecule containing five carbons that has lost the -OH (hydroxyl group) on its 2’ (2 prime) carbon
Phosphate group
Group of four oxygen atoms surrounding a central phosphorus atom found in the backbone of DNA
Nitrogenous base
An alkaline, cyclic molecule containing nitrogen
Nucleotides
Molecules that consist of a five-carbon sugar (deoxyribose or ribose) with a nitrogenous base attached to their 1’ carbon and a phosphate group attached to their 5’ carbon
Antiparallel
Parallel but running in opposite directions; the 5’ end of one strand of DNA aligns with the 3’ end of the other strand in a double helix.
Complementary base pairing
Pairing of the nitrogenous base of one strand of DNA with the nitrogenous base of another strand; adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
Glycosyl bond
A bond between a sugar and another organic molecule by way of an intervening nitrogen or oxygen atom
Friedrich Miescher
- Late 1860s
- Isolated nonprotein substance from nucleus of cells; named this substance nuclein
Frederick Griffith
- 1920s
- experimented using mice and two different strains of pneumococcus bacteria (virulent and nonvirulent); observed that when heat-treated virulent pneumococcus was mixed with nonvirulent pneumococcus and was injected into healthy mice dealt resulted
- Discovered the process of transformation
Joachim Hammerling
- 1930s
- experimented using green alga Acetabularia; observed that regeneration of new appendages was driven by the nucleus-containing “foot” of the alga
- hypothesized that hereditary information is stored in the nucleus
Oswald Avery, Maclyn McCarty, and Colin MacLeod
- 1944
- demonstrated that DNA was the transforming principle of pneumococcus bacteria
Erwin Chargaff
- 1949
- discovered that in the DNA of numerous organisms the amount of adenine is equal to the amount of thymine, and the amount of guanine is equal to that of cytosine.
Alfred Hershey and Martha Chase
- 1952
- used radioactively labeled viruses, infected bacterial cells; observed that the infected bacterial cells contained radioactivity originating from DNA of the virus
- suggested that DNA is hereditary material
Rosalind Franklin
- 1953
- produced an X-ray diffraction pattern of DNA that suggested it was in the shape of a double helix
James Watson and Francis Crick
- 1953
- deduced the structure of DNA using information from the work of Chargraff, Franklin, and Maurice Wilkins
Mitosis
Division of the nucleus of a eukaryotic cell into two daughter nuclei with identical sets of chromosomes.
Cytokinesis
Division of cytoplasm and organelles of a cell into two daughter cells.
Template
A single-stranded DNA sequence that acts as the guiding pattern for producing a complementary DNA strand.
Semiconservative
Process of replication in which each DNA molecule is composed of one parent strand and one newly synthesized strand.
DNA helicase
The enzyme that unwinds double-helical DNA by disrupting hydrogen bonds.
anneal
the pairing of complementary strands of DNA through hydrogen bonding
single-stranded binding proteins (SSBs)
a protein that keeps separated strands of DNA apart
DNA gyrase
the bacterial enzyme that relieves the tension produced by the unwihding of DNA during replication
replication fork
the region whers the enzymes replicating a DNA molecule are bound to untwisted, single-stranded DNA
replication bubble
the region where two replication forks are in close proximity to each other, producing a bubble in the replicating
DNA
DNA polymerase III
the enzyme responsible for synthesizing complementary strands of DNA during DNA replication
deoxyribonucleoside
triphosphates
molecules composed of a deoxyribese bonded to three phosphate groups and a nitrogenous base
RNA (ribonucleic acid) primer
a sequence of 10060 RNA bases that is annealed to a region of single-stranded DNA for the purpose of initiating DNA replication
primase
the enzyme that builds
RNA primers
leading strand
the new strand of DNA that is Synthesized continuously during DNA replication
lagging strand
the new strand of DNA that is synthesized in short fragments, which are later joined together
Okazaki fragments
short fragments of DNA that are a result of the synthesis of the lagging strand during DNA replication
DNA polymerase I
an enzyme that removes RNA primers and replaces them with the appropriate deoxyri-bonucleotides during DNA replication
DNA ligase
the enzyme that joins
DNA fragments together by catalyzing the formation of a bond between the 3’ hydroxyl group and a 5’phoshate group on the sugar-phospate backbones
exonuclease
an enzyme that cuts outnucleolides at the end of a DNA strand
genes
a sequence of nucleotides in DNA that performs a specific function such as coding for a particular protein
proteins
complex molecules composed of one or more polypeptide chains made of amino acids and folded into specific three-dimensional shapes that determine protein function
amino acid
the monomer unit of a polypeptide chain that is composed of a carboxylic acid, an amino group, and a side group that differentiates it from other amino acids
transcription
the process in which
DNA is used as a template for the production of complementary messenger RNA molecules
translation
the process by which a ribosome assembles amino acids in a specific sequence to synthesize a specific polypeptide coded by messenger RNA
messenger RNA (mRNA)
the end product of transcription of a gene, mRNA is translated by ribosomes into protein
transfer RNA (tRNA)
a form of RNA that is responsible for delivering amino acids to the ribosomes during the process of translation
ribosomal RNA (rRNA)
a form of RNA that binds with ribosomal protein to form ribosomes
RNA polymerase
enzyme that transcribes DNA into complementary mRNA
codon
sequence of three bases in
DNA or complementary mRNA that serves as a code for a particular amino acid
start codon
specific codon (AUG) that signals to the ribosome that the translation commences at that point
stop codons
specific codons that signal the end of translation to a ribosome
upstream
region of DNA adjacent to the start of a gene
promoter
sequence of DNA that binds RNA polymerase upstream of a gene
template strand
the strand of DNA that the RNA polymerase uses as a guide to build complementary mRNA
coding strand
the strand of DNA that is not used for transcription and is identical in sequence to mRNA, except it contains uracil instead of thymine
terminator sequence
sequence of bases at the end of a gene that signals the RNA polymerase to stop transcribing
primary transcript
mRNA that has to be modified before exiting the nucleus in eukaryotic cells
5’ cap
7-methyl guanosine added to the start of an primary transcript to protect it from digestion in the cytoplasm and to bind it to the ribosome as part of the initiation of translation
poly-A polymerase
enzyme responsible for adding a string of adenine bases to the end of mRNA to protect it from degradation later on
poly-A tail
a string of 200 to 300 adenine base pairs at the end of an mRNA transcript
exons
segments of DNA that code for part of a specific protein
introns
noncoding region of a gene
spliceosomes
particles made of RNA and protein that cut introns from mRNA primary transcript and joins together the remaining coding exon regions
mRNA transcript
mRNA that has been modified for exit out of the nucleus and into the cytoplasm
reading frame
one of three possible phases in which to read the bases of a gene in groups of three
anticodon
group of three complementary bases on tRNA that recognizes and pairs with a codon on the mRNA
aminoacyl-tRNA
a tRNA molecule with its corresponding amino acid attached to its acceptor site at the 3’ end.
A (acceptor) site
site in the ribosome where tRNA brings in an amino acid
P (peptide) site
site in the ribosome where peptide bonds are formed between adjoining amino acids on a growing polypeptide chain
release factor
a protein involved in the release of a finished polypeptide chain from the ribosome
housekeeping genes
genes that are switched on all the time because they are needed for life functions vital to an organism
transcription factors
proteins that switch on genes by binding to DNA and helping the RNA polymerase to bind
gene regulation
the turning on or off of specific genes depending on the requirements of an organism
lactose
a disaccharide that consists of the sugars glucose and galactose
B(beta)-galactosidase
the enzyme responsible for the breakdown of lactose into its component sugars, glucose and galactose
operon
a cluster of genes under the control of one promoter and one operator in prokaryotic cells; acts as a simple regulatory loop
operator
regulatory sequences of
DNA to which a repressor protein binds
lac operon
a cluster of genes under the control of one promoter and one operator; the genes collectively code for the enzymes and proteins required for a bacterial cell to use lactose as a nutrient
Lac I protein
a repressor protein that binds to the lac operon operator, preventing RNA polymerase from transcribing the lac operon genes
repressor protein
regulatory molecules that bind to an operator site and prevent the transcription of an operon
signal molecule
a molecule that activates an activator protein or represses a repressor protein
inducer
a molecule that binds to a repressor protein and causes a change in conformation, resulting in the repressor protein falling off the operator
trp operon
a cluster of genes in a prokaryotic cell under the control of one promoter and one operator, the genes govern the synthesis of the necessary enzymes required to synthesize the amino acid tryptophan
corepressor
a molecule (usually the product of an operon) that binds to a repressor to activate it
mutations
changes in the DNA sequence that are inherited
silent mutation
a mutation that does not result in a change in the amino acid coded for and, therefore, does not cause any phenotypic change
missense mutation
a mutation that results in the single substitution of one amino acid in the resulting polypeptide
nonsense mutation
a mutation that converts a codon for an amino acid into a termination codon
substitution
the replacement of one base in a DNA sequence by another base
deletion
the elimination of a base pair or group of base pairs from a
DNA sequence
insertion
the placement of an extra nucleotide in a DNA sequence
frameshift mutation
a mutation that causes the reading frame of codons to change, usually resulting in different amino acids being incorporated into the polypeptide
point mutations
mutations at a specific base pair in the genome
translocation
the transfer of a fragment of DNA from one site in the genome to another location
transposable elements
segments of DNA that are replicated as a unit from one location to another on chromosomal DNA
inversion
the reversal of a segment of DNA within a chromosome
spontaneous mutations
mutations occurring without chemical change or radiation but as a result of errors made in DNA replication
mutagenic agents
agents that can cause a mutation
induced mutations
mutations caused by a chemical agent or radiation
coupled transcription-translation
a phenomenon in which ribosomes of bacteria start translating an mRNA molecule that is still being transcribed
endosymbiotic
physical and chemical contact between one species and another species living within its body, which is beneficial to at least one of the species
fission
asexual reproduction typical of bacteria in which the cell divides into two daughter cells
nucleomorph
tiny nucleus containing genomic material found within a eukaryotic endosymbiotic structure originally believed to be derived from primitive red alga
chromatin
complex of DNA and histone proteins located in the nucleus of eukaryotes
histones
positively charged proteins that bind to negatively charged DNA in chromosomes
nucleosome
a complex of eight histones enveloped by coiled DNA
supercoiling
DNA folded into a higher level of coiling than is already present in nucleosomes
variable number tandem repeats (VNTRs)
repetitive sequences of
DNA that vary among individuals;
also known as microsatellites
telomeres
long sequences of repetitive, noncoding DNA on the end of chromosomes
centromeres
constricted region of chromosome that holds two replicated chromosome strands together
pseudogenes
DNA sequences that are homologous with known genes but are never transcribed
LINEs
repeated DNA sequences
of 5000 to 7000 base pairs in length that alternate with lengths of DNA sequences found in the genomes of higher organisms
SINEs
repeated DNA sequences of 300 base pairs in length that alternate with lengths of DNA sequences found in the genomes of higher organisms
