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Biology Test over Chapters 12 and 13

Terms in this set (67)

transformation
process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria.
bacteriophage
kind of virus that infects bacteria
base pairing
principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine.
replication
process of copying DNA prior to cell division
DNA polymerase
principle enzyme involved in DNA replication
Telomere
repetitive DNA at the end of a eukaryotic chromosome
RNA
single-stranded nucleic acid that contains the sugar ribose
Messenger RNA
type of RNA that carries copies of instruction for the assembly of amino acids into proteins from DNA to the rest of the cell
Ribosomal RNA
type of RNA that combines with proteins to form ribosomes
Transfer RNA
type of RNA that carries each amino acid to a ribosome during protein synthesis
Transcription
synthesis of an RNA molecule from a DNA template
RNA polymerase
enzyme that links together the growing chain of RNA nucleotides during transcription using a DNA strand as a template
Promoter
specific region of a gene where RNA polymerase can bind and begin transcription
Exon
expressed sequence of DNA; codes for a protein
Polypeptide
long chain of amino acids that makes proteins
genetic code
collection of codons of mRNA, each of which directs the incorporation of a particular amino acid into a protein during protein synthesis
codon
group of three nucleotides bases in mRNA that specify a particular amino acid to be incorporated onto a protein
translation
process by which the sequence of bases of an mRNA is converted into the sequence of amino acids of a protein
anticodomn
group of three bases of a tRNA molecule that are complementary to the three bases of a codon of mRNA
gene expression
process by which a gene produces its product and the product carries out its function
mutation
change in the genetic material of a cell
point mutation
gene mutation in which a single base pair in DNA has been changed
frameshift mutation
mutation that shifts the "reading frame" of the genetic message by inserting or deleting a nucleotide
mutagen
chemical or physical agents in the environment that interact with DNA and may cause a mutation
polyploidy
condition in which an organism has extra sets of chromosomes
a british scientist who wanted to learn how certain types of bacteria produce the serious lung disease known as pneumonia.
who was Frederick Griffith and what did he want to do
he isolated two very similar typw of bacteria from mice. both strains gre very well in culture plates in hisl ab, but one of them caused pneumonia. the disease causing bacteria-Sstrain- caused smooth colonies to grow, where the harmless bacteria-r strain produced rough edges
what griffith did
S strain
disease causing bacteria
R strain
harmless bacteria
first griffith took a culture of the S-strain, heated the cells to kill them, then injected it into mice. the mice survived, suggesting that the cause of pneumonia was not a toxin from these disease causing bacteria
next step with S strain
he then mixed the heat-killed S strain bacteria with the live harmless bacteria from the ar strain, injected it into a mouse and the mouse died from pneumonia. these two by themselves caused no harm, but with each other harm.
the next step with mixing the two
Griffith reasoned that some chemical factor that could change harmless bacteria into disease-causing bacteria was transferred from the heat-killed cells of the S strain into the live cells of the R strain. he called this transformation
transformation
Canadian biologist who wanted to determine which molecule in the heat-killed bacteria was most important for transformation.
who and what did Avery do
him and his team extracted a mixture of various molecules from the heat-killed bacteria. thy treated this molecule with enzymes that destroyed organic compounds and other molecules like acid RNA. transformation still occurred. since all of them were destroyed none of them could have been responsible for transformation
the first step of avery
his team repeated this step one more time, both they used enzymes that would break down a different nucleic acid- DNA. when they destroyed the DNA, transformation did not occur. there was one possible explanation for this: DNA was the transforming factor
the second part of averys experiment
they collaborated in studying viruses- tiny, nonliving particles tht can infect living cells.
Hershey and Chases finding
Hershey and Chase studied a bacteriophage that was composed of a DNA core and a portein coat. they wanted to determine which part of the virus(th protein coat or the DNA core) entered the bacterial cell.
what Hershey and Chase wanted to do
the pair grew viruses in cultures containing radioactive isotopes of phosphorus-32 and sulfur-35. this was clever because phosphorus isnt in proteins and sulfur isnt in DNA. if they found sulfur-35 then the protein was injected, but if they found phosphorus0-32 it wold be the DNA.
first par of what hershey and
they injected them and waited a few minutes for the viruses to inject their genetic material. they then seperated the viruses from the acteria and tested he bacteria for radioactivity. nearly all the radioactivty was found in phosphorus-32(DNA).
the experiment part of hershey and chase
• Nucleic acids are long, slightly acidic molecules originally identified in cell nuclei
• Nucleic acid are made up of nucleotides, linked together to form long chains
• The nucleotides that make up DNA are shown
nucleic acids and nucleotides in DNA
DNA has four kinds of nitrogen bases, adenine, thyming, guanine, and cytosine. the nucleotides in DNA are joined by covalent bonds formed between sugar and the phosphate group.
structure of DNA
• Erwin Chargaff discovered that the percentages of adenine and thymine bases are almost equal in any samples of DNA
• The same thing is true for the other two nucleotides, guanine and cytosine
• The observation that A=T and G=C became known as Chargaff's rules
chargaff's rules
• Used a technique called X-ray diffraction to get information about the structure of the DNA molecule, first she purifies a large amount of DNA then stretches the DNA fibers in a thin glass tube so thatthe strandss are parallel, then she amis a powerful X-ray beam at the concentrated DNA samples and recorded the scattering patterns from the DNA.
franklins X rays
thye built a three-dimensional nodels of the molecule that were made of cardboard and wire. they twisted and stretched the models in various ways, but heir best efforts did nothing. watson was shown a copy of franklins x-ray pattern in 1953.
watson and crick
the double-helix two strands of DNA run in oppostie directions. this arrangement enables the nitrognous bases on both strands to come into contact at the center of the molecule.
antiparallel strands
the DNAunzips into two strands and then produces two new complementary strands following the rules of base pairing.
DNA replication
DNA replication is carried out by a series of enzymes. these enzymes first unzip a molecule of DNA by breaking the hydrogen bonds between base pairs and unwindin the two strands of the molecule. the principle enzyme for DNA replication is DNA polymerase.
enzymes in DNA replication
the tips of chromosomes are known as telomeres. this DNA is difficult to replicate. cells use a special enzyme, telomerase, to solve this problem by adding short, repeated DNA sequences to the telomeres. in stem cells or embryonic cells it helps to prevent genes from being damaged or lost during replication.
telomeres
• In most prokaryotes, DNA replicated does not stary until regulatory proteins bind to a single starting point on the chromosomes. replication in prokaryotic cells starts from a single point and proceeds i two directions until the entire chromosome is copied.
prokaryotic DNA replication
in eukaryotic cells, replication may begin at dozens or even hundreds of places on the DNA molecule, proceeding in both directions until each chromosome is completely copied.
eukaryotic DNA repliction
there are three important differences 1. the sugar in RNA is ribose instead of deoxyribose 2. RNa is generally singlestranded and not double-stranded, and 3 RNA contains uracil in place of thymine
comparing DNA and RNA
- Most genes contain instructions for assembling amino acids into proteins
- The RNA molecules that carry copies of these instructions are known as messenger RNA.
messenger RNA
- Proteins are assembled on ribosomes, small organelles composed of two subunits.
- These subunits are made up of several ribosomal RNA molecules and as many as 80 different proteins
ribosomal RNA
When a protein is built, a third type of RNA molecule transfers each amino acid to the ribosome as t is specified by the coded messages in mRNA. These molecules are known as transfer RNA.
transfer RNA
• The base sequences of the transcribed RNA complement the base sequences of the template DNA.
• In prokaryotes, RNA synthesis and protein synthesis take place in the cytoplasm.
• In eukaryotes, RNA is produced in the cell's nucleus and then moves to the cytoplasm to play a role in the production of protein.
• Transcription requires an enzyme, known as RNA polymerase, that is similar to DNA polymerase.
• RNA polymerase binds to DNA during transcription and separates the DNA strands.
• It then uses one strand of DNA as a template from which to assemble nucleotides into a complementary strand of Rn.
transcription
• Promoters are signals in the DNA molecules that show RNA polymerase exactly where to begin making RNA.
• Similar signals in DNA cause transcription to stop when a new RRNA molecule is completed.
promoters
• These pre-mRNA molecules have bits and pieces cut out of them before they can go into action.
• The portions that are cut out and discarded are called introns.
• In eukaryotes, introns are taken out of pre-mRNA molecules while they are still in the nucleus.
• The remaining pieces, known as exons, are then spliced back together to form the final mRNA.
RNA editing
1. the translation begins when a ribosome attached to an mRNA molecule in the cytoplasm. as each codon pases through the ribosome, tRNAs bring the proper amino acids into the ribosome. one at a time, the ribosome then attached the amino acids to the growing chain, each tRNA molecule carries one kind of amino acid and three unpaired bases. 2. the ribosomes help form a peptide bond between the 1st and 2nd amino acids- methionine and phenylalnine, also the bond holding the 1st tRNA molecule to its amino acid is brokenand the ine continues 3. the polypeptide chain continues to grow until the ribosome reaches a stop codon on the mRNA molecule, which makes it release the newly formed polypeptide and the mRNA molecule
steps of translation
mRNA carries the coded message that directs the process
tRNA- deliver the right amino acid called for by each codon on the mRNA.
rRNA- help hold ribosomal proteins in place and help locate the beginning of the mRNA message.
mRNA, tRNA and rRNA in translation
the central dogma of molecular biology is that information is transferred from DNA to RNA to protein
molecular biology
gene mutations that involve changes in one or a few nucleotides are known as point mutations because they occur at a single point in the DNA sequence. point mutations include subsituttions, insertions, and deletions
point mutations
in a substitution one base is changed to a different base.subsitutions usually affect no more than one amino acid
substitution of mutations
insertions and deletions are point mutations in which one base is inserted or removed from the DNA sequence. if a nucleotide is added or deleted, the bases are still read in groups of three, bu those groupings shift in every codon that follows the mutation. they are called frameshift mutations
insertions and deletions of frameshift mutations
chromosomal mutations involve changes in the number or structure of chromosomes. these mutations can changed the location of genes on chromosomes or even can change the number of copes of some genes. deletion- deletes a chromosomes, duplication- produces an extra copy of the chromosome,inversion- reverses the direction of parts of the chromosome, trans location- part of one chromosomes breaks off and attaches to another
chromosomal mutations
some mutations arise from mutagens, chemical or physical agents in the environment. examples could be pesticides, tobacco smoke, or environmental pollutants. physical mutagens- x rays or ultra violet light.
mutagens
some harmful mutations are the ones that change protein structures or gene activity. they result in genetic disorders.
harmful affects of mutations
mutations often produce proteins with new or altered functions that can be useful to organism in different or changing environments
beneficial effects of mutations
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