The Molecular Basis Of Inheritance

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what makes up a chromosome

Back 1

DNA

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genes are located on the

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chromosomes

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Griffin

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he discovered transformation

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transformation

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bacteria have the ability to transform harmless cells into virulent ones by transferring some genetic factor from one bacteria cell to another

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Avery, MacLeod, and McCarty

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they found that the factor that causes Griffith's transformation is DNA
-DNA is the genetic material responsible for transformation

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Hershey and Chase

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-proved that DNA from the viral nucleus not protein from the viral coat, was infecting bacteria and producing thousands of progeny

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Hershey and Chase's experiment

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-tagged bacteriophages with the radioactive isotopes Phosphorus and Sulfur.
-since proteins contain sulfur and not phosphorous, and DNA contains phosphorous and not sulfur,
-the radioactive phosphorous labeled the DNA of the phage viruses while sulfur labeled the protein coat of the phage virus.
-found that radioactive phosphorous always entered the bacterium while the radioactive sulfur remained outside the cell

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Rosalind Franklin

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-carried out X-Ray crystallography analysis of DNA that showed that DNA was in the shape of a helix

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Watson and Crick

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-proposed the double helix structure of DNA

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Meselsohn and Stahl

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-proved that DNA replicates in a semiconservative fashion

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Friedrich Miescher

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first isolated DNA from pus

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Robert Feulgen

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invented DNA -specific stain

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Erwin Chargaff

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adenine bonds with thymine
cytosine bonds with guanine

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X-ray crystallography

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-technique used to determine the 3 dimensional structure of a molecule

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antiparallel

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the two strands run in opposite directions

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DNA is a polymer of

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nucleotides

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the nitrogenous bases are of opposite chains are paired to one another by

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hydrogen bonds

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adenine nucleotide bonds to thymine by a ___hydrogen bond

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double

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cytosine nucleotide bonds to guanine by a ____hydrogen bond

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triple

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In RNA, thymine is replaced with____

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uracil

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replication begins at special sites called

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origins of replication

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the two strands of DNA separate to form

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replication bubbles

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at each end of a replication bubble is a

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replication fork

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replication fork

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a Y-shaped region where the new strands of DNA are elongating.

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what enzyme catalyzes the elongation of the new DNA strands

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DNA polymerase

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DNA polymerase catalyzes the elongation of the new DNA strands in the_______direction

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5' to 3' direction

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RNA primer

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the preexisting chain that consists of RNA in which DNA polymerase adds nucleotides to the 3' end of

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primase

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enzyme that joins RNA nucleotides to make the primer

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leading strand

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the strand that is formed toward the replication fork, in an unbroken linear fashion

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lagging strand

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the strand that is formed in the direction away from the replicationn fork

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the lagging strand is made up of

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okazaki fragments

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DNA ligase

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enzyme that joins the okazaki fragments into one continuous chain

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helicase

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enzyme that untwists the double helix at the replication fork

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single-stranded binding proteins

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hold the two DNA strands apart

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DNA topoisomerases

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make "cuts" in the DNA that lessen the tension on the tightly wound helix

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mismatch repair

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proofreading, and corrects any errors

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what carries out mismatch repair?

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DNA polymerase

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to protect against the loss of genes at the ends of the chromosomes, eukaryotes...

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have special nonsense nucleotide sequences (TTAGGG) at the ends of chromosomes that repeat thousands of times

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telomeres

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protective ends of the chromosome to protect against possible loss of genes (TTAGGG)

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telomerase

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enzyme that creates telomeres and maintains them

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transcription

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the process by which DNA makes RNA

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three types of RNA

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mRNA, tRNA, and rRNA

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transfer RNA

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-shaped like a clover leaf
-carries amino acids to the mRNA at the ribosome

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ribosomal RNA

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structural
-makes up the ribosome

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ribosomes are formed in the

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nucleolus

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transcription consists of 3 phases

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1) initiation
2) elongation
3) termination

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initiation of transcription

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1) RNA polymerase recognizes and binds to DNA at the promoter region
2) transcription factors recognize the TATA box within the promoter and mediate the binding of RNA polymerase to the DNA
3) transcription initiation complex is formed
4) once RNA polymerase is attached to promoter, DNA transcription of the DNA template begins

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recognizes and binds to DNA at the promoter region

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RNA polymerase

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RNA polymerase binds to the____-during transcription

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promoter (TATA box within the promoter)

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transcription initiation complex

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the completed assembly of transcription factors and RNA polymerase bound to the promoter

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elongation in transcription

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1) RNA polymerase adds nucleotides to the 3' end of a growing chain
2) RNA polymerase pries the 2 strands of DNA apart and attaches RNA nucleotides

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transcription unit

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the stretch of DNA that is transcribed into an mRNA molecule during elongation in transcription

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codons

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triplets of bases
-code for specific amino acids

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Termination of transcription

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1) the final stage in transcription
2) elongation contines for a short distance after the RNA polymerase transcribes the termination sequence
-at this point, mRNA is cut free from the DNA template

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RNA processing

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before the newly formed mRNA strand is shipped to ribosome in the cytoplasm, it is altered

1) a 5' cap consisting of modified guanine nucleotide is added to the 5' end.
2) a poly (A) tail, consisting of a string of adenine nucleotides, is added to the 3' end
3) introns are removed by snRNPs and splicesomes

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5' cap

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-consists of a modified guanine nucleotide
-helps the RNA strand bind to the ribosome in the cytoplasm

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poly (A) tail

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-consists of a string of adenine nucleotides
-added to the 3' end
-tail protects the RNA strand from degradation by hydrolytic enzymes
-helps the ribosome attach to the RNA
-facilitates the release of the RNA into the cytoplasm

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snRNPs

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they remove introns

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translation

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the process by which the codons of an mRNA sequence are changed into an amino acid sequence

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aminoacyl-tRNA synthetase

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a specific enzyme that makes sure that the correct amino acid is joined to the correct tRNA

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AUG

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start codon

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stop codons

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UAG, UGA, UAA

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wobble2)

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the relaxation of base pairing rules

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ribozymes

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RNA molecules that function as enzymes
-can catalyze its own excision of introns

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translation steps

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1) mRNA becomes attached to a subunit of the ribosome
2) elongation continues as tRNA brings amino acids to the ribosome
3) tRNA first attatches to the A site, then moves to the P site, and finally leaves in the E site
4) a polypeptide chain is formed
5) termination of an mRNA strand is complete when a ribosome reaches on of the three stop codons
6) release factor breaks the bond between the tRNA and the last amino acid of the polypeptide chain

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simpleste mutation

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point mutation

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point mutation

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base-pair substitution, a chemical change in just one base pair in a single gene

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sickle cell anemia results from a____mutation

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single point mutation

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insertion / deletion

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the addition of one base pair / the loss of one base pair

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insertions/deletions result in a____

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frameshift

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missense mutation

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-when point mutations or frameshifts change a codon into a stop codon, in which translation will be altered

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capsid

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a protein coat that encloses DNA or RNA of a virus

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bacteriophages

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viruses that infect bacteria

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lytic cycle)

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1) the phage enters a host cell
2) takes control of the cell machinery
3) replicates itself
4) causes the cell to burst
5) releases a new generation of infectious phage viruses

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lysogenic cycle

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1) viruses replicate without destroying the host cell
2) the phage virus becomes incorporated into a specific site in the host's DNA
3) remains dormant within the host genome (prophage)
4) as the host cell divides, the phage is replicated along with it and a single infected cell gives rise to a population of infected cells
5) at some point, an environmental trigger causes the prophage to switch to the lytic phase

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prophage

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a phage genome that has been inserted into a specific site in a bacterial chromosome

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temperate viruses

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viruses capable of both modes of reproducing, lytic and lysogenic, within a bacterium

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retroviruses

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viruses that contain RNA instead of DNA and replicate in an unusual way

1) RNA serves as a template for the synthesis of complementary DNA

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retroviruses

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enzyme that directs the reverse transcription for retroviruses

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HIV is an example of a

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retrovirus

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transduction

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transfer of bacterial DNA by phages from one cell to another

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2 types of transduction

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generalized and restriced

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generalized transduction

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moves random pieces of bacterial DNA as the phage lyses one cell and infects another during the lytic cycle

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restricted transduction

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involves the transfer of specific pieces of DNAw

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bacterial chromosome

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a circular, double-stranded DNA molecule, tightly condensed into a nucleoid

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does a nucleoid have a nuclear membrane?

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no

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the main method of reproduction for bacteria is by

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binary fission

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plasmid

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a foreign, small, circular, self-replicating DNA molecule that inhabits a bacterium

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pili

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cytoplasmic bridges that connect adjacent cells during conjugation

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conjugation

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form of sexual reproduction when two adjacent cells allow DNA to move from one cell to another through pili

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R plasmids

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make the cell in which it is carried resistant to specific antibiotics

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the______is an important model of gene regulation

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operon

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operon

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a set of genes and the switches that control the expression of those genes

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jacob and Monod

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discovered the operon

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the____operon is switched off until it is induced to turn on

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Lac operon

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the_____operon is always in the on position until it is not needed and becomes switched off

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tryptophan operon

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If a repressor binds to an operator,

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RNA polymerase is prevented from binding to the promoter and transcription of the genes is blocked

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noncompetitive inhibition

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2 substances are competing for two active sites, one of which blocks the other

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allolactose

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if it is present in the environment, it acts as an inducer

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inducer

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binds to the repressor and causes it to change its shape or conformation

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a repressible operon

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tryptophan

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tryptophan operon

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it is continuously switched on unless turned off by a corepressor
-repressor is usually inactive
-therefore, RNA polymerase is free to bind to the promoter and transcribe the structural genes, resulting in the productin of tryptophan

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prions

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misfolded versions of a protein normally found in the brain

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transposons

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transposable genetic elements
-also called jumping genes

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Barbara McClintock

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discovered transposons

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transposase

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the enzyme responsible for moving the sequence from one place to another

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insertion sequences

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consist of only one gene which codes for transposase

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complex transposons

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longer than insertion sequences and include extra genes

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recombinant DNA

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means taking DNA from 2 sources and combining them into one molecule

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uses of recombinant DNA or gene cloning

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1) to produce a protein product in large quantities inexpensively
2) to replace a nonfunctioning gene in a person's cells by gene therapy
3) to prepare multiple copies of a gene for analysis
4) to engineer bacteria to clean up the environment

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the technique of gene cloning

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1) isolate a gene of interest
2) insert the gene into a plasmid
3) insert the plasmid into a vector
4) clone the gene
5) identify the bacteria that contain the selected gene and harvest it from the culture

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vector

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a cell that will carry the plasmid

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restriction enzymes cut DNA at____

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specific recognition sites

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sticky ends

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single stranded DNA that is cut staggered

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restriction fragments

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the fragments that result from the cuts made by restriction enzymes

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restriction enzymes are used during

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gene cloning

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gel electrophoresis

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separates large molecules of DNA on the basis of their rate of movement through an agarose gel in an electric field
-the smaller the molecule, the faster it runs

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DNA is negative/positive and thus flows from the (cathode/anode) to the (cathode/anode)

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1) negative
2) cathode (-)
3) anode (+)

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if DNA is going to be run through a gel for gel eletrophoresis, it must be first cut up by_____

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restriction enzymes so that the pieces are small enough to migrate through the gel

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a______can also identify the location of a specific sequence within the DNA

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DNA probe

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DNA probe

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a radioactively labeled single strand of nucleic acid molecule used to tag a specific sequence in a DNA sample

-the probe bonds to the complementary sequence wherever it occurs, and the radioactivity enables scientists to detect its location

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polymerase chain reaction

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-a cell free automated technique by which a piece of DNA can be rapidly copied or amplified
-billions of copies of a fragment of DNA can be produced in a few hours

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the restriction fragment pattern is different/same in every individual

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different

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since restriction fragment patterns are different in every individual, these differences have been named_____

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RFLPs

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a RFLP analysis of someone's DNA gives a human ______

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DNA fingerprint that look slike a bar code