molecular biology Flashcards
what is the characteristics of genetic material
-replication
-storage of information
-expression of that info
-variations of mutation
early studies inducated that genetic material resides in the…
nucleus
when the nucleus was stained with specific dyes it was shown to consist of…
proteins and nucleic acid
in body calls the amount of DNA was constant, how ever in gametes in was
reduced to 1/2
what is nucleic acid
it is polymers consisting of many nucleotide monomers, including DNA and RNA
what components do nucleotides consist of
-nitrogenous base
-a pentose (ribose 5 c sugar)
-a phosphate group
what are the two kinds of nitrogenous bases
purines, double rings (adenine, guanine)
Pyrimidines, single rings (cytosine, thymine, uracil)
what is nucleoside composed of
a nitrogenous base and a ribose/deoxyribose sugar
how are nucleosides and nucleotides named according to
the specific nitrogen base (A,C,G,T,U)
what is thymine replaced with in RNA
uracil
what are the 3 major types of RNA
mRNA messenger
tRNA transfer
rRNA ribosomal
what is mRNA
messenger RNA is a transcript of the gene that carries information (as a sequence of codons) for the synthesis of proteins
what is tRNA
transfer RNA is an RNA molecule that functions as an interpreter between nucleic acid and protein language by picking up specific amino acids and recognizing the appropriate codons in the mRNA
what is rRNA
ribosomal RNA is the most abundant type of RNA which together with proteins forms the structure of ribosomes
for the hereditary material how is the genetic information coded in the DNA molecule
the basis information must lie on the linear sequence of the nitrogenous bases, i.e the arrangement of the bases
for the hereditary material how is the information passed on from one cell to the next (i.e. during mitosis)
it must be because of the complimentary base pairing of nitrogenous bases, that one strand serves as a template to form a new strand (DNA replication)
in hereditary material how does the genetic material function
it must be that the DNA passes on its information (transcription) where this uses in the cell function
what is the DNA replication process
the process in which DNA is duplicated (DNA—>DNA)
what did meselson and stahl exprarament demostrate
it showed that DNA replication is semi-conservitive
what is a semi conservative process
in which a double helix gives rise to double helices, each with an old strand and a newly synthesized strand
what is the molecular process of DNA replication
-untwisting of the DNA molecule (occurs by breaking of H bonds between N bases, promoted by certain enzymes
-each of two strands now serve as a template to synthesize a new complementry strand
-a enzyme called DNA polymerase helps in the linking of free nucleotides to form a new strand
-nucleotides are always added 3’-end (which has a free OH) of the new strand
-the template (old) and complementry (new) strands are anti parallel; the 3’-end of one strand in paired with 5’-end of the other
-both parent strands are replicated and replication in eukaryotic cells proceeds in many locations of each strand froming DNA peices
-DNA peices are linked together by enzyme DNA ligase
-the two DNA molecs are identical, i.e in the base sequence to the parent molec
-each DNA molec is 1/2 the old and 1/2 the new molec- semi conservative
what is the structure of RNA
it is usually a single strand polynucleotide although in somecases it may fold up on itself
what pyrimidines is replaced with uracil in RNA
thymine
what is the sugar molecule in RNA
it is ribose instead of deoxy
what are the 3 possible mechanisms for DNA repliation
1) semiconservative mechanism
2) conservative mechanism
3) dispersive mechanism
what is the semiconservative mechanism for DNA replication
DNA replication produces DNA molecules with one parental strand and 1 newly made strand
what is the conservative mechanism for DNA replication
DNA replication produces 1 double helix with both parental strands and the other with two new daughter strands
what is the dispersive mechanism for DNA replication
DNA replication produces DNA strands in which segments of new DNA are with the parental DNA
what is the leading strand of DNA replication
the strand that is going the 3’—5’ way
what is the legging strand in DNA replication
the strand that is going the 5’—3’ way
what is helicase protein
it unwinds DNA helix
what is single stranded binding protein enzyme
stabilizes single stranded DNA and prevent the two strands at the replication fork form reforming double stranded DNA
what is topoisomerearse enzyme
it avoids twisting of the DNA ahead of the replication fork (in circular DNA) by cutting the DNA, turning the DNA on one side of the break in the direction opposite to that of the twisting force, and rejoining the strands
what is the enzyme primase
it assembles RNA primers in the 5’—3’ direction to initiate a new DNA strand
what is the enzyme DNA polymerase III
main replicaiton enzyme in ecoli; it extends the RNA primer by adding DNA nucleotides to it
what is DNA polymerase I enzyme
esherichia coli enzyme that uses its 5’—3’ exonuclease activity to remove the RNA of the previously synthesized okazaki fragment, and uses its 5’—3’ polymerization activity to replace the RNA nucleotides with DNA nucleotides
what is the sliding clamp enzyme
tethers DNA polymerases III to the DNA template, making replication more efficent
what it the enzyme DNA ligase
it seals the nick left between adjacent bases after RNA primers replaced with DNA
why can bacteria replicate much faster then eukaryotes
because bacteria have one single origin whereas eukaryotes require multiple origins
how fast can bacteria replicate compared to eukaryotes
it advances at a rate of about 500-1000 nucleotides per second in bacteria and about 50-100 per second in eukaryotes
what is gene expression
its the flow of genetic information from the genotype to the phenotype
DNA-RNA-protein
what is the one gene one enzyme (polypeptide) hypothesis
a single gene controlled the sysntesis of a single enzyme
what is the central dogma
it is the process of DNA (transcription) RNA (translation) protein
-can also go from RNA to DNA
what is transcription
its the process by which the info encoded in DNA is made into a complementary RNA. the segments of DNA transcribes into RNA molecules that can encode proteins are said to produce messanger RNA (mRNA). other segments of DNA are copied into RNA molecules called non-coding RNAs (ncRNAs)
what is translation
it is the process of synthesizing a specific polypeptide by using the information encoded in the mRNA on a ribosome
what happens to most genes
most are transcribes into mRNA and then the mRNA is translated into polypeptides
where does gene expression take place in prokaryotes
both transcription and translation occur in the cytoplasm due to the absence of nucleus
where does gene expression take place in eukaryotes
transcription occurs int he nucleus and translation occurs in the ribosomes present on the rough endoplasmic membrane in the cytoplasm
what is a gene
an organization of DNA sequences that enables a segment of DNA to be transcribed into RNA and ultimately results in the formation of a functional product
what is the gene composed of
the promoter, the regulatory sequence, the transcribed region and the terminator
what is the promoter portion of a gene
the site in the DNA where RNA polymerase binds to begin transcription
what is the regulatory sequence of a gene
the sites binding to regulatory proteins control whether a gene is turned on or off
what is the transcribed part of a gene
a region of a DNA that is transcribed into a RNA molecule
what is a terminator part of a gene
a sequence that causes the RNA strand to be released from the transcription complex
what is transcription
DNA directed RNA synthesis (DNA–RNA)
what is the molecular process of transcription
-initation of transcription requires transciption factors binding to promoter region of a gene
-TFs recuit DNA polymerase binding to a promoter region (with TATA box in eukaryotes and pribnow box TATAAT i prokaryotes
-unwinding of the DNA double helix
-in given region of DNA only one strand (called template strand) acts as a template. the template runs in the 3’-5’ direction
-elogation:RNA polymerase catalyzes the transcription, and U rather than T incorporates into RNA
-transcription ends at a termination site (termenator)(with an AAUUAAA signal for polyadenylation)
what are the products of transcription
transcripts- RNAs (mRNA, tRNA, rRNA)
what is the location of eukaryotic and prokaeryotic transcription
prokaryotic: cytoplasm
eukaryotic: nucleus
what is the initiation of transcription on pro and eukaryotic cells
pro: a single sigma factor
euk: 5 general transcription factors
how many polymerases do eukaryotes and procaryotes have
pro: a single type
euk: three types of polymerases (II,I&III)
in eukaryotes what polymerizes transcribes what
RNA polymerase I transcribes rRNA genes, RNA polymerases II transcribes mRNA, miRNA, snRNA, and snoRNA genes and RNA polymerases III transcribes tRNA and 5S rRNA genes
what does a typical eukaryotic protein coding gene have both of in transcription
a coding sequence (exons) and a non-coading sequence (internal non-coading sequences-interons;flaking sequences-cap and tail)
in transcription what is a exon
a coding portion of a gene
in transcription what is a intron
a non-coading portion of a gene that is excised form the RNA transcription
what is RNA splicing
the removal of introns and joining of exons in euakaryotic RNA, forming a mRNA molecule with a continuous coding sequence
what is intron RNA defined by
specific sequences within the intron and the intron-exon boundaries
where does mRNA splicing occur
in a spliceosome (a large RNA-protein complex) before mature RNA
how does tRNA and rRNA slicing occur
they are self spicing by a ribozyme
what are biological functions of of introns
-alternate splicing generates different mRNA molecules form the same RNA transcript thus producing different proteins
-they may also contribute to genetic diversity
-may also regulate gene expression
RNA processing also involves a flanking sequence what are the benefits to this
-could regulate the stability of mRNA in the cytoplasm
-seem to facilitate the export of mRNA
-help ribosomes attach to the 5’ end
in RNA processesing+flanking what is capping
a 7-methylguanosine attached to the mature eukaryotic mRNAs at the 5’ ens
in RNA processesing+flanking what is tailing
a tail is added to the most mature eukaryotic mRNAs at the 3’ end
what is the genetic code
the nucleotide info that specifies the amino acid sequence of a polypeptide; the genetic code consists of triplets (codons) of nucleotides. each codon specifies an amino acid in a polypeptide or a signal to either start or terminate peptide synthesis
how many possible codons is there
since there is four bases there is 64 possible codons
what is a start codon and what does it inducate
(AUG) indicates starting point of translation, and codes for methionine
what are the stop codons and that do they inducate
(UAA, UGA, UAG) inducate end of translation
how many codons code for particular amino acids
60
since there are only 20 amino acids the genetic code could be _____ for certain amino acids but the code is not____
redundant, ambiguous
is the genetic code universal
yes. genes can be transcribed and translated after being transplanted form one species to another
how ever the genetic codes of different organisms are often biased towards using one of the several codons that encode the same amino acids over the others-codon usage bias
