chapter 17 Flashcards
○ What is the link between genotype and phenotype
§ Proteins
○ What is gene expression
Process by which dna directs the synthesis of proteins
What are the two stages of gene expression
Transcription and translation
○ Who was the first to suggest that genes dictate phenotypes through enzymes
Archibald garrod
What did archibald garrod postulate
Symptoms of disease reflect an inability to make a particular enzyme
what is one gene-one enzyme hypothesis
§ That a gene dictates the production of a specific enzyme
what did american biochemist and geneticist george beadle speculate about drosophillia
each mutation affecting eye color blocks pigment synthesis at a specific step by preventing production of the enzyme that catalyzes that step
What experiment did beadle and tatum do
They chose to study the protein-coding genes required for a specific nutritional acitivity
They caused mutations in genes by bombarding the neurospora with x rays
what are some examples of nonenzymic proteins
kertain and hormonal insulin
Proteins that are not enzymes are what
gene products
How many polypeptides does hemoglobin contain
Two and because of that two genes code for the protein
What is the function of hemoglobin
Oxygen transporting protein
what is alternative splicing
Eukaryotic gene can code for a set of closely related polypeptides
what provides the instructions for making proteins
genes
what is the bridge between dna and protein synthesis
nucleic acid RNA
what is the difference between dna and rna
§ Dna is deoxyribose and rna is ribose
And dna sequence = atgc and rna sequence = augc
How many nucleotides do genes have
hundreds and thousands of them
What is transcription
§ Synthesis of rna using information in the dna
What is mRNA
Messenger RNA because it carries a genetic message from dna to the protein-synthesizing machinery of the cell
What happens during translation
he mRNA molecule is trnaslated into an amino acid sequence of polypeptide
Where does translation happen
ribosomes
○ What are ribosomes
§ Molecular complexes that make proteins
Transcription and translation is similar for what
Bacteria and eukaryotes
○ What does bacteria not contain
A nuclei
Since bacteria does not have a nuclei what problems does it face with transcription and translation
Nuclear membrane does not separate bacterial dna and mRNA from ribosomes and that means the translation of mrna can begin while transcription is still in process
○ What is the importance of the nuclear membrane
Separate the transcription from translation in space and time
○ Where does transcription occur
§ In the nucleus but mrna is transported to the cytoplasm for translation
Where does translation occur
§ In the cytoplasm
What does the transcription of a protein encoding gene lead to
Pre mRNA
○ What is primary transcript
The initial RNA transcript from any gene
○ What was the central dogma theory
§ Idea that the flow of dna information went in one way
How many nucleotide bases are there for each amino acid
§ 4 nucleotide bases to specify 20 amino acids
What is the flow of information from gene to protein based on
§ Triplet code
○ What is the triplet code
§ The genetic instructions for a polypeptide chain are in written in the dns as a series of nonoverlapping, three-nucleotide words
○ What is the template strand
§ One strand that is being transcribed because it provides the pattern or template for the sequence of nucleotides being transcribed
○ What way is a rna molecule strand synthesized
§ Antiparallel direction to the template strand
What are codons
mRNA nucleotide triplets
What way are codons written
5’ to 3’
What is the coding strand
The non template dna strand
○ What does rna polymerase do
§ Pries the strands of dna apart and joins the complimentary rna nucleotides to the dna template strand which then elongates the rna polynucleotide
○ What way does rna polymerase assemble
§ 5 to 3 direction
○ What end does rna polymerase add to
§ 3 end
○ What is the difference between dna polymerase and rna polymerase
§ Rna polymerase can start a chain from scratch and they don’t need a primer
○ What is the promotor
§ Dna sequence where rna polymerase attatches and initiates transcription
○ In bacteria what is the sequence that signals the end of transcription
§ Terminator
○ What is the transcription unit
§ Stretch of dna downstream from the promotor that is transcribed into an rna molecule
○ What type of rna polymerase does bacteria have
§ The kind that synthesizes mrna but other types of rna in gene expression (ribosomal rna)
○ How many rna polymerases do eukaryotes have
§ 3 in the nuclei
○ What is the function of rna polymerase 2
§ Pre-mRNA synthesis
What do the other eukaryotic rna polymerases do
§ Transcribe molecules that are not translated into protein
○ What are the 3 stages of rna transcription
Initiation, elongation, termination
○ What is the start point
§ The nucleotide where rna polymerase actually begins synthesizing the mrna
○ What happens in the initiation stage of rna transcription
§ Rna polymerase binds to the promotor
§ Polymerase unwinds dna stands and starts synthesis @ start point
○ What happens in the elongation stage
§ Polymerase moves downstream
§ Unwinds the dna and elongates the rna transcript 5 to 3
§ Dna strands re-form a double helix
○ What happens in the termination stage
§ The rna transcript is released
§ Polymerase detaches from dna
○ What is a difference between the way the rna poly binds to the promotor in bacteria and eukaryotes
§ Eukaryotes they use transcription factors
○ What are transcription factors
Proteins that help guide the binding of rna polymerase and initiation of transcription
○ What is the transcription initiation complex
§ Complex of transcription factors and rna poly 2 bound to the promotor
○ What is the TATA box
§ Crucial promotor dna sequence which forms the initiation complex at a eukaryotic promotor
What happens after the transcription factors are attatched to the promoto
§ Enzyme unwinds the two dna strands and begins transcribing the template strand at the start point
Rna polymerase adds nucleotides to what end
3 end
○ What is the affect of many polymerase molecules
Increases the amount of mrna transcribed and it helps the cell make the encoded protein in large amounts
○ What is a difference between the termination in bacteria and eukaryotes
§ In bacteria transcription proceeds through a terminator sequence in the dna and it functions as the signal
§ Eukaryotes rna ply2 transcribes a sequence on the dna called the polyadenylation signal sequence
○ What happens during rna processing
§ Both ends of the primary transcript are altered
○ How is the pre-mrna modified
§ 3 end(synthesized first) recieves the 5 cap
○ What is the 5’ cap
§ Modified form of guanine added onto the 5’ end after transcription added to the pre-rna
what is the reading frame
subsequent codons are read in groups
of three nucleotides
what is rna processing
both ends of the primary transcript are altered.
what is the poly-a-tail
At the 3 end, an enzyme adds 50 to 250 adenine nucleotides
what is the function of the poly-a-tail
They facilitate the export of mRNA from the nucleus.
○ They help protect mRNA from hydrolytic enzymes.
○ They help the ribosomes attach to the 5 end of the mRNA.
what is rna splicing
removal of a large portion
of the RNA molecule
what is an intron
Noncoding segments of nucleotides called intervening regions
what is an exon
are eventually expressed, usually by being translated into amino
acid sequences.
what do snRNPS
recognize the splice sites
what is a splicesome
remove introns in protein-encoding genes
when does splicing occur
without proteins
what are the properties of rna
single stranded
contain functional groups
can
what is alternative splicing
process of selecting different combinations of splice sites within a messenger RNA precursor (pre-mRNA) to produce variably spliced mRNAs.
what does the splicesome do
interacts with certain sites along an intron, releasing the introns and joining
together the two exons that flanked the introns
because of introns
a single gene can encode for more than one kind of polypeptide
trna molecule is…
a translator and turns mrna into an amino acid
what is the function of trna
transfers amino acids from cytoplasmic pool to growing polypeptide
what is an anticodon
at the end of the trna
what is the site of translation
the ribosome
where is protein made in eukaryotes
nucleolous
what does the p site do
holds the tnra of the growing polypeptide chain
what does the a site do
holds the trna carrying the next amino acid
where does translation take place
in the ribosomes
what is the function of rrna
main constituient between a and p site and it is a catalyst for peptide bond formation
what are point mutations
changes to a single nucleotide gene
what is a nucleotide pair substitution
replacement of one nucleotide and its partner
what is a silent mutation
no observable effect on the phenotype
missense mutaions
change one amino acid to another
what is a nonsense mutation
causes translation to be terminated prematurely
what is a mutagen
physical and chemical agents
what is gene editing
altering genes in a specific way
