General Bio I Ch 10 SLOs + Learning Curve
snRNPs
(small nuclear ribonucleoproteins) composed of RNA and protein molecules, recognize the splice sites, join with additional proteins to form a spliceseome
An mRNA molecule has 540 codons. It must have at least ______ nucleotides
1,620
There are ____ different amino acids in the genetic code and each corresponds to __ codon. Each codon contains __ nucleotides.
20 ; 1 ; 3
Inosine, which is sometimes found at the ____ end of an anticodon, can pair with any of the bases normally seen in RNA except __.
5' ; G
A stretch of 150 nucleotides in a gene would code for ____ codons and ____ amino acids
50 ; 50
Explain which type of mutations are most likely to result in a protein change and why.
A Frame-Shift Mutation will most likely result in a protein change because all the amino acids are affected by the mutation and it results in a nonfunctional protein, (that used to be functional).
missense mutation
A base-pair substitution that results in a codon that codes for a different amino acid.
Explain the role of the codon in protein synthesis.
A codon is a sequence of three DNA or RNA nucleotides that corresponds with a specific amino acid or stop signal during protein synthesis. Codons provide the key that allows these two languages to be translated into each other.
During RNA splicing, what occurs directly before the intron forms a closed loop?
A cut is made in between the upstream exon and the intron
spliceosome
A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.
silent mutation
A mutation that changes a single nucleotide, but does not change the amino acid created.
nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
gene
A segment of DNA on a chromosome that codes for a specific trait
codon
A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid
messenger RNA (mRNA)
A type of RNA, synthesized from DNA and attached to ribosomes in the cytoplasm; it specifies the primary structure of a protein.
start codon
AUG (methionine)
transfer RNA (tRNA)
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
Discuss how coding regions are interrupted by introns in eukaryotes.
Coding regions, exons, have noncoding regions, introns, interspersed with them. These introns must be removed before translation takes place.
exons
Coding segments of eukaryotic DNA.
sense codon
Codon that specifies an amino acid in a protein.
transcription factors
Collection of proteins that mediate the binding of RNA polymerase and the initiation of transcription.
ribosome
Cytoplasmic organelles at which proteins are synthesized.
central dogma of biology
DNA -> RNA -> Protein
Name the location within the cell of: DNA replication, transcription, and translation.
DNA Replication takes place in the nucleus Transcription takes place in the nucleus Translation takes place in the ribosome
Explain how transfer RNAs carry specific amino acids and bind to specific codons.
Each tRNA binds to one specific amino acid. Which of the 20 amino acids is attached is determined by the anticodon that is attached to the middle of the tRNA.
Briefly describe the elongation step of translation
Elongation: Charged tRNA enters the open A site of the large ribosomal subunit. The tRNA releases the start codon (methionine) and the tRNA moves 3 bases down to the E site and then to the P site. The growing polypeptide is transferred to the amino acid in the A site & the ribosome shifts down one codon. The uncharged tRNA in the E site returns to the cytosol to get recharged and the one in the P site goes to the E site. This repeats and the polypeptide chain grows.
RNA polymerase
Enzyme similar to DNA polymerase that binds to DNA and separates the DNA strands during transcription
True or false, any alteration of the genes for hemoglobin in polypeptides will affect the protein's function.
False
wobble
Flexibility in the base-pairing rules in which the nucleotide at the 5' end of a tRNA anticodon can form hydrogen bonds with more than one kind of base in the third position of a codon.
Give an overview of the roles of transcription and translation in the expression of genes.
Genes are expressed as RNAs, many of which are then translated into proteins. Gene expression involves: Transcription: Where the information in a DNA sequence (a gene) is copied by base pairing into a complementary RNA sequence Translation: Where the RNA sequence is used to synthesize the amino acid sequence of a polypeptide.
initiation complex
In translation, a combination of a small ribosomal subunit, an mRNA molecule, and the charged tRNA; formed at the onset of translation.
Describe the process by which DNA is transcribed to mRNA.
Information coded in the sequence of nucleotide bases in DNA is passed to a sequence of nucleotide bases in RNA
Briefly describe the initiation step of translation
Initiation: Once the small ribosomal subunit is in place, the anticodon on the tRNA bonds with the start codon. After that, the large ribosomal subunit joins and the initiation complex is complete.
Name the three major steps involved in transcription and briefly describe the major events that occur during each step.
Initiation: RNA Polymerase binds to the promoter and starts to unwind the DNA strands Elongation: RNA Polymerase moves along the DNA template strand from 3' to 5' and produces the RNA transcript by adding nucleotides complementary to the DNA template to the 3' end of the growing RNA. Termination: When the RNA Polymerase reaches the termination site, the RNA transcript and polymerase are released from the template.
What are the two components of pre-mRNA processing?
Introns are removed from the pre-mRNA transcript & Exons are spliced together A 5' cap is added to the 5' end of pre-mRNA and a Poly A tail is added to the 3' end
What feature makes tRNA unique compared with other functional RNAs?
It contains the modified nucleotide inosine
Explain how the concept of the gene has changed over time.
It was believed that one gene encoded for one enzyme This isn't true because not every gene is making a protein that's an enzyme It was then believed that one gene encoded for one protein This is also not true because in the quaternary level of structure in proteins the protein is made up of multiple polypeptides, each coming from separate genes. It's now believed that one gene encodes for one polypeptide
poly A tail
Modified end of the 3' end of an mRNA molecule consisting of the addition of some 50 to 250 adenine nucleotides.
The rate of synthesis for a particular protein increases. What''s the most likely cellular manifestation?
More polysomes
introns
Noncoding segments of nucleic acid that lie between coding sequences.
Using tRNA as an intermediary, each mRNA attracts __________ amino acid to the growing polypeptide chain
Only one
translation
Process by which mRNA is decoded and a protein is produced
RNA splicing
Process by which the introns are removed from RNA transcripts and the remaining exons are joined together.
Briefly describe the process of splicing and why it is necessary for eukaryotic transcription.
Process that removes the introns and splices the exons together.Requires introns have certain characteristics, consensus sequences; short stretches of DNA that appear with little variation across different introns. Splicing is necessary for eukaryotic transcription because it removes the introns, the noncoding regions, from the eukaryotic genes. If this didn't happen, the extra nucleotides in the mRNA would be translated by the ribosome and a nonfunctional protein would result.
List three differences between prokaryotic and eukaryotic gene expression
Prokaryotic Gene Expression: Transcription & Translation- occur at the same time within the cytosol Gene Structure- DNA sequence usually not interrupted by introns Modification of mRNA after initial transcription before translation- Usually none Eukaryotic Gene Expression: Transcription & Translation- Transcription occurs in the nucleus, translation occurs in the cytosol Gene Structure- Transcribed regions (exons) often interrupted by noncoding introns Modification of mRNA after initial transcription before translation- Introns spliced out of pre-mRNA; 5' cap and 3' poly A tail added to mRNA.
Describe the role of RNA polymerase, the promoter, and transcription initiation site in the process of transcription.
RNA Polymerase: Binds to the promoter and starts to unwind the DNA strands. Moves along the DNA template strand from 3' to 5' and produces the RNA transcript by adding nucleotides complementary to the DNA template to the 3' end of the growing RNA. The Promoter: RNA polymerase binds to it in order to unwind the DNA strands to start the transcription The Transcription Initiation Site: Where the RNA polymerase and promoter bind to start the transcription
During elongation in transcription...
RNA polymerase adds new nucleotides to the 3' end of the growing RNA strand
termination of transcription
RNA polymerase reaches a terminator sequence (Stop codon) and detaches from the template
elongation (transcription)
RNA polymerase unzips the DNA and assembles RNA nucleotides using one strand of DNA as a template.
termination site
Region of DNA that tells the polymerase when transcription should conclude.
_____________________ make up about 80% of total RNA in a cell
Ribosomal RNA (rRNA)
In a "degenerate" genetic code, the ______ amino acid is encoded by ___________ codons.
Same ; multiple
consensus sequences
Short stretches of DNA that appear, with little variation, in many different genes.
Be able to create and recognize the following types of mutations: silent, missense, nonsense, frame-shift.
Silent Mutations: Occurs when a DNA substitution alters the codon but not the encoded amino acid. Results in no change in the amino acid sequence. Missense Mutations Occurs when a DNA substitution alters the codon so that it encodes for a different amino acid. Inmost cases will result in a single amino acid change in the protein, which may or may not cause a change in function. Nonsense Mutations: Results in a change from a sense codon to a stop codon, causing a premature termination of translation and a shortened protein. Likely to be loss-of-function mutations Frame-Shift Mutations: Results in the insertion or deletion of one or more (but not a multiple of 3) base pairs in the coding sequence. The insertion or deletion of a nucleotide in the coding region will cause the reading frame to be out of register, leading to different triplets being read, and an altered sequence of amino acids downstream of the frame-shift in the resulting (often shortened) polypeptide. Usually loss-of-function mutations because they affect so many amino acids in the protein.
Discuss the significance of the start and stop codons in protein synthesis.
Start Codon: The initiation signal for translation; AUG, codes for methionine. Stop Codons: Cause the termination of translation; UAA, UAG, UGA
Describe the template and coding strands
Template strand is the one that's transcribed Coding strand contains the gene
Briefly describe the termination step of translation
Termination: The newly completed polypeptide separates from the ribosome. The ribosome splits back into small and large subunits.
5' cap
The 5' end of a pre-mRNA molecule modified by the addition of a cap of guanine nucleotide.
A, P, E sites
The A site is the point of entry for the charged tRNA. The P site is where the peptidyl tRNA is formed in the ribosome. And the E site which is the exit site of the now uncharged tRNA after it gives its amino acid to the growing peptide chain.
template strand
The DNA strand that provides the pattern, or template, for ordering, by complementary base pairing, the sequence of nucleotides in an RNA transcript.
Explain the significance of the anticodon in translation.
The anticodon determines what amino acid gets attached to the tRNA since it has to be complementary to the mRNA codon for the amino acid that is being carried.
A, U, G, C
The bases found in RNA
During RNA splicing, what must occur directly before the excised intron is degraded in the nucleus?
The downstream exon is cleaved at the intron junction and spliced to the upstream exon.
Explain what is meant by the "redundancy of the genetic code" and how this is relevant for protein synthesis.
The genetic code is said to be redundant because more than one codon can code for the same amino acid. this is relevant for the synthesis of proteins because redundancy in the code helps prevent errors in protein synthesis.
one-gene-one-polypeptide
The idea, since shown to be an oversimplification, that each gene in the genome encodes only a single polypeptide—that there is a one-to-one correspondence between genes and polypeptides.
transcription initiation site
The part of a gene's promoter where synthesis of the gene's RNA transcript begins.
what structure or molecule brings tRNA and mRNA together?
The ribosome
stop codon
UAG, UAA, or UGA; the codon that ends all RNA.
loss-of-stop mutation
a change from a stop codon to a sense codon
frame-shift mutation
a mutation involving the addition or loss of nucleotides
ribozyme
a type of RNA that can act as an enzyme
rRNA (ribosomal RNA)
an organelle that contains most of the RNA in the cell and that is responsible for ribosome function
the current genetic code evolved _____ the ______________________
before ; common ancestor of all extant life
small subunit of ribosome
binds to mRNA during translation
Consensus sequences involved in splicing are located at the
boundaries of introns and exons
coding regions
exons, sequences of DNA that serve as instructions for making proteins
anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
Many eukaryotic gene sequences are interrupted by
introns
large subunit of ribosome
joins amino acids to form a polypeptide chain
splice sites
junctions of the introns and exons where mRNA precursor is cut and joined
If inosine were not present in anticodons, there would be _______ wobble, and _______ different types of tRNAs would be needed to match the different codons.
less; more
Which type of molecules transfers information from the nucleus to the cytoplasm in a eukaryotic cell?
mRNA
initiation of translation
mRNA is attached to a subunit of the ribosome, the first codon is always AUG
In nucleic acid hybridization, the DNA being studied first is heated. This is done to ___________________
make it single-stranded
Describe the observations in humans that led to the one-gene-one-enzyme hypothesis and one-gene-one-polypeptide hypothesis.
one-gene-one-enzyme hypothesis: This hypothesis was drawn after observing that enzyme knockouts are inherited in a Mendelian manner (which was observed during research by English physician Archibald Garrod, into a certain kind of genetically determined biochemical disease described as "inborn error of metabolism") because given that the sequence of amino acids determines protein function, it was assumed that a mutant phenotype arises from a change in the protein's amino acid sequence. one-gene-one-polypeptide hypothesis: This hypothesis was drawn when it became known that genes could also encode non-enzyme proteins.
pre-mRNA
precursor mRNA; the first strand of mRNA produced by gene transcription that contains both introns and exons
gene expression
process by which a gene produces its product and the product carries out its function
one-gene-one-enzyme
proposed by beadle and tatum, the hypothesis proposing that each gene encodes a specific protein product and controls a distinct function
The genetic code is best described as
redundant but not ambiguous
promoter
specific region of a gene where RNA polymerase can bind and begin transcription
AUG is a _____ codon
start
What type of molecule "decodes" the information present in the mRNA?
tRNA
transcription
the organic process whereby the DNA sequence in a gene is copied into 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
The adapters that allow translation of the four-letter nucleic acid language into the 20-letter protein language are called
transfer RNAs
tRNA (transfer RNA)
type of RNA molecule that transfers amino acids to ribosomes during protein synthesis
ribosomal RNA (rRNA)
type of RNA that makes up the major part of ribosomes