Exam 2 Review (Ch. 14-18, 21) Flashcards
(c) introns
- Introns are removed (spliced out) during the pre-mRNA stage in the nucleus. When they end up leaving the nucleus, they do not have their introns.
(b) snRNA
- The spliceosome is made up of 5 RNA molecules + 300 proteins, the 5 RNA molecules are varying ribonucleoprotein particles (snRNPs). These snRNPs are composed of proteins associated with small nuclear RNAs (snRNA). Overall, the molecules associated with the spliceosome are snRNAs, proteins, and snRNPs (U1, U2, U4, U5, U6).
(d) shuffling the order of the exons in the mRNA relative to their order in the DNA
- The exons cannot be shuffled around in mRNA. Introns can be alternatively spliced out and change how exons are put together. An alternative’ cleavage site and polyadenylation sites can also cause differing exons. Also, mRNA editing can take place between bases in some positions.
(a) have a cloverleaf shape for their secondary structure
- All tRNA molecules share their cloverleaf shape with an anticodon that attaches to the codon on mRNA. This is their secondary structure which is created by a previous sequence of nucleotides.
(c) dicer
- The dicer chops up the miRNA molecules so they can further be bound with proteins to create RISC. Then RISC pairs with mRNA and inhibits translation.
(c) 18S rRNA
- The 18S RNA is a part of eukaryotic ribosomes, so that is why this answer is NOT a bacterial ribosomal rRNA.
(b) lncRNAs encode several regulatory proteins
- long-NON-CODING RNAs do not encode for proteins, so this statement would not be true.
(a) some of these four amino acids are specified by more than one codon
- Based on the statement given, there is a UUU and CCC codon made, but also UUC, CCU, etc.. codons. There are four amino acids created from many different codon combinations, so this draws the conclusions that the four amino acids created are specified by more than one codon.
Ex. proline = CCU, CCG, CCC, and CCA.
(d) 5’ CAC 3’ and 5’ CAU 3’
** tricky **
- Contrary to the Watson-Crick base pairing rules, there can be a Wobble Hypothesis that happens in base pairing where the 3rd codon position can vary based on what is available. Because many codons can code for the same thing (ex. Proline) the last codon position can have 2-4 different options based on the resulting amino acid.
(c) 3; start codon
- There are three possible reading frames when assigning amino acids to an mRNA sequence. Only one reading frame can be read at a time and each time an exon begins, the reading frame picks up with translation.
(e) both c and d: there is one aminoacyl tRNA synthetase for each of the 20 amino acids AND each aminoacyl tRNA synthetase recognizes a different tRNA.
- The reason why each aminoacyl-tRNA is different is because during it’s creation, tRNA binds with its respective amino acid and then giving rise to it’s unique aminoacyl-tRNA (ex. Alanine + tRNA = tRNA^ala + Ala = Ala-tRNA^ala). Each aminoacyl-tRNA synthetase recognizes a different tRNA due to the unique regions (red in the figure) which distinguish between tRNAs.
(c) rRNA in the large subunit of the ribosome
- The large subunit of the ribosome is located on top during the translation process. When using the rRNA, the large subunit is able to link amino acids together and spit them out through the top of the unit.
(b) secondary
- Beta-pleated sheets are a secondary structure form. Along with a double-helix, these are composed of smaller subunits such as a nucleotide sequence.
(b) regulatory
- Regulatory genes affect other genes during transcription or translation. They will “regulate” how processes occur in other genes, therefore their products do interact.
(a) modification of chromatin
- Chromatin is found only in eukaryotic genes. Any regulation that occurs with chromatin has to take place in a eukaryotic gene.
(c) operator
- The operator is the region attached to the promoter where the regulator protein binds to turn off transcription.
(d) repressible; repressor
- When transcription is normally ON and needs to be turned OFF, then the operon is repressible (think about the lac operon). Any regulatory protein that is involved in a repressible operon is called a REPRESSOR.
(e) CAP-cAMP loses its affinity to DNA
- Cyclic AMP is more attracted when there are low levels of glucose because it does control the levels of glucose in the body.
(d) both A and B; they bind ligands and they have catalytic activity
- You might think they have catalytic activity when thinking about ribozymes (enzymes) but we are talking about proteins. Proteins bind ligands and they can change conformation just as ribozymes and riboswitches can do.
(a) alternative splicing of pre-mRNA
- In eukaryotes, there is a nucleus where pre-mRNA splicing is the last stop before RNA is transferred into the cytoplasm as mature RNA.
(d) both A and B; Methyl groups are added to the tails of histone proteins and repression or activation of transcription occurs
- “Methyl”ated means that methyl groups are added to the tails of histone proteins. When methylation occurs, a repression or activation property happens and transcription is affected. Remember that the histone proteins are only in eukaryotes.
(e) RNA interference
- RNA interference allows for suppressed genes to be turned on or edited to allow the gene of interest to be expressed. This would be the best method. This included methods such as a dicer and RISC.
(c) inheritance of traits not coded by DNA sequence
- Epigenetics is the turning on of genes due to environmental factors. This can involve methylation patterns but overall it is traits not coded by the original DNA sequence.
(d) both A and B; causes silencing of a gene (Dnmt3) and causes increased expression of a number of genes
- The silencing of the Dnmt3 gene allows for the Queen to be larger and more distinguished from the other bees. Also, because of this silencing, it allows for other genes to be expressed more such as the increased size and reproductive abilities.
(c) basal transcription apparatus
- The basal transcription apparatus is not used to regulate gene transcription, it is simply what attracts the RNA polymerase to the promoter site and allows for transcription. to occur.
