(Ch 10-11) Transcription/Translation Flashcards
What does a Christmas tree structure represent?
an active transcription of a gene
What is the primary structure of a protein?
The linear sequence of amino acids (stabilized by peptide bonds between adjacent amino acids)
What is the secondary structure of protein?
The alpha helix and beta-pleated sheet (stabilized by hydrogen bonds between backbone atoms of non-adjacent amino acids; no R groups are involved in bonding at the level)
What is the tertiary structure of a protein?
The 3D shape (bonding is between R groups of nonadjacent amino acids; involves disulfide bridges between cysteine residues, ionic or salt bridges, hydrogen bonds, hydrophobic interactions)
What is the quaternary structure of a protein?
Involves more than one polypeptide chain serving as subunits in a larger complex (all bond types may be involved:. Not all proteins have a quaternary structure.
Name two types of tertiary structures.
Globular or fibrous
How do sugars of RNA and DNA differ?
Sugar of RNA has a 2’ hydroxyl group that is not found in the sugar of DNA.
What type of mutation results in no change to the amino acid sequence?
Silent mutation
What is a poly-A tail?
A string of 50-150 adenine-containing nucleotides added to the trimmed 3’ end of the mRNA
What events cause a gene to suffer from “position effects”?
A gene that has been moved from one chromosomal region to another via inversion or translocation, or genes that are introduced by a virus, or genes close to where a virus is inserted
Name the two types of nucleotides and the three components of a nucleotide
a. Ribose and Deoxyribose
b. 1 pentose sugar, 1 phosphate group, 1 nitrogenous base
Name and describe the three alternative forms of DNA.
B-form - “biologically relevant, “ Watson and Crick
A-form - right-handed helix, compact, exists under dehydration
Z-form - left-handed helix, from synthetic DNA with C-G pairs
What are introns?
Non coding sequences that interrupt the coding sequences (exons) of genes. They are common in eukaryotic cells but rare in bacterial cells.
True or False: Transfer RNA (tRNA) is attached to an amino acid.
True
Where are ribosomal RNA (rRNA) located in eukaryotes?
Cytoplasm
True or False: the DNA transcription start point for the mRNA is different from the translation start point for the tRNA
True
tRNA start point AUG
Many different types of RNA are made by transcription. Which two untranslated RNAs were mentioned in class as the most clinically important and what are their functions?
miRNA-micro RNA, inhibits translation of mRNA
siRNA-small interfering RNA, triggers degradation of other RNA molecules
True or False: During transcription of a gene, only one of the two nucleotide strands of DNA are used.
True. During transcription, the strand that is used is termed the template strand whereas the other strand is called the non-template strands and is not ordinarily transcribed.
What are the three critical regions of the transcription unit?
The promoter, RNA-coding sequence, and a terminator
What is the fate of the excised piece of pre-mRNA, and what is this piece called?
The lariat is broken down unto nucleotides for recycling.
List 2 contributions to genetics that the nematode has made.
Genetics of development
Apoptosis (programmed cell death)
Genetic control of behavior
Aging
What is the basic unit of the genetic code?
A codon. A codon is a set of bases that encode a single amino acid.
What do chaperones do?
Chaperones are also called ‘heat-shock proteins’ and are present in all cells. The are responsible for the correct folding of proteins and help proteins reach their correct tertiary structure.
True or false: Histones are acidic and therefore negatively charged.
False. Histones are basic and therefore positively charged. The tails of histone proteins probably interact with the negatively changed phosphate groups of DNA.
List two things that can affect the variability in the stability of mRNA.
5’ cap
Poly-A tail
True or false: DNA mutations are genetic, and always heritable.
False. DNA mutations are genetic, but not always heritable. (A mutation in a somatic cell may not be heritable).
What is Signal Hypothesis?
Says that proteins secreted out of the cell contain an intrinsic signal that governs them to and across membranes
Who postulated the signal hypothesis?
Blobel postulated (then demonstrated) that proteins secreted out of the cell contain an intrinsic signal that governs them to and across membranes and allows for their localization in the correct location of the cell.
polycistronic transcription
a single prokaryotic transcript can carry instructions for construction of several different proteins. Only in Prokaryotes NOT in Eukaryotes.
Main Difference in translation between Prokaryotes and Eukaryotes
Prokaryotes have polycistronic transcripts while eukaryotes do not.
This means a single prokaryotic transcript can carry instructions for construction of several different proteins, while each eukaryotic transcript can be used to build just one protein.
Which is more stable eukaryotic mRNAs or prokaryotic mRNAs
Eukaryotic mRNAs are more stable due to processing and have much longer half-life in the cytosol (hours compared to minutes)
Posttranslational Modification of Proteins
Proteins are modified in several ways after they are released from the ribosome:
1) Phosphorilation of tyrosines: this activates or deactivates the protein
2) Attachement of carbohydrates (glycoproteins) in the rough ER then golgi apparatus.
3) Cleavage or trimming or the protein. (removal of signal sequences, removal of initial methionine residue, cleavage of zymogens (or proenzyme) is an inactive enzyme precursor)
4) Complexing with metals (Mag2+, Fe, etc.) Co-factors)
What is ‘wobble’?
Wobble is relaxed pairing at the third position in a codon
Which bacterial enzyme removes RNA primers from new DNA strands?
DNA Pol I
What does an initiator protein do?
Binds to origin and separates strands of DNA to initiate replication.
True or false, bacteria transcription and translation can be coupled.
True
Nucleosome is composed of what?
Histones with base-pairs of DNA around it
Which is usually cleaved out, the Exon or Intron?
Intron
Acidic amino acids (polar)
Glutamic acid, aspartic acid (COOH)
Basic amino acids (polar)
Lysine, Arginine, Histidine (NH+)
Polar amino acids
Serine
Threonine
Asparagine
Glutamine
Cysteine
Tyrosine
Non-polar amino acids
Glycine
Alanine
Valine
Leucine
Isoleucine
Proline
Methionine
Phenylalanine
Tryptophan
