Ribosomes Flashcards
(8 cards)
Why did Woese and Fox base their musings on rRNA genes?
Because they hypothesized that it would be slow to evolve and that mutations would not be tolerated
What are ribosomes responsible for?
Translating mRNA into protein
Describe the different structures to rRNA
Begins as 16S rRNA, which is simply a long strand of RNA that folds into an intricate, 2D pattern. It then folds more into a 3D shape that is bound by proteins to form the 30S ribosomal subunit . It then turns into a complete 70S ribosome, which results when the 30S subunit (small) is joined to the 50S subunit (large). The 50S subunit is comprised of 2 rRNA species (23S and 55S) and 34 proteins, while the 30S subunit is composed of the 16S rRNA and 19 proteins. A base change in the piece of rRNA that scaffolds the 30S subunit would not be well tolerated.
What are differences and similarities between the ribosomes of bacteria, archaea, and eukaryotes? Which two are more closely related?
The sedimentation coefficients are the same for bacterial and archaeal subunits; however, there are more proteins bound to the archeal subunit, and these proteins have sequence similarity to proteins found in similar roles in the eukaryotic small subunit. The archaeal enzyme is therefore more similar to eukaryotic than prokaryotic ribosomes. Accessory proteins are very similar between archaea and eukaryotes; archaeal proteins (when purified) can function when mixed with eukaryotic ribosomal preparations. Other evidence, such as enzymes involved in DNA synthesis and the fact that both archaea and eukaryotes use histone packages to package DNA, shows that archaea are more closely related to eukaryotes.
Steps to take if a new form of life was found
- First obtain a sample and isolate DNA
- Use specific primers and polymerase chain reaction to amplify ribosomal DNA gene sequences
- Obtain chromatograms with waves for each DNTP (grey Gs, green As, red Ts, blue Cs)
- Use the chromatograms to determine the DNA sequence of the amplicons
- Using data processing and bioinformatic analysis, the DNA sequence will be compared to known ribosomal DNA sequences
Give the genome organization, membrane composition, cell wall structure, antibiotic sensitivity, DNA packaging, motility, and organisms of bacteria
Prokaryotic, unbranched fatty acid chains attached to glycerol by Ester linkages, pepidoglycan, unique, nucleoid associated proteins (NAPs), flagella rotate
Examples include gram-positive, gram-negative, mycobacteria, mycoplasma, and cyanobacteria
Give the genome organization, membrane composition, cell wall structure, antibiotic sensitivity, DNA packaging, motility, and organisms of archaea
Prokaryotic, branched hydrocarbon chains attached to glycerol by ether linkages (making them more stable and able to withstand high temperatures and acid concentrations), unique (LACK peptidoglycan), not unique, histones, archaella rotate
Examples include methanogens, extreme halophiles, and hyperthermophiles; abundant in environments that are hostile to all other life forms (outlier organism) - many do not require sunlight for photosynthesis or oxygen for respiration
Give the genome organization, membrane composition, cell wall structure, antibiotic sensitivity, DNA packaging, motility, and organisms of eukarya
Eukaryotic, unbranched fatty acid chains attached to glycerol by ester linkages, LACK peptidoglycan (some have cell walls, some do not), not unique, histones, flagella whip or beat
Examples include animals, fungi, plantae, and protists
