Genetic Molecules Flashcards
Objectives 3-5 are most important 1. For the 20 naturally occurring L-amino acids found in proteins, (i) know their corresponding common names; (ii) know their corresponding three-letter abbreviations; and (iii) know their corresponding one-letter abbreviations. 2. Know the classification of side chains according to whether they are (i) aliphatic versus aromatic; (ii) nonpolar versus polar; (iii) neutral polar versus charged polar; and (iv) acidic
Which amino acids are aromatic?
Polar: Tyrptophan, Phenylalanine
Non-polar: Tyrosine, Histidine
Which amino acids are polar?
Cysteine, Asparagine, Serine, Threonine, Glutamine
Which amino acids are charged?
Postive: Arginine, Lysine
Negative: Aspartate, Glutamate
Which amino acids are Basic?
Arginine, Histidine, Lysine
Which amino acids are acidic?
Aspartate, Glutamate
Which amino acids are nonpolar?
Alanine, Leucine, Isoleucine, Glycine, Methionine, Valine, Proline
What are the five characteristics of the genetic code?
- Codons- 5’ to 3’ mRNA three base sequence that codes for a protein (binds a tRNA anticodon)
- Translation- 61/64 codons code for amino acids (start = AUG = Met)
- Termination- stop codons = UGA, UAA, UAG’
- Sequential/non-overlapping- reads three letters, one amino acid at a time.
- Degeneracy- 64 possible codons, all amino acids (except Met and Trp) can be specified by more than one codon.
What are the main difference between prokaryotic and eukaryotic mRNA?
Eukaryotic mRNA is monocistronic (single gene per coding sequence) and contains a 5’-cap and a Poly-A tail.
Prokaryotic mRNA is polycistronic and does not have a cap or tail.
What are the main differences between RNA and DNA?
DNA is double stranded and anti-parallel, contains a deoxyribose sugar, and is composed of ATCG
RNA is single stranded, contains a ribose sugar and is composed of AUCG
Describe the steps in prokaryotic DNA synthesis.
Initiation: AT-rich origin of replication is found, helicase unzips the strand, and single-strand binding proteins stabilize the cell.
Elongation: primase places short strands of RNA in the 5’ to 3’ direction, DNA polymerase synthesizes in the 5’ to 3’ direction. the 3’ to 5’ strand (leading strand) is synthesized continuously. The lagging strand is synthesized in okazaki fragments.
DNA Polymerase I excises RNA primers and replaces with DNA
DNA ligase catalyzes 3’ to 5’ phosphodiester bond formation and seals “nicks” on the lagging strand
Is a primer need for synthesis of mRNA?
No
How is supercoiling caused and what relieves it?
Prokaryotic DNA is circular and postive supercoils are produces as helicase unwinds dsDNA during replication
DNA gyrase introduces negative supercoils into the DNA to relieve superhelical tension and seperate chromosomes after replication
What are different types of DNA damage and how can they be repaired?
Deamination- NH2 replaced with O
Thymine dimers- UV energy binds two adjacent thymines
Interstrand cross linking- thymine dimers across strands
Base excision repair
Nucleotide Exision repair
What is the function of telomerase?
Linear chromosomes shorten with each cell division. Once shortened to a critical length, cells cannot divide. This shortening is caused by the lagging strands inability to complete replication.
Telomerase enzyme lenthens telomeres by repeated addition of a standard nucleotide sequence
How is PCR used to amplify specific DNA sequences?
- Strand seperation
- primer annealing
- DNA synthesis (with Taq polymerase)
- repeat
Requirements:
template DNA, primer DNA, dNTPs, Taq polymerase
