Unit 2 - Genetic Code and Mutation Flashcards
DNA neucleotide structure
A DNA neucleotide is cromprised of a sugar, one of 4 nitrogenous bases, and up to three phosphate groups
Deoxyribose / 1’3’5’ rule
*Deoxyribose is the sugar of a DNA neucleotide. It has 5 carbons denoted as 1’ 2’ 3’ 4’ and 5’
*the nitrogenous base is attached to the 1’ end, a Hydroxl (OH) is attached to the 3’, and 1-3 phosphates are attached to the 5’ end (1’3’5’ rule)
RNA neucleotide structure
*Same as DNA however Thymine (T) is replaced with uracil (U) and the sugar is ribose rather than deoxyribose
DNA replication (3)
*DNA replication is semiconservative. Each strand in the double helix acts as a template for synthesis of a new, complementary
strand.
*During DNA replication, one new strand (the leading strand) is made as a continuous piece. The other (the lagging strand) is made in small pieces.
*DNA replication requires other enzymes in addition to DNA polymerase, including DNA primase, DNA helicase, DNA ligase, and topoisomerase.
Enzymes in DNA replication (5)
*Helicase: unwinds the double helix
*DNA primase mankes an RNA primer with a 3’ end
*DNA polymerase binds neuleotids to the 3’ end made my the primer
*topoisomerase makes little nicks to relieve tension
*DNA ligase repairs the nicks left by topoisomerase and the primer
RNA synthesis (transcription) (5)
*Transcription is the process in which a gene’s DNA sequence is copied (transcribed) to make an RNA molecule.
*RNA polymerase is the main transcription enzyme. ALwys binds in 5’ - 3’ direction
*Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins).
*RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule.
*Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished.
Transription in bacteria vs eukaryotes (2)
*In bacteria, RNA polymeraise binds directally onto the promoter region of the template strand. In Eukaryotes, Basal Transcription factors (BTF) bind to the TATA sequence, which the RNA polymeraise can then bind to. (TATA -> BTF -> RNA polymeraise)
*In bacteria, termination happens when a Rho-factor seperates the template from the RNA. IN humans, the stop codon within the template tells RNA polymeraise to stop
Purine
Adine and Guanine
Pyrimidine
Thymine and Cytocine and Uracil
Leading and Lagging Strand
*DNA is made differently on the two strands at a replication fork.
*One new strand, the leading strand, runs 5’ to 3’ towards the fork and is made continuously.
*The other, the lagging strand, runs 5’ to 3’ away from the fork and is made in chunks at a time called Okazaki fragments.
mRNA
*Messenger RNA
*Produced by protien producing genes
*Short-lived intermediate between DNA and a protien
*Only type of RNA to under go TRANSLATION
Coding vs template strand
Template strand is what polymeraises read off of for Transcription, the coding strand is just the inverse of the template strand (ie A-T or C-G)
post-transriptial processing (3)
*When an RNA transcript is first made in a eukaryotic cell, it is considered a pre-mRNA and must be processed into mRNA.
*A 5’ cap is added to the beginning of the RNA transcript, and a 3’ poly-A tail is added to the end.
*In splicing, some sections of the RNA transcript (introns) are removed, and the remaining sections (exons) are stuck back together.
terminator
In bacteria, this is the Rho-factor. In eukaryotes this is the stop codon
Enhancer
enhancers increase gene expression for a specific gene (ie from green to super green eyes)
