Part 5: Molecular Genetics Flashcards
Heterochromatin
Genetic material at is tightly wound into chromosomes, genes generally inactive
Euchromatin
Genetic material that is loose in the cell, available for transcription
Double helix
Long twisted ladder shape of DNA
Nucleotides
Subunits of DNA
5C sugar
Part of a nucleotide, ribose or deoxyribose
Nitrogenous base
A, T (U in RNA), C, or G
Adenine
A
Purine (2 rings)
Guanine
G
Purine (2 rings)
Cytosine
C
Pyrimidine (1 ring)
Thymine
T
Pyrimidine (1 ring)
Phosphodiester bonds
Linkages between nucleotides
Base pairing
Predictable matching of the nitrogenous bases of nucleic acids
A-T or U
C-G
Complementary
One strand of DNA (ideally) fits together perfectly with the other strand because of base pairing
Antiparallel
Property of DNA that strands are opposite to each other (i.e. one strand is 5’-3’ and the other is 3’-5’)
Hydrogen bonds
Bonds between nitrogenous bases on opposite DNA strands
DNA replication
Copying of DNA
Helicase
The enzyme that unwinds the DNA at the beginning of DNA replication
Replication fork
The place where the unwound DNA meets the still wound DNA, and the helicase is present to unwind the DNA
Topoisomerase
Enzyme that goes down the strand of DNA before helicase to prevent tangling and breaking of the DNA while it os being split
DNA polymerase
Adds the new nucleotides to the template strands of DNA
RNA primase
Short strand of RNA nucleotides that is attached to the 5’ end that must be replace by DNA polymerase
Leading strand
Strand that goes from 5’ to 3’ copying, so DNA replication can happen continuously
Lagging strand
3’ to 5’ strand, copied discontinuously
Okazaki fragments
Pieces of DNA formed on the lagging strand that are eventually pasted together to form a new strand of DNA
DNA ligase
The enzyme that pastes the Okazaki fragments together
Semiconservative
Half of each parent strand is conserved and used in the daughter strands
Transcription factors
Proteins that control the transfer of genetic info from DNA to RNA
Uracil
U
Replace thymine
mRNA
Messenger RNA, copies the info stored in the DNA, and carries it to the ribosome
rRNA
Ribosomal RNA, makes up ribosomes
tRNA
Transfer RNA, shuttles amino acids to the ribosomes
Protein synthesis
Transcription, RNA processing, translation
Transcription
Direct copying of the code for proteins from DNA; initiation, elongation, termination
Promoters
The special sequences of DNA at which RNA polymerase binds and transcription begins
Sense strand/template strand
Strand that is used as the template for the production of the RNA sequence
Antisense strand
The strand that is not used during transcription
New RNA will have the same sequence as that strand, but replacing T with U
RNA polymerase
The molecule responsible for traveling down the strand of DNA and correctly pairing the RNA nucleotides to form mRNA (does it split the chain?)
Exons
The regions that express the code for polypeptides
Introns
No coding regions of mRNA
Spliceosome
RNA protein complex that removes introns
Poly A tail
String of Adenines that is added to the 3’ end of the mRNA
5’ cap
Added to the 5’ end of mRNA to make transport across the nuclear membrane easier
Codon
Groups of 3 bases that code for specific amino acids
Redundant, but not ambiguous
Anticodon
Part of tRNA that matches up with the codon of the mRNA to place its amino acid on the chain
Translation
The process by which mRNA, via tRNA, creates a polypeptide chain
RNA–>protein
A, P, and E sites
Places on a ribosome where the tRNA attaches, the polypeptide is released, and exits
Primary structure of a protein
The string of amino acids in a polypeptide
Secondary structure of a protein
Alpha helix or beta-pleated sheets
Tertiary structure of a polypeptide
Folding of the polypeptide into a 3D structure
Quaternary structure of a protein
2+ polypeptides join to form protein
Chaperonins
Proteins that supervise and aid in the folding of new proteins
Mutation
A wrong sequence of DNA, and therefore RNA and polypeptides
Base substitutions
Length of the polypeptide is not changed, just a base pair is substituted for another
Missense mutations
Codon is altered in such a way that one amino acid is replaced with another
Nonsense mutations
Codon is changed in such a way that protein synthesis is terminated early
Silent mutations
Mutations that usually occur in the 3rd base of a codon and do not change the protein at all
Gene rearrangements
Mutations that affect many of the base pairs and codons, often change the length of the mRNA
Insertions
An extra base is inserted into the sequence, disrupting the entire sequence of codons
Deletions
A base pair is removed from the mRNA, disrupting the entire sequence of codons
Duplications
Result in an extra copy of genes, usually caused by an unequal crossing over during meiosis or chromosome rearrangements
Inversions
Result from changes in the orientations of chromosomal regions
Translocations
Result from chromosomal breaking and rejoining in a way that a DNA sequence or gene is lost repeated, or interrupted
Gene expression
How the genetic sequence of an organism contributes to its appearance or functions
Recombinant DNA
Combined DNA from multiple sources that creates a unique DNA not found in nature
Genetic engineering
Branch or science that creates new organisms or products by transferring genes between cells
Restriction enzymes
Enzymes used to cut certain parts out of eukaryotic DNA and plasmids (nonessential bacterial DNA) to create an insertion site for the eukaryotic DNA
Transformation
Plasmid DNA is combined with he bacteria and placed under conditions that favor the uptake of the DNA
Gel electrophoresis
The process by which DNA fragments can be separated according to their molecular weight
Restriction fragment length polymorphisms (RFLPs)
Differences between the DNA fragments of members of the same species
DNA fingerprinting
RFLPs produced from DNA left at a crime scene are compared to RFLPs from the DNA of suspects
Polymerase chain reaction (PCR)
The process by which we can make billions of identical genes in a matter of hours
DNA is placed in a test tube, which is heated and cooled rapidly. Each time the DNA is heated, the hydrogen bonds break between the strands, and Taq polymerase can add nucleotides on both sides of the DNA, creating 2 identical strands of DNA (repeated over and over again)
Lytic cycle
Lagging strand virus immediately starts using the host cell’s machinery to replicate the genetic material and create protein capsids, which spontaneously assemble into viruses and cause the cell to lyse, or break open, releasing the viruses
Lysogenic cycle
Virus incorporates itself into the host genome, remains dormant until triggered to switch to the lytic cycle
Retroviruses
Use reverse transcriptionase to convert their RNA genomes into DNA so they can be inserted into a host genome
High mutation rates, no error-proofing mechanisms
