DNA, Genetics, Genes Flashcards
Chromosomes
DNA swirled around protien after protein (histones) to make chromosomes, in eukaryotic
In prokaryote, loose (no nucleus)/in loops, smaller loops = plasmids
DNA
- Deoxyeribonucleic Acid, stores genetic information (to make protiens/enzymes).
- Made of nucleotides: A/G-Purines (2 rings), T/C-Pyrimidines (1 ring)
- Phosphodiester bond takes place between 3’ and 5’ carbon
- Double helix, anti-parallel
- G-C, A-T
- Genes: sequence of nucelotides that code for specific proteins (some)
- Genome (only small % codes for protiens)
DNA Replication
- Unwinding: Helicase enzymes binds/unwind (origin of replication, eukaryote may have many, prokaryote has 1) (fork of replication)
- Single Strand Unwinging Protein prevent strands from rebinding
- Positive Supercoils - DNA gyrase (topoisomerase) creates Negative Supercoils
- Primase/RNA polymerase binds to both and adds RNA primer
- RNA primer is signal to DNA polymerase to bind and start replication by adding nucleotides
- Original strand - Parent strand, New strand - Daughter strand
- Semi-conservative, one strand is new the other is kept
- Bidirectional process as DNA polymerase can only read in 3’ to 5’ direction, creating in 5’ to 3’
- More primase on lagging strand to signal DNA polymerase to backtrack and create lagging strand in Okazaki fragments (opposite direction to Helicase)
- RNA primer removed, DNA ligase bonds Okazaki fragments w/ phosphodiester bonds
RNA
- Used for protein synthesis
- Ribose sugar (instead of deoxyribose)
- Uracil (pyrimidine), not Thymine
- Single stranded, moves out of nucleus to rough ER
- mRNA (messenger RNA): DNA transcribed to mRNA, codes for protiens with ribosomes (translate), eukaryote: 1mRNA for 1 protein, prokaryote: 1 mRNA for several proetins)
- rRNA (ribosomal RNA): make up part of ribosomes (w/ proteins)
- tRNA (transfer RNA): Has codons which translate nucleotides to amino acids. Has amino acid which will add onto polypeptide chain
RNA transcription
- RNA used to prevent damage to DNA
- Happens in nucleus or mitochondria
- In eukaryote: 3 types of RNA polymerase (1 for each type of RNA)
- Initiation: Find initiation point, initiation factors find promoter region (initiation sequence of nucleotides (common sequence - consensus sequence) that signal RNA polymerase to begin unwind and copy, create transcription bubble
- Elongation: Synethsis. RNA polymerase can only read in 3’ to 5’ direction, only uses one strand (sense/coding strand, other: antisense/template strand). DNA Polymerase can fix mistakes, RNA polymerase cannot (more mistakes)
- Termination: Termination sequence (set of nucleotides that signal end of replication). Protiens help with termination
RNA Translation
- Genetic code used by ribosome to translate from RNA to protiens (central dogma, idea that information flows DNA-RNA-Protiens)
- RNA used as template, translated using codons (sequence of 3 nucelotides that code for an amino acid)
- Codons must be 3 to provide enough version for each type of amino acid, several codons can code for one amino acid (codon redundancy/degeneracy)
- tRNA has anti-codon that fits with mRNA codons
- Stop codon at end to signal end of proteins
Genotype vs Phenotype
Genotype: genetic expression of traits
Phenotype: physical expression of traits
DNA mutations
- Can be beneficial (natural selection), neutral (codon redundancy) or harmful
- Ex. Sickle cell anemia can’t be affected by HIV
- Can be caused by mistakes in replication, by chemicals/radiation
Fredrick Griffiths
1928: Serilogical testing
* Streptoccus pnuminae
* Rough strain (nonvirulent): Mouse survives
* Smooth strain (virulent): Dies
* Heat treated smooth: Mouse survives
* Heat treated smooth + rough: Mouse dies
* Transforming factor: something is transferred between strains
Avery-McCarty-Macleod
30s-40s: Find transforming factor
* Isolated major molecules (of bacteria): RNA, protiens, DNA
* If DNA broken, bacteria could not transform, proof of transforming factor
* Ignored by scientists (thought is was proteins)
Hershey-Chase/Blender expiriment
Definitive proof of DNA (50s)
* Used bacteriophages (virus that infects bacteria), sulfer w/ red dye (proteins) and phospherus w/ green dye (DNA). Only green dye was transforming
James Watson/Francis Crick
James Watson/Francis Crick: structure of DNA
Erwin Chargaff: Amount of A=T/G=C, chargaff’s rule
