| A | B |
|---|
| Amino acids | An organic molecule with a carboxyl and an amino group. They are the monomers of polypeptides, which coil to form proteins. In translation, the mRNA information is turned into an amino acid sequence (built from the amino side to the carboxyl side of the AA) |
| Codons | mRNA nucleotide triplets. Usually one codon corresponds to one amino acid. Ex. AUG = Met (start codon) |
| Anticodons | tRNA triplet sequences that correspond with codons on mRNA and bring the specific amino acid to the ribosome to the ribosome during translation. Ex. codon = AUU, anticodon = UAA |
| Start/stop sequence | The AUG sequence is a start codon that signals the protein-synthesizing machinery to start translating mRNA at that location. The UGA/UAC/UAA sequence signals synthesis to stop |
| C/N terminus | An amino acid sequence is built from the N-terminus (the amino side of the AA) to the C terminus (the carboxyl side). The building of this sequence occurs during translation in the cytoplasm |
| Central dogma of molecular bio | DNA codes for RNA which codes for proteins that impact an organisms phenotype |
| Where does TRANSCRIPTION occur and what does it do? | In the nucleus in eukaryotes. In the cytoplasm for prokaryotes. It uses DNA as a pattern to make mRNA, which is a form of genetic code that exits the nucleus via the nuclear pores because DNA is too large to do so |
| Transcription step 1: Initiation | a) Transcription factors attach to the promoter region (TATA box in eukaryotes) b) RNA polymerase II binds to transcription factors to form a transcription initiation complex c) DNA unwinds at the site of RNA poly II attachment |
| Promoter region | The TATA box sequence serves as part of the promoter region in eukaryotes |
| TATA box sequence | Determines which DNA strand will serve as a template. Different templates result in different RNA products and thus proteins. Serves as a promoter region in eukaryotes |
| Transcription step 2: Elongation | RNA polymerase adds nucleotides to the 3' end, so new strands of mRNA are built 5' to 3' |
| Transcription step 3: Termination | In PROKARYOTES, transcription ends when RNA polymerase reaches a terminator sequence (end product = mRNA). In EUKARYOTES, transcription ends when a polyadenylation sequence is encountered (end product = pre-mRNA) |
| Post-transcriptional modification | ONLY in eukaryotes (occurs in nucleus). A methylated cap is added to the 5' end of pre-mRNA and a poly-A tail is added to the 3' end. RNA splicing is done by the splicesome enzyme to remove introns and piece together exons. After this, mRNA is no longer pre-mRNA, and it exits via nuclear pores |
| Where does TRANSLATION occur? | In cytoplasm for both prokaryotes and eukaryotes. It uses GTP and is endergonic overall |
| Translation step 1: Initiation | a) ribosome's small subunit is bound to initiator tRNA b) ribosome moves so tRNA can bind to AUG (start), and establishes a codon reading frame c) tRNA binds to the start codon d) large subunit of ribosome is added to form translation initiation complex |
| Codon reading frame | How the body determines which three nucleotides will be read as a single codon |
| Translation step 2: Elongation | a) codons on mRNA are read by tRNA and tRNA moves from the A to P to E sites on ribosome b) tRNA adds one AA at a time c) the mRNA moves through the ribosome, 5' end first d) ribosome moves too (tRNA is released at the E site) |
| Translation step 3: Termination | a) mRNA reaches a stop codon (UUA/UUC/UUG) b) release factor binds to stop codon at A site c) water (not an AA) is added to the end of the polypeptide chain, which then exits through the exit tunnel on large subunit e) translation assembly is recycled |
| Post-translational modification | Occurs in eukaryotes and prokaryotes. Affects protein's secondary and tertiary structures. AAs removed off N terminus, cleavage/binding done to make quaternary structure, functional groups added |
| Fate of modified proteins? | Modified proteins can chill in the cytoplasm or be tagged with signal peptides. Once tagged they can be sent to a specific place in the cell (via endomembrane) or exit the cell (via secretory system) |
| Point mutations: silent | A silent mutation changes one nucleotide but wobble ensures that said change isn't shown in phenotype |
| Point mutations: missense | Changes one base pair in a way that changes an amino acid. Only mutation responsible for variations of a trait b/c it can be passed on |
| Point mutations: nonsense | Results in premature termination of protein sequence. This is the worst of the point mutations |
| Insertion/deletion mutations | Addition or subtraction of one or more nucleotides. Causes frameshift, the worst mutation of all, that throws off the codon reading frame |
| When are genes expressed? | 1. Durring development 2. New tissue production 3. Any time! Environmental changes or the presence of other organisms can cause gene expression |
| Why is gene expression modified? | 1. Life history/developmental stages 2. Specialization (in multicellular organisms) 3. Environmental changes (exogenous sex determination results in the temperature modifying gene expression) |
| How can gene activity be regulated? | {1-6 for eukaryotes, 1/2 for prokaryotes} 1. Chromatin modification 2. Transcription 3. RNA processing 4. RNA degradation 5. Controlling Translation 6. Regulating activity of protiens |
| Gene regulation 1: Chromatin modification | Occurs in both proks/euks. Condensation makes DNA no longer expressed; genomic imprinting; epigenetic inheritance (methylation or changes in histone proteins) |
| Gene regulation 2: Transcription | Occurs in both proks/euks. Affected by control elements (noncoding, and upstream, meaning near the 5' end) in genome that bind to transcription factors, which can be impacted by diet, drugs, hormones etc |
| Transcription factors | Enhancers, activators, repressors bind to sites within the promoter region during transcription and stimulate or turn off transcription |
| Gene regulation 3: RNA processing | Only in euks. Alternative RNA splicing can occur; results in interons and exons switching roles. It can be intentional or accidental. RNA sequences can also be blocked by siRNA or miRNA, which stop translation |
| Gene regulation 4: RNA degradation | Only in euks. mRNA breaks down, usually due to poly-A tail removal. Degradation speed impacts how quickly organisms can react to the environment. Prokaryotes dont have a poly-A tail but can break RNA down faster than euks |
| Gene regulation 5: Controlling translation | Only in euks. Initiation blocked (permanently or temporarily), usually by not making initiator tRNA. Also global control: all protein production turned on/off, usually by environmental cues |
| Gene regulation 6: Regulatory activity of proteins | Only in euks. Post-translational modification. Selective degradation of proteins (this happens in Huntington's, when the vesicle can't fuse with lysosome so cell accumulates toxic waste) |
| Gene expression | Creates a connection between genotype and phenotype. The product of a protein coded for by a particular stretch of DNA. Most cells within an individual have the same genome, however, very few of these genes are expressed in any one cell. It can be modified and regulated. Consists of two steps: transcription and translation |
| Factors that help populations maintain allelic or genotypic diversity | 1. Diploidy 2. Disruptive selection 3. Heterosis 4. Frequency-dependent selection |
| Diploidy | When an individual has two copies of each allele. Helps retain more polymorphism |
| Heterosis | Aka the heterozygote advantage. Heterozygotes have higher fitness than homozygotes |
| Disruptive selection | When selection favors 2 extremes rather than one intermediate trait. The two extremes are different so polymorphism is maintained |
| Frequency-dependent selection | When a more rare genotype is favored by selection. Ex: Mimicry - Mimicry only works when the mimicker is less frequent than the species that they are mimicking, ie. with milk snakes mimicking venomous coral snakes |
| Population | A group of individuals of the same species in the same space/time that can interbreed |
| Evolution | Only happens to populations; only acts upon phenotype; must happen over one or more generations |
| What are 5 forces that cause evolution? | 1. Mutations 2. Migration 3. Non-random mating 4. Natural selection 5. Genetic drift *[All decrease diversity except mutations and sometimes migration] |
| Evolutionary forces: Mutations | Mutations is the only one of the forces that only adds genetic diversity. Most mutations are bad/deleterious |
| Evolutionary forces: Migration | Can add diversity (if its coming in) or reduce diversity (if individuals are leaving) |
| Evolutionary forces: Non-random mating | Means that selection for a mate isn't based on chance. Can result in inbreeding/outbreeding depressions |
| Evolutionary forces: Natural selection | Only way to directly increase fitness |
| Evolutionary forces: Genetic drift | Random loss of alleles from a population. 2 causes are founder effect and bottleneck effect |
| Inbreeding vs. outbreeding depression | Inbreeding: fitness reduced because offspring are more likely to be homozygous. Outbreeding: fitness reduced because offspring not adapted to local environment due to very different adaptations of parents |
| Founder effect vs. bottleneck effect | Founder effect: population started by small number of individuals; can cause frequency of harmful alleles to be higher. Bottleneck: a large population shrinks drastically, seen with endangered species |
| Gene flow | The transfer of alleles between populations, can be a source of new alleles but reduces genetic differences between pops over time |
| Genetically viable populations | Those with enough individuals to avoid inbreeding depression; evolve with environmental changes; and avoid expressing deleterious mutations |
| Demographically viable populations | Those that simply have high numbers |
| Endangered species | Are at risk of extinction in the wild due to low N, low Ne and/or low genetic diversity |
| HIPPO: factors that may cause a species to become endangered | Habitat destruction; Invasive species: Population growth; Pollution; Overexploitation |
| All about ribosomes | They are made in the nucleolus and are exported from the nucleolus to the cytosol or rough ER. They have a large and small subunit with 3 tRNA binding sites, E, P, A |
| Goals of conservation genetics: | 1. Increase genetic diversity, heterozygosity, and rare genes 2. Improve zoo breeding programs (use genetics to determine mates that will produce heterozygous offspring) 3. Protect endangered species (using genetic analysis of meat or ivory to track trade and hunting of endangered species) |
| Genetic consequences of bottlenecks: | Although N (pop numbers) can recover relatively quickly, it takes years for genetic diversity to recover (400+ years). This is because only mutations result in new variations of traits, and most of them are deleterious. |
| N vs Ne | N refers to the population size as a whole. Ne refers to the members of the population that are able to produce offspring (ie. Ne= the number of individuals who contribute to the next generation's gene pool). Sometimes individuals in a pop contribute to N but not Ne (too old/young to mate, sterile, etc) |
| CITES categories (from worst off to best off) | E (extinct, not present on earth); EW (extinct in wild, still in zoos etc); CR (critically endangered); EN (endangered); VU (vulnerable); NT (near threatened); LC (least concern: no problems now/none anticipated) |
| Genetic erosion | The loss of diversity from a threatened or endangered population over time (extinction vortex describes how this happens and can doom a species) |
