Protein Synthesis
What three nucleotide sequence is on mRNA and calls for amino acid?
Codon
Which type of mutation changes a single nucleotide base to another? (Example: A -> G)
Point mutation
Name two lines of evidence scientists use to infer common ancestry among species.
Examples: fossil record and DNA sequence similarity (also homologous structures, embryology, biogeography).
What is natural selection in one sentence?
Darwin determined the statement of differential survival and reproduction of organisms with heritable traits that increase fitness.
What term describes the position an organism occupies in a food web, including what it eats and what eats it?
Trophic levels show where an organism is on the food chain and helps to determine level of order.
Name the molecule that brings specific amino acids to the ribosome during translation.
tRNA
Which mutation type involves insertion or deletion of nucleotides and often causes a shift in reading the codons?
Frameshift mutation
What are homologous structures and what do they indicate about relatedness?
Homologous structures are body parts with similar anatomy from a common ancestor; they indicate shared ancestry.
Define gene flow and genetic drift and give one example of each.
Gene flow: movement of alleles between populations (immigration); Genetic drift: random changes in allele frequencies (founder effect).
Using the 10% energy transfer rule, if primary producers have 50,000 kcal, how much energy is available to secondary consumers? (Show steps.)
Primary producers 50,000 kcal → primary consumers 5,000 kcal → secondary consumers 500 kcal. So secondary consumers get 500 kcal.
Where in the cell does transcription occur, and where does translation occur?
Transcription occurs in the nucleus of the cell. Translation occurs in ribosomes.
Explain why a silent mutation might not change the phenotype even though the DNA sequence changed.
Silent mutations are point mutations to a DNA strand that results in the same amino acid therefore does not change the overall protein or its function.
How can DNA sequence comparisons be used to infer evolutionary relationships?
More similar nucleotide sequences imply more recent common ancestry; sequence alignments and phylogenetic trees quantify relatedness.
Explain stabilizing, directional, and disruptive selection and give a biological example for each.
Stabilizing: favors intermediate (human birth weight); Directional: shifts mean phenotype (peppered moth during industrial melanism); Disruptive: favors extremes (beak-size divergence in heterogeneous habitats).
Define carrying capacity and name two density-dependent and two density-independent limiting factors.
Carrying capacity: maximum population size an environment can sustain. Density-dependent: disease, competition; Density-independent: drought, temperature extremes.
400 — Population: all individuals of one species in an area (e.g., wolves in Beaverhead County). Community: all interacting species in an area (e.g., wolves, deer, plants in same area).
Given the mRNA sequence CUC AAG UGC UUC, what is the amino acid sequence?
Leu-Lys-Cys-Phe
Which mutation (missense, nonsense, frameshift) is typically most destructive and why?
Frameshift mutations are the most destructive because an insertion or deletion of the nucleotide results in a shift in the reading frame of codons on the amino acid, therefore changing all the amino acids after the mutation.
Determine an example of a vestigial structure.
Examples: Pelvis bones on whales, spurs on snakes, tailbone on humans
Using Hardy-Weinberg, write the formula for calculating heterozygote frequency and explain what each symbol represents.
Heterozygote frequency = 2pq, where p = frequency of dominant allele, q = frequency of recessive allele, p + q = 1.
Explain the difference between a population and a community and give one example of each.
Population: all individuals of one species in an area (e.g., wolves in Beaverhead County). Community: all interacting species in an area (e.g., wolves, deer, plants in same area).
Describe the roles of mRNA, tRNA, and rRNA in protein synthesis and explain how they interact at the ribosome.
mRNA - "messenger" RNA that copies the DNA strand and turns into into RNA in the process of transcription
tRNA - "transfer" RNA that brings the specific amino acids to the ribosome that is complementary to the codon being read on the mRNA
rRNA - "ribosomal" RNA is the location of where translation occurs in the cell
All three RNA molecules come together in the process of translation and work together to take the instructions of the DNA to create a specific protein.
Provide a short explanation of how a point mutation in a coding sequence can cause a missense mutation and lead to altered protein function; include one concrete example (amino-acid level).
Example: a point substitution changes UUU (Phe) to UAU (Tyr) — amino acid substitution can change protein structure and impair function.
Describe three types of data (molecular, anatomical, embryological) that together strengthen a claim of common ancestry and give one specific example for each.
Molecular: similar DNA/protein sequences (e.g., cytochrome c across species); Anatomical: homologous limb bones (vertebrate forelimbs); Embryological: shared early developmental patterns (pharyngeal pouches in vertebrate embryos).
Present a short (3–4 sentence) explanation of how mutation, gene flow, genetic drift, and natural selection interact to change allele frequencies in a population over time; include which factors are random and which are non-random.
Mutations introduce new alleles (random). Gene flow moves alleles between populations (often nonadaptive). Genetic drift randomly changes allele frequencies especially in small populations. Natural selection non-randomly increases frequencies of alleles that confer higher fitness.
Describe how nutrient runoff leads to eutrophication and the likely long-term impacts on aquatic ecosystems.
Nutrient runoff also called eutrophication (N, P) → algal blooms → decomposition consumes dissolved oxygen → hypoxia/anoxia → fish and invertebrate die-offs, reduced biodiversity, altered food webs.