Final Exam Review May 2024 HONORS

Molecular Biology and Genetics

Protein Synthesis

  • Process involving tRNA, mRNA, and rRNA: Translation

  • mRNA Production Location: Nucleus (in eukaryotes)

  • Amino Acid Chain from DNA Template (TCC AAT GGC TTA TTT GCA):

    • First, transcribe the DNA template into mRNA: AGG UUA CCG AAU AAA CGU

    • Then, use a codon chart to translate the mRNA sequence into an amino acid sequence: Arginine - Leucine - Proline - Asparagine - Lysine - Arginine

  • STOP Codons:

    • UAA, UAG, UGA. These codons signal the termination of translation, causing the ribosome to release the polypeptide chain.

  • Mutation Types:

    • Substitution (Point Mutation): A single nucleotide base is replaced with another.

    • Insertion: An extra nucleotide base is added into the sequence.

    • Deletion: A nucleotide base is removed from the sequence.

    • Point Mutation: A mutation affecting only one or very few nucleotides in a gene sequence.

    • Silent Mutation: A substitution that does not change the amino acid sequence due to the redundancy of the genetic code.

    • Frameshift Mutation: Insertion or deletion of nucleotides that are not multiples of three, which disrupts the reading frame and changes the entire amino acid sequence downstream.

  • tRNA Function:

    • tRNA (transfer RNA) carries specific amino acids to the ribosome during protein synthesis. It recognizes the mRNA codon through its anticodon and ensures the correct amino acid is added to the growing polypeptide chain.

  • RNA Molecule from DNA Template (AGCTCA): UC GAGU

  • Control of Gene Expression:

    • The regulation of when and where a gene is transcribed and translated into a protein. This control allows cells to produce specific proteins only when needed, conserving energy and resources. This can occur at various stages, including transcription, translation, and post-translational modification.

  • Sketch of DNA to mRNA:

    • A double-stranded DNA molecule with RNA polymerase transcribing one strand into a single-stranded mRNA molecule.

  • Process in Sketch: Transcription

Meiosis and Genetic Variation

  • Significance of Crossing Over:

    • Increases genetic variation by exchanging genetic material between homologous chromosomes during meiosis.

  • Meiosis Products:

    • Meiosis produces four genetically different haploid cells (gametes).

  • Sketch of Translocation Chromosomal Mutation:

    • A diagram showing a piece of one chromosome breaking off and attaching to another non-homologous chromosome.

  • Mutations Not Passed to Offspring:

    • Mutations in somatic cells (non-sex cells) are not passed on to offspring.

Mendelian Genetics

  • Phenotypic Ratio of Bb Pp x Bb Pp Cross (Black fur dominant over red fur, Horns dominant over no horns):

    • This is a dihybrid cross. The expected phenotypic ratio is 9:3:3:1 (9 black fur with horns, 3 black fur without horns, 3 red fur with horns, 1 red fur without horns).

  • Probability of Albinism in Heterozygous Mice Cross:

    • Albinism is a recessive trait. If both parents are heterozygous (Aa), the probability of an offspring having albinism (aa) is 25% or 1/4.

  • Blood Type Phenotypes from Heterozygous A and B Parents:

    • A mom with heterozygous A blood (AO) and a dad with heterozygous B blood (BO) can produce offspring with phenotypes A, B, AB, or O.

  • Sickle Cell Genotype Percentages (Affected x Carrier):

    • Sickle cell is an autosomal recessive trait. Crossing an affected individual (aa) with a carrier (Aa) results in:

      • Aa (carrier): 50%

      • aa (affected): 50%

      • AA (unaffected): 0%

Genetic Analysis and Evolution

  • Technique to Determine Chromosomal Abnormality in Embryo:

    • Amniocentesis or Chorionic Villus Sampling (CVS) are used to detect chromosomal abnormalities in an embryo.

  • Low Genetic Diversity in Cheetahs due to Genetic Drift:

    • Low genetic diversity can lead to increased susceptibility to diseases, reduced ability to adapt to environmental changes, and higher risk of extinction.

  • Selective Pressure for Adaptation to Find Food in Trees:

    • Competition for resources (food) is the selective pressure that most likely caused the adaptation.

  • Gradualism in Fossil Record:

    • A series of sketches showing an organism gradually changing its form over time in the fossil record. Each sketch would represent a slightly different form, showing a smooth transition.

  • Determining Closely Related Organisms from Amino Acid Chart:

    • Organisms with the most similar amino acid sequences in their proteins are most closely related.

  • Cladogram Interpretation:

    • Be able to identify which organisms share the most recent common ancestor on a given cladogram.

  • Humerus Bone in Different Organisms:

    • This represents homologous structures, indicating common ancestry and divergent evolution.

  • Faster Predator Introduced into Ecosystem:

    • The prey population would likely decrease, and natural selection may favor individuals with traits that help them evade the new predator.

  • Human Activity Reducing Species Population in a Lake:

    • Pollution, overfishing, habitat destruction (e.g., draining the lake), or introduction of invasive species.

  • Impact of Population Reduction in a Food Web:

    • Other organisms in the food web will be affected. Predators of the reduced organism may decline in population, while prey of the reduced organism may increase.

  • How Animals Acquire Nitrogen/Amino Acids:

    • By consuming other organisms (plants or animals).

  • Stored Energy in a Community:

    • Producers have the greatest stored energy.

Ecological Relationships and Energy

  • Symbiotic Relationships:

    • Mutualism: Both organisms benefit (e.g., a bee pollinating a flower).

    • Commensalism: One organism benefits, and the other is neither harmed nor helped (e.g., barnacles on a whale).

    • Parasitism: One organism benefits at the expense of the other (e.g., a tick on a dog).

  • Producers vs. Consumers:

    • There are more producers than consumers because energy is lost at each trophic level due to the second law of thermodynamics. Only about 10% of the energy is transferred from one level to the next.

  • Wildfire Impact on Carbon Cycle:

    • Wildfires release stored carbon dioxide into the atmosphere, contributing to greenhouse gas emissions.

Ecological Succession

  • Ecological Succession:

    • Decomposing pioneer plants enrich the soil with nutrients, allowing larger, more complex species like trees to grow and outcompete the pioneers.

Plant Biology

  • Plant Hormones and Functions:

    • Auxins: Promote cell elongation and apical dominance.

    • Gibberellins: Promote stem elongation, germination, and flowering.

    • Cytokinins: Promote cell division and delay senescence.

    • Abscisic Acid (ABA): Promotes dormancy and closes stomata during water stress.

    • Ethylene: Promotes fruit ripening and senescence.

  • Water Movement in Plants:

    • Water enters the plant through root hairs via osmosis, moves through the cortex to the xylem, is transported up the stem via transpiration pull (cohesion-tension theory), and exits through the stomata in the leaves.