BIO 1120: Exam 3 Answer Key

BIO 1120: EXAM 3 (70 PTS.) ANSWER KEY

This document includes the answer key to Exam 3 of the BIO 1120 course. The exam comprises 35 multiple-choice questions, with each question contributing 2 points worth a total of 70 points. Answers should be indicated on the provided Scantron form, and students are permitted to keep this copy of the exam for reference. An answer key will be posted on the course Pilot page later.

Organismic Energy Harvesting

  • Question 1: (Energy Harvesting in Organisms) Almost all energy used by living organisms on Earth is derived from sunlight. An exception includes bacteria that derive energy from trace chemical compounds like H2S found in deep-sea vents.

    • Key term for organisms capable of harvesting energy from light or chemical sources without needing energy-rich molecules from other organisms:
      c. Autotrophs

    • Other terms provided:

    • a. Haploids

    • b. Diploids

    • d. Heterotrophs

    • e. Polytrophs

Photon Energy and Wavelength

data,

  • Question 2: (Energy of Photons) High energy photons, such as X-rays, can damage cells by being absorbed by critical components like DNA.

    • Photon type with the most energy:
      e. X-rays (λ = 0.1 nm)

    • Other photons listed:

    • a. Visible light (λ = 500 nm)

    • b. Microwaves (λ = 1 m)

    • c. Infrared (λ = 2,000 nm)

    • d. Radio waves (λ = 1 km)

Proton Concentration in Photosynthesis

  • Question 3: (Proton Concentration in Photosynthesis) Swings in proton concentration during photosynthesis can lead to pH differences across thylakoid membranes.

    • pH inside thylakoids if external stroma pH is 8:
      a. 0.05

    • Options include:

    • b. 5

    • c. 8

    • d. 5,000

    • e. 5imes10−35 imes 10^{-3}

Krebs Cycle and Energy Extraction

  • Question 4: (Krebs Cycle Steps) Hans Krebs elucidated an 8-step pathway for energy extraction from acetyl-CoA.

    • Steps where usable energy (GTP, NADH, FADH) is harvested:
      b. 1, 3 and 1, respectively

    • Other options given included various combinations of energy outputs.

Chlorophyll and Plant Cell Color

  • Question 5: (Chlorophyll Absorption) Chlorophyll primarily absorbs visible light, except green light.

    • Part of plant cell that would show the strongest green color:
      a. The thylakoid compartment

    • Other options provided include various chloroplast parts.

Glycolysis and Krebs Cycle Location

  • Question 6: (Glycolysis and Krebs Cycle Locations) Glycolysis occurs in the cytoplasm of eukaryotic cells.

    • Location of the Krebs cycle within eukaryotes:
      a. The mitochondria

    • Alternative locations proposed were not relevant to the Krebs cycle.

RuBisCO Functionality

  • Question 7: (Role of RuBisCO) Ribulose-1,5-bisphosphate carboxylase (RuBisCO) is a large enzyme predominant in green leaves.

    • Primary substrate it uses along with ribulose-1,5-bisphosphate:
      a. Carbon dioxide

    • Other options included oxygen, citrate, pyruvate, and glucose.

Carbon Fixation

  • Question 8: (Carbon Fixation Mechanics) Carbon fixation involves converting gaseous carbon (CO2) to solid carbohydrates using energy from ATP and NADPH.

    • Source of that energy within chloroplasts:
      d. Through the light reactions of photosynthesis

    • Other processes listed were inaccurate sources of energy.

Haploid Organisms

  • Question 9: (Haploid Life Cycle) Identifying organisms with predominant haploid states.

    • Correct organism with most life in haploid state:
      c. Escherichia coli

    • Other options included corn plants, chimpanzees, guppies, and Drosophila melanogaster.

Prokaryotic Cell Division

  • Question 10: (Prokaryotic Division Mechanics) Prokaryotic cell division is simpler compared to eukaryotic.

    • Process by which prokaryotic cells divide:
      b. Binary fission

    • Other options provided convoluted terms unrelated to the division process.

The Founder of Cytogenetics

  • Question 11: (Founder of Cytogenetics) Walther Flemming established the concept of mitosis in 1878. At which point in the cell cycle are chromosomes least condensed?

    • When chromosomes are least condensed:
      a. Interphase

    • Other stages included late prophase, anaphase, metaphase, and metaphase II.

Identifying Cell Stages in Mitosis

  • Question 12: (Mitosis Imagery) Assessing characteristics featured in a late prophase versus anaphase depiction.

    • Feature that distinguishes late prophase from early anaphase:
      c. Chromosomes are highly condensed

    • Offensive distinctions listed were unrelated to chromosome condensation.

Nuclear Membrane Reformation During Mitosis

  • Question 13: (Nuclear Envelope Formation) Components of nuclear membranes reorganize at mitosis' conclusion.

    • Stage of mitosis when nucleolus and membranes reform:
      c. Telophase

    • Confusing alternatives included metaphase options and interphase stages.

Meiosis Duration versus Mitosis

  • Question 14: (Meiosis vs. Mitosis Timing) The longer duration of meiosis is attributed to the formation of the synaptonemal complex.

    • Stage of meiosis that takes longer than in mitosis:
      a. Prophase I

Germ Line versus Somatic Cells

  • Question 15: (Germ Line Cells) Germ line cells give rise to gametes, differing from somatic cells.

    • Correct disparity between germ line and somatic cells:
      b. Meiosis and mitosis both take place in germ line cells. Somatic cells only undergo mitosis.

Differences in Anaphase

  • Question 16: (Anaphase Comparisons) Examining distinctions in anaphase between mitosis and meiosis.

    • Key difference:
      d. Chromatid pairs remain attached at their centromeres in meiosis.

Cancer Understanding Evolution

  • Question 17: (Cancer Etiology) Historical context of cancer understanding diverges significantly.

    • Current leading cause of common cancers:
      e. Mutations to genes involved in control of the cell cycle.

Taxol and Cancer Cells

  • Question 18: (Effects of Taxol) Taxol, an anti-cancer drug, affects mitotic spindle formation.

    • Why Taxol is more detrimental to cancer cells:
      e. Most cancer cells are dividing uncontrollably but division of normal cells is under tight control.

Interphase Chromosome Doubling

  • Question 19: (Interphase Stages) Chromosome number doubling occurs during interphase.

    • Part of interphase where chromosome doubling occurs:
      b. S

Mendel’s Pea Plant Experiments

  • Question 20: (Gregor Mendel and Pea Plants) Mendel’s work was foundational in genetics.

    • Feature that made pea plants suitable for Mendel's experiments:
      d. They were available in several true-breeding varieties and could be grown in large numbers.

Mendel's Principle of Alleles

  • Question 21: (Mendel's Genetic Insights) Conclusion on alleles from Mendel’s research: distinct segregation without blending.

    • Comparison of allele ratios found in gametes vs. liver cells:
      a. The ratios are the same.

C-value and Complexity

  • Question 22: (C-value Understanding) The C-value refers to total DNA quantity within an organism's nucleus; it doesn’t correlate with complexity.

    • Chromosome number in salivary glands of fruit flies if unfertilized egg cells have 4 chromosomes:
      b. 8.

Phenylketonuria (PKU) Genetics

  • Question 23: (PKU Inheritance) PKU is a recessive inherited condition screened at birth.

    • Percentage of children of a PKU-affected mother and unaffected father likely to have PKU:
      a. 0%.

Effects of Untreated PKU

  • Question 24: (Consequences of PKU Without Treatment) Untreated PKU can result in various severe conditions.

    • Type of gene that causes several distinct effects:
      a. Pleiotropic.

Chiasma Formation in Meiosis

  • Question 25: (Impact of Chiasma on Cooperation Frequencies) Average of chiasma formation seen during prophase I in humans.

    • Effect on gene mapping studies:
      d. Genes that seem to be relatively far from each other may really be tightly linked.

Thomas Hunt Morgan’s Discoveries

  • Question 26: (Heritable Traits and Chromosomes) Morgan linked traits to chromosomes.

    • Conclusion regarding traits compared to chromosomes:
      c. He found that many traits were coded for on each of the four chromosomes.

Human Genetics and Pedigrees

  • Question 27: (Human Pedigree Analysis) Conclusion drawn from human pedigrees can be intricate given their generation timelines.

    • Conclusion about grandmother’s genetic states in a pedigree:
      d. She is a heterozygote for a dominant trait.

Mendelian Inheritance in Cats

  • Question 28: (Fur Color Inheritance) Inheritance of fur color among cats observed through a mating example.

    • Simplest explanation for inheritance of only black cats in litters from black and tan-colored parents:
      d. An allele for black fur is dominant to an allele for tan fur. The black cat was homozygous.

Aleutian Mink Offspring Outcome

  • Question 29: (Offspring Traits in Aleutian Mink) Analyzing coat color inheritance in minks.

    • Expected outcome coat colors of offspring:
      a. 1 Aleutian:1 brown.

Inheritance of Male-Pattern Baldness

  • Question 30: (Genetic Histories in Male-Pattern Baldness) X-linked traits such as male-pattern baldness are examined through family lines.

    • Relative most likely to have the same gene as a man with male-pattern baldness:
      e. His daughter's son.

Advantages of Genetic Mixing in Meiosis

  • Question 31: (Meiosis and Genetic Diversity) Meiosis yields a mix of chromosomes from both parents in gametes, enhancing genetic variance.

    • Advantage of this genetic mixing:
      d. It allows advantageous genes to lose their association with disadvantageous ones.

Dwarfism and Homozygous Genes

  • Question 32: (Lethal Genes and Progeny Ratios) Genes can be lethal in homozygous forms, such as in dwarfism cases.

    • Expected ratio of dwarf to normal-sized children from two dwarfs:
      c. 2:1.

Signal Transduction Pathways

  • Question 33: (Examples of Plasma Membrane Receptors) Various receptors involved in signal transduction pathways illustrated.

    • NOT an example of a plasma membrane receptor:
      b. Phosphorylation relay receptors.

Hemophilia A and Queen Victoria

  • Question 34: (Queen Victoria’s Genetics) Examining lineage transmission of Hemophilia A through genetic inheritance in her family.

    • Conclusion regarding Queen Victoria’s genotype:
      b. No, she must have had one mutant and one normal X chromosome.

Alkaptonuria and Gene Study

  • Question 35: (Pedigree Genotype Interpretation) The study of Alkaptonuria emphasized the link between genes and enzymes.

    • Genotype of individual “1” in the pedigree:
      c. aa