Keystone Exam Module 2 Review Questions

Cell Cycle

• G1 Phase (First Gap of Interphase):
  • The cell grows.
• S Phase (Synthesis of Interphase):
  • The cell copies its chromosomes, resulting in the X-shape during Prophase.
• G2 Phase (Second Gap of Interphase):
  • The cell continues to grow and prepares for cell division.
• Mitosis (M Phase):
  • The nucleus and its contents divide, distributing evenly to form two daughter nuclei.
• Cytokinesis (M Phase):
  • The cytoplasm divides, resulting in two new cells.

Mitosis vs. Meiosis

Stages of Mitosis

• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase

Stages of Meiosis

• Prophase I
• Metaphase I
• Anaphase I
• Telophase I (with Cytokinesis I)
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II (with Cytokinesis II)

Chromosomal Mutations

• Original Chromosome: A B C D E F G H I J K
  • Duplication: A B B B C D E F G H I J K (Duplication of B)
  • Deletion: A B C D E F G H J K (Deletion of gene I)
  • Inversion: A B C D H G F E I J K (Inversion of F, G, H, E)
  • Duplication: A B C D D E F G H I J K (Duplication of D)
  • Inversion: D C B A E F G H I J K (Inversion of A, B, C, D)
  • Deletion: A F G H I J K (Deletion of genes B, C, D, E)
• Translocation:
  • Chromosome 1: A B C D E F G Q R
  • Chromosome 2: L M N O P H I J K
  • Mutation type: translocation

Nondisjunction

• Definition: Mutation that causes a gamete to be (n+1) or (n-1)
• (n+1) in humans:
  • $n + 1 = 23 + 1 = 24$
• (n-1) in humans:
  • $n - 1 = 23 - 1 = 22$

Sex Chromosomes

• Male = XY
• Female = XX

X-Linked Recessive Traits (Example: White-eyes in Fruit Flies)

• White-eyes is an X-linked recessive trait in fruit flies.
• Red-eyes is the dominant form.
• Cross: Heterozygous female (XRXw) x White-eyed male (XwY)
• Offspring:
  • 1 of every 2 girls will have white yes
  • lof every 2 males will have white eyes
  • lof every 2 males will have red eyes.

Blood Type Inheritance

• Man: Type A, Woman: Type B, Child: Type O
• Genotypes:
  • Man: IAi
  • Woman: IBi
  • Child: ii
• Possible blood types for future children: Type A, Type B, Type AB, Type O.
  • 1 Type AB : 1 Type B : 1 Type A: 1 Type D (they could produce any of the four blood types)

Codominance and Incomplete Dominance (Example: Horse Coat Color)

• Cross: Homozygous red horse x Homozygous white horse → Roan offspring (both red and white hairs present).
• (a) Inheritance Pattern: Codominance
  • Both colors are present, not a blending of traits.
• (b) Incomplete Dominance: Roan would be a new blend of white and red (like pink).
• (c) Cross: Roan x Roan (RR')
  • Genotypic ratio: 1 RR : 2 RR' : 1 R'R'.
  • Phenotypic ratio: 1 red : 2 roan : 1 white.

Dominant Traits (Example: Extra Digits)

• Juan: Extra digits (dominant), Alicia: Normal digits
• Extra digits = E, Normal digits = e
• Genotypes: Juan (Ee), Alicia (ee)
• Cross: Ee x ee
• Offspring: 1/2 expected to have extra digits.

Dihybrid Cross

• Cross: Tall (T), yellow (g) plant (mother was short) x Short (t), yellow (g) plant
• Genotypes: Ttgg x ttgg
• Genotypic Ratio = 8 Ttgg : 8 ttgg
• Phenotypic Ratio = 8 tall, yellow: 8 short, yellow

Pedigree Analysis

• Mode of inheritance for pedigree below: X-linked recessive (mostly males, not all generations affected)
• Instructions given regarding coloring to show autosomal dominant inheritance.

PCR (Polymerase Chain Reaction)

• Purpose: To make 100 billion identical copies of a DNA sequence within a few hours.
• Applications:
  • Diagnose diseases.
  • Identify bacteria and viruses.
  • Match criminals to crime scenes (even with small DNA samples).

Gel Electrophoresis

• Purpose: To sort and measure DNA strands.
• Applications:
  • Match individuals at crime scenes.
  • Paternity tests.
• Principle: DNA is negatively charged, so it moves toward the positive end of the gel. Shortest strands move the farthest.

Gene Therapy

• Goal: To put a corrected copy of a gene in a person (delivered through a vector) to replace a flawed one.
• To fix genetic problems at their source.

Cloning Methods

• Artificial Embryo Twinning:
  • Results in identical twins. Two babies are born to a surrogate mother, clones of each other.
• Somatic Cell Nuclear Transfer (SCNT):
  • One baby is born to a surrogate mother, and that baby is a clone of a living person (the somatic cell donor).

Lab Equipment

• Vortexes: Used to mix up samples in the lab.
• Centrifuges: Used to spin down samples and separate out contents (most dense on bottom, least dense on top).

DNA

• Blueprint of life.
• Made of nucleotides (sugar, phosphate group, nitrogenous base).
• Shape: Double helix.

DNA Complementary Strand

• Original: A C T T A G C G C T A A A T G G C T C G A T
• Complementary: T G A A T C G C G A T T T A C C G A G C T A

Gene

• Basic unit of heredity.
• Located on chromosomes.

DNA vs. RNA

Transcription (DNA → RNA)

1. RNA polymerase binds to a promoter; DNA unwinds
2. One side of DNA is used as a template and RNA polymerase adds free nucleotides (using complementary base pair rules for RNA)
3. RNA polymerase reaches terminator; new RNA is released
   • Before leaving the nucleus as mRNA, non-coding regions (introns) are removed and only coding regions (exons) will be spliced together and will exit the nucleus with the “message”

Translation (RNA → Protein)

1. mRNA binds to ribosome at the start codon (AUG)
2. Codons on mRNA are “read” and tRNA brings in the correct amino acid (codons correspond to anticodons on tRNA). Amino acids are linked together with peptide bonds in the correct order as each codon is “read”
3. Stop codon is reached and the newly made polypeptide (protein) is released
   • There are P and A sites on ribosomes. P site (left) = holds the growing chain of amino acids; A site (right) = where the next amino acid is brought in

Codon vs. Anticodon

• Both consist of a set of three bases (“triplets”).
• Codon is on mRNA, and anticodon is on tRNA.
• Anticodons correlate with the codons so each tRNA will bring in the correct amino acid.

Codon Chart

mRNA Mutations

• Original mRNA Base Sequence: AUG CCA UGG ACG CGC UGA
  • New mRNA Base Sequence: AUG CCA UAG ACG CGC UGA
    • Substitution causing a nonsense (since UAG = stop)
  • New mRNA Base Sequence: AUG CAU GGA CGC GCU GA
    • Deletion causing a frameshift
  • New mRNA Base Sequence: AUG CCA UGG UAA ACG CGC UGA
    • Insertion causing a nonsense because a stop codon was inserted
  • New mRNA Base Sequence: AUG CAA UGG ACG CGC UGA
    • Substitution causing a missense (CCA codes for Proline, but CAA codes for Glutamine)
  • New mRNA Base Sequence: AUG CCA GUG GAC GCG CUG A
    • Insertion causing a frameshift
• Silent mutation: A base substitution that results in the same amino acid being coded for.
• Point mutation: A mutation that occurs in just one base

Evidences for Evolution

1. Molecular Biology
   • Comparing DNA, RNA, amino acids in proteins in different organisms.
   • More similarities indicate a closer relationship.
2. Comparative Embryology
   • Comparing early life stages to determine relatedness.
3. Fossils
   • Using superposition, relative age, and absolute age to determine historical fossil sequence in strata.
   • Good for hard parts of animals, parts rich in minerals.
   • Soft parts and soft organisms rarely fossilize.
4. Biogeography
   • Studying the distribution of animals around the world.
   • Closely related organisms adapted to different environments in nearby regions.
   • Seemingly unrelated organisms with similar adaptations to similar environments in far apart regions.
5. Comparative Anatomy
   • Studying homologous, analogous, vestigial structures and transitional species to determine ancestry and relatedness

• Evidence cannot be 100% proven

Descent with Modification (Darwin’s 4 Points of Natural Selection)

1. Overproduction
   • More offspring are produced than can survive in the environment due to limited resources.
2. Genetic Variation
   • Individuals have different traits because they receive different alleles from their parents.
   • Some traits are better than others and provide a favorable adaptation, while other traits may put an organism at a disadvantage.
3. Struggle to Survive
   • Organisms compete for the limited resources with whatever traits they have.
   • Those with the best adaptations outcompete others, while the others die out.
4. Differential Reproduction
   • Those with more successful adaptations survive longer and reproduce more.
   • Over time, the favorable traits become the most frequent alleles in the population, as the other alleles die out

Homologous vs. Analogous vs. Vestigial Structures

Hierarchy of Life (Broadest to Most Specific)

Life → Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species

Fitness in Evolution

• The ability to survive and produce viable fertile offspring.
• Offspring must also be able to have viable offspring of their own.

Scientific Name

• Gray Wolf: Canis lupus
  • Canis is the genus.
  • lupus is the species.

Binomial Nomenclature

• Circle the terms used in binomial nomenclature to name the grizzly bear.

Cladogram

• (a) Four organisms that have jaws: tuna, salamander, turtle, leopard
• (b) One organism that has hair: leopard
• (c) Two organisms that come from an amniotic egg: turtle, leopard
• (d) Which organism has neither a vertebral column, jaws, four walking legs, amniotic egg, nor hair: lancelet

Cladogram

• (a) Organism the raccoon is most closely related to: red panda
• (b) Whether bears are more closely related to giant pandas or to red pandas: giant pandas

Genetic Drift

• Change in the gene pool of a population due to chance.
• Especially impactful in smaller populations.
  • Bottleneck effect: An event (earthquake/flood) drastically reduces population size.
  • Founder effect: Colonization of a new location by a small number of individuals.

Types of Selection

• Stabilizing selection: Average form of a trait is selected for while either extremes are selected against; this is the type of selection thought to be most common
• Disruptive selection: Both of the extreme forms of the trait are selected for, while the average trait is selected against
• Directional selection: One of the extreme forms of a trait is selected for while the other extreme form and the average form of the trait are both selected against

Allopatric vs. Sympatric Speciation

• Allopatric speciation:
  • Speciation event after geographic isolation (canyon, river, etc.).
  • Original population separates into different populations.
  • Over thousands/millions of years, populations can no longer interbreed.
  • If so, they are now two different species
• Sympatric speciation:
  • Speciation event after reproductive isolation.
  • Live in the same area but have different niches breed only with those of the same niche, or perhaps some type of sexual selection occurs.
  • Over time, they may not breed together anymore.
  • If that’s the case then they are now two different species

Adaptive Radiation

• The evolution of many new species from a common ancestor introduced to a new and diverse environment.
• Example: The 14 finch species in the Galapagos Islands likely evolved from a single small population of ancestral birds that colonized one of the islands.

Symbiotic Relationships

• Commensalism: One organism benefits, the other is neither helped nor harmed.
• Mutualism: Both organisms mutually benefit.
• Parasitism: One organism benefits (the parasite), while the other organism is harmed (the host).

Ecological Hierarchy (Biosphere to Organism)

• B = Biosphere: The thin layer of Earth where life exists
• E = Ecosystem: Consists of the biotic (living) and abiotic (nonliving) components in an area
• C = Community: Only the living organisms in an area (but all of them, regardless of species)
• P = Population: All members of a single species living at the same place and time
• O = Organism: A single individual member of the species

Food Web

• Organisms: pelican, herring, zooplankton, tuna, krill, phytoplankton, humpback whale, bacteria, great white shark.
  • a. Producer: phytoplankton
  • b. Primary consumer: zooplankton, krill
  • c. Secondary consumer: herring, humpback whale (could be tertiary too, depends on pathway)
  • d. Tertiary consumer: pelican, tuna, great white shark (if you go from phytoplankton to krill to tuna or humpback whale to the shark…though if you go from phytoplankton to zooplankton, etc. then it ends up actually being a quaternary consumer)
  • e. Decomposer: bacteria
  • f. Abiotic factors: sunlight, water, pH and salinity level of water, rocks, sand, mud, etc.
  • g. Density-dependent limiting factors: predation, disease, competition, etc.
  • h. Density-dependent limiting factors affect the population more or less dependent on how dense the population is
    • Dense populations can much more easily transfer communicable (contagious) disease through the population faster, predators do better when more prey is available but once they strain the prey population and thin out their density then the prey goes down in numbers, causing predators to also do poorly…as predators do poorly, prey starts doing better – but then in return predators start doing better, etc. (their success directly depends on the other organism’s success, or how dense the predator population is versus the prey population)
  • Density-independent limiting factors impact dense and not very dense populations the same proportionally.
    • For instance, hurricanes, tornadoes, floods, etc. will wipe out the organisms in its way (regardless of density). In this ecosystem, something like the effects of global climate change that causes ocean acidification could be a density-independent limiting factor.

Environmental Problems

1. Overpopulation
2. Global warming (climate change)
3. Deforestation
4. Ozone depletion

• Ranking and justification based on severity and impact.
• Reasons why:
  * Global warming will affect all of Earth. As sea levels rise from melting glaciers and ice caps, weather patterns will change, diseases will spread (e.x. tropical diseases), crops won’t grow in their normal locations so this will affect food supply; changing climates also mean more migration, more extinction, etc. In other words, its effects are massive and global.
  * Ozone depletion is also global, as more UV radiation also affects food supply, damages crops, affects human health (e.x. skin cancer), etc.
  * Overpopulation is also global, affecting health and sanitation worldwide with more waste produced, a greater food supply needed, etc.
  * With deforestation, this affects everyone globally as well – hurting land fertility, causing erosion, affecting oxygen levels, etc.

Global Warming

• Humans burn too many fossil fuels, releasing too much CO2, a greenhouse gas.
• The greenhouse gases are in higher concentration so even greater amounts of heat are trapped and radiated back down to Earth, warming it (too much).

Ozone Depletion

• Humans made products that release ozone-depleting chemicals.
• Chlorofluorocarbons (CFC’s) were commonly used as coolants in air conditioners, refrigerators, as propellants in hair spray cans, etc. and when released into the air, the CFC’s go up into the atmosphere. When UV radiation strikes a CFC molecule, it is broken and a chlorine atom released. The chlorine then attaches to an ozone (O3) molecule, breaking it into chlorine monoxide and O2. Then when a free atom of oxygen attaches to ClO (chlorine monoxide), the O is released as O2, leaving the Cl atom left to do it all over again. One CFC alone can destroy 100,000 ozone molecules.

Population Growth

• Exponential growth graph (labeled)
• Logistic growth model (labeled) The moose population curve after 1994 would drop and then level off between 1,400 and 1,200 moose.
• Human population: Currently growing exponentially
  • Many developed countries now follow the “demographic transition” which is like the logistic growth model but instead of hitting carrying capacity, the population is stabilizing (low growth) due to choice – choosing to have less children. Developing countries don’t always have access to contraception, birth control, good health/sanitation/medicine so in many of these countries they are still growing exponentially as they tend to have more children either out of choice (e.x. wanting more kids to help work in an agrarian society, wanting to have “enough” sons to take care of them based on certain society’s viewpoints on gender, fear that some of the children will die so wanting to have more, etc.) or out of lack of the ability to prevent it.

Biomes