MCAT Bio 2.2

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MCAT Bio 2.2
2012-08-02 15:31:07

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  1. Incomplete Penetrance
    Occurs when the individual has the allele but is not expressed in the phenotype.
  2. Co-dominance
    Two of the same gene and both are dominant and both are expressed.

    ex- Blood type...IaIb gives you AB blood, IaIo gives you type A, IbIo gives you type B, and IoIo gives you type O...spotted horses and parts of the animal's skin one allele is expressed to give one color and in other areas the other allele is expressed to give the other color
  3. Incomplete Dominance
    One allele is not completely dominant over the other, thus you get a mixed phenotype.
  4. According to the MCAT, when do you have genetic linkage?
    When there is any deviation from Mendelian ratios.
  5. Gene pool
    The complete set of unique alleles in a population...small gene pool= not a lot of genetic diversity and large gene pool= lots of diversity.
  6. Evolution
    Any change to the heritable characteristics (DNA) of a species across several generations or over time.
  7. Polymorphism
    A completely unique phenotypic trait that is expressed in different members of the same species...ex- black man vs a white woman.
  8. Niche
    The way an animal lives.

    Fundamental niche - an organism in a particular environment could grow any way it wanted and feed off whatever it felt like if there was no competition.

    Realized niche - Because all species do live in competitive environments and do have more superior competitors competing with them for resources a species may have to adapt to a particular niche (way of life) to which it is most highly adapted.
  9. Natural Selection
    Non-random process by which certain alleles (traits) become either more or less common in a population due to the effects of those traits on the fitness of the individual with emphasis on those alleles that contribute to reproductive success in particular. It is a mechanism of evolution but is not evolution itself.
  10. Speciation
    When one species in different environments evolves into two different species.
  11. Adaptive radiation
    Same species with different adaptations.

    Ex. Galapogos Island finches.
  12. Evolutionary Bottleneck
    Some random event kills off a large portion of a population indiscriminately...the most fit individuals do NOT necessarily survive...these events INCREASE genetic drift bc with a much smaller gene pool random matings and assortment of gametes will have a much larger outcome on the gene pool of the population.
  13. Genetic Drift
    The random fluctuations in the allele frequencies in a population.
  14. Carrying capacity
    The population size that the local environment can support.
  15. R-selected population
    Rapid growth, numerous offspring, offspring mature rapidly and don't require a lot, if any, post-natal care. dies quickly. predominates in unstable/unpredictable environments. usually have small body size. i.e. bacteria.
  16. K-selection
    Pop size is close to carrying capacity. roughtly constant pop size. low reproduction rate, offspring large and require more post-natal care. Predominates in stable/predictable enviroments. i.e. humans.
  17. Hardy-Weinberg Assumptions
    • 1) Large population
    • 2) No mutation
    • 3) No immigration or emigration
    • 4) Random mating
    • 5) No natural selection
  18. Hardy-Weinberg Equations
    • p2 + 2pq + q2 = 1
    • p + q = 1

    • p - dominant allele frequency in a population
    • q - recessive allele frequency in a population
    • p2 - percentage of individuals with homozygous dominant genotype
    • 2pq - percentage of individuals with heterozygous genotype
  19. Taxonomy
    (Domain), Kingdom, Phylum, Class, Order, Family, Genus, Species
  20. Human Taxonomy
    Eukarya, Animalia, Chordata (vertebrae and skull), Mammalia, Primates, Hominidae, Homo, Sapiens
  21. Symbiosis
    The "living together of unlike organisms".
  22. Mutualism
    Any relationship between members of different species in which each member derives a benefit from the relationship.
  23. Commensalism
    A relationship in which one individual benefits and the other individual is not significantly harmed OR helped.
  24. Parasitic
    One member of the relationship benefits while the other is harmed.
  25. Virus
    A small infectious agent that can ONLY replicate inside the cells of another living organism.
  26. Latent period
    The virus is dormant inside the cell of another organism...means that it is there and capable of functioning but it has not started to divide and replicate.
  27. Virulence
    A measure of how likely an infection (via the virus) is to occur and how severe the symptoms are in the organism it infects after infection.
  28. Which of the following is a virus likely to be classified as?A) Highly virulent
    B) Optimally virulent
    C) Low virulent
    Optimally virulent..if the parasite/virus infects the host and causes symptoms so severe that the host dies before the virus has time to infect another host then the virus dies and thus its genetic material is less fit...this is just as bad for the virus as a virus with a low virulence that has a hard time infecting hosts.
  29. Provirus
    The viral genome that is integrated into the host's DNA.
  30. Reverse Transcriptase
    Retroviruses have RNA as their genetic material so they have a reverse transcriptase that converts their RNA into DNA which can then be inserted into the host's genome transcribed by the host cell's transcription machinery to replicate the virus.
  31. Retrovirus
    RNA virus that uses reverse transcriptase to turn its RNA into DNA.
  32. Gram Positive Characteristics
    • Stain purple (high amount of peptidoglycan retains dye)
    • Very thick cell walls
    • Form endospores
    • Single cell membrane
  33. Gram Negative Characteristics
    • Stain pink (bc the relatively low amount of peptidoglycan)
    • Relatively thin cell wall
    • Do NOT form endospores
    • Contain two cell membranes (inside and outside of the cell wall)
  34. Bacteria characteristics
    ALL bacteria are prokaryotes...they all have at least one cell membrane, a cell wall, and secrete some sort of capsule...they don't have any complex membrane-bound organelles...they have a single circular DNA chromosome and several small circular DNA molecules called plasmids.
  35. Three types of bacteria
    • Bacilli - rod-shaped
    • Cocci - round-shaped
    • Spirilla - spiral-shaped
  36. Conjugation
    The building of a sex pilus between two bacteria cells. The donor cell has to be F+ while the recepient must be F- (lacking F plasmid).
  37. Transformation
    Pick up DNA from environment
  38. Transduction
    Viruses accidentally incorporate host genetic material into their nucleic acids.
  39. Prokaryotes vs. Eukaryotes
    Prokaryotes: bacteria only , cell wall present, no nucleus but nucleoid, no membrane bound organelle, unicellular, smaller ribosomes

    Eukaryotes: protists, fungi, plants, animals, cell wall only in fungi and plants, contains a nucleus and membrane bound organelle, smaller ribosomes.
  40. Difference between mitosis and binary fission
    Mitosis occurs in eukaryotes and involves spindle fibers; does not allow for exponential growth. Binary fission occurs only in prokaryotes; no spindle fibers; allows for exponential growth.

    Both result in daughter cells that recieve full copies of parental chromosome. However, with binary fission, daughter cells may get unequal distribution of plasmids.
  41. Chemotroph vs Phototroph
    Chemotrophs gain their energy via the oxidation of chemical compounds that they get from their env't...Phototrophs get their energy by harnessing the energy of photons (light).
  42. Autotroph vs. Heterotroph
    • Autotrophs - the organism can rely on CO2 as a carbon source.
    • Heterotrophs - must consume organic materials for their carbon.
  43. Why do telomeres get shorter with each cell replication?
    Because the enzymes that copy the DNA cannot proceed to the very end of the strand. Telomeres, long repeating sections of DNA that do not contain genes, protect the chromosome from degradation. The telomeres are shortened after each replication instead of losing important gene-bearing sections of the strand.
  44. Diazotrophs
    Bacteria that can convert N2 in the atmosphere into NH3 and NH3 into NO3
  45. Fungi characteristics
    • 1) Chemoheterotrophic (they do NOT have chloroplasts)...all fungi are saprophytic (they live off dead organisms)
    • 2) They digest their food BEFORE they ingest it
    • 3) Fungi have cell walls made of CHITIN (as opposed to the cellulose that make up cell walls of plants)
  46. Fungal Reproduction
    • Fungi spend most of their life as haploid (this is their growth phase which is also called hyphae - haploid.
    • Yeasts primarily reproduce by a process called budding which is basically the same as binary fission except that it is an unequal division (one of the new cells is much larger than the other).
    • Most fungi can reproduce sexually and asexually
  47. Fungal sexual vs asexual reproduction
    When life is hard due to stress, bad environment, little food, etc fungi reproduce sexually because this increases the chances of new phenotypic traits that will be more favorable due to increased genetic variability. However, when life is good fungi reproduce asexually.