1. In a cell, (nuclear) DNA is enclosed in the nucleus.
2. Division of the nucleus, called mitosis, occurs before division of the cytoplasm,
called cytokinesis.
3. The important roles of cell division—in particular, mitosis—are reproduction, growth
and development, and tissue renewal.
4. The two parts of the cell cycle are interphase and mitotic phase. During the phase that
takes most of the time (interphase), DNA replicates and during the other phase it
condenses, which is necessary before the cell can divide.
5. Chromosomes are composed of chromatin, which is a mix of DNA and structural
proteins.
6. Compare and contrast sister chromatids and homologous chromosomes. Sister
chromatids are genetically identical, while homologous chromosomes are NOT (one
came from mom, one from dad).
7. In anaphase, sister chromatids and the place where they are connected (centromere)
are separated by the mitotic spindle to make 2 cells. The DNA made in both cells is
genetically (identical).
8. Cell cycle checkpoints control the cell cycle and thus cell growth.
9. Cancer cells are different from normal cells in that they grow uncontrollably (they
ignore cell cycle checkpoints). They are not inhibited by things normal cells are,
including density (and cell size).
10. Mitotic reproduction is (asexual), while meiosis happens in (sexual).
11. What four things contribute to genetic variation? Mutations, biparental inheritance,
random fertilization and meiosis. Describe those. Mutations are random changes in
our genes. Biparental inheritance (bi=two, parental=parent) is the fact that we inherit
genes from 2 parents, thus increasing genetic variation. What two mechanisms are
there in meiosis that contribute to genetic variation? Crossing over and independent
assortment of chromosomes (chromosomes can line up in any pattern in the middle of
the cell during metaphase).
12. Mitosis produces 2 clones (genetically identical cells) while meiosis produces 4
haploid genetically different cells (gametes).
13. Humans have 23 pairs of homologous chromosomes, which can be seen in a special
test called a karyotype; each pair is genetically (different), and each chromatid of
each pair is genetically (different).
14. Crossing over, which happens at the chiasmata, occurs during what phase of meiosis?
Prophase I It creates recombinant chromosomes.
15. Synapsis happens during what phase of meiosis? What is synapsis? Prophase I;
synapsis is the pairing of homologous chromosomes (when the pairs come together).
16. During anaphase I, pairs of homologous chromosomes are pulled apart, which are
genetically (different), by microtubules attached to the kinetochore.
17. During anaphase II, sister chromatids are pulled apart, which are genetically
(different). Why are they that way? Crossing over happened!!!
18. When do we see tetrads? Meiosis I Dyads? Meiosis II and mitosis
19. After telophase II, there are 4 genetically (different), (haploid) cells that are called
gametes in humans (and other mammals).
20. When looking at the steps in each of the phases of meiosis and mitosis, what is the
key difference between meiosis I and meiosis II? Mitosis and meiosis II? In meiosis I,
homologous chromosomes are separated, while in meiosis II sister chromatids are
separated. In mitosis AND meiosis II, sister chromatids are separated; however, the
sister chromatids in meiosis II are genetically DISTINCT.
21. What errors may occur during meiosis that causes syndromes, and what are some of
those syndromes? Some chromosomes may be missing or there may be extras in
some cells, causing syndromes such as Turner, Klinefelter and Down syndromes.
22. The blending hypothesis predicts that genetic material from the parents blend in the
offspring, eventually leading to a uniform population; while the particulate hypothesis
predicts genetical material from parents are passed to offspring as discrete heritable
units, which will NOT lead to a uniform population.
23. The work of Gregor Mendel, who started the field of genetics, supports the
(particulate) hypothesis.
24. He started with the parental or (P) generation, cross-pollinated them, created the (F1)
generation and then self-pollinated those to create the (F2).
25. He discovered that the F1 offspring had the (dominate) trait and that the (recessive)
trait reappeared in the F2 offspring in a 3:1 ratio. This ratio can be demonstrated by
drawing a Punnett square.
26. This lead to his belief that everyone has two “particles,” one from each parent. They
are now called alleles. Each “particle” is found on one chromatid in homologous
chromosomes. During meiosis (anaphase I), the “particles” are separated.
27. Describe the Law of Segregation as it applies to the “particles” and to chromosomes.
Alleles are segregated during gamete production so that each gamete has only one
allele. Chromosomes are segregated during gamete production so that each gamete
has only one of that chromosome.
28. Describe the Law of Independent Assortment as it applies to the “particles” and
chromosomes. Each pair of alleles segregates independently of other allele pairs
during gamete formation. Each chromosome segregates independently of other
chromosomes during gamete formation as well—the orientation of the homologous
chromosome pair (and sister chromatids) of meiosis is random.
29. You are given a purple flower. Purple is its (phenotype). Since purple is a dominant
trait, you perform a test cross to determine its (genotype).
30. T or F: If a flower is pink but its parents were red and white, it is an example of
pleiotropy. False—this is an example of incomplete dominance!
31. What is incomplete dominance? Does it support the particulate hypothesis?
Incomplete dominance is when there is no “dominant” allele—the phenotype of the
offspring is a blend of the parents. This DOES support the particulate hypothesis
because the F2 generation has the phenotypes of the P generation and the blended F1
generation!!!
32. Compare and contrast pleiotropy and polygenic inheritance. For pleiotropy,
MULTIPLE characters are affected by ONE gene; for polygenic inheritance, ONE
character is affected by MULTIPLE genes.
33. Sickle cell disease is an example of pleiotropy.
34. Sutton’s Chromosome Theory of Heredity proposed that alleles (Mendel’s
“particles”) are present at specific loci (locations) on chromosomes.
35. Morgan did many tests on flies. He discovered wild type and mutant phenotypes.
Define those. Wild type traits are the normal, natural phenotypes. Mutant phenotypes
are unusual and not found in nature. What is a “vestigial” trait? One that causes an
organ to be small and degenerate resulting from a mutation.
36. Since the mutant phenotype was found only in males, Morgan discovered sex-linked
traits. How did his discovery relate to the Theory of Heredity? It supported
chromosome theory of heredity because he found a gene that existed on a particular
chromosome.
37. What are “sex-linked” genes? How do they cause certain disorders? Sex-linked genes
are those that are found on the sex chromosomes. Females have two X chromosomes
and males only have one; if a disease is recessive on the X chromosome, males are
more easily affected (they have either the dominant allele or the recessive allele, but
females can have AA, Aa or aa).
38. What are linked genes? Do they follow Mendel’s Law of Independent Assortment?
Those that are located on the same chromosome and thus tend to be inherited
together. They do NOT follow the Law of Independent Assortment because their
order is not independent of one another!
39. A dog that is heterozygous for two traits (i.e. BbHh) mated with a dog with recessive
genes (bbhh). The majority of the puppies (90%) had the phenotypes of their parents.
What does this suggest about the two traits? How did some puppies NOT have the
phenotypes of their parents? It suggests that they are linked! Recombination, a.k.a.
crossing over, must have occurred to create a variance in phenotypes.
40. Those puppies that didn’t have either parent’s phenotype are called recombinant
offspring.
41. The probability of recombination depends on the distance between the genes on the
chromosome and is higher when they are farther apart.
42. What is genomic imprinting? During gamete formation, some genes “silence” one of
their two alleles (so it’s not expressed). It depends on whether the allele came from
mom or from dad. (It is NOT considered “sex-linked”!)
43. Lamarck’s Theory of Evolution had two ideas. What were they? Describe them. Are
either valid? “Use and disuse”—changes in an individual’s phenotype; if you don’t
use a trait, you don’t pass it on. “Inheritance of acquired traits”—if a trait is acquired
during an individual’s lifetime, it is passed to the offspring (the genotype). Only “use
and disuse” seems valid.
44. What are Darwin’s two main ideas of his Theory of Evolution? Describe them. Are
either valid? “Descent with modification”—that all living things share a common
ancestry and that the species on Earth have changed through time. “Natural
selection”—how species have changed through time; a process of the environment
acting on species to “select” for particular traits. Both are considered valid!
45. The environment limits the population of salmon; only some live to reproduce. How
does this relate to natural selection? The environment acts on the species so that only
those salmon with the “preferred” traits survive to reproduce and pass on those
“preferred” traits.
46. T or F: Natural selection leads to perfectly adapted species. FALSE
47. Natural selection acts on the (individual). Evolution acts on the (population). Does
this mean individuals can evolve? (No!)
48. Natural selection is adaptive to the environment.
49. T or F: Evolution always leads to more complex species and explains the origin of
life on Earth. FALSE for both statements! (Evolution may lead to a simpler species!)
50. Name some key evidence supporting Darwin’s theory. Observation that although
species could reproduce to make endless individuals, populations remain stable in
size due to limited resources; artificial selection; comparative anatomy (comparing
the anatomy of similar structures throughout species); DNA sequencing; fossils;
similarities in embryos; etc. Specifically, what is artificial selection? How does it
support the theory? Artificial selection is when there is selective breeding for a
desired trait. It supports natural selection—that only traits that the environment
selects for will be passed on.
51. We say evolution acts on the population, but what about pesticide resistance? Is that
an example of an individual insect evolving? Explain. It does not support the
evolution of an individual! Those insects that have a different gene or a mutation
from the others in a population survives, thus reproducing offspring with that gene.
The population of this insect has evolved, not the individual (that one was just lucky).
52. In microevolution, a population—a localized group of organisms of the same
species—is studied by looking at their gene pool, or total composition of genes (at
that time).
53. What is allelic frequency? Why do we analyze it over and over for a population? It is
the proportion of a population that has an allele. We look at it over and over to see if
the population is evolving!
54. What does the Hardy-Weinberg theory state? Are his conditions realistic? What does
his equation show? The theorem states that allele frequencies in a population will
remain constant between generations if a population meets 5 UNREALISTIC
conditions: very large size, no migration, no mutations, no natural selection and
random mating. His equation (p2 + 2pq + q2 = 1) shows that allele frequencies will
not change through time (if the above conditions are met).
55. There are 2 main causes for microevolution. Describe each and how it affects
populations. Genetic drift is a change in the allele frequencies due to a random
chance; it can lead to allele fixation (where a gene has only one allele in the
population) and affects small populations. Natural selection is the other cause; it
results in alleles being passed to offspring in numbers unlike the frequencies of the
parental generation, adapting the population to the environment.
56. In what 2 effects can genetic drift have a huge impact? Describe them. The
Bottleneck Effect—when most of the population is killed so that some genetic
variability is lost—and the Founder Effect—when a few members of a population
establish a new population so that genetic variability is lost.
57. There are 3 modes of natural selection. What are they, and when do they occur?
Directional selection—shifting the frequency curve in one direction, common when
the environment changes; disruptive selection—the environment favors individuals
with both the extreme types of the phenotypes; and stabilizing selection—
environment acts against the extreme phenotypes.
58. Sexual reproduction (increases) (genetic) diversity within a population. Do you know
how? Meiosis—random fertilization, crossing over, independent assortment, etc.
59. Natural selection works on that diversity, (decreasing) (phenotypic) diversity within a
population. (Do you know how?) It “selects” for certain traits, decreasing the
frequency of the other traits. Plus, it doesn’t matter if your genotype is AA or Aa—as
long as you have that dominant trait and you survive in the environment, it will be
selected.
60. In spite of natural selection, there are 3 things that help to keep genetic diversity.
What are they? Diploidy (less favorable traits/alleles can remain in heterozygous, i.e.
Aa, individuals), heterozygote advantage (some individuals heterozygous for a
specific trait may have the advantage—ex. Sickle cell anemia) and neutral variation
(a particular trait has little or no impact on reproductive success just hangs out).
61. Speciation, or the origin of new species, is a way of increasing biological diversity.
How does this process occur? 2 populations have no gene flow/become genetically
isolated (no reproduction) and then differences gradually accumulate over time,
causing reproductive isolation and then 2 species!
62. There are two patterns of speciation. What are they? Do both increase biological
diversity? Anagenesis—the accumulation of heritable changes within one
lineage/species—and cladogenesis—the splitting of a gene pool, so each split gives
rise to a new species. Only cladogenesis increases diversity (1 species becomes 2).
63. Reproductive barriers can occur within a species; these barriers can be pre-zygotic or
post-zygotic. What are examples of each? Pre-zygotic: habitat isolation (species
inhabitat different habitats), temporal isolation (species breed at different times),
behavioral isolation (behaviors not compatible), gamete isolation (egg and sperm
can’t make a zygote) and anatomical incompatibility. Post-zygotic: zygote dies,
hybrid in F1 generation is infertile/sterile or there is a sterile F2 generation.
64. T or F: There is only one way to identify a species: the Biological Species Concept.
FALSE!
65. What does the biological species concept state? Individuals between 1 or more
populations that have the potential to interbreed in nature and produce viable (fertile)
offspring are one species. What are some limitations of this concept? The F1
generation is not always sterile between 2 very different populations, some
geographically isolated populations don’t have a chance to mate in nature, it doesn’t
help identify fossils and a majority of the species on earth are asexual.
66. There are two ways that speciation occurs geographically. Describe each. Allopatric
speciation is when two populations of a single species become isolated and sympatric
speciation is when two populations of a single species are not geographically isolated.
67. What is adaptive radiation? One species splits into many different species in a short
period of time (due to populations spreading out to new environments with strong
natural selection).
68. “Macroevolutionary changes accumulate through time.” What does that mean? How
did complex organs (i.e. eyes) evolve? Speciation happens from many small changes
over time, leading to large changes in populations in the future. Complex organs
evolved this way. What part of Darwin’s theory does this statement relate to? Descent
with modification—over time lineages changed…
69. T or F: Over time, trends in evolution can result from adaptations to a changing
environment…meaning that evolution is always making more complex beings.
FALSE (the first part is true, but not the second)