exam 2 Flashcards
what is monophyletic group?
Group with a common ancestor and every one of its descendant species.
what is a paraphyletic group?
a group with a common ancestor but does not contain every descendant species
what is a polyphyletic group?
a group that does not contain a common ancestor of its members (ex: more than one common ancestor)
What is a root in a phylogenetic tree?
the basal (most ancestral) lineage on a phylogenetic tree
What is a node in a phylogenetic tree?
a branch point on a phylogenetic tree
What is a taxon in a phylogenetic tree?
a general term for a group of related organisms (ex: species, genus, etc)
What are homologous traits?
A. Traits that are functional and adaptive in one species but are not functional in another species.
B. Traits that are found in two or more species because the species have inherited this trait from their common ancestor.
C. traits that were originally selected for one function and then co-opted for a different function.
D. Traits that are found in two or more species because the species live in similar environments and independently evolved the traits due to shared selective pressure.
B.
Bats and hummingbirds both have wings and can fly. This is due to _____.
A. Divergent evolution
B. Convergent evolution
C. Co-adaptation
D. Co-evolution
B.
The basic conceptual approach to phylogenetic tree building assumes that:
A. Shared characters are homoplasies
B. Vestigial traits are not relevant.
C. Species with many characters states in common are more closely related than those with few character states in common.
C.
What is the fundamental idea behind parsimony?
A. The best phylogeny is the one that both explains the observed character data and posits the fewest evolutionary changes for a group of taxa.
B. The computed number of morphological or molecular distances between taxa indicates their relatedness.
C. The best phylogeny is the one that posits the greatest number of evolutionary changes for a group of taxa.
A.
Convergent evolution occurs when?
A. Two or more populations or species become more similar to each other because they are exposed to similar selective conditions.
B. Closely related populations or species diverge from one another because natural selection operates differently on each of them.
A.
What is synapomorphy?
A derivative trait that is shared in two populations because it was inherited from a recent common ancestor.
What is symplesiomorphy?
An ancestral character states shared by two or more lineages in a particular clade
What is polytony?
A node on a phylogenetic tree that has more than two branches arising from it.
What is a homologous trait?
A trait shared by two or more species because it was inherited from a common ancestor
What is homoplasy?
A trait that is similar in two species because of convergent evolution.
What is polarity?
The order in which different variants of a trait evolved over evolutionary time.
A type of mutation in which a region of one chromosome is moved to a different chromosome is called____?
A. Deletion
B. Translocation
C. Inversion
D. Duplication
B.
FEEDBACK: A translocation is a mutation in which a section of one chromosome moves to a nonhomologous chromosome (they could also be reciprocal if there is an exchange between nonhomologous chromosomes). A chromosomal deletion entails the loss of a large section of a chromosome. In contrast, duplication refers to an addition to the chromosomal segment and will result in additional genetic material. Finally, an inversion involves a 180° flip in a section of a chromosome. Study Figure 6.17 and compare all types of chromosomal aberrations.
An addition or deletion of one or two base pairs in a gene sequence results in a ______ mutation.
A. Transversion
B. Nonsense
C. Frameshift
D. Transition
C.
FEEDBACK: Because codons are made of three nucleotides, when an insertion or deletion mutation involves any number of codons that is not a multiple of three, it produces a frameshift mutation, which affects the translation of other codons and thus affects the production of amino acids and proteins. When an insertion or deletion mutation involves a multiple of three nucleotides, it does not disrupt the reading frame (the way in which adjacent base pairs are grouped into triplets and translated into amino acids). Examine Figure 6.16 on in-frame and frameshift mutations.
If one human protein contains 400 amino acids, how many nucleotides need to be in the exon of the corresponding gene to properly code for it?
A. 400
B. 120
C. 1200
D. 40
C.
FEEDBACK: The genetic code specifies the relation between codon triplets and the amino acids for which they code. If a polypeptide (primary structure of a protein) is 400 amino acids long, there should also be at least 400 codons in the corresponding mRNA. Each codon consists of three nucleotides, so 400 × 3 = 1200. The gene itself might be much longer than 1200 base pairs though because, at least in eukaryotes, the processed mRNA corresponds with exon sequences.
In sickle cell anemia, a point mutation leads to a replacement of one amino acid in a hemoglobin molecule, in a unit responsible for transportation of oxygen. This and any other mutation in a gene that causes a change in the amino acid sequence in a polypeptide chain is known as a __________ mutation.
A. Synonymous
B. Nonsense
C. Missense
D. Silent
C.
FEEDBACK: If the substitution causes the production of a different amino acid, such as in the case of sickle cell anemia, it is known as a missense mutation. If a base substitution does not change the amino acid that a codon normally produces, it is known as a synonymous mutation (also called a silent mutation). Finally, if a base substitution creates a stop codon where there was none previously, it is known as a nonsense mutation. Read the subsection titled “Genetic Variability and Mutation” in Section 6.3 and examine Figure 6.15.
In the 1850s and 1860s, Gregor Mendel bred pea plants and examined the way that traits were passed down across generations. His conclusions, although not accepted during his lifetime, established the foundation for the field of genetics. Of the choices listed, what is the most relevant summary of Mendel’s conclusions?
A. Garden pea plants are the best experimental model system to study heredity.
B. The hereditary factors responsible for traits such as seed shape and flower color are inherited as discrete units.
C. Recessive factors of inheritance blend after the first filial generation.
D. Hereditary material must be a nucleic acid.
B.
FEEDBACK: In the mid-1800s, a predominant view among naturalists was that traits blend together and therefore could be lost in future generations. This understanding of heredity was a limitation for Charles Darwin’s theory, and although Mendel and Darwin worked at about the same time, they did not know of one another. Mendel was an Augustinian monk and a plant breeder in the Austro-Hungarian Empire. With his fine mathematical skills, Mendel established the first genetic experiment and the discipline of genetic analysis. In his experimental research with tens of thousands of pea plants that he had bred, he concluded that traits do not blend, but rather that they are discrete in nature. Mendel named his discrete entities “factors of heredity” (today known as genes). Almost a century later, it became clear that genes are composed of DNA.
In their experiment in 1943 using E. coli, Salvador Luria and Max Delbrück tested two alternative hypotheses. The random mutation hypothesis and the acquired inherited resistance hypothesis make different predictions about the distribution of resistant mutants that will be observed upon exposure to bacteriophage (viruses that can infect and kill E. coli). Which of the following predictions, if proven, would support the acquired inherited resistance hypothesis?
A. At the time of exposure to the phage, all E. coli cells will be phage-sensitive. The process of exposure to the phage will induce phage resistance in a small fraction of the bacterial cells.
B. There will be wide variation in the number of phage-resistant E. coli colonies on each agar plate.
C. Regardless of the origin of these mutations, resistance to the phage will be heritable and will result in colonies of phage-resistant E. coli cells.
D.The phage-resistant E. coli cells will arise by random mutation even before the phage is present.
A.
FEEDBACK: Luria and Delbrück proposed two hypotheses. The first one (random mutation) predicts that prior to exposure to the phage, a few resistant E. coli cells will arise by random mutation. Once exposed to the phage, most cells will be killed, but the resistant cells will not. Instead they will reproduce and form new resistant colonies. The second hypothesis (acquired inherited resistance) proposes that at the time of exposure to the phage, all bacterial cells will be phage-sensitive. The process of exposure to the phage will induce phage resistance in a small fraction of the bacterial cells. This resistance will then be heritable, and the cells with induced resistance will go on to produce colonies of resistant cells. Compare the two hypotheses in Figures 6.20 and 6.21.
What is an important difference between transmission genetics and population genetics?
A. Transmission genetics deals with genotypes of individuals, while population genetics deals with genotype frequencies in a population.
B. Transmission genetics is based on quantitative models, while population genetics is based on qualitative models.
C. Transmission genetics requires information about inheritance, but population genetics does not.
D. Transmission genetics uses molecular biology, but population genetics does not.
A.
FEEDBACK: Transmission genetics characterizes the way the genotype of an individual offspring is related to the genotype of its parents. Population genetics deals with how genotype frequencies in a population are related to those of the parental population. Both types of genetics use quantitative models, molecular biology, and information about inheritance. See the beginning of Section 7.1 titled “Individual-Level versus Population-Level Thinking.”
What is phylogeny?
The study of the branching relationships between populations over evolutionary time.
How are phylogeny trees built up?
Analysing distribution of traits across populations.
What does phylogeny allow us to understand?
Evolutionary relationships between groups enable us to reconstruct the tree of life and gain insight into the history of evolutionary changes.
What are traits used for in phylogenetic trees?
They are used to infer patterns of ancestry and descent among populations. They are depicted on the trees.
By mapping traits onto trees what can we infer?
Possible to study the sequence and timing (history) of evolutionary events.
Are phylogenetic trees hypothesis?
Yes, they allows us to hypothesize between groups and tests it once we have additional evidence.
What are interior nodes? (Where branches meet)
Represents ancestral populations that are the common ancestors of the taxa at the ends of their branches.
What is a sister taxa?
Taxa derived from the same node.
What are two types of phylogenetic tree format? Are they the same?
Tree format or ladder format. They have the same info
Does rotating a node change relationships between taxa?
Nope, relationships are the same
When is a polytomy used for?
In cases where relationships among three or more groups are unresolved.
What is the purpose of phylogenetic tree?
The purpose is to use them is to figure out the evolutionary relationships between taxa and to identify “natural” group among taxa,those that reflect their true evolutionary relationships.
What is a clade?
A group of taxa that shared a common ancestor.
Are all classes monophyletic?
Yes
