Orange Coast College Dr. Jan Goerrissen’s Spring 2017 Biology A100 Exam 3 Study Guide and Review (based on textbook questions)

Describe the process of DNA replication: the ingredients needed, the steps in the process, and the final product.
Ingredients: Original DNA, nucleotides, several enzymes and other proteins, including DNA polymerase and DNA ligase. Steps: Original DNA strands separate at a specific site (origin of replication), free nucleotides hydrogen-bond to each strand according to base-pairing rules, and DNA polymerase covalently bonds the nucleotides to form new strands. New nucleotides are added only to the 3′ end of a growing strand. One new strand is made in one continuous piece; the other new strand is made in a series of short pieces that are then joined by DNA ligase. Product: Two identical DNA molecules, each with one old strand and one new strand.
What is the name of the process that produces RNA from a DNA template? What is the name of the process that produces a polypeptide from an RNA template?
transcription; translation
A geneticist found that a particular mutation had no effect on the polypeptide encoded by a gene. This mutation probably involved . . .
A) deletion of one nucleotide
B) alteration of the start codon
C) insertion of one nucleotide
D) substitution of one nucleotide
Describe the process by which the information in a eukaryotic gene is transcribed and translated into a protein. Correctly use these words in your description: tRNA, amino acid, start codon, transcription, RNA splicing, exons, introns, mRNA, gene, codon, RNA polymerase, ribosome, translation, anticodon, peptide bond, stop codon.
A gene is a polynucleotide sequence with information for making one polypeptide. Each codon — a triplet of bases in DNA or RNA — codes for one amino acid. Transcription occurs when RNA polymerase produces RNA using one strand of DNA as a template. In prokaryotic cells, the RNA transcript may immediately serve as mRNA. In eukaryotic cells, the RNA is processed: A cap and tail are added, and RNA splicing removes introns and links exons together to form a continuous coding sequence. A ribosome is the site of translation, or polypeptide synthesis, and tRNA molecules serve as interpreters of the genetic code. Each folded tRNA molecule has an amino acid attached at one end and a three-based anticodon at the other end. Beginning at the start codon, mRNA is moved relative to the ribosome a codon at a time. A tRNA with a complementary anticodon pairs with each codon, adding its amino acid to a polypeptide chain. The amino acids are linked by polypeptide bods. Translation stops at a stop codon, and the finished polypeptide is released. The polypeptide folds to form a functional protein, sometimes in combination with other polypeptides.
The nucleotide sequence of a DNA codon is GTA. A messenger RNA molecule with a complementary codon is transcribed from the DNA. In the process of protein synthesis, a transfer RNA pairs with the mRNA codon. What is the nucleotide sequence of the tRNA anticodon?
The base sequence of the gene coding for a short polypeptide is CTACGCTAGGCGATTGACT. What would be the base sequence of the mRNA trancsribed from this gene? Using the genetic code in Figure 10.8A, give the amino acid sequence of the polypeptide translated from this mRNA. (Hint: What is the start codon?)
mRNA: GAUGCGAUCCGCUAACUGA; amino acids: Met-Arg-Ser-Ala-Asn
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Which of the following did not influence Darwin as he synthesized the theory of evolution by natural selection?
A) examples of artificial selection that produce large and relatively rapid changes in domesticated species
B) Lyell’s Principles of Geology, on gradual geologic changes
C) comparisons of fossils with living organisms
D) Mendel’s paper describing the laws of inheritance
Natural selection is sometimes described as “survival of the fittest.” Which of the following best measures an organism’s fitness?
A) how many fertile offspring it produces
B) how strong it is when pitted against others to its species
C) its ability to withstand environment extremes
D) how much food it is able to make or obtain
In an area of erratic rainfall, a biologist found that grass plants with alleles for curled leaves reproduced better in dry years, and plants with alleles for flat leaves reproduced better in wet years. This situation would tend to __________. (Explain you answer)
A) cause genetic drift in the grass population
B) preserve genetic variation in the grass population
C) lead to stabilizing selection in the grass population
D) lead to uniformity in the grass population
B (Erratic rainfall and unequal reproductive success would ensure that a mixture of both forms remained in the population.)
If an allele is recessive and lethal in homozygotes before they reproduce, . . .
A) the allele will be removed from the population by natural selection in approximately 1,000 years
B) the allele will likely remain in the population at a low frequency because it cannot be selected against in heterozygotes
C) the fitness of the homozygous recessive genotype is 0
D) both b and d are correct
In a population with two alleles, B and b, allele frequence of b is 0.4. B is dominant to b. hat is the frequency of individuals with the dominant phenotype if the population is in Hardy-Weinberg equilibrium?
A) 0.16
B) 0.36
C) 0.48
D) 0.84
It seems logical that natural selection would work toward genetic uniformity; the genotypes that are most fit produce the most offsring, increasing the frequency of adaptive alleles and eliminating less adapative alleles. Yet there remains a great deal of genetic variation within populations. Describe some of the factors that contribute to this variation.
Genetic variation is retained in a population by diploidy and balanced selection. Recessive alleles are hidden from selection when in the heterozygote; thus, less adaptive or even harmful alleles are maintained in the gene pool and are available should environmental conditions change. Both heterozygote advantage and frequency-dependent selection tend to maintain alternate alleles in a population.
(Look in Orange Coast College Biology Concepts and Connections textbook 2nd edition for the data) A population of snails is preyed on by birds that break the snails open on rocks, eat the soft bodies, and leave the shells. The snails occur in both striped and unstriped forms. In one area, researchers counted both live snails and broken shells. Their data are summarized below: Which snail form seems better adapted to this environment? Why? Predict how the frequencies of striped and unstriped snails might change in the future.
The unstriped snauls appear to be better adapted. Striped snails make up 47% of the living population but 56% of the broken shells. Assuming that all the broken shells result from the meals of birds, we would predict that bird predation would reduce the frequency of striped snails and the frequency of unstriped individuals would increase.
Which concept of species would be most useful to a field biologist identifying new plant species in a tropical forest?
A) biological
B) ecological
C) morphological
D) phylogenetic
The largest unit within which gene flow can readily occur is a . . .
A) population
B) species
C) genus
D) phylum
Bird guides once listed the myrtle warbler and Audubon’s warbler as distinct species that lived side by side in parts of their ranges. However, recent books showed them as eastern and western forms of a single species, the yellow-rumped warbler. Most likely, it has been found that these two kinds of warblers . . .
A) live in similar habitats and eat similar foods
B) interbreed often in nature, and the offspring are viable and fertile
C) are almost identical in appearance
D) have many genes in common
Which of the following is an example of a postzygotic reproductive barrier?
A) One Ceanothus shrub lives on acid soil, another on alkaline soil
B) Mallard and pintail ducks mate at different times of year
C) Two species of leopard frogs have different mating cells
D) Hybrid offspring of two species of jimsonweeds always die before reproducing
Biologists have found more than 500 species of fruit flies on the various Hawaiian Islands, all apparently descended from a single ancestor species. This example illustrates . . .
A) polyploidy
B) temporal isolation
C) adaptive isolation
D) sympatric isolation
A new plant species C, which formed from hybridization of species A (2n = 16) with species B (2n = 12), would probably produce gametes with a chromosome number of . . .
A) 12
B) 14
C) 16
D) 28
A horse (2n = 64) and a donkey (2n = 62) can mate and produce a mule. How many chromosomes would there be in a mule’s body cells?
A) 31
B) 62
C) 63
D) 126
What prevents horses and donkeys from hybridizing to form a new species?
A) limited hybrid fertility
B) limited hybrid viability
C) hybrid breakdown
D) gametic isolation
Which of the following factors would not contribute to allopatric speciation?
A) A population becomes geographically isolated from the parent population
B) The separated population is small, and genetic drift occurs
C) The isolated population is exposed to different selection pressures than the parent population
D) Gene flow between two populations continues to occur
Explain why allopatric speciation would be less likely on an island close to a mainland than on a more isolated island.
There is more chance for gene flow between populations on a mainland and nearby island. This interbreeding would make it more difficult for reproductive isolation to develop and separate the two populations.
What does the term punctuated equilibria describe?
The term punctuated equilibria refers to a common pattern seen in the fossil record, in which most species diverge relatively quickly as they arise from an ancestral species and then remain fairly unchanged for the rest of their existence as a species.