Biology final

In class, we discussed the role that various processes can play in the human sexual life cycle. Which of the following best describes the role that fertilization plays in this life cycle?

Fertilization restores the chromosome number by fusing haploid nuclei into a diploid zygote

Which of the following is TRUE regarding the steps of the cell cycle?

G2 phase is characterized by cell growth and prep for cell division. Chromosomes have already been replicated by the time the cell enters this phase.

Why does dosage compensation/inactivation occur for X chromosomes, but NOT for autosomal chromosomes?

Human cells contain 2 copies of every autosomal chromosome, so no dosage compensation is needed.

Which of the following BEST demonstrates the this idea? "The amount and distribution of yolk in the egg affects cleavage and blastocoel formation"

If the yolk is moderate and concentrated at one pole of the egg, this will lead to asynchronous division.

Imagine you have discovered a new species of sea urchin. You have collected a sea water sample that contains sperm and egg from this species. After looking at these cells, you discover that the gametes each have n = 4 chromosomes, and these unreplicated chromosomes have a mass of 2 pg. Which of the following is an accurate conclusion you could draw about the somatic cells of this animal?

In G1, somatic cells would contain 8 chromosomes and 4 pg of DNA.

In class, we learned about the role of induction in pattern formation. Which of the following is an example of induction in this process?

In Spemann and Mangold (1924), the transplanted dorsal lip caused the formation of dorsal features (including the neural tube) on the ventral side of the gastrula.

In class, we spent time discussing the law of independent assortment as it relates to both meiosis and Mendelian inheritance. Which of the following statements provides an example of this idea?

Independent assortment occurs when tetrads line up independently along the metaphase plate in meiosis I. Mendel demonstrated how independent assortment allowed for new phenotypic combinations of traits to arise in offspring.

For the trait color blindness, individuals can inherit dominant alleles (normal color vision) or recessive alleles (color blindness). Assume an individual who is heterozygous for this trait produces a child with an XY individual who has normal color vision. Which of the following statements is FALSE regarding predictions about the phenotype of the offspring?

It is not possible for the child to be color-blind from this cross.

Which of the following is NOT an example of how changes in cell movement play a role in embryonic development?

Microtubules constrict at one end of ectoderm cells, causing a them to form a wedge during neurulation.

Which of the following was the conclusion of the experiment conducted by Johnson and Rao (1970)?

Molecules present in the cytoplasm trigger and coordinate events in the cell cycle.

Which of the following BEST describes the reasoning for why mutations in homeotic genes can produce major changes in morphology?

Mutations in homeotic genes can lead to major changes in morphology, even producing new species over time.

Assume that, when this operon is in the current state as shown above, that there is no transcription of genes 1, 2 and 3. Is this figure of an operon an example of positive or negative regulation? How do you know?

Negative regulation; the function of the regulatory protein is to shut down transcription of the genes in the operon.

Which of the following is NOT an example of how checkpoints internally regulate the cell cycle?

PDGF can signal to a cell to grow and divide.

Thalidomide was a drug used in the 1950s and 1960s to cure various issues such as insomnia, gastritis, and tension. Women used it during pregnancy to alleviate morning sickness; many of these women gave birth to children who had arm and leg defects but were otherwise healthy. This outcome suggests that thalidomide most likely influenced _____.

Pattern formation

In class, we discussed the role of meiosis, mitosis, and fertilization in the sexual life cycle. Given this, how do these processes relate to chromosome number? Fertilization______ chromosome number. Meiosis______ chromosome number. Mitosis_____ chromosome number.

restores, reduces, conserves

Which of the following BEST describes the role of the universality of the genetic code in terms of the evolutionary history of life?

The universality of the code suggests that this code was present in a very early common ancestor to all present day organisms and has been preserved throughout evolutionary history.

Which of the following is TRUE for a cell that is 2n = 60?

There will be 30 tetrads during metaphase I of meiosis I.

How do the size of a zygote and a blastula compare?

They are the same size; the early cell divisions result in an increased number of cells but do not increase the amount of cytoplasm during each instance of mitosis.

As a biologist, you come across a new insect species. You are trying to identify the mechanism of sex determination for this species. You karyotype and mate different individuals of this species and find the following information: - There is no Y chromosome - Sex determination is independent of factors such as temperature and social environment. - All individuals have X chromosomes, but some have more than others. Which of the following is the BEST conclusion you can draw, based on this information?

This is most likely X0 sex determination since there is no Y chromosome and other factors do not determine sex in this species.

You are studying gastrulation in a new species of organism. You observe the following details:

Triploblast, protostome. This organism's development is similar to a Planaria worm.

Gene Q codes for a morphogen that regulates the anterior-posterior axis of an insect. High concentrations of the Q morphogen result in the formation of structures associated with the anterior/head of the animal. In a hypothetical study, researchers were able to decrease the acetylation of gene Q, making gene Q unacetylated. What effect could this have on development?

Unacetylated genes are not easily accessible for transcription because the DNA is compact. The expression of gene Q will be decreased, potentially resulting in no formation of an anterior/head region in the insect.

Which of the following is TRUE regarding the Steward's (1950s) carrot experiment and Gurdon et al. (1975) nuclear transplantation experiment?

While both studies supported the "differential expression of genetic material" hypothesis, Gurdon et al. (1975) highlighted the role of differentiation on the genetic potential of a nucleus.

Which of the following statements is TRUE regarding the structures in this figure? Correct!

While cell division does take place between structures (C) and (D), these structures are the same size.

Imagine that I asked you the following question: "What is the probability of producing an offspring with the genotype aabbcc from the following mating? AaBbCc x AaBbCc" We can think of the genotype of a single locus (gene) as a single independent event. Given this information, would you use the "AND" or "OR" rule to answer this question?

"AND" rule, because this rule predicts the probability of observing multiple independent events. The outcome of each event is not influenced by the other.

Parent A has the genotype AaBbDD and parent B has the genotype aabbDd. Assuming complete dominance and independent assortment, what proportion of the progeny will be expected to phenotypically resemble Parent A?

1/4

How many different kinds of genotypes are possible among offspring produced by the following two parents? DdQQRr x ddQqRr

12

Imagine you discover a new proto-oncogene involved in the development of cancer. You predict three different ways in which the gene may be mutated to result in uncontrolled cell growth (i.e. cancer). Which of the following would NOT be a prediction you would make?

A mutation produced a defective transcription factor that failed to inhibit cell division.

Which of the following MOST accurately describes a theory and hypothesis in science?

A theory is broad and well substantiated, while a hypothesis is a proposed explanation. Both are consistent with available evidence of the natural world.

Henrietta Lacks was a woman whose cervical cancer cells were obtained during a biopsy in the 1950s. These cells have been grown in cultures ever since (without her knowledge or permission). Over these many years, researchers around the world have obtained samples of these immortal and constantly dividing "HeLa" cells on which to perform a wide variety of research. Recently, the findings of some HeLa-cell research have been questioned because scientists argue that results based on populations of HeLa cells 10 years ago (for example) may not be comparable to results obtained using populations of these cells today. Which of the following BEST describes a potential explanation for this argument?

Although mitosis produces identical cells, mutations have likely occurred that make direct comparisons and extensions of research on these cells over long periods of time problematic.

Which of the following BEST describes a role cytoplasmic determinants (CDs) play in animal embryonic development?

CDs present in the gray crescent direct development of dorsal features such as the neural tube in amphibians.

Which of the following is TRUE regarding cell differentiation and cell determination? Correct Answer

Cell determination results in the expression of tissue-specific proteins that give cell types their unique structure and function.

What is the relationship between cell division, cell differentiation, and gene regulation?

Cell division alone would result in a big ball of undifferentiated cells. Cell differentiation occurs as a result of regulation of certain genes, leading to specialized structure and function of cells.

In a hypothetical study, researchers discovered a new species of animal and analyzed the yolk of their egg cells. The researchers found the following: the egg contains a lot of thick yolk, and the yolk that is present is evenly distributed throughout the egg cell. Which of the following predictions is the BEST, given this information?

Cell division will be synchronous, but may not penetrate the yolk at all, confining cell division to a location containing just nucleus and cytoplasm.

Assume you are researching characteristics of the stages of animal embryonic development in a new species of amphibian. At a particular point in development, you note the following: - Cell division is occurring - Regulation of gene expression in cells is taking place - Cells are moving to different parts of the structure Which of the following stages of animal embryonic development could you rule OUT in this case? Why could it NOT be this particular stage?

Cleavage. This stage results in a blastula, which is hollow ball of undifferentiated cells, so no gene regulation or movement is not a characteristic of this stage.

In class, we discussed the experiment by Morgan and Lynch (1912) on linkage. Based on this study, what is the relationship between crossing over and linkage?

Crossing over can disrupt the physical linkage of two genes on a chromosome.

In class, we discussed the various ways that genetic variation is generated via meiosis. Which of the following is TRUE regarding crossing over?

Crossing over involves generating new allelic combinations along the length of sister chromatids

Which of the following BEST describes a limitation of methods used for cloning?

Dedifferentiating (reprogramming) the DNA in cells for cloned embryos leads to increased methylation.

Imagine a cell that is 2n = 50. Which of the following is TRUE regarding this cell?

During prophase II of meiosis II, each daughter cell will contain 50 sister chromatids.

Thyroxin hormone levels can determine pattern formation in spadefoot tadpoles, depending on environmental signals. Which of the following is NOT an example of how these tadpoles exhibit developmental plasticity?

Environmental signals do not cause differences in gut morphology between carnivores and omnivores.

Consider an E. coli cell that contains the tryp (tryptophan) operon. Assume there is a mutation in the regulatory protein of this operon, that makes the regulatory protein unable to assume its active form, regardless of the presence of tryptophan. Which of the following is TRUE regarding the enzymes encoded by the tryp operon in this cell?

Enzymes needed for tryptophan synthesis would always be produced.

Hydrangeas will be blooming soon! These plants have different flower colors depending on the pH of the soil they are planted in. Imagine that two hydrangea plants with identical genotypes are planted in two separate yards. One hydrangea produces pink flowers, while the other produces blue flowers. These individuals are bred together to produce offspring. The offspring are planted in a new yard, and produce purple-ish flowers. Based on this information, these phenotypes can BEST be explained by______.

Phenotypic plasticity; environmental factors affect the phenotype.

Biologically, why would an urchin egg cell evolve to prevent against polyspermy?

Polyspermy results in two many sets of chromosomes, with chromosomes apportioned unequally in blastomeres.

Which of the following is FALSE regarding the scientific method, theories, and hypotheses?

Predictions are proposed explanations for an observed phenomenon that is based on knowledge and consistent with available evidence

Imagine a scenario in which the regulatory protein in the figure above had a mutation. This mutation would disallow the protein to assume its active form, causing it to remain inactive. Which of the following is the MOST likely outcome, given this scenario?

Proteins 1, 2, and 3 from the genes in this operon would always be produced.

Spemann and Mangold (1924) transplanted dorsal lip cells from one gastrula to another, and concluded that the dorsal lip played a role in organizing the dorsal region of the embryo. It is known that the dorsal lip contains "gray crescent". Why is this significant?

The "gray crescent" region in frog embryos contains CDs that signal for the development of dorsal features.

What is the relationship between the gray crescent, blastopore, and neurulation?

The blastopore forms on the future dorsal side of the blastula, just below the gray crescent. The dorsal lip of the blastopore therefore contains CDs necessary for formation of dorsal tissues, such as those in neurulation.

In an experiment with fruit flies, researchers "knocked out" the bicoid protein, making it nonfunctional. What were the results of this study, and how were these results interpreted? Correct!

The formation of two posterior ends due to the absence of bicoid expression; bicoid protein is a morphogen specifying head-specific structures.

A true breeding red flowered plant is mated with a true breeding yellow flowered plant (P generation). Flower color in this plant is controlled by a single gene. Their F1 offspring are all orange-flowered. Two of these orange-flowered plants are mated together, and produce an F2 generation of 100 offspring. 25 offspring are red, 50 offspring are orange, and 25 offspring are yellow flowered. Which of the following is the BEST statement regarding this scenario?

The gene exhibits incomplete dominance, because the phenotypic ratio = 1:2:1 in the F2 generation.

Assume you are a researcher investigating the regulation of expression of gene A. You discover that in a particular eukaryotic cell, there is decreased expression of gene A. Which of the following is the BEST example of a possible point of control that could explain this observation?

The histones associated with gene A are unacetylated, resulting in decreased transcription of this gene.

Which of the following BEST describes a difference between Mendel's monohybrid and dihybrid crosses?

The monohybrid cross was concerned with a single locus, while the dihybrid cross was c

Imagine that during meiosis I, a mutation in a cell results in the failure of microtubules to bind at the kinetochores on some chromosomes. Which of the following is the MOST likely result of such a defect?

The resulting daughter cells will not receive the correct number of chromosomes.

Imagine there was an abnormality with the sperm in this figure, causing the acrosomal process to fail to penetrate the jelly coat in step [2]. What do you predict would happen in the fertilization process?

The sperm and egg would likely fail to recognize each other via their bindin and receptor proteins, so step [3] is unlikely to proceed.

Imagine a diploid cell in G1 that contains 40 pg of DNA. Which of the following is TRUE regarding this cell and mitosis?

in G2, the cell will contain 80 pg of DNA.