BIOL 1306 General Biology I Chp 21 HW

Chapter 21 Question 9 QUANTITATIVE Imagine a situation in which a morphogen has its source at the posterior end of a Drosophila embryo. Every 120 μm from the posterior pole, the morphogen concentration decreases by 1/3. If a cell required 1/27th the amount of morphogen found at the posterior pole to form part of a leg, how far from the posterior pole would the leg form?

360 μm

Pattern Formation A. Which of the following statements about pattern formation are true? B. Classify each phrase or term as applying to fly A only, fly B only, or both fly A and fly B. The term "Hox genes" applies to clusters of homeotic genes found in many different animals, including fruit flies. After segmentation genes have established the body segments, Hox genes trigger the development of segment-specific body structures in the correct locations. For more on Hox genes, see Hints 2 and 3.

A. -Positional information controls pattern formation. - Differential gene expression affects the developmental process in animals. -Homeotic genes code for transcription factors that control the development of segment-specific body parts. - Cells receive molecular signals that communicate their position in relation to other cells. B. Fly A ONLY: "wild type," "possesses normal Hox genes," "exhibits normal pattern formation" Fly B ONLY: "exhibits abnormal pattern formation," "homeotic mutant," "possesses mutant Hox genes' Both Fly A and Fly B: "produces transcription factors triggering gene expression for segment-specific structures"

HHMI Video: The Making of the Fittest: Evolving Switches, Evolving Bodies (Stickleback) A. How did some stickleback populations come to live exclusively in fresh water? B. Why do some stickleback populations lack pelvic spines? Select all that apply. C. Why did Kingsley and his team cross marine and freshwater sticklebacks? D. What did researchers discover about the genetic mutation causing the loss of pelvic spines? Select all that apply. E. Bell and collaborators painstakingly documented a population of fossil sticklebacks from an ancient freshwater lake over a 20,000-year period. The prevalence of sticklebacks with full and reduced pelvises changed over time. Which is true? F. How do multiple lines of evidence (from the field, the fossil record, and molecular genetics) work together to illustrate stickleback evolution? Select all that apply.

A. Some stickleback populations became trapped in lakes that formed at the end of the last ice age. B. - In lakes with dragonfly larvae, pelvic spines can be disadvantageous, allowing the predatory larvae to grab the fish -In lakes where there are no large predatory fish, there is no advantage to having pelvic spines. C. To find the location of the gene(s) causing the difference between stickleback populations with and without spines. D. -It occurred in a similar DNA region in freshwater stickleback populations all over the world. -It is found in a regulatory region (a "switch") upstream of the coding region of the Pitx1 gene. E. The population of fish with pelvic spines that arrived in the lake at time B evolved a reduced pelvis over time (beginning at time C). F. -If the same morphological changes occur in the fossil record as in living populations, we might deduce that the genetic mechanism discovered in the living populations might be responsible for the changes observed in fossils. -The fossil data show a pattern of evolution over long stretches of time. -Genetic evidence reveals the precise molecular mechanism responsible for the change in pelvic structures in stickleback populations. -Data obtained by analyzing living fish in lakes show the selective pressures present in different environments

Activity: Role of bicoid Gene in Drosophila Development A. A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a _____. B. The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo. C. The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the _____. D. What triggers the translation of bicoid mRNA? E. The bicoid gene is a type of _____ gene. F. The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the _____. G. What process produces the gradient of bicoid protein in a fertilized egg? H. Bicoid mRNA is translated in _____. I. Which of these regions is most likely to develop into the Drosophilia's head? J. The bicoid gene is transcribed by _____.

A. two-headed fly B. the establishment of the anterior-posterior axis C. head D. fertilization of the egg E. egg-polarity F. abdomen G. diffusion H. the fertilized egg I. A J. nurse cells

Chapter 21 Blue Thread Question 3 Which is the best evidence that a Hox gene found in flies and a Hox gene found in mice are homologous? See Section 21.3

All animals have a similar gene.

Chapter 21 Question 6 How is determination distinct from differentiation?

Determination occurs when a cell commits to a particular way of specializing but does not show any obvious specialized properties. Differentiation is the process of becoming a specialized cell by showing more and more characteristics associated with a particular cell type.

Chapter 21 Question 7 What is the connection between genetic regulatory cascades and the observation that differentiation is a step-by-step process? Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

Differentiation is triggered by the production of regulatory TRANSCRIPTION factors, which INDUCE other TRANSCRIPTION factors, and so on−a sequence that constitutes a regulatory cascade−as development progresses. At each step in the cascade, a new subset of genes is ACTIVATED−resulting in a step-by-step process to FULLY DIFFERENTIATED cells.

Chapter 21 Question 10 Some stickleback fish develop protective spines, and other stickleback fish are spineless. Spine development is controlled by the expression of a gene known as Pitx1. The spineless phenotype is due to a mutation in Pitx1 that results in no expression of Pitx1 during development in regions where spines would otherwise form. When scientists compared the Pitx1 coding sequence in spined and spineless fish, they found this sequence was the same in both types of fish. Propose plausible hypotheses for the location of this mutation and for how it alters spine development. Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

Hypothesis 1: The mutation FALLS in a regulatory region of the Pitx1 gene that controls Pitx1 expression in the spine-forming region during development. Hypothesis 2: If the mutation PREVENTS Pitx1 expression where spines form, then spine formation WILL NOT occur during development, resulting in spineless fish, while the Pitx1 coding region is NORMAL.

Chapter 21 Blue Thread Question 6 Would it be easier for an investigator to change the outcome of differentiation if a cell used cytoplasmic determinants or induction to produce specialized daughter cells? See Section 21.1

Induction, because this could be easily changed by changing the cell's environment.

Chapter 21 Question 16 Which of the following statements about the DNA in one of your brain cells is true?

It is the same as the DNA in one of your heart cells.

Chapter 21 Blue Thread Question 8 Why does a mutation in a Drosophila pair-rule gene affect the expression of segment polarity genes but not gap genes? See Section 21.3

Pair-rule genes are located above segment polarity and below gap genes in the regulatory gene cascade.

Chapter 21 Blue Thread Question 7 Why did the researchers have to attach a "general" promoter to the cDNAs for this experiment? See Section 21.4

The general promoter would facilitate the transcription of the cDNA gene immediately in all the cells in which it is placed.

Chapter 21 Question 5 A friend is interested in isolating genes that are expressed solely in liver cells but only has access to skin cells. She asks you for advice on whether to start her studies. What will you say? Drag the terms on the left to the appropriate blanks on the right to complete the sentences.

You can tell her that she CAN START her work because all cells of an individual should be genetically EQUIVALENT, meaning they HAVE the same sets of genes, though the gene CAN BE NOT expressed (used to produce a final gene product, typically a PROTEIN) in a cell.

Chapter 21 Question 3 What is a homeotic mutant?

an individual with a structure located in the wrong place

Chapter 21 Question 5 When we compare animal development to plant development, we find that _____.

animal cells, but not plant cells, migrate during morphogenesis

Chapter 21 Question 17 Within a cell, the amount of protein made using a given mRNA molecule depends partly on _____.

the rate at which the mRNA is degraded