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Environmental Influence on Gene Networks

Lesson 1 – Introduction

Created through a partnership between

teachers, students and scientists

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Why?

After a week on the beach?

In What Ways do Cells Change in Response to a Dynamic Environment?

Define “dynamic” for students as “ever-changing.” Allow students to offer other “whole body” changes (e.g. hair changing to grey with age, eye color changing from birth, other pre-programmed changes such as hair turning curly after puberty, or changes resulting from diseases such as the formation of cancer) and point out that if the whole body changes, and the whole body is made of cells, then cells must be changing also.

Skin cells change by producing more melanin in response to the sun’s radiation. Sunburn is the body’s reaction when DNA is directly damaged by UV-B light. The damage triggers DNA repair and the production of melanin (a photo-protectant pigment) for preventing future damage. Melanin takes UV photons and turns them into harmless amounts of heat. The damage results in restored DNA, the replacement of new skin cells with a higher level of melanin.

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Same caterpillar...

Why?

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Why?

Same flamingo...

Flamingo feathers obtain their wonderful rosy pink color from pigments in the organisms they eat. The flamingos’ feathers, legs, and face are colored by their diet, which is rich in alpha and beta carotenoid pigments. Carotenoids in crustaceans such as those in the flamingo diet are frequently linked to protein molecules, and may be blue or green. After being digested, the carotenoid pigments dissolve in fats and are deposited in the growing feathers, becoming orange or pink. The same effect is seen when shrimp change color during cooking. The amount of pigment laid down in the feathers depends on the quantity of pigment in the flamingo’s diet. An absence of carotenoids in its food will result in new feather growth that is very pale; the existing pigment is lost through molting. San Diego Zoo Flamingos

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Same fly...

Why?

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Why?

Same plant...

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Identical Twins

Same DNA, different fingerprints

How can this be?

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Which part(s) can change temporarily?

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Mount St. Helens

WHY does a changing environment have an influence on cells?

What mechanisms are in place to allow cells to change?

How can WE test these?

Nasa.gov

This Slide asks students to think of ways a scientist might test how the environment influences gene expression. Mt. St. Helens is pictured with a decade of geological change that has impacted the plant growth in this area. The photos give one big example of how environments are always changing - sometimes in small ways and sometimes in very big ways. An organism’s genes help them respond to those changes. Lead students through the questions. Brief answers:

1) The cell must conserve as much energy (and nutrients) as possible and does this by only making the proteins it needs, when it needs them. Said another way, backing up from protein synthesis to the gene level, it only expresses the genes it needs, when it needs them, to save energy. Use analogies that make sense to your students, such as, if you have 4 homework assignments due this week, you will do the one tonight that is due tomorrow instead of doing them all at the same time when that is not needed.

2) Cells are surrounded by membranes that are typically semi-permeable. Their local environment is the solution they are in and this changes according to diffusion/osmosis, etc. These cells are packed in an increasingly larger environment (similar to stackable wooden dolls) that is also permeable to the outside environment. Ways our environment impacts us: through our openings (mouth, nose, eye sockets, etc.) and even through our skin if it has a cut or even if it’s not damaged, as is the case with u-v waves. Cells are susceptible to the outside environment.

3) Cells change in response to stimuli from the environment. Examples of cellular responses: movement of materials through pumps, diffusion, etc. or the movement of the cell itself via cilia, a flagellum, etc. or a change in gene expression to make a new protein or to stop or change the amount of current protein synthesis.

4) We can put cells into an environment and systematically change that environment and measure how the cell responds. A few examples of ways to measure that change include gene expression changes via microarray, position of cells, and growth of cells or populations.

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Model Organisms

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Some biological processes operate exactly the same in many different organisms.

Halobacterium salinarum processes its genetic material in a way that is very similar to the way humans do!

Slides 10-12 (Model Organisms). Discuss the use of model organisms such as fruit flies or mice. Since changing the environment on an observable level can be difficult with a complex, multi-leveled organism, we can use model organisms. Halobacterium is, in particular, a model organism for both experts and beginning scientists due to its non-hazardous nature. Note: Halobacterium salinarum (Halo) is not a moneran (bacteria) but belongs to Domain Archaea.

http://www.ucmp.berkeley.edu/archaea/archaea.html

NOTE: Fortunately for research scientists, biological processes have been found to operate exactly the same in many different organisms. The “Krebs cycle” (the process cells use to extract energy from sugars) is the same across most species. Hemoglobin (essential for blood to carry oxygen to cells) is the same across different species of vertebrates. Because biological processes operate the same in various species, including both very simple and very complex life forms, scientists can use simpler organisms for their initial studies of biological systems.

We call this sort of simpler study case a “model organism”. The simplicity of a model organism allows a scientist to more easily zero in on the properties and functions of interest, without having to sort out the complexity arising from additional systems embodied in more complex organisms. For instance, scientists can study yeast cells to understand how sugars are metabolized in many species (including in humans), without having to deal with the additional complexity from other systems in complex organisms (such as contracting muscles). Moreover, small organisms (such as yeast cells) reproduce quickly, allowing biologists to study multiple strains and generations of an organism in a short time.

Model organisms are carefully selected to provide simple cases for our initial studies of biological systems. They simplify our initial research, yet still provide data-rich and flexible experimental “systems” for us to examine. They are vital to our initial biological discoveries. Research findings from model organisms must be confirmed by also studying humans. But studies on model organisms are crucial to eventually answering the central biological questions regarding human life.

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Model Organisms

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Model organisms are relatively simple, but their properties and functions of interest are similar to those in more complex organisms.

Halobacterium salinarum is SAFE for beginning scientists to use.

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Model Organisms

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The environment can also be more easily controlled in model organism studies.

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Explore How Halo Change in a �Dynamic Environment

Which environmental conditions are characteristic for Halo?
What experiment could be feasibly (or fairly easily with our equipment) completed to test how Halo respond to an environmental change?�

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