ALABAMA BIOLOGY ALIGNMENT
Text Resources Digital Resources Classroom Kits (Available from Carolina Biological) hudsonalpha.org/kits ERH = HudsonAlpha's Educator Resource Hub hudsonalpha.org/educatorhub
Growth and Development 3 Develop and use models to explain how events during the cell cycle lead to the formation of new cells and repair of multicellular organisms, including cell growth, DNA replication, separation of chromosomes, and sep- aration of cell contents.
Chromosocks ® Modeling Meiosis & Mendel’s Laws ® Meiosis Video (ERH) Collecting Cancer Causing Changes ™
3a Construct an explanation of the process of DNA replication during cellular division (S-phase).
Chromosocks ® Modeling Meiosis & Mendel’s Laws ® Chromosock Mitosis (ERH)
3b Using observations of cell growth, construct an explanation of how the cell cycle leads to differentiation in tissue development.
HNPCC: Investigating Hereditary Cancer ® Collecting Cancer-Causing Changes ™ Cell Cycle Regulation: Videos (ERH) Cell Cycle Regulation: Growth Factors Video Cell Cycle Regulation: Mutations Video Cell Cycle Regulation: Processes Video
Photosynthesis and Respiration 5b Use models of the reactants and products of photo- synthesis to illustrate the conversion of light energy into stored chemical energy within cells.
HudsonAlpha Guidebook 2018/19: Genetics, Plant Growth and Photosynthesis (pgs. 20-21)
GENETICS, PLANT GROWTH AND PHOTOSYNTHESIS
Chromatin Remodeling Drives Gene Expression Across Plant Development
Light Energy
The transitions between phases of a plant’s life cycle are triggered by environmental conditions such as the amount and length of sunlight, temperature and moisture levels. At the molecular level, many of these transitions are controlled by changing how the DNA is folded and packaged. In order to fit within the confines of the nucleus, DNA is wound around histone proteins, forming a complex known as chromatin. The level of chromatin condensation varies across the genome. Transcription factors and RNA polymerase can access their target promoter and enhancer sequences for genes within loosely wound DNA. In contrast, genes located in tightly packed regions of chromatin are not transcribed. The transition between open and packed chromatin regulates which genes are active and which are silent. Different cells activate different genes, controlled in large part by chromatin accessibility. For example, a plant’s leaf and flower cells contain the same set of genes, but activate and silence distinctive combinations by differentially controlling levels of chromatin packing (see figure below) .
oxygen
water
carbon dioxide
CO
2
O 2
H
2 0
Flowering occurs in response to environmental factors such as temperature, day length and climate. When conditions are favorable, leaf cells produce one or more flower-triggering (FT) proteins. These enter the plant phloem and are transported to a part of the plant called the shoot apex (where flowers will ultimately develop). In shoot apex cells, FT proteins binds to specific transcription factors and activate the genes that initiate flowering.
Biomass Production Plants convert > 5% of sun energy into biomass
6CO 2 + 6 H 2 0
C 6 H 12 0 6 + 6O 2
transcriptionally active germination genes
Fruiting The fruit protects seeds and helps ensure their dispersal from the parent plant. Fruits can be dry (like grains) or fleshy. Hundreds of genes control the process of ripening to accumulate the sugars, acids, pigments and aromatic molecules that make fruit attractive to animals.
Folding and unfolding in the same DNA nucleus
Photosynthesis uses sunlight to assemble = molecules of sugar from water and carbon =dioxide, producing oxygen as a byproduct. It incorporates the inorganic carbon from carbon dioxide into organic molecules like glucose. This allows the cell to access the carbon at a later time in order to build other molecules such as proteins and nucleic acids. Photosynthesis is one of the most important activities on our planet. It occurs in green plants, algae and some bacteria and is the foundational process for life — the origin of earth’s oxygen as well as the source of energy for cellular function.
loosely wound DNA
Germination Seeds contain proteins called phytochromes that are activated by various wavelengths of light. Some phytochromes are present in dry seeds, while others appear after the seed absorbs water. In the presence of light, activated phytochromes travel into the nucleus, where they repress genes associated with dormancy and activate those required for germination.
transcriptionally active flowering genes
loosely wound DNA
silent flowering genes tightly wound DNA
silent germination genes tightly wound DNA
DNA wrapped
around histone
proteins
Dormancy delays germination until growth conditions are favorable. During their formation on the mother plant, seeds acquire dormancy to prevent germination until after they have been dispersed. Seeds gradually lose their
This process of chromatin modification is controlled by a set of proteins called chromatin remodelers, which convert the energy stored in ATP into mechanical movement to shift the positioning of histone proteins, exposing or hiding DNA sequences. Researchers are still uncovering how environmental factors trigger chromatin remodelers to activate or silence genes required for developmental processes like germination, flowering and fruiting. Recent advances in sequencing technology now allow scientists to map changes in chromatin condensation and transcription rate over time, uncovering patterns in gene regulation. These patterns provide an opportu- nity to better understand the environmental and genetic factors controlling the plant’s lifecycle.
dormancy status in response to environmental factors such as light, temperature, moisture and soil conditions.
chloroplast anatomy
Photosynthesis Pigments Photosynthesis takes place in specialized pigment- containing compartments called chloroplasts . These pigments absorb different wavelengths of light to capture the energy required by photosyn- thesis. The primary pigment is chlorophyll a, which absorbs violet-blue and orange-red light. It reflects green wavelengths, which is why chlorophyll-con- taining plant cells are green. Other pigments capture different wavelengths of light energy and channel it to chlorophyll a. Many of these pigments also protect chlorophyll a from light damage. These include chlorophylls b and c (which absorb blue light), carotenoids (that capture bluish-green light) and phycobilins (found in cyanobacteria and red algae and absorb red, orange, yellow and green light). Scientists have recently discovered that some cyanobacteria use a completely different kind of chlorophyll (chlorophyll f) to carry out photosyn- thesis in very shady spaces by absorbing infrared wavelengths of light.
CO 2
CO 2
C3
Approximately 85% of green plants use the “standard” C3 photo-
C4 plants divide photosynthesis into two different
Many plants that live in hot dry environments use another form of photosynthesis
The C4 process uses more ATP energy, but it is more than recovered by minimiz- ing photorespiration during drought or high temperature. C4 plants can achieve high rates of photosynthesis with their stomata only partially open, reducing overall water loss. C4 is used by about 3% of vascular plants, includ- ing corn, sugarcane and broccoli.
C4
Agriculture is currently facing many serious challenges from increasing scarcity of resources, yet as consumers, we expect production to continue to keep pace with an increas- ing human population. At HudsonAlpha we are se- quencing the genomes of multiple plant species, and then using this information to understand the genes involved in traits that make plants grow more efficient- ly — increasing yields and drought tolerance, while decreasing the need for fertilizers and pesticides.
carbon dioxide CO 2
synthesis pathway. The first step of the process uses the enzyme rubisco to incorporate carbon dioxide into a three-carbon inter- mediate. Unfortunately, rubisco often grabs oxygen rather than carbon dioxide, producing a toxic byproduct that the cell has to spend additional energy breaking down. This wasteful process is known as photorespiration and it happens more frequently when plants close their stomata to minimize water loss or when temperatures are high.
types of leaf cells. Carbon dioxide is captured in meso- phyll cells, fixed into a simple four-carbon molecule and transported to the chloro- plasts of neighboring bundle sheath cells. There the car- bon dioxide is released and enters the Calvin cycle, just as in C3 photosynthesis. The high concentration of carbon dioxide in the bundle sheath cells decreases the likelihood that rubisco will incorrectly incorporate oxygen.
called crassulacean acid metabolism (CAM). This pathway minimizes photo- respiration and water loss by keeping stomata completely closed during the day. At night, the stomata open, allowing carbon dioxide to enter the leaves where it is fixed into a four carbon molecule called malate and stored inside vacu- oles. During the day the stored malate is transported to chloroplasts and broken down to release carbon dioxide, which enters the Calvin cycle. Similar to C4 photosynthesis, CAM requires additional ATP energy. Examples include slow grow- ing plants such as cacti, and pineapples.
mesophyll cell
CO 2
night
Calvin cycle
bundle sheath
CO 2
CO 2
day
Calvin cycle
Calvin cycle
mesophyll cell
glucose
glucose
glucose
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SCIENCE FOR LIFE
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