Evolutionary Dating and Radiometric Techniques

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Questions and Answers

What is the primary role of SH2-containing proteins in the context of Receptor Tyrosine Kinases (RTKs)?

To hydrolyze GTP, thus inactivating the RTK signaling pathway.

To bind to phosphorylated tyrosines on the RTK, allowing for the recruitment of multiple downstream proteins. (correct)

To facilitate the dimerization of RTK monomers upon ligand binding.

To directly phosphorylate tyrosine residues on the RTK dimer.

A mutation in the Ras protein is found in approximately what percentage of cancers, and what is the effect of such mutation?

2%, enhancing the hydrolysis of GTP to GDP.

10%, preventing the binding of ligands to RTKs.

50%, leading to decreased cell division.

30%, causing the Ras protein to continuously signal cell division. (correct)

How do ligand-gated ion channels facilitate the flow of ions across the cell membrane?

They indirectly cause ion flow by activating a secondary messenger cascade.

They change their shape upon signal binding thus opening a channel for ions to flow passively. (correct)

They use ATP hydrolysis to actively transport ions against their concentration gradient.

They require a conformational change induced by phosphorylation by an RTK to open.

What is the key distinction between ligand-mediated and receptor-mediated RTK dimerization?

Ligand-mediated dimerization involves a single, paired ligand joining monomers, where as receptor-mediated uses a single unpaired ligand that causes a conformational change allowing dimerization. Signup and view all the answers

During RTK activation, what is the direct consequence of the cross-linked dimer formation?

The phosphorylation of the opposite RTK monomer within the dimer. Signup and view all the answers

What is the direct role of cAMP in cellular signaling?

To activate protein kinase A (PKA). Signup and view all the answers

In the context of plant stomata regulation, what is the immediate effect of abscisic acid (ABA) binding to its receptor?

It creates a calcium ion gradient that forces H2O and salts out of guard cells. Signup and view all the answers

Which of the following is the direct reactant used to produce cAMP?

Adenosine triphosphate (ATP) Signup and view all the answers

What is the role of phospholipase C (PLC) in the inositol phosphate pathway?

It cleaves PIP2 into DAG and IP3. Signup and view all the answers

How does IP3 contribute to the cellular signaling cascade?

It diffuses into the cytoplasm to bind to calcium channels and release Ca2+. Signup and view all the answers

What is the function of protein kinase A (PKA) in the cAMP pathway?

To phosphorylate target proteins. Signup and view all the answers

What is the role of CREB in the cAMP/PKA pathway?

When activated, it binds to CRE to activate gene transcription. Signup and view all the answers

Which of the following best describes the effect of water following potassium and chloride ions into plant guard cells?

It causes the stomata to open due to turgor pressure increase. Signup and view all the answers

Which dating method is most suitable for determining the age of very old volcanic rock samples?

Radiometric dating using Potassium-40 Signup and view all the answers

What is a key characteristic of punctuated equilibrium in evolutionary theory?

Evolutionary rate that varies Signup and view all the answers

In cell communication, which type of signaling involves hormones traveling through the circulatory system?

Hormonal signaling Signup and view all the answers

What role do kinases and phosphatases play in cellular signaling?

They regulate signaling by adding and removing phosphate groups Signup and view all the answers

What is a characteristic of cytoplasmic receptors in cell signaling?

They bind to hydrophilic signal molecules that can easily permeate the plasma membrane Signup and view all the answers

In the context of GPCRs, what is the role of adenylyl cyclase?

To convert ATP to cAMP, a second messenger Signup and view all the answers

Which is a direct example of artificial selection?

The breeding of wolves to create different dog breeds Signup and view all the answers

What happens to the potassium-40 and argon-40 ratio within volcanic rock as the rock ages?

The amount of Potassium-40 decreases relative to Argon-40 Signup and view all the answers

During GPCR activation, what causes the conformational change of the GPCR?

The binding of a hormone or ligand Signup and view all the answers

What is the significance of gaps in the fossil record?

They represent a period of time where no fossils have been found for a particular species Signup and view all the answers

What is the term for the gradual emergence of an animal's form?

Epigenesis Signup and view all the answers

What distinguishes housekeeping proteins from other proteins?

They are required by all cells. Signup and view all the answers

Which process involves a cell becoming measurably different from other types?

Differentiation Signup and view all the answers

What is the term for the point when cells commit to a certain cell type?

Determination Signup and view all the answers

What hypothesis states that the segregation of developmental determinants occurs during cell mitosis?

Weismann’s Hypothesis Signup and view all the answers

What did John Gurdon's experiment in 1968 demonstrate about frog cells?

All cells have identical genetic material. Signup and view all the answers

Which term refers to cells that can differentiate into any type of cell?

Totipotent Signup and view all the answers

What role do cytoplasmic determinants play in cell differentiation?

They determine cell fate through invisible molecules. Signup and view all the answers

Which process is defined as the communication between different cell types leading to specific developmental pathways?

Induction Signup and view all the answers

What causes the disruption of roles in individual segments during development?

Mutations in homeotic genes Signup and view all the answers

What is the primary function of cAMP phosphodiesterase?

To break down cAMP Signup and view all the answers

What occurs during the early prophase I stage of meiosis?

Chromosomes condense into pairs Signup and view all the answers

How does ADH (Antidiuretic Hormone) affect the kidneys when blood becomes too salty?

Stimulates thirst and water reabsorption Signup and view all the answers

Which of the following hormones is considered a tropic hormone?

Thyroxine Signup and view all the answers

During which phase of the menstrual cycle does ovulation occur?

Ovulation Phase Signup and view all the answers

Which part of the male reproductive system produces milky fluid that enhances sperm mobility?

Prostate gland Signup and view all the answers

What is the role of Sertoli cells during spermatogenesis?

They provide nourishment and support to developing sperm cells Signup and view all the answers

What triggers the release of glucagon from the pancreas?

Low blood glucose levels Signup and view all the answers

In male gametogenesis, which hormone is responsible for stimulating Leydig cells to produce testosterone?

LH (Luteinizing Hormone) Signup and view all the answers

Which mechanism prevents polyspermy after a sperm fertilizes an egg?

Cortical reaction that hardens the zona pellucida Signup and view all the answers

What is the primary function of endorphins in the body?

Dulling perception of pain Signup and view all the answers

Which statement best describes the purpose of Mendel's Law of Segregation?

It ensures that each gamete carries only one allele per trait. Signup and view all the answers

What is the role of the hypothalamus in the regulation of hormones from the anterior pituitary gland?

It synthesizes hormones that control the release of anterior pituitary hormones. Signup and view all the answers

What function does melatonin serve in animals?

Influences reproductive cycles based on season Signup and view all the answers

Study Notes

Day 1: Evolutionary Dating

Fossil record shows progression of evolution, revealing transitions among extinct and living species
Gradualism: Evolutionary rate is constant/linear
Punctuated Equilibrium: Evolutionary rate varies. Organisms develop new traits/characteristics due to environmental pressures, natural selection, or mutations
New adaptations allow organisms to thrive in previously unavailable environments.
Adaptive radiation: Examples include the evolution of bats or similar adaptations (flight, echolocation, various diets).
Gaps: Periods of time where no fossils are found for specific species

Radiometric Dating

Measures Carbon-14 or Potassium-40 to determine age.
Carbon-14: Effective for more recent samples (~50,000 years). Used for organic samples.
Potassium-40: Effective for rocks/volcanic minerals (not fossils). Used for samples with ages from hundreds of thousands to billions of years.
Potassium-40 decays into Argon-40. Measuring the ratio of Potassium-40 to Argon-40 determines the age of volcanic rocks.
Radiometric dating is used to determine the age of rocks/volcanic minerals, and some organic samples.

Artificial Selection

Humans selectively choose desired traits to create new breeds. Example: Breeding wolves to develop various dog breeds, breeding chickens to produce particular comb types.

Natural Selection

Better-adapted organisms are more likely to survive and reproduce.
Without mortality, populations would increase exponentially.
Variations that increase survival and reproduction are more likely to be passed to offspring.

Day 2 & 3: Cell Communication

Direct signaling via gap junctions (small molecules pass between connected cells without crossing plasma membranes)
Indirect signaling (cytoplasmic receptors):
- Autocrine: Signal molecule sent and received by the same cell.
- Paracrine: Signal received by a nearby cell (e.g., nitric oxide, histamine).
- Hormonal: Signal released by endocrine cells, travel through the circulatory system.
- Synaptic: Electrical signals stimulate neurotransmitter release.

Kinases and Phosphatases

Kinases: regulate signaling by adding phosphate groups (PO₄)
Phosphatases: regulate signaling by removing phosphate groups (PO₄)

Reception

Cytoplasmic (hydrophilic signals): Signals easily permeate plasma membrane, bind to receptors in the cytoplasm, and activate them.
Transmembrane (hydrophobic signals): Transport signal molecules from outside to inside the cell.
GPCRs (G-protein coupled receptors):
- Signal/ligand binds to extracellular GPCR; causing a conformational change.
- The 7-transmembrane region of the GPCR undergoes a conformational change.
- GPCR activates G-protein (GDP to GTP), the G-protein dissociates into a subunit + β and γ subunits.
- Activated a subunit binds to adenylyl cyclase; activating it
- ATP is converted to cAMP (second messenger)
- The α subunit eventually hydrolyzes GTP to GDP and returns to β + γ subunits.

Other Receptor Types

Ligand-gated ion channels: Signal molecules bind to receptors which then open and allow ions to flow across the membrane.
Enzyme-linked receptors such as RTKs (receptor tyrosine kinases): Ligands bind to receptors which become activated and phosphorylate tyrosines on the receptor (e.g., RTK activation by growth factors).

Day 3 & 4: Hormones

Chemical signals secreted by endocrine cells, regulate bodily functions.
Secreted locally or into circulatory system, pathways with more steps offer greater regulation.
Hormones can be long distance signal molecules via diffusion or circulatory systems
Posterior Pituitary (PP) gland: extension of brain, releases oxytocin (labor contraction, milk release) and ADH (controls water reabsorption in kidneys).
Anterior Pituitary (AP) gland: originated as mouth tissue, releases tropic hormones (stimulate other endocrine glands) or hormones that directly influence target tissues.
Examples of hormones and their functions are given in this section.

Day 5: Meiosis

Meiosis is a type of cell division that reduces the chromosome number by half, producing gametes (sperm and egg cells).
Homologous chromosomes: pairs of chromosomes (similar in size and shape), each carrying the same genes.
Genetic diversity is enhanced through crossing over (recombination) during prophase 1.

Day 6: Gametogenesis & Fertilization

Gametes (sperm and egg): Sex cells produced through meiosis.
Sperm motility: optimal at neutral or basic pH

Day 7: Conceptual & Genetic Bases of Development

Preformation hypothesis: The embryo is pre-formed in the sperm or egg.
Epigenesis hypothesis: The embryo develops progressively.
Housekeeping proteins: Found in all cells
Determination: Commitment of cells to specialize.
Differentiation: Making a cell type measurably different from other cell types, typically via protein synthesis.
Morphogenesis: Development of shape/form from cells.

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Description

Explore key concepts in evolutionary dating, including gradualism and punctuated equilibrium, as well as adaptive radiation examples. Learn about radiometric dating methods like Carbon-14 and Potassium-40, crucial for determining the ages of various specimens. This quiz aims to deepen your understanding of evolution and dating processes in geology.