Which example is part of the scientific method?

Mendel developed theories of genetics that scientists around the world use today.

From experiments with garden peas, Mendel developed a simple set of rules that accurately predicted patterns of heredity. He discovered that plants eitherself-pollinateorcross-pollinate, when the pollen from one plant fertilizes the pistil of another plant. He also discovered that traits are eitherdominantorrecessive. Dominant traits are expressed, and recessive traits are hidden.

Mendel’s Theory of Heredity

To explain his results, Mendel proposed a theory that has become the foundation of the science of genetics. The theory has five elements:

• Parents do not transmit traits directly to their offspring. Rather, they pass on units of information calledgenes.
• For each trait, an individual has two factors: one from each parent. If the two factors have the same information, the individual ishomozygousfor that trait. If the two factors are different, the individual isheterozygousfor that trait. Each copy of a factor, orgene, is called anallele.
• The alleles determine the physical appearance, orphenotype. The set of alleles an individual has is itsgenotype.
• An individual receives one allele from each parent.
• The presence of an allele does not guarantee that the trait will be expressed.

The sequence of amino acids in a gene determines the primary structure of a protein. The components necessary fortranslationare located in the cytoplasm. Translation is the making of proteins by mRNA binding to a ribosome with the start codon that initiates the production of amino acids. Apeptide bondforms and connects the amino acids together. The sequence of amino acids determines the protein’s structure, which determines its function.

One step of the scientific method is to analyze information or data collected from the experiment to conclude whether the hypothesis is supported.

Recall that these make up thescientific method,described below:

• Problem:The question created because of an observation.Example: Does the size of a plastic object affect how fast it naturally degrades in a lake?
• Research:Reliable information available about what is observed.Example: Learn how plastics are made and understand the properties of a lake.
• Hypothesis:A predicted solution to the question or problem.Example: If the plastic material is small, then it will degrade faster than a large particle.
• Experiment:A series of tests used to evaluate the hypothesis. Experiments consist of anindependent variablethat the researcher modifies and adependent variablethat changes due to the independent variable. They also include acontrol groupused as a standard to make comparisons.
  • Example: Collect plastic particles both onshore and offshore of the lake over time. Determine the size of the particles and describe the lake conditions during this time period.
• Observe:Analyze data collected during an experiment to observe patterns.
  • Example: Analyze the differences between the numbers of particles collected in terms of size.
• Conclusion:State whether the hypothesis is rejected or accepted and summarize all results.
• Communicate:Report findings so others can replicate and verify the results.

The cell cycle is an organized process divided into two phases:interphaseand theM (mitotic) phase. During interphase, the cell grows and copies its DNA. After the cell reaches the M phase, division of the two new cells can occur. The G1, S, and G2phases make up interphase.

• G1:The first gap phase, during which the cell prepares to copy its DNA
• S:The synthesis phase, during which DNA is copied
• G2:The second gap phase, during which the cell prepares for cell division

It may appear that little is happening in the cell during the gap phases. Most of the activity occurs at the level of enzymes and macromolecules. The cell produces things like nucleotidesfor synthesizing new DNA strands, enzymes for copying the DNA, and tubulin proteins for building the mitotic spindle. During the S phase, the DNA in the cell doubles, but few other signs are obvious under the microscope. All the dramatic events that can be seen under a microscope occur during the M phase: the chromosomes move, and the cell splits into two new cells with identical nuclei.

The protein disc that holds two sister chromatids together is what collectively makes a chromosome. A gene is a segment of DNA, deoxyribonucleic acid, which transmits information from parent to offspring. A single molecule of DNA has thousands of genes. A chromosome is a rod-shaped structure that forms when a single DNA molecule and its associated proteins coil tightly before cell division.

Chromosomes have two components:

• Chromatids: two copies of each chromosome
• Centromeres: protein discs that attach the chromatids together

Human cells have 23 sets of different chromosomes. The two copies of each chromosome are called homologous chromosomes, or homologues. An offspring receives one homologue from each parent. When a cell contains two homologues of each chromosome, it is termed diploid (2n). A haploid (n) cell contains only one homologue of each chromosome. The only haploid cells humans have are the sperm and eggs cells known as gametes.

If the cohesion between particles decreases, then the particles must be undergoing a phase change that allows particles to move farther apart. This happens when a substance vaporizes and turns from liquid to gas. Any phase change that moves to the right in the diagram above requires energy to be added to the system because the substance has more energy at the end of the phase change. The phase changes aremelting,vaporization (boiling), andsublimation. When energy is added, particles move faster and can break away from each other more easily as they move to a state of matter with a higher amount of energy. This is most commonly done by heating the substance.

In solids, particles are usually closer together than in other states of matter because of the strong cohesive forces between the particles.

• Solids, liquids, gases, and plasmas differ from one another in the amount of energy that the particles have and the strength of the cohesive forces that hold the particles together.
• Cohesion is the tendency of particles of the same kind to stick to each other.
• A solid has the lowest amount of energy because its particles are packed close together. Liquids have more energy than a solid, and gases have more energy than solids or liquids because the cohesive forces are very weak.

A neutralization reaction is a type of acid-base reaction where an acid and base react to form a salt and water.

In an aqueous solution, a base increases the hydroxide concentration (OH–), while an acid increases the hydrogen ion (H+) concentration. Sometimes,neutralization reactionsalso occur. This type of reaction happens when an acid and a base react with each other to form water and salt. Salt is typically defined as anionic compoundthat includes any cation except H+and any anion except OH–. Consider the following example of a neutralization reaction between hydrobromic acid (HBr) and potassium hydroxide (KOH).

HBr+KOH→KBr+H2O

Not all neutralization reactions proceed in the manner where all reactants are in the aqueous phase. In some chemical reactions, one reactant may be a solid. The neutralization reaction can still proceed to completion.

A person can be a universal blood donor or acceptor. A universal blood donor has type O blood, while a universal blood acceptor has type AB blood.

There are several different types or groups of blood, andthe major groups are A, B, AB, and O. Blood group is a way to classify blood according to inherited differences of red blood cellantigensfound on the surface of a red blood cell. The type ofantibodyin blood also identifies a particular blood group. Antibodies are proteins found in the plasma. They function as part of the body’s natural defense to recognize foreign substances and alert the immune system.

Depending on which antigen is inherited, parental offspring will have one of the four major blood groups. Collectively, the following major blood groups comprise the ABO system:

• Blood group A: Displays type A antigens on the surface of a red blood cell and contains B antibodies in the plasma.
• Blood group B: Displays type B antigens on the red blood cell’s surface and contains A antibodies in the plasma.
• Blood group O: Does not display A or B antigens on the surface of a red blood cell. Both A and B antibodies are in the plasma.
• Blood group AB: Displays type A and B antigens on the red blood cell’s surface, but neither A nor B antibodies are in the plasma

In addition to antigens, the Rh factor protein may exist on a red blood cell’s surface. Because this protein can be either present (+) or absent (-), it increases the number of major blood groups from four to eight: A+, A-, B+, B-, O+, O-, AB+, and AB-.