Science - 2018-19
BIO.5 e-h, j - Cell Growth & Heredity
The student will investigate and understand common mechanisms of inheritance and protein synthesis. Key concepts include
e) historical development of the structural model of DNA;
f) genetic variation;
g) the structure, function, and replication of nucleic acids;
h) events involved in the construction of proteins; and
j) exploration of the impact of DNA technologies.
Bloom's Levels: Analyze; Understand
- All living things reproduce to produce more of their own kind.
- All cells come from other cells.
- Genetic information is passed from generation to generation by DNA; DNA controls the traits of an organism.
- I can explain why and how DNA has solved many medical and criminal mysteries.
- I can explain why some populations have gone extinct or have significant developmental issues.
- I can explain how DNA becomes damaged and what problems may result.
- I can use my DNA to predict what diseases I may have later in life.
UNDERSTANDING THE STANDARD
- Once DNA was shown to be the genetic material, a race among scientists took place to work out its structure. Studies of the amounts of each DNA base in different organisms led to the concept of complementary base-paring. Interpretations of X-ray photographs of DNA were used to describe the shape and dimensions of the molecule. An analysis of this and other available data led to a structural model for the DNA double helix.
- DNA is a polymer consisting of nucleotides. A DNA nucleotide is identified by the base it contains: adenine (A), guanine (G), cytosine (C) or thymine (T). DNA is a double-stranded molecule. The strands are composed of covalently bonded sugar and phosphate molecules and are connected by complementary nucleotide pairs (A-T and C-G) like rungs on a ladder. The ladder twists to form a double helix.
- The double helix model explained how heredity information is transmitted and provided the basis for an explosion of scientific research in molecular genetics. The sorting and recombination of genes in sexual reproduction results in a great variety of gene combinations in the offspring of any two parents.
- The genetic code is a sequence of DNA nucleotides in the nucleus of eukaryotic cells. Before a cell divides, the instructions are duplicated so that each of the two new cells gets all the necessary information for carrying on life functions. Cells pass on their genetic code by replicating their DNA.
- DNA stores the information for directing the construction of proteins within a cell. These proteins determine the phenotype of an organism. The genetic information encoded in DNA molecules provides instructions for assembling protein molecules. The code is virtually the same for all life forms.
- During DNA replication, enzymes unwind and unzip the double helix and each strand serves as a template for building a new DNA molecule. Free nucleotides bond to the template (A-T and C-G) forming a complementary strand. The final product of replication is two identical DNA molecules.
- Inserting, deleting, or substituting DNA bases can alter genes. An altered gene may be passed on to every cell that develops from it, causing an altered phenotype. An altered phenotype may be neutral, beneficial or detrimental. Sometimes entire chromosomes can be added or deleted, resulting in a genetic disorder. These abnormalities may be diagnosed using a Karyotype.
- In order for cells to make proteins, the DNA code must be transcribed (copied) to messenger RNA (mRNA). The mRNA carries the code from the nucleus to the ribosomes in the cytoplasm. RNA is a single-stranded polymer of four nucleotide monomers. A RNA nucleotide is identified by the base it contains: adenine (A), guanine (G), and cytosine (C) or uracil (U).
- At the ribosome, amino acids are linked together to form specific proteins. The amino acid sequence is determined by the mRNA molecule.
- DNA technologies allow scientists to identify, study, and modify genes. Forensic identification is an example of the application of DNA technology.
- Eugenics, a pseudo-science of selective procreation, was a movement throughout the twentieth century, worldwide as well as in Virginia, that demonstrated a misuse of the principles of heredity.
- The Human Genome Project is a collaborative effort to map the entire gene sequence of organisms. This information may be useful in detection, prevention, and treatment of many genetic diseases. The potential for identifying and altering genomes raises practical and ethical questions.
- Cloning is the production of genetically identical cells and/or organisms.
In order to meet this standard, it is expected that students will
e) describe the basic structure of DNA and its function in inheritance.
describe the key events leading to the development of the structural model of DNA.
f) evaluate karyotype charts and make a determination of the genderand genetic health of the individual.
provide examples of reasons for genetic diversity and why it can be an advantage for populations.
provide examples of mutations that are lethal, harmful, and beneficial.
g) explain the process of DNA replication.
h) given a DNA sequence, write a complementary mRNA strand (A-U, T-A, C-G and G-C).
explain the process of protein synthesis, including DNA transcription and translation.
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