Summary
Summary Biol 1103 Exam 3 Study Notes
- Course
- BIOL 1013
- Institution
- Baton Rouge Community College
This is a comprehensive and detailed exam study note for Biol 1103. *Essential Study Material!!
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General Biology I – Exam 3 Study Notes: Chapters 9-12--Chapter 9—
Terms:
Gene therapy: Correcting or replacing mutated genes as a treatment for genetic disease.
Hemoglobin: The oxygen-carrying protein in red blood cells.
Beta-Globin: One of the proteins that makes up the hemoglobin.
Mutation: A change in the nucleotide sequence of a DNA molecule.
Point Mutation: A mutation that alters a single DNA nucleotide.
Missense Mutation: A point mutation that changes the amino acid sequence of the encoded protein.
Silent Mutation: A point mutation that does not change the amino acid sequence of the encoded protein.
Frameshift Mutation: A shift in the reading frame such that codons start and end at an alternative position.
Mutagen: Any chemical or physical agent that can damage DNA by changing its nucleotide sequence.
Gene Editing: A way to change the sequence of a gene.
Crispr: A genome-editing tool based on a natural defense system in bacteria.
Somatic Cells: Nonreproductive cells of the body.
Germ Cells: Reproductive cells of the body.
Chapter 9 Notes:
Normal red blood cells carry oxygen flow freely in the bloodstream-- a normal red blood cell is round flexible and carries abundant oxygen.
Sickled red blood cells clump together and block the flow of blood and oxygen. They also do not survive as long as normal red blood cells-- they have an
irregular shape and carry very little oxygen. Complications of Sickle Celled Disease can include: anemia, extreme pain, blood clots, stroke, and death.
Recall from chapter 8 that during gene expression DNA is first transcribed into mRNA which Is then translated into protein. Groups of 3 mRNA nucleotides,
called codons, specify amino acids according to the genetic code. In people with sickle cell disease, the original codon in the beta-globin mRNA, GAG, is
changed to GUG. As a result, when the mRNA is translated into a protein, glutamic acid (Glu) is the normal protein that becomes valine (Val) this amino acid
alters the change of the physical shape and chemical properties of the protein.
Mutations alter the nucleotide sequence of DNA. If a mutation changes the coding region of a gene, the resulting protein may have an altered structure and
function. In this case, altered hemoglobin causes cells to take on a sickled shape, and interferes with the ability of red blood cells to carry oxygen to tissues.
(Refer to the diagram for this)
Mutations are changes in the nucleotide sequence of DNA. There are several ways a person can end up with a mutation: It may have been inherited; it may
have occurred randomly during the DNA replication; Or it may have been a result of environmental insult.
o Inheritance: a mutation in the beta-globin gene can be inherited either from one parent or the other. If the mutation is inherited from both parents, then the offspring will have
sickle cell disease.
o DNA replication errors: mistakes can happen during DNA replication. Most, but not all, mistakes are corrected by repair enzymes. On average, one mutation occurs for every 10
billion base pairs that are replicated.
o Mutagens examples: many components of the environment, our food, and even ourselves can cause mutations.
Radiation - UV radiation, X-rays.
Chemicals - pollution and pesticides, smoking, alcohol, char (blackened bits) on meats cooked at high temperatures.
Infectious agents - some viruses, like hepatitis C.
Cellular reactions - cellular processes produce mutagenic free radicals.
Example of Gene Therapy for Sickle Cell Disease:
o A modified virus serves as the vector to introduce a normal beta-globin gene to hematopoietic (blood-forming) stem cells isolated from a patient with sickle cell disease. Once
stem cells have been obtained from the patient, they are infected with the engineering virus. The beta-globin gene carried by the virus is incorporated into a host cell’s
chromosome. The genetically modified cells are then grown in the lab. So that are many of them that can be introduced back into the patient, where they will produce normal
beta-globin, which will be incorporated into the normal hemoglobin in red blood cells that will not sickle.
CRISPR Adds Precision to Genetic Engineering:
o CRISPR is a genetic engineering method that can precisely modify specific gene sequences. Molecular tools target a specific DNA sequence, which then can be used to insert, , or
alter a DNA sequence at that site.
1. The DNA-cutting enzyme is added to the DNA containing the target sequence to be modified.
2. The enzyme is designed to specifically bind to the target sequence and cut the DNA in this precise location.
3. Once the DNA is cut, scientists can modify or add a specific DNA sequence in this location.
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, Mutations can be hereditary or non-hereditary: mutations that occur in sperm or egg cells are germ-line mutations that can be passed on to offspring. These
inherited mutations are then found in every cell of the offspring, including egg or sperm cells, and can be passed on to the subsequent generations. Somatic
mutations are those that can occur in any cell in the body other than sperm or egg cells. These mutations are not inherited but may cause disease in the
individual that acquires them.
o Germ-line gene therapy (hereditary): genetic alterations made to cells that become sperm or eggs, or to early embryonic cells, are passed onto every cell in an offspring.
o Somatic gene therapy (nonhereditary): genetic alterations that are made to somatic cells are not passed on to offspring.
Driving Questions & Answers:
Question 1. What are mutations, what is their impact, and how do they occur?
o Mutations or changes in the nucleotide sequence of DNA.
o The different types of mutations include point mutations, insertions and deletions, translocations, and inversions.
o The effect of a mutation depends on where it occurs in the genome, and whether it changes the amino acid sequence of a protein.
o Mutations can occur spontaneously during DNA replication. They can also be caused by environmental triggers such as tobacco, ultraviolet radiation, chemicals, and viruses, and
by chemicals naturally produced in the body.
Question 2. How can genetic engineering be used to treat genetic diseases?
o Viruses are useful tools in genetic engineering because they make good vectors.
o CRISPR is a genome editing tool adapted from enzymes found in bacteria. It can be used to make changes to DNA at specific locations.
o Mutations that occur in the body (somatic) cells will be found only in the descendants of that cell. Mutations that occur in germ cells (sperm and eggs) will be inherited by
offspring and therefore will be present in all the cells of that offspring's body.
o Using CRISPR to modify germ cells is not a currently accepted therapy for genetic diseases.
Question 3. Are all mutations harmful?
o The impact of a mutation may vary, depending on the environment in which it's found.
o Mutations can be beneficial, harmful, or neutral in the terms of the effect they have on survival and reproduction.
Chapter 10—
Terms:
Cancer: A disease in which cells divide repeatedly and without restraint, in some cases forming a tumor.
Cell Division: The process by which a cell reproduces itself; Cell division is important for the normal growth, development, maintenance, and repair of an organism.
Cell Cycle: The ordered sequence of stages through which a cell progresses to divide. The stages include Preparatory Phases (G 1, S, G2) and division phases (mitosis and cytokinesis).
Interphase: This stage of the cell cycle in which dividing cells spend most of their time, preparing for cell division. There are three distinct subphases: G 1, S, and G2.
Sister Chromatids: The two identical DNA molecules that result from the replication of a chromosome during the S phase.
Mitosis: The segregation and separation of replicated chromosomes during cell division.
Cytokinesis: The physical division of a cell into two daughter cells.
Carcinogen: Any substance that causes cancer. Most carcinogens are mutagens.
Cell Cycle Checkpoint: A cellular mechanism that ensures that a stage of the cell cycle is completed accurately.
Apoptosis: A type of cell death; Often referred to as cellular suicide.
Tumor: A mass of cells resulting from uncontrolled cell division.
Centromere: The specialized region of a chromosome where the sister chromatids are joined; It is critical for proper alignment and separation of sister chromatids during mitosis.
Mitotic Spindle: The microtubule-based structure that separates sister chromatids during mitosis.
Sporadic: Cancers that are caused by non-inherited (acquired) mutations.
Proto-Oncogene: A gene that codes for a protein that helps cells divide normally.
Tumor Suppressor Gene: A gene that codes for a protein that monitors and checks cell cycle progression. When these genes mutate, tumor suppressor proteins lose normal function.
Oncogene: A mutated and overactive form of a proto-oncogene. Oncogenes drive cells to divide continually.
Benign Tumor: A non-cancerous tumor whose cells will not spread throughout the body.
Malignant Tumor: A cancerous tumor whose cells can spread throughout the body.
Metastasis: The spread of cancer cells from one location in the body to another.
Contact Inhibition: A characteristic of normal cells that prevents them from dividing once they have filled space and are in contact with their neighbors.
Anchorage Dependence: The need for normal cells to be in physical contact with another layer of cells or a surface.
Angiogenesis: The growth of new blood vessels.
Chemotherapy: Treatment using toxic chemicals that kill cancer by interfering with cell division.
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