bisc 100 - Lecture 24:Regulation of Gene expression

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Flashcards on bisc 100 - Lecture 24:Regulation of Gene expression, created by Chelsi Souch on 10/08/2016.
Chelsi Souch
Flashcards by Chelsi Souch, updated more than 1 year ago
Chelsi Souch
Created by Chelsi Souch over 7 years ago
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p53 gene BPDE binds to a gene within these cells called p53. BPDE causes mutations in the p53 gene that deactivate the protein p53 CODES FOR A PROTEIN TO HELP SUPPRESS TUMORS
How and Why Genes Are Regulated? Cells with the same genetic information can develop into different types of cells through gene regulation, mechanisms that turn on certain genes while other genes remain turned off. • Regulating gene activity allows for specialization of cells within the body
What does it mean to say that genes are turned on or off? Genes determine the nucleotide sequence of specific mRNA molecules, and mRNA in turn determines the sequence of amino acids in proteins (DNA → RNA → protein) • A gene that is turned on is being transcribed into mRNA, and that message is being translated into specific proteins. • The overall process by which genetic information flows from genes to proteins is called gene expression.
The Regulation of DNA Packing Cells may use DNA packing for long-term inactivation of genes. • X chromosome inactivation • occurs in female mammals, • takes place early in embryonic development, and • is when one of the two X chromosomes in each cell is inactivated at random
The Initiation of Transcription The initiation of transcription is the most important stage for regulating gene expression
RNA Processing and Breakdown Within a eukaryotic cell, transcription occurs in the nucleus, where RNA transcripts are processed into mRNA before moving to the cytoplasm for translation by the ribosomes. • RNA processing includes the • addition of a cap and tail, • removal of any introns, and • splicing together of the remaining exons
Gene regulation affects two important processes 1. cloning and 2. cancer.
The Genetic Potential of Cells • All body cells contain a complete complement of genes, even if they are not expressing all of them. • A single differentiated plant cell can undergo cell division and give rise to a complete adult plant.
Plant cloning now used extensively in agriculture. For some plants, such as orchids, cloning is the only commercially practical means of reproducing plants. In other cases, cloning has been used to reproduce a plant with specific desirable traits, such as high fruit yield or resistance to disease. Seedless plants (such as seedless grapes, watermelons, and oranges) cannot reproduce sexually, leaving cloning as the sole means of mass-producing these common foods.
Reproductive Cloning of Animals Nuclear transplantation involves replacing the nucleus of an egg cell or a zygote with a nucleus removed from an adult body cell. • If the animal to be cloned is a mammal, further development requires implanting the early embryo into the uterus of a surrogate mother. • This type of cloning is called reproductive cloning because it results in the birth of a new animal.
Reproductive Cloning First mammal cloned was in 1996, cloned from an adult cell. A sheep named Dolly
Practical Applications of Reproductive Cloning Since the first success in 1996, researchers have cloned many species of mammals, including mice, horses, dogs, mules, cows, pigs, rabbits, ferrets, camels, goats, and cats. (a) The first clone (b) Cloning for medical use (c) Clones of endangered animals
Why is reproductive cloning used? In agriculture, farm animals with specific sets of desirable traits might be cloned to produce identical herds. • In research, genetically identical animals can provide perfect “control animals” for experiments. • Reproductive cloning is used to restock populations of endangered animals.
Conservationists argue that cloning may detract from efforts to preserve natural habitats. • does not increase genetic diversity, and • is therefore not as beneficial to endangered species as natural reproduction.
Practically, cloning of mammals is extremely difficult and inefficient. Only a small percentage of cloned embryos develop normally and • they appear less healthy than naturally born kin.
Embryonic Stem Cells In mammals, embryonic stem cells (ES cells) are obtained by removing cells from an early embryo and growing them in laboratory culture. Embryonic stem cells can divide indefinitely and, under the right conditions, can (hypothetically) develop into a wide variety of different specialized cells.
The Genetic Basis of Cancer Cancer includes a variety of diseases in which cells escape from the control mechanisms that normally limit their growth and division. • This escape involves changes in gene expression.
Viruses that cause cancer can become permanent residents in host cells by inserting their nucleic acid into the DNA of host chromosomes.
• A gene that causes cancer is called an oncogene.
A normal gene with the potential to become an oncogene is called a proto-oncogene
• A cell can acquire an oncogene from - a virus or • the mutation of one of its own proto-oncogenes. For a proto-oncogene to become an oncogene, a mutation must occur in the cell’s DNA. • Three kinds of changes in DNA that can produce active oncogenes are shown in the next slide. • In all three cases, abnormal gene expression stimulates the cell to divide excessively
Tumor-Suppressor Genes Changes in genes whose products inhibit cell division are also involved in cancer. • These genes are called tumor-suppressor genes because the proteins they encode normally help prevent uncontrolled cell growth
The Process of Science: Are Childhood Tumors Different? Observations: Specific mutations can lead to cancer. • Question: Are different kinds of cancer associated with specific mutations? • Hypothesis: Young patients with medulloblastoma (MB) harbor unique mutations. (MB is the most common pediatric brain cancer and the deadliest form of childhood cancer.) • Each tumor had an average of 11 mutations. • This is 5–10 times fewer mutations than are found in adult MB patients. • Young MB patients therefore seem to have fewer, but deadlier, mutations.
The Progression of a Cancer The development of a malignant tumor is accompanied by a gradual accumulation of mutations that • convert proto-oncogenes to oncogenes and • knock out tumor-suppressor genes
Inherited Cancer Multiple genetic changes are required to produce a cancer cell. • This helps explain the observation that cancers can run in families. • An individual inheriting an oncogene or a mutant version of a tumor-suppressor gene is one step closer to accumulating the necessary mutations for cancer.
Most cancers arise from mutations that are caused by carcinogens, cancer-causing agents found in the environment, including • ultraviolet (UV) radiation and • tobacco products.
The Evolution of Cancer in the Body • First, all evolving populations have the potential to produce more offspring than can be supported by the environment. Second, there must be variation among individuals of the population. • Third, variations in the population must affect survival and reproductive success
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