Genetics Lecture Notes Week 1 - Lectures 1 and 2
Genetics Lecture Notes Week 1 - Lectures 1 and 2 85033 - GEN 3000 - 002
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85033 - GEN 3000 - 002
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This 5 page Class Notes was uploaded by Toni Franken on Monday January 11, 2016. The Class Notes belongs to 85033 - GEN 3000 - 002 at Clemson University taught by Kate Leanne Willingha Tsai in Summer 2015. Since its upload, it has received 122 views. For similar materials see Fundamental Genetics in Biomedical Sciences at Clemson University.
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Date Created: 01/11/16
GEN 3000 – Notes Set 1, 01/08/2016 Dr. Tsai, Clemson University Chapters 1 and 2 Chapter1: Genetics: (Note, definitions are separated by semicolons) The experimental Science of Heredity; The study of heredity and the variation of inherited characteristics; the branch of biology that deals with heredity, especially the mechanisms of hereditary transmission and the variation of inherited characteristics among similar or related organisms; The study of the patterns of inheritance of specific traits – relating to genes and genetic information – also known as heredity. All of these definitions include the idea of heredity. In this genetics class, there are 3 sectors/forms we will look at. Transmission Genetics: Mendel’s work (peas), generational genetics. Genetic information passed from one generation to the next. Molecular Genetics: The fine details within the big picture. The “why?” and “how?” – Involves DNA Replication>transcription>translation(RNA)>protein creation. This process is the central idea. Population Genetics: Genetics on a broader scale that spans multiple generations of a population. This is especially relevant in the work of Darwin and theories of evolution. Why is it important: Modern Society depends on genetics and the use of the science of genetics for fuel, fiber, food, medicine, biotechnology, and more. It is the basis of the study of genetic diseases, susceptibility and resistance, family history, and targeted medicines for specific genomes. Dwarfism, muscular dystrophy, and other disorders are heavily gene linked. On top of that, the industry of healthcare is an enormous part of the US economy, resulting in about $2 trillion per year, which breaks down to $8608 per person in that year. This is about 17.9% of the GDP. As a fun fact, hemophilia (a clotting disorder – inability to clot properly), nicknamed “The Royal Disease,” was historically found in the royalty of Europe, and is sometimes even attributed to the collapse of the monarchy at that time. Model Organisms Used in Genetic Studies: E.coli: used to study colon cancer and other cancers. S. Cerevisiae: used to study cancer and Werner Syndrome. D. melanogaster: used to study disorders of the nervous system, as well as cancer. C. elegans: used to study diabetes. D. rerio: used to study cardiovascular disease. M. musculus: used to study LeschNyhan disease, cystic fibrosis, fragileX syndrome, among others. Canis lupus familaris: Aka the dog used to study genetics in general. Genetics Through History: We’re not really sure when humans started questioning the idea of WHY things happen across generations. Historically we can see that some domestication (principles of heredity) was first demonstrated 10 – 12,000 years ago. Artificial fertilization was seen 2880 years ago. And Hindu writings 2000 years ago suggested avoiding spouses with undesirable traits, considering they noticed a trend of heredity. 8000 – 1000 BC – domestication of animals began in earnest, but there wasn’t as much going on in the realm of genetics. The 1600s was when the majority of hypotheses and theories began to show up. Then, the 1800s, Darwin and Mendel revolutionized the way humans looked at genes. Original Theories: A couple of concepts took hold originally: Pangenesis: Specific particles (called gemmules) carry information from the body to reproduce organs which are passed to embryo at conception. Needless to say, this fell out of favor. At this time, sperm and egg hadn’t been visualized, but the concept of gemmules was similar to gametes. The term gene, did, however, come from this early theory. This idea led to the idea of inheritance of acquired characteristics – the idea also was that learned skills would be passed onto the next generation. (artist passes on artistic knowledge to children). Robert Hooke in 1665 discovered a cell using a microscope. The invention and use of the microscope to see cells, and thus gametes, led to the idea of Preformationism: The idea that inside egg or sperm is a tiny version of an adult (this tiny person was called a homunculus). Fertilization allows it to grow and develop. Originally the homunculus was thought to be in the sperm, then maybe in the egg. Then, the idea of blending inheritance was born, suggesting that offspring are a blend of parents. Schleiden and Schwann came up with the cell theory, and proposed it in (1839) – cells are the basic unit of all living things, and they divide and arise from preexisting cells, even on the single cellular level. Never just a sudden appearance of an organism. In the 1850’s, Darwin published his work. He lived from 1809 – 1882. He developed the theory of evolution through natural selection. (His published work was “On the Origin of Species” – 1856) – heredity was the fundamental of evolution, and created the idea that evolution and natural selection are based on the passing of genes. However, at this time, people didn’t understand what was happening on an individual level, let alone a population level, devaluing his work at the time. Gregor Mendel was working about the same time as Darwin. (18221884) – Discovered basic principles of heredity (1866). However, this work went largely ignored until the 1900s. He crossed pea plants and analyzed patters of transmission. Walter Flemming: observed the division of chromosomes (1879) Then it was discovered in 1885 that hereditary information is contained in the nucleus. August Weismann: The idea of inheritance of acquired characteristics was hard put to die out. So, Weismann experimented by cutting off the tails of mice for 22 generations. This showed that tail length did not change in subsequent generations. The germplasm theory was then developed, which suggested cells of the reproductive system carry complete sets of information. The idea that the sperm and egg carry preexisting information. It wasn’t until the mid1900s that we see a lot of progression in genetics, which is when we realize that Mendel’s work is correct. We went from the beginning of 1900s showing that genes are on chromosomes, to 2003 when the entire human genome is defined. Chapter 2: Chromosomes and Cellular Reproduction (Mitosis/Meiosis): Prokaryote: Has a cell wall and a plasma membrane, contains ribosomes and DNA. Tend to be small and less complex. Contain no membranebound nucleus. It includes the classifications of eubacterium and the archaebacterium. Archaebacterium contain characteristics of bacteria and eukaryotes. Eubacteria = true bacteria. Eukaryotes: Has a nucleus, and is relatively large and complex with multiple linear DNA molecules. Contain membrane bound organelles and a cytoskeleton. There are 3 major groups of life: eubacteria, archaea, eukaryotes. Eu = “true”; Pro = “pre”; Karyote = “nucleus” All oeganisms have different numbers of base pair genomes. E. Coli – 4.7 Million base pairs of genomes. Trypanosoma brucei – 27 Million base pairs. Human – 3.4 Billion base pairs (we like to think we’re incredibly complex, but compare our genomes to the following organisms). Tiger Salamander – 31 Billion base pairs. Marbled Lungfish – 13 Billion base pairs. Gonganlax polyedra – 98 billion base pairs. T. Rex – 1.9 Billion Base Pairs. The microscope opened our eyes to the world of cell physiology. It was dveloped and used by Zacharias Janssen, Robert Hooke, and Antoni van Leeuwenhoek. These scientists began to differentiate microorganisms, and began to be able to tell the difference between eukaryotic and prokaryotic cells. The nucleus is very important to genetics, because that’s where genetic information is stored – basis of mitosis and meiosis. Genetic information is also contained in the mitochondrion (powerhouse of the cell), as well as chloroplasts in plants. Ribosomes are very important in the process off hereditation. Characteristics of DNA: Bacterial DNA is somewhat sporadic and spread out. DNA is more compact in eukaryotes. The chromosome of Eukaryotes is the result of DNA complexed to proteins. This form (chromosome) is the most compact DNA will ever be during cellular division. During the majority of the cell cycle in eukaryotes, it will be called chromatin that is bound by histone proteins. This is different than prokaryotes.. Viruses are NOT cells. They contain a viral protein coat, and a core of genetic information. They can only reproduce inside of a host cell, and it has been discovered that most viruses are closely related, according to genetic sequence, (evolutionarily) to their host. Cellular Reproduction: Cellular reproduction (prokaryotes): Contains a single, circular chromosome attached to the plasma membrane. The chromosome begins to replicate, and the plasma membrane grows, causing two chromosomes to separate, followed by separation of organism into two individual cells. Each cell is identical. 1 bacterium divides every 20 minutes = 10 billion bacteria in 10 hours. This is called binary fission. NOTE: In genetics, there are very few absolutes, usually there are exceptions to every rule. Cellular Reproduction (eukaryotes): Eukaryotes typically have 2 sets of chromosomes per cell as a result of sexual reproduction. One set from mother, one from father (called homologous pairs). If there are 2 sets of genetic information, a cell is diploid (2n – most eukaryotic cells). If a cell has only 1 set of genetic information, it is haploid (1n – reproductive cells.) Only our reproductive cells are haploid. The rest of our cells are diploid. Humans have 23 chromosome homologous pairs that have the same structure as their counterparts. They will carry the same TYPE of genes, but they can determine different characteristics. Ex: hair color allele in the gene may be red on one half, and blonde on the other half. Chromosome structure: Centromere: Can be located anywhere along the chromosome length. It is incredibly important, because without it, you can lose that chromosome. It is a landing spot for the kinetochore that will form and be instrumental in the movement of chromosomes. We also use the centromere to count chromosomes. If you have a distinct centromere, we have a distinct chromosome. Two sister chromatids, a duplicated chromosome and its partner, are attached at the centromere. Both chromatids together are considered one chromosome. There are four major types of chromosomes classified by centromere location: Metacentric – divided equally by the centromere. Submetacentric – a short arm (p arm) and a q arm (long arm) towards the middle of the chromosome. Acrocentric – very very small p arm (all dog chromosomes, except sex, are acrocentric). Telocentric centromere at very end of the chromosome, no p arm. Telomere: End of a chromosome – acts as a cap that protects the chromosome (like a shoelace tip). You don’t want to lose your telomeres. They are essential on each end of your chromosome. Cell cycle: Genetics focuses on M phase Mitosis, or nuclear and cell division.. Interphase: ~ 15 hours G1: Cell is metabolically active, functioning as a cell. No time limit. This is where the cell grows. ~ 5 hours G0: Arrested, nondividing stage, short. Sometimes cyclical and repeats. G1/S checkpoint: Beyond this point, the cell is committed to divide. It is going to take inventory and make sure it is healthy and large enough for division. S: Genetic information is replicated. The diploid cell gets copied. ~ 7 hours G2: Checking health, make sure it has finished replicating the DNA ~ 3 hours G2/M checkpoint: Check health, then enter M phase. M Phase (Mitosis/Cell Division): ~ 1 hour Prophase: ~ 36 minutes Metaphase: ~ 3 minutes Anaphase: ~ 3 minutes Telophase ~ 18 minutes During the M phase, there is the M, or Spindleassembly, checkpoint which is very important. The cell cycle must be maintained, and progress appropriately. If control is lost cancer can develop. This can be used to treat cancer by targeting specific points of the cell cycle.
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