BIL 250 Notes Weeks 1-2
BIL 250 Notes Weeks 1-2 BIL 250
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This 8 page Class Notes was uploaded by Jessica Vitale on Monday August 29, 2016. The Class Notes belongs to BIL 250 at University of Miami taught by Dr. Wang in Spring2015. Since its upload, it has received 31 views. For similar materials see Genetics in Biology at University of Miami.
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Date Created: 08/29/16
Chapter 1 Applications of recombinant DNA technology - understanding gene function - drug development - plant and animal production - forensics - plant and animal husbandry - medical advances Chromosome theory of inheritance - inherited traits are controlled by genes residing on chromosomes that are transmitted by gametes DNA is the carrier of genetic information. It was difficult for some scientists to accept that DNA is the carrier of genetic information because Genes possess a variety of functions. Since proteins can contain up to 20 different amino acids, while DNA is made up of only four different nucleotides, proteins should have more functional variations. It seemed likely that proteins should be the genetic material. Genes take part in the production of proteins through the processes of transcription and translation. They are the functional units of heredity. Chromosomes carry genes and take part in cell division during mitosis and meiosis. The central dogma of molecular genetics (DNA RNA protein) serves the basis of modern genetics because DNA and RNA are discrete chemical entities, they can be isolated, studied, and manipulated in a variety of experiments that define modern genetics. How many different proteins, each with a unique amino acid sequence, can be constructed with a length of 8 amino acids? - 25600000100 Restriction enzymes cut double-stranded DNA at particular base sequences. Then short single-stranded overhangs are generated so that ends from one fragment can anneal with ends from another (assuming the same enzyme used). When a vector is cleaved with the same endonuclease, complementary ends are created such that ends, regardless of their origin, can be combined and ligated to form intact double-stranded structures Impacts of biotechnology on crop plants in the US - development of transgenic crops - spread of transgenes from genetically modified crops to wild plants Chapter 1 - the development of nutrionally-enhanced crops - development of pest-resistant crops - development of herbicide resistant crops - quicker identification of hazardous organisms in food Arguments for and against human gene patenting by companies and individuals - Patents can protect the investments of individuals and institutions that develop needed and useful products. - Mechanisms need to be in place to protect consumers to ensure that relatively free and fair access to genetic tools is available. - Preventing the holding of patents for genes or genetic tools could reduce the incentive for pursuing the research that produces genes and genetics tools. The use of model organisms advanced our knowledge of genes that control human diseases because: - What is learned in one organism can usually be applied to all organisms. - Most model organisms have peculiarities (ease of growth, genetic understanding, abundant offspring) Discoveries in genetics have been recognized with so many Nobel Prizes because: - Genetics provides the framework for universal biological processes. - Genetics aided rational drug design. - Genetics helps to explain species stability and diversity. - Genetics guided our understanding of living systems. If you were in a position to control the introduction of a GM primary food product (rice, for example), what criteria would you establish before allowing such introduction? - Likelihood of cross-pollination and environmental impact Risks discussed at the BioDemocracy meeting: - Safety of genetically modified organisms to human health. - Ecological harmony. - Biotechnical applications to weapons development. A fundamental property of DNA's nitrogenous bases that is necessary for the double-stranded nature of its structure is complementarity. Bioinformatics is a discipline involved in the development of hardware and software for processing, storing, and retrieving nucleotide and protein data Chapter 1 Arabidopsis is a model organism for the study of plant biology. Performation: the fertilized egg contains a complete miniature adult (homunculus) Lower LDL cholesterol levels with a drug that binds to PCSK9 proteins. In nonviral system the nature of hereditary substance is DNA. Example of a mutant: white-eyed Drosophila. Translation medicine: process in which genetic findings are directly translated into new and improved methods of diagnosis and treatment Epigenesis: an organism develops from the fertilized egg by a succession of developmental events that transform the egg into an adult Chapter 2: Mitosis & Meiosis Steps in the eukaryotic cell cycle …G1 – S – G2 – M – G1… Both haploid and diploid cells can undergo mitosis. • In prophase, the microtubules of the spindle apparatus begin to assemble from individual tubulin subunits. As the identical chromatids of each pair of sister chromatids condense during this stage, they are held together by cohesin proteins. • Prometaphase is marked by fragmentation of the nuclear envelope, expansion of the spindle into the nuclear region, and attachment of some spindle fibers to the chromosomes via the kinetochores. • Metaphase, marked by the alignment of chromsomes along the metaphase plate, is brought about by kinetochores aligning and then remaining motionless relative to the poles of the cell. • In anaphase, the cohesin proteins are cleaved, and the kinetochores move toward the poles of the cell, separating the sister chromatids. As telophase proceeds, the kinetochore microtubules of the spindle disassemble. As the chromosomes reach the poles of the cell, the nuclear envelopes of the two new daughter nuclei form. • Prior to metaphase, the mitotic spindle is constructed by lengthening microtubules that extend from each centrosome. • In metaphase, the kinetochore microtubules have attached each pair of sister chromatids, and the nonkinetochore microtubules overlap extensively at the metaphase plate. • During anaphase, the kinetochore microtubules shorten as the chromosomes move toward the poles of the cell. At the same time, the nonkinetochore microtubules lengthen and push past each other, elongating the cell. By the end of telophase, all the microtubules associated with the mitotic spindle have disassembled. DNA content is halved in both meiosis I and meiosis II. Ploidy level changes from diploid to haploid in meiosis I, and remains haploid in meiosis II. During pachynema of prophase I crossing over takes place. A tetrad is composed of one pair of homologous chromosomes at synapsis of prophase I. Sister chromatids separate in anaphase II Homologous chromosomes are a pair of chromosomes, one maternal and one paternal, that come together during fertilization. They have the same centromere position, and the same genetic loci (genes); however the DNA sequence is not identical. Crossing over between homologous chromosomes during prophase I of meiosis generates genetic diversity in the offspring. Homologous chromosomes pair up along the midline during metaphase I of meiosis, and move apart during anaphase I. Sister chromatids are the result of the replication of a single chromosome. They are identical in DNA sequence (apart from mutation or crossing over with a chromatid from a homologous chromosome). During metaphase of mitosis, chromosomes line up down the midline and sister chromatids separate during anaphase. In meiosis, sister chromatids separate during meiosis II. Chapter 2: Mitosis & Meiosis 7 chromosomes present in the mature ovum 5 chromosomes present in the second polar body After fertilization by a normal sperm, a trisomy chromosome is created Chromatin: unfolded genetic material making up chromosomes that exists when cells are not undergoing division Chromosomes exist in homologous pairs in diploid organisms centromere: the constricted region where the general appearance of each chromosome is established o metacentric, submetacentric, acrocentric, telocentric o p arm – shorter arm (p for petite) o q arm – longer arm Locus: gene site diploid (2n), haploid (n) Homologous chromosomes are a double structure consisting of two parallel sister chromatids connected by a common centromere. Haploid gametes contain one member of each homologous pair of chromosomes. Sexdetermining chromosomes: often not homologous in size, centromere placement, arm ratio or genetic content Mitosis partitions chromosomes into dividing cells karyokinesis: nuclear division – genetic material is partitioned into daughter cells cytokinesis: cytoplasmic division Cell cycle: events that occur from the completion of one division until the completion of the next o Interphase: the replication of DNA of each chromosome G1, S, G2 G0 – phase cells enter in which they do not multiply Meiosis reduces the chromosome number from diploid to haploid in germ cells and spores. Crossing over: genetic exchange between members of each homologous pair of chromsomes Tetrad: 4 chromatids Reductional division: the first division in meiosis I, # of centromeres, each representing one chromosome is reduced by one half Dyad: 2 sister chromatids joined at a common centromere Equational division: the second division of meiosis II The development of gametes varies in spermatogenesis compared to oogenesis Spermatogenesis o Takes place in the testes o Sperm cells produced all contain the haploid number of chromosomes and equal amts of cytoplasm Oogenesis o Formation of ova (eggs) in the ovaries o Daughter cells have equal amt of genetic material but not cytoplasm Chapter 2: Mitosis & Meiosis o Results in 2 polar bodies and an ootid (which develops into the mature ovum) Meiosis is critical to sexual reproduction in all diploid organisms. Video Lecture Questions Cells get the right number of chromosomes after each division by chance, by diverse uses of mechanical tension from mitotic forces, and by chromosome chemistry Chapter 3: Single-Gene Inheritance Pure bread – pure breeding Recombination occurs: - prophase I biological property example: disease resistance Mendel’s Law of Segregation states that allele pairs segregate equally into gametes during meiosis. This means that a gamete will have only one allele of any given gene, and that the probability of a gamete having one allele or the other is equal (and therefore ½, or 50%, for either allele). The genotype frequencies inside a Punnett square are calculated using the product rule: The probability of two independent events occurring simultaneously is the product of their individual probabilities. Selfing: self-fertilization of individuals P1: parental generation F1: first filial generation F2: second filial generation Reciprocal crosses: the results of the crosses are not sex-dependent (i.e. Mendel’s monohybrid crosses) Mendel’s Postulates 1. Genetic characters are controlled by unit factors existing in pairs in individual organisms 2. When two unlike unit factors responsible for a single character are present in a single individual, one unit factor is dominant to the other which is said to be recessive 3. During the formation of gametes, the paired unit factors separate, or segregate, randomly so that each gamete receives one or the other with equal likelihood. 4. During gamete formation, segregating pairs of unit factors assort independently of each other Testcross: a cross between an individual whose genotype at one or more loci may be unknown and an individual who is homozygous recessive for the gene or genes in question Mendel’s dihybrid ratio- 9:3:3:1 Theory of continuous variation: offspring are a blend of their parents’ phenotypes n The Binomial Theory: (a+b) = 1 - a & b are probabilities - n is the total - What is the probability that in a family with 4 children two will be males and two will be females? Chapter 3: Single-Gene Inheritance o A= male= ½ o B= female= ½ o N=4 o (a+b) = a + 4a b + 6a b + 4ab + b 3 4 o 6a b describes 2 males and 2 females 2 2 6(1/2) (1/2) = 3/8 Chi Square Analysis evaluates the influence of chance on genetic data - The outcomes of independent assortment and fertilization, like coin tossing, are subject to random fluctuations from their predicted occurrences as a result of chance deviation - As the sample size increases, the average deviation from the expected results decreases - Null hypothesis (H 0 – there is no real difference between the measured values and the predicted values o Rejected: observed deviation is not attributed to chance alone o Fails to be rejected: any observed deviations are attributed to chance - X = ∑ (o – e) /e - Degrees of freedom (df) = n -1 o N= # of possible outcomes o Df increases with increasing n, but not necessarily with increasing # of subjects - Probability value (p value) o When p<0.05 reject the hypothesis of a 1:1:1:1 ratio Independent assortment explains why a collection of meiotic products that includes gametes of genotype Ab will also include gametes of genotype AB in roughly the same proportion.
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