BIOL 120 Week 3 Notes
BIOL 120 Week 3 Notes BIOL120
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This 8 page Class Notes was uploaded by Julia Delaluz on Saturday February 27, 2016. The Class Notes belongs to BIOL120 at Towson University taught by Dr.Partain in Winter 2016. Since its upload, it has received 12 views. For similar materials see Principals of biology in Biology at Towson University.
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Date Created: 02/27/16
BIOL 120 Principles of Biology (Dr. Partain) Week 3 Notes (2/192/26) GENETICS Heirarchy of Genetic Information Traits: o an inherited characteristic controlled by genes found on DNA Chromosomes: o structural unit containing part or all of an organisms genome consisting of DNA and its associated proteins o Pairs: in sexually reproducing organisms, one of the pair in inherited from dad, one from mom These are called homologous pairs o Karyotype: A pictorial arrangement of a full set of an organism’s chromosomes In humans, there are 22 pairs of autosomes and 1 pair of sex chromosomes o Chromatids: One of the two identical strands of chromatin or half of a replicated chromosome Genes: o A segment of a chromosome that carries specific information about a trait o Contains info about anything your body needs o Sometimes, genes carry mutations that cause disease or changes in traits o They are instructions carried by DNA These instructions are for building all of the proteins that the cells require Genome: o The entire suite of genes present in an organism o Each cell in your body has a complete set of instructions about how to make your cells, their components, and their component’s components This set of instructions is called your genome Your body has about 100,000,000,000,000 cells Francis Watson & James Crick described DNA’s structure in 1953, won Nobel Prize in 1962 o Description was built largely on work of Rosalin Franklin, who took xray diffraction images of DNA DNA & It’s Structure Deoxyribonucleic Acid The information molecule stored in the nucleus of eukaryotic cells and in the cytoplasm of prokaryotic cells Composed of nucleotides Nucleotides have 3 parts: o a phosphate o a sugar (deoxyribose for DNA nucleotides) o one of 4 bases: Adenine (A) Guanine (G) Thymine (T) Cytosine (C) Complementary Bases: o There is a specific pattern of the bases that connect the two strands o Called complementary base pairs, like the steps of a spiral staircase A always bonds across from T C always bonds across from G Because of this, if only one strand of DNA is known, the other can be easily deciphered Ex: one side ATCGGCA Other side TAGCCGT SugarPhosphate Backbone: o Connected end to end to form a structure that is like the hand rail of the spiral staircase o Like you backbone, the sugarphosphate backbone supports and gives shape to the DNA molecule Chromosome A long, single molecule of DNA and associated proteins Housed in nucleus Can carry hundreds of genes along its length Each cell has a complete set of chromosomes o All genes are present DNA: molecule of heredity that stores info required for making all of the proteins required in a cell o Manages information o stores information o duplicates information when needed o transfers and decodes information when needed RNA: information carrying molecule composed of nucleotides PROTEIN SYNTHESIS 2Step Process o 1. Transcription DNApolymer of nucleotides (two complementary strands) copying of DNA gene into RNA o 2. Translation RNApolymer of nucleotides (single strand) Decoding the copied RNA sequences and producing the protein for which it codes RNA is translated into a protein (polymer of amino acids), enzyme is made o Example: DNA one side TAGCAG DNA other side ATCGTC RNA Translation AUCGUC (RNA does not have T, it has U) MEITOSIS Happens in Somatic Cells (body cells) o Mitosis (happens everywhere but sex cells) For growth and repair Makes identical copies Happens in Germ Cells (sex cells) o Meiosis To make gametes (eggs/sperm) Makes unique cells ½ chromosomes # one of each type of chromosome OVERVIEW OF CELL DIVISION Interphase Mitosos Cytokinesis CELL CYCLE Interphase: o longest phase of cell o Protein synthesis o Suicide? o DNA is copied (replication) Chromosomes are uncondensed (when they can be used) (unduplicated) Mitosis: o Chromosomes are condensed (X shape) (duplicated) (duplicated splits) o DNA is split equally into two halves of the chromosome o Moving to opposite sides of the cell Cytokinesis: o Parent cell is divided in half into two daughter cells PROTEIN SNYTHESIS VS. DNA REPLICATION SIMILARITES: A. DNA unzips and unwinds B. Free nucleotides are matched C. Takes place during Interphase DIFFERENCES: A. Protein Synthesis starts in the nucleus, continues in Ribsomones a. DNA Replication all takes place in the nucleus B. Protein Synth. is a 2step process a. DNA rep. is not VARIATIONS Brain and nerve cells form in the embryo and then never divide Many leaf cells: divide as young leaves, stop dividing and simple increased in size by growing Bone marrow cells: divide rapidly; forming as many as 20,000 new cells per minute CANCER Is a two part failure in the cell cycle o When the cell is unable to repair DNA, stop growth, or commit suicide Benign tumor not mutated, just a mass of cells, not aggressive o Formed if cell division is over stimulated Malignant tumor mutation occurred o Formed if cell cannot correct mutation, supposed to kill the cell Problem with tumor suppressor gene mutated cell will keep going, invading surrounding tissue become malignant, cancerous tumor SUMMARY of CANCEROUS CELLS Uncontrolled cell division Suppressor genes are unable to turn off growth, repair DNA, or cause cell suicide Metastasis causes cells to migrate They are immortal Detecting Cancer Risk factors: chemical, sun exposure, nutrition & health, age Genetic testing: looking for mutations Detecting chemicals in the blood: certain cancer cells secrete proteins that are detectable in the blood Biopsy: take a portion of tumor and examine the cells Treating Cancer Chemotherapy: highly toxic chemicals that will kill cells Cancer cells become resistance at 1 cell per million. Average tumor contains 1 billion cells, so ~1,000 are resistant Radiation Therapy: high energy radiation pointed at tumor cells will destroy DNA, therefore destroying the cell What do we need to Pass along our heritage? Something to pass along: info about the organism A mode of passing it along A way of determining its value to the organism What are we passing along? DNA… has all the instructions for making a new organism What is the Mode? Sexual Reproduction: o Two unique individuals contrinbuting half of their own DNA toward the production of a new individual o New individual has its own unique set of DNA Asexual Reproduction: o A single individual gives rise to identical offspring o No new combos of DNA are produced except through random mutation Asexual Reproduction: o Passing along an exact copy of instructions to an individual o ADVANTAGES: Guarantees passing along genes to one’s offspring No care for young required All individuals can reproduce Easier to carry out/more efficient Happens at a faster rate more offspring can be made o DISADVANTAGES: No genetic diversity produced Large accumulation of mutations Possible increased susceptibility to diseases or environmental change Sexual Reproduction: o Combines info from 2 individuals to produce a new, unique individual o ADVANTAGES: Huge amount of genetic diversity Fewer amounts of mutations Fights disease o DISADVANTAGES: Social behavior increases risk of spreading disease Physically demanding/time consuming: growing and raising offspring Requires time at the cellular level Time & energy devoted to finding the “right” mate Only some can reproduce How Many Chromosomes are In Our Gametes? Germ Cells (gametes): egg and sperm: in humans 23 chromosomes, one form each of the pairs Somatic cells: every other cell in the body: in humans 23 pairs or 46 How Are Gametes Made? o Diploid “stem” cells undergo Meiosis and become haploid cells o Diploid: having a full set of chromosomes, one from each parent. IN humans that means 23 pairs of chromosomes for a total of 46. o Haploid: having half the # of chromosomes, one form pair, for a total of 23 (in eggs and sperm) 8 million gamete possibilities per individual With sexual reproduction: 8 million (male) x 8 million (female) = 64 trillion possible differing offspring *not including mutations Meiosis process by which chromosomes number is reduced in half to produce the gametes diploid cells are put through a process Chromosomes match up as a homologous pair, one from mom and one from dad They trade genes Two sets pulled to opp ends of the cell that turns them into haploid cells these cells then become sperm or egg Diversity Arises From Sexual Reproduction & Random Fertilization o Alleles from 2 parents Genetic Recombination: o Independent Assortment Homologous pairs (one from mom & one from dad) are situated at the metaphase state. The homolog’s orientation is as random as the flip of a coin o Crossing Over: Gene for gene exchange of genetic info between members of a homologous pair of chromosomes occurs during meiosis I, it is believed to occur several times on each homologous pair o Diploid cells have 23 pairs Sex Determination in Humans Formation of Twins o Identical: One sperm has fertilized one egg, it splits, and the genetics are identical o Fraternal: Two eggs, fertilized by different sperm Modern Genetics Gregor Mendel: o Father of genetics o Published his work on peas in 1865 Mendel’s ideas… o Law of Segregation (from meiosis): Each organism has 2 hereditary unites for each trait and during gamete formation These units segregate from each other and pass on to different gametes. Each gamete receives only one copy (allele) o Law of Independent Assortment (from meiosis I): In the formation of gametes, the distribution of hereditary unites for one trait is independent of the distribution of hereditary units for the other unit Different traits are inherited independently of each other Mendelian Inheritance Terms Genotype: genetic composition of an individual Phenotype: physical traits Allele: alternate versions of the same gene o The effect of and individual’s genotype on her phenotype depends on the nature of the alleles she carries Dominant: when one allele completely covers up the other allele for a gene Recessive: when one allele is completely covered up by the other allele in a gene Homozygous: genotype where the alleles are the same Heterozygous: genotype where the alleles are different o Heterozygous genotype carries the gene but does not have it themselves. Ex: BALDNESS, GENOTYPE Bb= not bald, but carries gene Punnett Square P p P Homozygous Heterozygous Dominant p Pp pp HeterozygouHRecessive