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Pennsylvania State University
BIOL 133
Denise Woodward

Bio 133 Chapter 1- Overview of genetics 1/9/13 Important Terms • Genes and alleles • DNAand RNA • Chromosomes • Genome • Genotype • Phenotype • Karyotype • Genetic Testing Genes and Alleles Gene – segment of DNA(a gene codes for production of a protein) Allele – variant of a gene Protein gives the animal a characteristic- example allele can code for a flower to be purple :: a white allele codes for no pigment. Example: Sickle-cell anemia • Caused by mutated gene - codes for component of hemoglobin (carries oxygen through out body) • An allele of the gene codes for a defective hemoglobin (doesn't make a functional protein) • Result is sickle-cell anemia. 3 billion base pairs in a human genome- 1 change can cause sickle cell-- changing from a T to an A-- makes an abnormal protein DNAand RNA • DNA = Deoxyribonucleic acid. (Sugar Oxyribose) – 4 DNAbuilding blocks:A, T, G, C – Double-stranded Aattaches to T, G attaches to C • RNA = Ribonucleic acid. Intermediary between genes and proteins. (Sugar Ribose) – 4 RNAbuilding blocks:A, U, G, C Ain DNA= a U in RNA- theres no T in RNA – Single-stranded Chromosomes • Long strand of DNAand proteins. Each chromosome contains many genes. • Humans: 46 chromosomes in all cells except sperm and eggs. – 23 from mom – 23 from dad Genomes • All genes in cells of a particular type of organism. • Human genome is approximately 20,000 genes • Corn has 30,000 genes and the worm C. elegans has 10,000 Genotype and Phenotype Genotype – alleles an organism contains Phenotype – how those alleles are expressed (what the organism looks like- appearance). Ex: Flower color PP = purple (homozygous) Pp = purple (heterozygous) pP = purple (heterozygous) pp = white (homozygous) Ratio 1:2:1 (genotype) 3:1 (phenotype) Karyotype • Chart that displays chromosome pairs in size order. - organize chromosomes into pairs in chart then arrange them by size • How can we use a karyotype? - Some genetic conditions can be viewed in a karyotype- ex. 1 extra, 1 less chromosome 3 chromosomes in the 21st pair (Trisomy 21) - Down syndrome - Large Genetic mutations radiation can cause a mutation Mendelian Traits • Gregor Mendel • Studied traits determined by a single gene. Mendelian Traits • One gene causes a specific phenotype (disease) - one gene determines 1 trait • Examples: Sickle-cell anemia, cystic fibrosis, hemophilia Are all genetic traits Mendelian? No: ex, eyes, height, skin color • How many genes determine human height? • How many genes determine eye, hair, and skin color? • How many genes determine the development of heart disease? ^^ these are polygentic traits- many genes involved 1/11/13 ONE GENE DOES NOT LEAD TO ONE DISEASE Multifactorial Traits • Atrait caused by one or more genes and the environment. • Examples: height (genetics and nutrition), hair color, hypertension, breast cancer, diabetes Breast Cancer • Genetic factors: BRCA1 and BRCA2 – genes that contribute to development of breast cancer. • Non-genetic factors: early menarche, late menopause, first child after age 30, hormone replacement therapy--- (all 4 increases estrogen and extra estrogen increase chance for cancer), alcohol use radiation exposure, chemical exposure, obesity. Risk is reduced by low-fat and high fiber diet, regular exercise. ***** most important- affects people more • Syndrome factors: Some breast cancers are related to other genetic syndromes (ex: Werner’s syndrome) Genetic Testing • Analysis of human DNA, RNA, chromosomes, proteins, or metabolites, to detect genotypes, mutations, or chromosomal changes • 2008: Genetic Information NondiscriminationAct (GINA) - insurance companies or employers cannot deny healthcare based on what is found in genetic testing • Direct-to-consumer genetic tests - no doctors involved - ex. 23andMe.com Cell Components and the Cell Cycle 1/11/13 Macromolecules (Macro-big) (organic-carbon) • Proteins • Carbohydrates • Lipids • NucleicAcids Proteins • Enzymes: speed up reactions • Provide structural support • *Control gene expression - cells have specific proteins that turn on a gene to determine where it will lie in the body- (skin cells become skin cells) Prions – rogue proteins - protein can become infected and change its shape - change in shape, changes the function (proteins can be infectious) • Cause “Mad Cow Disease” Carbohydrates (sugars) • Provide energy for cell metabolism • Provide structural support • Provide cell identity Starch turns into glucose --- cannot digest cellulose Lipids (fats) • Provide energy (dietary fats) • Are main component of cell membranes • Many are hormones (chemical messengers) Ex of lipids- estrogen, testosterone NucleicAcids • *Genetic material • Energy source- ATP Organelles • Nucleus • Endoplasmic reticulum • Golgi apparatus • Lysosomes • Peroxisomes • Mitochondria • Cell Membrane • Cytoskeleton • Modifications to these structures can result in disease 1/14/13 Nucleus genetic material- DNAnever leaves nucleus Endoplasmic Reticulum connected to nucleus- two types: Rough: site of protein synthesis for export out of cell- ribosomes attached Smooth: detoxify toxins--- no role ins production of proteins Liver has a large amount of smooth ER- detox Golgi Apparatus Proteins are modified and labeled for transport outside cell (export) Lysosomes Contain digestive enzymes that breakdown cellular material (gets rid of worn out/ no functional organelles--- get recycled----- increase efficiency of cells) Peroxisomes produce bile for fat digestion Mitochondria Maternally inherited, have their own genes ProduceATP- necessary for cells to do work Cytoskeleton maintains cell shape and structure Helps move substances around cells What role does the cytoskeleton play in cancer cells? Cancer- uncontrolled cell division Dividing cells use cytoskeleton to move chromosomes apart. if cytoskeleton is disrupted, cell cannot divide Cell Membrane Made of phospholipids and proteins control movements of substances in and out of cell What are ions? something with a pos/neg charge---- How do ions move through the cell--- travel through what happens if someone has faulty ion channels? Cellular disorders that result in disease - HPP and abnormal Na+ channels - Long QT syndrome and K+ channels - Cystic fibrosis and Cl- Channels Why are disease that result from faulty ion channels considers genetic disease? Ion channels are proteins and proteins are coded for by DNA Cell Division • Mitosis or Meiosis • Mitosis – cell division for growth, repair (cloning division – daughter cells are genetically identical to parent cell) • Meiosis – cell division for reproduction (produces eggs and sperm and generates genetic variation) before a cell divides its a single strained, then it doubles to replicate The 2 strands of the replicated chromosome are “chromatids”. They are genetically identical to each other. Cell Cycle • Interphase – chromosomes are replicated ---- most of the cell cycle--- everything but mitosis--- S phase of interphase is when DNAis being relicated • Mitosis – division of nucleus and cytoplasm. Control of Cell Cycle • Most cells divide a limited number of times • Telomeres (tips of chromosomes) are degraded with each mitosis Apoptosis • Programmed cell death • “Death receptor” receives signal for cell to die – enzymes in cell begin degrading cell components Stem Cells 1. Totipotent cells – cells that can differentiate into any cell type Chapter 3 Meiosis and Development Meiosis – why does this happen? 2. Cell division for reproduction 3. Diploid cell (2n)  4 haploid cells (1n) o Mitosis: 1 (2n)  2(2n) = cloning 4. Each daughter cell is different from others 5. Generates genetic diversity equation used to determine the # of chromosome combination that are possible 2^n = # of combos n= # of chromosomes pairs how many different combinations are possible in a diploid cell of 8 chromosomes? 2^4 Meiosis I • Prophase I • Metaphase I • Anaphase I • Telophase I • Meiosis I: reduces ploidy level and separates homologous chromosomes Homologous chromosomes • Chromosomes w/ same size, shape, and linear arrangement of genes (can have different alleles) Meiosis I: reduction division Meiosis II: equational division Prophase I – What happens? • Chromosomes condense • Homologous chromosomes synapse (attach to each other) • Crossing over can occur Crossing Over • Crossing over produces • genetic diversity When a cell with 2 chromosome pairs goes through meiosis, how many different chromosome arrangements are possible? • 4 possible chromosome arrangements When a cell with 3 chromosome pairs goes through meiosis, how many different chromosome arrangements are possible? • 8 possible chromosome arrangements n # possible arrangements = 2 n=# of homologous pairs IndependentAssortment • Metaphase I • Non-homologous chromosomes line up independently of each other After meiosis, gametes mature into sperm and eggs • Where are sperm formed in the human male? • Where are eggs formed in the human female? Spermatogenesis • Spermatogonium (2n): precursor to sperm cells • Spermatogonium  (Mitosis)  primary spermatocyte (2n) • primary spermatocyte  (Meiosis I)  secondary spermatocyte (1n) • secondary spermatocyte (Meiosis II)  spermatid Spermatogenesis • Each spermatid then develops flagella and becomes individual spermatozoa • Sperm are small and do not house many organelles (nucleus and mitochondria) Contains nucleus and acrosome (digestive enzymes to enter egg) Oogenesis • Oogonium (2n): precursor to egg cells • Oogonium  (Mitosis)  primary oocyte (2n) • primary oocyte  (Meiosis I)  secondary oocyte and polar body (1n) • secondary oocyte  (Meiosis II)  ovum and polar body Oogenesis • Ovum gets most of the cytoplasm • Eggs arrest in Prophase I until puberty – then continue to metaphase II and arrest again until fertilization Prenatal Developmen
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