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Transcript
TOPIC 1 : Introduction to the Cell & Cell Theory The Cell Theory 1. All living things are composed of one or more cells. 2. Cells are the basic units of structure and function in an organism. 3. Cells come only from existing cells. Cells are Diverse… both in size, shape, and internal organization. Why Are Cells So Small? Transport- Cell volume to surface area ratios favor small size. Control- Nucleus to cytoplasm consideration. How small can a cell be? Mycoplasmas - bacteria that are 0.1 to 1.0 mm. (1/10 the size of regular bacteria). Note: 1.0 mm = one millionth of a meter All cells have…… Plasma (cell) Membrane Nucleus (eukaryotes only) Cytoplasm (an area) Organelles (structures with specialized functions) Cell Types Prokaryotes- simple cells that do not have internal membranes example = bacteria Eukaryotes- more complex cells that do have internal, membrane-bound structures examples = plants and animals Timeline Prokaryotic Organisms: First appeared 3.5 BYA include bacteria and cyanobacteria Eukaryotic Organisms: First appeared 2.0 BYA include protists, fungi, plants and animals Key Differences: Prokaryotes • Lack a nucleus and other membrane bounded structures. • Have small ribosomes • DNA is not organized into chromosomes • Flagella are not made of microtubules and does not have a 9+2 structure • Cell walls are made of peptidoglycan, not cellulose Eukaryotes • • • • • Have a nucleus and other membrane bounded structures. Have large ribosomes DNA is organized into chromosomes Flagella are made of microtubules and have a 9+2 structure Cell walls are made of cellulose Examples Prokaryotic Eukaryotic Nucleus Eukaryotic Prokaryotic TOPIC 2 : The Organization of Living Things Key Concept As multicellular organisms develop, their cells differentiate (change & separate) and form levels of organization Why it Matters: Humans (we are multicellular) can have different kinds of cells, tissues, organs, and organ systems Unicellular Organisms “uni-” = one Prokaryotes are unicellular organisms Some algae, some protists, and some eukaryotes (yeasts), are unicellular Can still do everything they need to stay alive Benefits over multicellular organisms: Need fewer resources Can live in harsher conditions Multicellular Organisms “multi-” = more than one Plants, animals, some protists, and most fungi are multicellular Start as a single cell many cells cells differentiate (change) into different types of cells cells group together Multicellular Characteristics Larger size = have less predators and have more options of things to eat Longer life – organism will continue to live even if a single cell dies Specialization – each type of cell has a specific job, making the organism more efficient Levels of Organization 1st Level: Cells 2nd Level: Tissues 3rd Level: Organs 4th Level: Organ Systems Cells Tissues Organs Organ Systems Level 1 : Cells Cells can be specialized (have a certain function) Function = job Function is related to the cell structure Structure = how parts of the cell are put together Shape Material it’s made from Structure of a brain cell is different from muscle cell Level 2: Tissues Tissue = group of cells that work together to do a specific job Ex: Heart muscle tissue is made of heart muscle cells Animals have 4 types of tissue: nerve, muscle, connective, protective Plants have 3 types of tissue : transport, protective, ground Level 3: Organs Organ = structure that is made up of 2 or more tissues working together to get a specific job done Ex: Stomach – muscle tissue moves food, special tissues make chemicals to digest food, connective tissue holds stomach together, nervous tissue sends messages back and forth between the stomach and brain Level 4: Organ Systems Organ system = group of organs working together to perform a specific function Each organ system has a specific job Ex: Digestive system is made of several organs including the stomach and intestines Structure of Animals Cells -basic unit of an animal’s structure -become specialized _______________________________ Tissues -made of cells that work together to perform a specific function __________________________________________ Organs -made of different types of tissues that work together to perform a specific function ____________________________________________________ Organ Systems -made of organs that work together to perform a specific function _____________________________________________________________ Organisms TOPIC 3: GENETICS Early Genetics • The study of genetics began with observations made by Gregor Mendel. • After noticing that the flowers his pea plants were either violet or white, Mendel began to study the segregation of heritable traits. Between 1856 and 1863 he cultivated and tested at least 28,000 pea plants. Remember that Mendel worked almost 150 years ago when nobody knew about genes or even the structures (chromosomes) that carry genes. Here are some traits observed by Mendel: Let’s consider a single gene… • A gene carries information that determines your traits. Traits are characteristics you inherit from your parents. • Genes are located in chromosomes. • Chromosomes come in pairs and there are thousands, of genes in one chromosome. Continued… • In humans, a cell’s nucleus contains 46 individual chromosomes or 23 pairs of chromosomes. • Half of the chromosomes come from one parent and half come from the other parent. Here is the detailed structure of a chromosome This is a human karyotype representing the 23 pairs of chromosomes in a male Definitions • Allele- discrete version of the same gene • Genotype- the genes of an organism for one specific trait • Phenotype- the physical appearance of a trait in an organism Definitions • Dominant trait refers to a genetic feature that “hides” the recessive trait in the phenotype of an individual. • The term "recessive” describes a trait that is covered over (or dominated) by another form of that trait and seems to disappear. • Homozygous= two alleles that are the same for a trait (Pure) • Heterozygous= two different alleles for a trait (Hybrid) • Genetics – study of how traits are passed from parent to offspring • Traits are determined by the genes on the chromosomes. • A gene is a segment of DNA that determines a trait. • Chromosomes come in homologous pairs, thus genes come in pairs. Homologous pairs – matching genes – one from female parent and one from male parent • Example: Humans have 46 chromosomes or 23 pairs. One set from dad – 23 in sperm One set from mom – 23 in egg • One pair of Homologous Chromosomes: Gene for eye color (blue eyes) Homologous pair of chromosomes Gene for eye color (brown eyes) Alleles – different genes (possibilities) for the same trait – ex: blue eyes or brown eyes Dominant and Recessive Genes • Gene that prevents the other gene from “showing” – dominant • Gene that does NOT “show” even though it is present – recessive • Symbol – Dominant gene – upper case letter – T Recessive gene – lower case letter – t Dominant color Recessive color • Both genes of a pair are the same – homozygous or purebred TT – homozygous dominant tt – homozygous recessive • One dominant and one recessive gene – heterozygous or hybrid Tt – heterozygous BB – Black Bb – Black w/ white gene bb – White Genotype and Phenotype • Combination of genes an organism has (actual gene makeup) – genotype Ex: TT, Tt, tt • Physical appearance resulting from gene make-up – phenotype Ex: hitchhiker’s thumb or straight thumb Punnett Square and Probability • Used to predict the possible gene makeup of offspring – Punnett Square • Example: Black fur (B) is dominant to white fur (b) in mice 1. Cross a heterozygous male with a homozygous recessive female. Black fur (B) Heterozygous male White fur (b) White fur (b) Homozygous recessive female White fur (b) Practice • We use two letters to represent the genotype. A capital letter represents the dominant form of a gene (allele) and a lowercase letter is the abbreviation for the recessive form of the gene (allele). • Example below: P=dominant purple and p= recessive white The phenotype for this flower is violet while its genotype (if homozygous) is PP. The phenotype for this flower is white while its genotype is pp (to be white the flower must have two of the recessive copies of the allele). Punnett Squares The Punnett square is the standard way of working out what the possible offspring of two parents will be. It is a helpful tool to show allelic combinations and predict offspring ratios. Before we go further lets review how to set up a Punnett Square… We begin by constructing a grid of two perpendicular lines. Next, put the genotype of one parent across the top and the other along the left side. For this example lets consider a genotype of BB crossed with bb. B b b B • Notice only one letter goes above each box • It does not matter which parent’s genotype goes on either side. Next, fill in the boxes by copying the column and row head-letters down and across into the empty spaces. B B b Bb Bb b Bb Bb Punnett Squares Now that we have learned the basics of genetics lets walk through some examples using Punnett Squares. W w WWW Ww w Ww ww Usually write the capital letter first Lets say: W- dominant white w- recessive violet Parents in this cross are heterozygous (Ww). Note: Make sure I can tell your capital letters from lowercase letters. What percentage of the offspring will have violet flowers? ANSWER: 25% (homozygous recessive) Red hair (R) is dominant over blond hair (r). Make a cross between a heterozygous red head and a blond. R r r r Rr rr Rr rr What percentage of the offspring will have red hair? 50% Let’s try some more… In pea plants, tall pea plants (T) are dominant over short pea plants (t). Construct a Punnett Square for a heterozygous tall pea plant and a short pea plant. t t T Tt Tt t tt tt What are the percentage of phenotypes? 50% tall 50% short Black eyes (R) is dominant over red eyes (r) in rats. Make a cross between a homozygous rat with black eyes and a rat with red eyes. r r R Rr Rr R Rr Rr What is the possibility of a red eye off springs? 0%