Transcript DNA
Mrs. Hooks 8th Grade Science Learning Targets 1. I can develop and use a model to show and describe the effects of structural changes to genes. 2. I can use and develop a Punnett Square to show genetic variations. 3. I can explain ways in which humans have influenced the inheritance of traits. 4. Explain how some genetic variations increase organisms probability of surviving and reproducing. 5. I can explain how natural selection has led to an increase or decrease in specific traits of organisms over time. Traits • Traits- all of the features an organisms has • Variations- inherited trait that makes an individual different from other members of the same species and results from a mutation in the organism – Genetic variation is a result of subtle differences in our DNA – Genetic variation is what makes us all unique, whether in terms of hair color, skin color or even the shape of our faces. (http://learn.genetics.utah.edu/content/basics/) Gene • Gene- a part of the DNA code on a chromosome. – Humans have tens of thousands of genes on their chromosomes Genotype- genetic makeup Phenotype- way an organism look or behaves, Physical characteristics (http://learn.genetics.utah.edu/content/basics/dna) DNA D.N.A. - Deoxyribonucleic Acid Molecule made of: 1. Deoxy Sugar 2. Combination of four nitrogen bases Either: a. Guanine b. Cytocine c. Thymine d. Adenine DNA • Nitrogen bases pair up – Cytosine & Guanine – Thymine & Adenine • Pairing creates a ladder shape • Angle of bonds creates a twist Ladder and Twist produces the famous “Double Helix” DNA • DNA resides in all cells – Inside the nucleus • Each strand forms a chromosome Cell Nucleus DNA DNA DNA is found in all living cells – It controls all functions a cell – It stores all the genetic information for an entire organism – Single cell like an amoeba – Multi cell like a human inside living Effects of the Environment • Environment can influence an organisms phenotype and genotype – Growth – Appearance – Gender under certain conditions Heredity- the passing of traits from parents to offspring • Alleles-different forms of a trait that make up a gene pair. • Represented by two letters. – Dominant- dominates, covers up – Recessive- is dominated or covered up Genetics-the study of how traits are inherited through the interaction of alleles. Father of Genetics • Gregor Mendel – Accomplishments • Studied math & Science • Experimented in 1856 on garden peas • 1st recorded study of how traits pass from one generation to the next • 1st person to trace one trait through several generations • 1st to use mathematics of probability to explain heredity. • 1900’s became Father of Genetics Father of Genetics • Studies He studied a trait by using different plants with different expressions of the trait and found that ALL new plants looked like ONE of the two parents. Hybrids- received different genotypes information, different alleles, for a trait from each parent. Purebread- organism that always produces same traits generation after generation Father of Genetics • Studies- Traits compared by Mendel – – – – – – – Shape of seeds Color of seeds Color of pods Shape of pods Plant height Position of flower Flower color Mendel’s Principles of Genetics 1. Traits are controlled by alleles on chromosomes 2. An allele’s effect is dominant or recessive. 3. When a pair of chromosomes separate during meiosis, the different alleles for a trait move into separate sex cells. Punnett Squares • Definition- Tool used to predict results in Mendelian genetics • Function- to show probability of possible genotypes and phenotypes for a trait. Genotype- genetic makeup Phenotype- way an organism look or behaves, Physical characteristics • Alleles determine traits: Homozygous- 2 alleles are the same TT- dominant tt- recessive Heterozygous- 2 alleles are different Tt- dominant • Practice – Hair Color – Eye Color – Height Brown ______ Blonde _______ Brown ______ Blue ______ Tall ______ Short ______ Environmental Impact over Time • Environmental influences which organisms can live in an area. – – – – – – Temperature Rainfall Pollution Height of mountains Volcanic eruptions Periodic flooding • Living factors affect species that ae present – Predators – Availability of food – 3 of organisms in am ecosystem Charles Darwin • After visisting the Galapagos Islands he began hypothesizing about reasons for diversity he observed. • Concluded: different, long-term, environmental influences on populations produced the variety of species and that they had changed over time Darwin’s Theory Diversity: The number and variety of species; having many different forms or types; the degree of genetic variation… Galápagos Finches The structure of each bird’s beak is an adaptation to the type of food the bird eats. Match each finch to the type of food you think it eats. Darwin’s Theory Factors That Affect Natural Selection What are the factors of natural selection that affect a group of sea turtles over time? Variation: Some turtles have harder shells. Overproduction: Turtles lay many eggs. Not all of the young will survive. Competition: Faster turtles escape predators. Definition Gradual process where biological traits become more or less common in a population because of inherited traits and interactions with their environment. Characteristics / Factors Affecting Variation in traits/adaptation, overproduction, competition, selection, environmental change, heredity/genes, Natural Selection Examples Variation Finches, Elephants, Peppered Moths Non-Examples Artificial Selection/Selective breeding: Humans breed animals and plants for specific traits. EX: Labradoodle Definition Process, over time, where there are changes in the genetic pool as the result of the organisms interaction with the ecosystem. Characteristics / Factors A change in genetic code through natural selection, mutations, genetic drift A change in the ecosystem Over time: slow or rapid, or punctuated Common Ancestors Evolution Examples • Similar structures in 2 different species • Variations in a species of 2 environments • A species that can avoid its predator Non-Examples Mountain ranges rising Leaves falling off trees Stretching and becoming flexible 8.2 Evidence of Evolution Fossils The fossil record contains examples of the transition from one species into another, as well as the origin of new physical features. Page 257 Evidence of Evolution Page 257 Similarities in Development These four organisms all look similar during their early development. What are similarities and differences among them? 2. Different limb and head shapes in later development. By looking at the early stages of development, scientists can infer evolutionary relationships and the possibility of common ancestors. Evidence of Evolution Homologous Structures The bones in a bird’s wing, a dolphin’s flipper, and a dog’s leg have similar structures. Which bones in the dog's leg match those in the flipper and which match those in the wing? Page 258 Homologous Structures Similar structures that related species have inherited from a common ancestor. Elephant Lab Elephants with Tusk Elephant Lab Elephants with Tusk Elephants with Tusk ✔ ✔ Human Genes and Mutations • Gene undergoes a change, errors occur in the DNA, certain chemicals, X rays and radioactive substances. • 2 Types we will cover: 1. Chromosome Disorder- Error during Meiosis can result in extra or less chromosomes. Usually leads to death Down syndrome- 3 copies of chromosome #21 2. Recessive Genetic Disorder-when both parents have a recessive allele for a disorder. Both parents are heterozygous Ex. Cystic Fibrosis Gender Determination XX- Females XY- Males • Egg has X chromosome • Sperm can have either X or Y chromosome Your gender is determined by your father.