- Slides: 20
Characteristics of Living Things ● Characteristics of living things are influenced by heredity and environment. Traits are influenced by both the environment and the genetics of the individual. Acquired traits are not inherited. ● Shaved head, dyed hair, increased weight due to overeating Genetic traits are inherited. ● Eye color, hair color, height
Hereditary Information Hereditary information is contained in genes, which are segments of DNA / genes are located in the chromosomes of each cell. Cells contain many thousands of different genes. One or many genes can determine an inherited trait of an individual.
Hereditary Info. Contd… Genes also contain information for the production of proteins. Before a cell divides, this information must be copied and divided evenly into the daughter cells. Review: DNA Replication Cell Division m. RNA codons / amino acids proteins
Types of Traits: Dominant v. Recessive Dominant: an organism with a dominant allele will always exhibit that form of the trait. ex. T If T represents Tall and t represents short, then… TT would be tall and Tt would be tall Recessive: an organism with a recessive allele tt would be short will exhibit that form only when the dominant allele is not present. ex. t
Codominance, Polygenic, and Sexlinked traits Codominant: when both alleles contribute to the phenotype. ex) speckled black and white chicken feathers Polygenic: Traits controlled by 2 or more genes. ex. ) Height and skin color Sex-linked traits: if a gene is found only on the Y or X chromosome. ex. ) Color blindness in males.
Types of Traits, con’t. The offspring of crosses between parents with different traits are called hybrids. Offspring of crosses between parents with the same traits are called purebreds. Genotype: the genetic combination of alleles. ex. Tt , TT, or tt Phenotype: the physical appearance of that trait. ex. Tall, short
Homozygous vs. Heterozygous Homozygous means the same (purebred) Heterozygous mean different (hybrid) Homozygous dominant= TT Heterozygous= Tt Phenotype would be Tall Homozygous recessive=tt Phenotype would be Short
Gregor Mendel was an Austrian monk who studied genetics using pea plants. Mendel is considered the “father” of genetics
Probability and Punnett Squares Mendel’s work involved probability and he used punnett squares: Probability = The likelihood that a particular event will occur ex. ) Coin flip. Probability can be used to predict the outcomes of genetic crosses. The gene combinations that might result from a genetic cross can be determined by drawing a diagram known as a Punnett Square.
Probability What is the probability you get a green m and m? What is the probability you will pick a #5 out of a deck of cards?
Punnett Squares The types of gametes (sex cells) produced by each F 1 (first generation) parent are shown on the top and left sides of the square. The possible gene combinations for the F 2 offspring appear in the four boxes that make up the square. You try: Cross a heterozygous Tall plant with a heterozygous Tall plant. How many plants will be tall? How many plants will be short?
Probabilities & Ratios of Outcomes In a heterozygous cross, Tt X Tt, you will always have a 3: 1 ratio of dominant to recessive traits for phenotype. (3 tall, 1 short) In a heterozygous cross, you will always have a 1: 2: 1 ratio for genotypes. (1 TT, 2 Tt, 1 tt)
Examples: Make a punnett square for each of these, then answer the question. . . 1. Cross a heterozygous tall plant with a homozygous short plant. What is the ratio of tall to short plants? 2. YY x yy: What are the genotype and phenotype ratios of the possible offspring? 3. Ggx. Gg: What are the genotype and phenotype ratios of the possible offspring?
Recombination of DNA naturally recombines during reproduction Recombination results in the great variety and diversity of life DNA Recombination explains how the offspring of two parents can have variation Example: Siblings can look very different from each other or very similar The amount of variation depends on the amount of recombination
Genetic Engineering The use of various methods to manipulate the DNA (genetic material) of cells to change hereditary traits or produce biological products. Genetic engineering techniques provide great potential and responsibilities. Ethical Question: What responsibilities come with the power to manipulate DNA?
Genetic Engineering: Friend or Foe? Genetically engineered products include: Plants that are resistant to diseases, insects, and herbicides. Drugs (human insulin, growth hormone) Bacteria designed to break down industrial wastes. Pros vs. Cons?
Tracing Traits: Using a Pedigree A pedigree is a diagram that traces the occurrence of a trait in a family.