© Fall 2005, Pflugerville ISD, 7th Grade Homeroom Warm Up List the 4 major layers of the Earth from the hottest to the coolest. Also list at least one fact about each layer.

© Fall 2005, Pflugerville ISD, 7th Grade Science Warm Up Scientist theorize that the Atlantic Ocean is slowly increasing in width. Which is the best approximation of the rate at which lithospheric plates beneath the Atlantic Ocean are moving? A.2 millimeters per year B.2 centimeters per year C.2 meters per year D.2 kilometers per year

© Fall 2005, Pflugerville ISD, 7th Grade Vocabulary Words You should be able to define all of the following words 1.Genes 2.Genotype 3.Phenotype 4.Chromosome 5.Inherited Trait 6.Recessive Trait 7.Dominant Trait 8.Heredity 9.Homozygous 10.Heterozygous

© Fall 2005, Pflugerville ISD, 7th Grade What is genetics? The scientific study of heredity

© Fall 2005, Pflugerville ISD, 7th Grade copyright cmassengale 5 Gregor Mendel ( ) The Father of Genetics

© Fall 2005, Pflugerville ISD, 7th Grade Gregor Johann Mendel  Austrian monk  Studied the inheritance of traits in pea plants  Developed the laws of inheritance  Mendel's work was not recognized until the turn of the 20th century 6

© Fall 2005, Pflugerville ISD, 7th Grade Gregor Johann Mendel  Between 1856 and 1863, Mendel cultivated and tested thousands of pea plants  He found that the plants' offspring retained traits of the parents copyright cmassengale 7

© Fall 2005, Pflugerville ISD, 7th Grade copyright cmassengale 8  Mendel stated that physical traits are inherited as “particles”  Mendel did not know that the “particles” were actually Chromosomes & DNA Particulate Inheritance

© Fall 2005, Pflugerville ISD, 7th Grade Why peas?  Can be grown in a small area  Produce lots of offspring  Produce pure plants when allowed to self- pollinate several generations  Can be artificially cross-pollinated copyright cmassengale 9

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel tested 7 traits: 1.Flower color 2.Flower position 3.Seed color 4.Seed shape 5.Pod shape 6.Pod color 7.Plant height

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel crossed flowers that were true- breeding for each characteristic. He crossed a purple (PP) flowered plant with a white (pp) flowered plant. (Parent Generation)

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas The first generation (F1) of plants all had purple flowers. Where did the white color go?? (Pp) (Pp) Purple Parent (PP) White Parent (pp)

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel took two of his first generation (F1 x F1) purple flowered plants and crossed them together. In the second generation (F2) he had 3 purple flowered plants, and 1 white flowered plant. (PP) (Pp) (pp) Purple Parent (Pp)

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel noticed in the first generation, all of the white flowers seemed to disappear. He called this a recessive trait. The white color faded into the background at first. It showed up in the next generation when he pollinated the flowers.

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas The color (purple) that seemed to mask over the recessive color was named the dominant trait.

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel was responsible for figuring out that each plant carried two sets of instructions for each characteristic (one from the “mom” and one from the “dad”). Like many scientists, his work was not accepted until after his death.

© Fall 2005, Pflugerville ISD, 7th Grade Let’s Review 1. If you crossed a true-breeding black rabbit with a true-breeding white rabbit, all of the offspring would be black. Which trait is dominant in rabbits: black fur or white fur? 2. Which trait is recessive?

© Fall 2005, Pflugerville ISD, 7th Grade Answer The trait for black fur is dominant over the trait for white fur. The white fur trait is recessive. (Bb) (Bb) (Bb) Black Rabbit (BB) White Rabbit (bb)

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Vocabulary 1.Heredity- the passing of traits from parent to offspring. 2. Dominant trait- the trait observed when at least one dominant allele for a characteristic is inherited 3. Recessive trait- a trait that is apparent only when two recessive alleles for the same characteristic are inherited

© Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas 4. Genes- a segment of DNA that carries hereditary instructions and is passed from parent to offspring. Genes are located on chromosomes. 5. Alleles- multiple forms of the same gene 6. Genotype- an organisms inherited combination of alleles 7. Phenotype- an organisms inherited appearance

© Fall 2005, Pflugerville ISD, 7th Grade Probability The likelihood of a particular event occurring. Chance Can be expressed as a fraction or a percent. Example: coin flip.

© Fall 2005, Pflugerville ISD, 7th Grade Punnett Square Developed by Reginald Punnett. A diagram used to show the probability or chances of a certain trait being passed from one generation to another.

© Fall 2005, Pflugerville ISD, 7th Grade Reading Punnett squares Gametes are placed above and to the left of the square Offspring are placed in the square. Capital letters (Y) represent dominant alleles. Lower case letters (y) represent recessive alleles.

© Fall 2005, Pflugerville ISD, 7th Grade Homozygous = when an organism possesses two identical alleles. ex. – YY or yy Heterozygous = when an organism possesses different alleles. ex. – Yy

© Fall 2005, Pflugerville ISD, 7th Grade Phenotype vs genotype Genotype  The genetic makeup  Symbolized with letters  Tt or TT Phenotype Physical appearance of the organism Expression of the trait Short, tall, yellow, smooth, etc.

© Fall 2005, Pflugerville ISD, 7th Grade Punnett square example

© Fall 2005, Pflugerville ISD, 7th Grade More Practice Unit A : Chapter 1 : Section 1

© Fall 2005, Pflugerville ISD, 7th Grade Punnett square review:

Science Closure In a certain breed of dog, short hair (H) is dominant to long hair (h). A short-haired dog (Hh) is crossed with a long- haired dog (hh). A Punnett square of this cross is shown below. What is the probability that one of the puppies produced by these parents will have short hair? A. 0% B. 25% C. 50% D.100% Unit A : Chapter 1 : Section 1

© Fall 2005, Pflugerville ISD, 7th Grade Science Closure The image shows a chromosome. What is located on the chromosome? A cells B genes C enzymes D organelles