Slide 1 / 141 Slide 2 / 141 7 th Grade PSI Inheritance and Variation of Traits 2015-11-02 www.njctl.org Slide 3 / 141 Table of Contents: Inheritance and Variation of Traits Click on the topic to go to that section Mendelian Genetics · Using Punnett Squares · Test Crosses · Genetic Mutations ·
Slide 4 / 141 Mendelian Genetics Return to Table of Contents Slide 5 / 141 Heredity Did you ever notice how much children look like their parents and their siblings? As you can see, it's not only something that happens in humans! This is true about all living things on Earth. Slide 6 / 141 Frequently Asked Questions I am sure that questions like these have crossed your mind before: Are children ever identical to their parents? · Why do some people look more like their dad and some look · more like their mom? How do I get traits from my parents? · Why are some people born with birth defects or diseases? · These questions (and more) will be answered in this unit!
Slide 7 / 141 Genetics & Heredity Here are two related terms that will show up quite a few times in this section. Try to define them with your table and then pull the tab for the definition: Genetics Heredity Slide 7 (Answer) / 141 Genetics & Heredity Here are two related terms that will show up quite a few times in this section. Try to define them with your table and then pull the tab for the definition: Genetics A branch of biology that studies genes , heredity , and variation of organisms Answer Heredity The passing of traits from parent to offspring (children) [This object is a pull tab] Slide 8 / 141 Review: Cells Earlier this year, we talked about the parts of the cell. We also talked about mitosis and meiosis and how these processes help organisms live and reproduce.
Slide 9 / 141 Review: Mitosis Mitosis is the process that helps individual cells reproduce. In mitosis, one "parent cell" reproduces its DNA and then splits into two identical "daughter cells". The daughter cells are completely identical to the parent cell. The Stages: Permission Granted: Jeff Sale - San Diego St Univ Slide 10 / 141 Review: Meiosis Meiosis occurs in all animals that reproduce sexually (2 parents). In meiosis, the cell splits in two individual sex cells without duplicating its DNA.This means that after meiosis, the sex cells have half of the DNA as a normal body cell. The human cell on the left has all 23 After meiosis, the pairs of pairs of chromosomes (one pair is chromosomes split. shown). This means that each sex cell ends Click on the cell to see what happens up with 23 individual chromosomes after meiosis! (1/2 of what they started with)! Slide 11 / 141 1 Where is all of the genetic information (DNA) found in the cell? A nucleus B cytoplasm C cell membrane D mitochondria
Slide 11 (Answer) / 141 1 Where is all of the genetic information (DNA) found in the cell? A nucleus Answer B cytoplasm A C cell membrane D mitochondria [This object is a pull tab] Slide 12 / 141 2 The process of creating new cells from existing cells is called mitosis. True False Slide 12 (Answer) / 141 2 The process of creating new cells from existing cells is called mitosis. True Answer True False [This object is a pull tab]
Slide 13 / 141 3 The purpose of mitosis is _______________. A growth of organisms B repair of damaged tissue C both A and B are true D Neither A nor B are true Slide 13 (Answer) / 141 3 The purpose of mitosis is _______________. A growth of organisms B repair of damaged tissue Answer C C both A and B are true D Neither A nor B are true [This object is a pull tab] Slide 14 / 141 4 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each daughter cell have after mitosis?
Slide 14 (Answer) / 141 4 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each daughter cell have after mitosis? Answer 46 total [This object is a pull tab] Slide 15 / 141 5 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each sex cell have after mitosis? Slide 15 (Answer) / 141 5 Each cell in the human body has 23 pairs of chromosomes. How many chromosomes total will each sex cell have after mitosis? Answer 23 total (1/2 of what was originally there!) [This object is a pull tab]
Slide 16 / 141 6 Meiosis leads to: A Four offspring cells B Genetic Variation C Cloning D Both A and B are true E A, B, and C are true Slide 16 (Answer) / 141 6 Meiosis leads to: A Four offspring cells B Genetic Variation Answer D C Cloning D Both A and B are true E A, B, and C are true [This object is a pull tab] Slide 17 / 141 7 After meiosis, the number of chromosomes is the same in the parent and offspring cells. True False
Slide 17 (Answer) / 141 7 After meiosis, the number of chromosomes is the same in the parent and offspring cells. True False. The number of False Answer chromosomes in the offspring is 1/2 the parent cell. [This object is a pull tab] Slide 18 / 141 Gregor Mendel In the 1800s, an Austrian monk named Gregor Mendel conducted a series of experiments that were designed to uncover how traits are passed on from parent to offspring. His experiments were aimed at addressing one of the most fundamental issues concerning heredity: What are the basic patterns of heredity? Slide 19 / 141 Two Prevailing Original Hypotheses At Mendel's time, there were 2 popular (and incorrect) ideas to explain heredity: 1. The “blending” hypothesis : This idea stated that genetic material from the two parents blends together ex: a red flower and a white flower will produce a pink flower
Slide 20 / 141 Two Prevailing Original Hypotheses 2. Inheritance of mutations: This idea stated that traits present in parents are modified as they are used or not used, and passed on to their offspring in the modified form. ex: A giraffe has a long neck because her parents kept stretching their own necks out to reach the leaves in the trees, and the long neck trait was passed on. Slide 21 / 141 Mendel's Experiments In order to complete his experiment, Mendel needed to choose an organism that had the following characteristics: - Usually small - Has a short life span - Inexpensive to take care of - Produce many offspring in a relatively short period of time - Easy to experiment with Why do you think these traits would be important to scientists? Talk about each one at your table and be prepared to share your thoughts. Slide 22 / 141 Mendel's Experiments How many living things can you think of that fulfill these guidelines? Make a list with the person sitting next to you. Click below to see what Mendel chose to work with. The garden pea
Slide 23 / 141 Mendel's Choice: The Pea Plant Mendel chose pea plants for his experiment because: There are many varieties with distinct traits (such as color). · He could easily control the matings through cross-pollination. · Each pea plant has both the male and female reproductive organs. · Slide 24 / 141 The Traits of Pea Plants Mendel chose to track 7 traits (or "observable characteristics") that only came in one of two forms. Slide 25 / 141 8 Pea plants were particularly a good choice for use in Mendel's experiments for all of the following reasons except that... A Peas show easily observed variations in a number of characters, such as pea shape and flower color. B It is possible to completely control matings between different pea plants. C It is possible to obtain large numbers of offspring from one cross. D Peas live for an unusually long time.
Slide 25 (Answer) / 141 8 Pea plants were particularly a good choice for use in Mendel's experiments for all of the following reasons except that... A Peas show easily observed variations in a number of characters, such as pea shape and flower color. B It is possible to completely control matings between Answer D different pea plants. C It is possible to obtain large numbers of offspring from one cross. [This object is a pull D Peas live for an unusually long time. tab] Slide 26 / 141 Experiment #1: Monohybrid Cross One of Mendel's experiments looked at flower color. A pea plant can either have purple or white flowers. For this experiment, he crossed a purple flower with a white one. This is called a monohybrid cross because the parent plants differ in only one trait, their flower color. Results: All of the offspring had purple flowers. "mono" = one Slide 27 / 141 Monohybrid Cross Mendel then mated two of the purple offspring plants. This cross produced 929 plants. Results: 705 of the 929 plants had purple flowers and 224 had white flowers Use a calculator - What percentage of these flowers were purple? _____________________%
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