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Bellwork: 4/2

This week's lesson focuses on Punnett squares and the principles of inheritance. Students will learn about genes, alleles, dominant and recessive traits, and how to use Punnett squares to predict possible genotypes and phenotypes. The lesson also covers Mendelian genetics and the laws of segregation and independent assortment.

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Bellwork: 4/2

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  1. Bellwork: 4/2 Put your phone up  Week 4/1 - 4/5 Have you ever done Punnett squares before? What is a gene? Allele? Give an example of a gene & its possible alleles.

  2. Today: • Bellwork • Part 2 Notes

  3. Materials • Unit Book

  4. This Week: • Mon/Wed*: Meiosis Model & Video • Tuesday: Part 2 Notes • Thurs/Fri*: Mendelian Traits Activity & Video

  5. Next Week: • Monday: PS Practice & Assign Project • Tues/Wed: Quiz, Sample Project, Pt. 3 Notes • Thursday: Dihybrid Practice & Pt. 4 Notes • Friday: Blood Type Practice & Pt. 5 Notes

  6. Homework • Meiosis Poster due… • 4th & 6th – Thursday • 5th & 7th - Friday

  7. Unit VI: Mendelian Genetics

  8. Part II: Monohybrid Crosses

  9. Objective ?s • What patterns of inheritance are observed across generations? • How do the combination of chromosomes received from each of our parents affect our body’s appearance and function?

  10. Vocab • Gene– a nucleotide sequence of DNA that encodes a protein • Example: Height • Allele– alternative forms of a gene (each individual has two alleles) • Example: Tall, short…

  11. Vocab • Dominant– overpowering trait • when dominant alleles are present, the organism will always exhibit that trait • Recessive– weaker trait • organisms will only exhibit recessive traits when the dominant allele is NOT present

  12. Vocab • Dominant– CAPITAL LETTER • Recessive– lowercase letter

  13. Vocab • Homozygous – having identical alleles for the trait • Homozygous Dominant = TT • Homozygous Recessive = tt • Heterozygous – having two different alleles for the trait • Tt

  14. Vocab • Phenotype– an organism’s expressed physical traits – the one you observe • Example: tall • Genotype – an organisms genetic makeup; the combination of alleles in the homologous chromosomes • Example: height – TT, Tt, tt

  15. Heredity Pre- Mendelian • Blending theory – heredity material from each parent blends in the offspring • Once blended, it is inseparable (cannot return to traits of parents • Example: red flowers crossed with white flowers create pink flowers

  16. Gregor Mendel • Austrian Monk • Studied science & mathematics at University of Vienna • While doing his genetic research he was a substitute natural science teacher at a local high school • Developed 2 laws of inheritance • Biological organism: garden peas

  17. Think! Why would Mendel choose to study peas?

  18. Why Garden Peas? • Detectable traits • Mendel chose seven features to examine • Easy to grow • Short life cycle

  19. Why Garden Peas? • Mating easy to control • Flowers contain both male & female reproductive organs • Allowed for both… • Self-fertilization– pollen fertilizes egg from same plant • Cross-pollination– pollen fertilizes egg from different plant

  20. Think! What would the difference between the self-fertilized offspring & the cross-pollinated offspring be?

  21. Mendel’s Laws of Inheritance • Developed 2 laws of inheritance: • Law of Segregation • Followed single trait (monohybrid cross) • Law of Independent Assortment • Followed two traits (dihybrid cross)

  22. Law of Segregation • Each individual has two alleles for each trait that separate during the formation of gametes • Alleles reside on homologous chromosomes • Gametes (haploid) contain only one allele • Fertilization brings two gametes together returning the 2 alleles to the offspring

  23. Purpose of Punnett Square • Examines the probability of getting a particular phenotype based on combination of gametes • Each square in a monohybrid cross represents 25% chance or ¼ probability

  24. Punnett Square Problem • Cross two guinea pigs Ff x ff F= short fur f=long fur Probability of long fur offspring? • Monohybrid Crosses– looking at a single trait • Identify genotype of parents • Determine possible gametes for each parent • Set up Punnett Square • Fill in square by combining allele from sperm and egg • Address question the problem asked

  25. Sample Problem • A plant that is homozygous recessive for shortness is crossed with a heterozygous tall plant. Using a monohybrid Punnett square, show what the offspring will look like. • List the phenotypes & their probabilities. • List the genotypes & their probabilities.

  26. Sample Problem • Tim & Jan both have freckles, a dominant trait (F) but their son Michael does not. Use a punnett square to show how this is possible. • List the phenotypes & their probabilities • List the genotypes & their probabilities

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