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Genetics Notes - Understanding Genes, Heredity, and DNA

This resource provides an overview of genetics, including the definition of genes, inheritance of traits, and the use of Punnett squares. It also includes a sample problem for practicing genetic crosses.

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Genetics Notes - Understanding Genes, Heredity, and DNA

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  1. 1. Please have these Items on your desk. Venn Diagram Agenda ScienceStarters Sheet Monday January 28, 2019 Day 1 Starter - Please copy down the vocabulary words below: • Anaphase: Chromatids separate and becomes new chromosome, chromosomes move to opposite ends of the cell • Telophase: Nucleus forms around each region of chromosomes • Cytokinesis: Cell membrane pinches and splits into two

  2. Table of Contents update 1/28 rplGenetics Notes Part 1pg89

  3. www.sciencequeen.net Whose got Genes? Genes, Heredity, & DNA Baker 2003/2004

  4. What are genes? • Genes are a segment of DNA on a chromosome that controls a particular trait. • Genes are located on the chromosomes in the nuclei. Each organims has a fixed number of chromosomes. • Humans have 23 pairs (46) chromosomes. • Genetics is the study of how traits are passed on from one generation to another Baker 2003/2004

  5. What is GENETICS? The study of how traits are inherited through the interactions of genes. Baker 2003/2004

  6. Define TRAIT • Ways of looking, thinking, or being • Traits that are genetic are passed down through the genes from parents to offspring Baker 2003/2004

  7. Describe RECESSIVE • A trait that is covered over, or dominated, by another form of that trait and seems to disappear • Hidden when the other copy of the gene contains the dominant allele. • A recessive allele shows up only when there is no dominant allele present • Shown with a lower-case letter Baker 2003/2004

  8. Describe DOMINANT • A trait that covers over, or dominates, another form of that trait • Trait that always shows up, even when only one of the two alleles is in the dominant form • Shown by a capital letter Baker 2003/2004

  9. Define GENOTYPE An organism's genetic makeup Baker 2003/2004

  10. Define PHENOTYPE Outward physical appearance and behavior of an organism Baker 2003/2004

  11. What is a PUNNETT SQUARE? • Used to determine the likely hood that the offspring receives a certain trait. • An uppercase letter stands for a dominant allele • Lowercase letters stand for recessive alleles Baker 2003/2004

  12. Who is the scientist? • Reginald Punnett and William Bateson were among the first English geneticists. • Punnett created the Punnett square in 1905. • He devised the Punnett square to depict the number and variety of genetic combinations. Baker 2003/2004

  13. Punnett Squares • Sample Problem 1.   In roses, red flowers are dominant over white flowers. What are the possible offspring when a homozygous red rose is crossed with a homozygous white rose. Baker 2003/2004

  14. Generation 1 (I Do) R R Red rose = RR white rose = rr R r R r r Genotype 4 Rr Phenotype 100% Red Rose R r r R r Baker 2003/2004

  15. Generation 2 (We do) R r r r R r r Red rose = Rr white rose = rr Genotype 2 Rr 2 rr Phenotype 50% Red 50% White R r r r r Baker 2003/2004

  16. Generation 3 (You do) R r Red rose = Rr Red rose = Rr R r R R R Genotype 1 RR 2Rr 1 rr Phenotype 75% Red 25% White R r r r r Baker 2003/2004

  17. References • Slideshow adapted from http://www.science-class.net/PowerPoints/Genetics.htm Baker 2003/2004

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