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Introduction to Genetics and Inheritance

This lesson provides an introduction to the study of genetics, including the inheritance of traits, the role of Gregor Mendel in genetics history, and the use of Punnett squares to predict the results of crosses. Students will learn about genotype and phenotype, as well as important vocabulary related to genetics.

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Introduction to Genetics and Inheritance

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  1. Genetics The study of genes and the inheritance of traits

  2. THE STUDENTS WILL: • Explain how traits are inherited • Identify the role of Gregor Mendel in the History of Genetics • Use a Punnett Square to predict the results of crosses. • Compare and Contrast the difference between an individual’s genotype and phenotype.

  3. Vocabulary: • heredity Phenotype • Allele Homozygous • Genetics Heterozygous • Hybrid • Dominant • Recessive • Genotype

  4. Inheriting Traits • Nose shape, eye color, and any other physical features are some of the traits that are inherited from parents.

  5. An organism is a collection of traits, all inherited from its parents.

  6. Heredity • The passing of traits from the parent to the offspring

  7. Generally, genes on chromosomes control all the traits that show up in an organism.

  8. Alleles? • The different forms of a trait that a gene may have are called alleles

  9. - When a pair of chromosomes separates during meiosis, alleles for each trait also separates into different sex cells

  10. Every sex cell has one allele for each trait….

  11. What is Genetics? The study of how traits are inherited through the interactions of alleles is the science of Genetics.

  12. Gregor Mendel- Father of Genetics • Austrian monk/ teacher • Began experimenting with garden peas in 1856 • Made use of Scientific Method • First to use the Mathematics of Probability to explain heredity. • -First to trace one trait through several generations. • -Died in 1884 (work unnoticed) • -His work was rediscovered in 1900

  13. Genetics in Garden

  14. Genetics in a Garden -Each time Mendel studied a trait, he crossed two plants with different expressions of the trait and found that the new plants all looked like one of the two parents.

  15. Genetics in a Garden Mendel called these new plants HYBRIDS because they received different Genetic information or different alleles, for a trait from each parent.

  16. Genetics in a Garden An organism that always produces the same traits generation after generation is called a PUREBRED.

  17. Hybrid An offspring that was given different genetic information for a trait from each parent. • Purebred An offspring that always produces the same traits generation after generation.

  18. Mendel’s cross between tall pea plants yielded all tall pea plants X =

  19. His cross between small pea plants yielded all small pea plants. X =

  20. Mendels’ cross between tall pea plants and small pea plants yielded all tall pea plants. X =

  21. Mendel then crossed these second generation tall pea plants and ended up with 1 out 4 being small. X =

  22. DOMINANT AND RECESSIVE TRAITS • Recessive Traits: Describes a trait that is covered over, or dominated, by another form of that trait and seems to disappear. -Weaker Trait Dominant Traits: Describes a trait that covers over, or dominates another form of that trait. -Stronger trait

  23. Traits compared by Mendel

  24. Using Probability to Make Predictions -A branch of mathematics that helps you predict the chance that something will happen.

  25. Mendel also dealt with Probability • Worked with a large number of plants to make his predictions accurate. • Studied almost 30, 000 pea plants over a period of 8 years.

  26. PUNETTE SQUARES -A handy tool used to predict results in Mendelian gentics.

  27. Punnett Squares -Letters represent dominant and recessive alleles

  28. HOW? An upper case letter stands for a dominant letter. - A lower case letter stands for a recessive allele

  29. Alleles • B – is considered a dominant allele • b – is considered a recessive allele BB – is dominant Bb or bB – is dominant bb - is recessive

  30. GENOTYPE & PHENOTYPE • Genotype- genetic makeup of an organism Ex. BB (Homozygous Dominant) • Phenotype- the way an organism looks and behaves Ex. Black Fur

  31. Alleles Determine Traits • Most cells in your body have 2 alleles for a trait. • These alleles are located on chromosomes within the nucleus of cells. Example: Trait- Height T - allele would be for Tall t - allele would be for short

  32. Alleles determine Traits • Homozygous- an organism with 2 alleles that are the same Ex. TT ( Tall), BB (Blonde Hair), tt, bb Heterozygous- an organism with 2 different alleles for a trait. Ex. Tt, Bb

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