GENEtics

1. GENEtics

2. Genetics: the scientific study of heredity • Heredity the transmission of characteristics from parent to offspring. • Trait:a characteristic passed from one parent to offspring Introduction to Genetics

3. Characteristics can be seen or are expressed as different forms, or alleles: • Trait: Blood Type; Form/allele: A, B, O • Trait: Guinea Pig ; Form/allele: rough, smooth • The different forms or alleles of a trait are produced as the result of proteins synthesized from the nucleotide sequence at the gene location Introduction to Genetics

5. NOTE: Just to confuse us, many geneticists use the term “trait” for both the trait (like fur color) and the form of the trait (white, black or brown.) Introduction to Genetics

6. There are three different types of traits: • 1) physical: traits that you can “see” • 2) physiological: traits that make you function • 3) behavioral: the way you act Introduction to Genetics

7. Nature vs. Nurture • characteristics that are determined by genes can be modified by the environment. • Examples: medical alterations, personality traits modified by parents Introduction to Genetics

8. Gene loci- the exact location of a gene segment on a chromosome • allele- the form of a gene-the nucleotide sequence at the gene location Location of Traits and Alleles

9. EXAMPLE • Trait: • Hair type • Alleles, or forms of a trait: • Curly, straight, wavy, etc. Location of Traits and Alleles

10. Gene pairs: • Two alleles that code for the same trait. • Found on a pair of homologous chromosomes • Maternal allele • codes for a protein that produces straight hair • Paternal allele • codes for same protein OR could code for protein for curly hair Location of Traits and Alleles

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13. How many traits do you have? There are approximately 20,000 genes in the human genome. Your DNA codes for thousands of different traits. • You inherit the trait or form of a characteristic from each of your parents. Do you always receive a form that is present in your parents? Could parents with brown hair have a child with blond hair? yes Location of Traits and Alleles

14. GENE: • Unit of hereditary information which is carried from parents to offspring • A segment of DNA which acts as a template for production of mRNAwhich then… • Holds the code for • A. protein-functional group of amino acids • B. polypeptide • C. trait or “part of a trait” Genes and Gene Products

15. Gene products are proteins (functional) or polypeptides: Polypeptides are combined with other polypeptides and molecules to form functional proteins. The outcome of the protein synthesis is seen or chemically measured as traits. Genes and Gene Products

16. Enzymes-Proteins which catalyze or speed chemical reactions and reduce the energy (ATP) needed for the reaction. • Example of enzyme and trait: Tyrosinase • speeds formation of melanin (skin) pigment • Abnormal form of tyrosinase-albinism Examples

17. Structural proteins-form body structures like skin, bones and muscles. • Example of protein and trait: Fibrillin • found in connective tissues around bones, muscles, veins, organs • Abnormal form of fibrillin • Marfan’ssyndrome (enlarged heart)

18. Others: Proteins which function to store materials, transport oxygen, function as hormones, etc. • Example of protein and trait: Hemoglobin • carries oxygen in red blood cells • Abnormal form of hemoglobin- sickle cell anemia • NOTE: If a gene does not code for the normal protein, it may usually produce a non-functional protein!!! • abnormal hexosaminidase-Tay-Sachs • abnormal CTFR carrier protein-Cystic Fibrosis.

19. The science of genetics originated over one hundred years ago in the 1860’s. In the gardens of a monastery in Austria, a monk named Gregor Mendel performed a series of experiments on garden peas. Trained as a mathematician, Mendel applied his knowledge of probability and numbers to study the genetics of peas. He was able to apply quantitative methods to the numerical data he collected. Mendel developed purebred lines of pea plants. He recorded the results of this experiments and made statistical notes. The Study of Genetics

20. The results of Mendel’s studies were so important that he is considered: Father of Genetics The Study of Genetics

21. Why PEAS? • Structure of the pea flowers • Presence of distinctive traits • Rapid reproduction cycle • Grow quickly • Produce large number of offspring • Cheap and easy to grow and maintain The Study of Genetics

23. Pea plants normally self-pollinate but cross-pollination is possible if the anthers of the plant are removed when the flower is young. The Study of Genetics

24. Self-pollination • female and male gametes (egg & pollen) from the same plant form a zygote • example: • natural situation in pea plants Self-Pollination

25. Cross-pollination • female and male gametes from two different plants form a zygote • example: • Mendel “painted” pollen from one plant onto the stigma of another plant Cross-Pollination

27. Gene location on homologs for seed color • Mendel studied characteristics in the parents and offspring of pea plants. The plants displayed several easily-observed characters in one of two contrasting traits or forms:

28. Mendel observed that there were two different types of pea plants: • A. Purebred Plants: • plants that, when self-pollinated, produce the same form of a trait in all offspring • Example: white flower plants that produce offspring with white flowers • B. Hybrid Plants: plants that, when self pollinated, produce more than one form of a trait in their offspring • Example: Purple flower plants that produce some purple and some white flowered offspring The Study of Genetics

29. Mendel performed his experiments with great patience and precision. He kept careful records. Mendel’s work spanned 10 years and involved over 280 genetic crosses producing some 28,000 pea plants. The Study of Genetics

30. Mendel was trained in mathematics and used his background in probability to analyze the results of his crosses.

37. As a result of his many years of careful study, Mendel’s work was summarized into three main laws. 1. The law of Dominance • States that if two alleles in a gene pair are different, then one allele can control the trait and the other one can be hidden. • Green seed color is seen in plants with the genotype Gg, when green (G) is dominant 2. The law of Independent Assortment • States that gene pairs segregate into gametes randomly and independently of each other. • Homologous pairs randomly separate in Metaphase I and Anaphase I of meiosis 3. The law of Segregation • States that each pair of genes segregates, or separates, during meiosis and each gamete contains one gene from each gene pair. • ½ or 50% chance a homolog will end up in a gamete MendeL’s Laws

39. Probability: • the chance that something will take place • Ways to express probability: • percents, ratios, fractions • Probability = the number of ways of achieving success the total number of possible outcomes Predicting the Characteristics of the Zygote:

40. Example: • 50%, or 1 in 2, or ½ chance that a coin will be “face up” when it lands. Predicting the Characteristics of the Zygote:

41. If we can predict the allele in a gamete, we can go further and predict the allele pairs that might be found in a genetic cross. • Example: • P1: peas with green pods (heterozygous Gg) X peas with green pods (heterozygous Gg) • Can you determine the exactoutcome of the above cross? • No, but you can predict POSSIBLE outcomes • Can you predict the outcome of the above cross? Yes Predicting the Characteristics of the Zygote:

42. What is the difference between expected (predicted) and observed (actual) results? • Predicted result is an outcome that COULD happen. • The actual result is the real outcome • If predicted results are not always the same as observed results, why determine them at all? • they can be used to predict the outcome of crosses that are important to economy and health Predicting the Characteristics of the Zygote:

43. NOTE: It is more important to understand what Punnett Squares represent than to be able to construct them! • What do the letters that run along the top and side columns of a Punnett square represent? • Possible allele forms from the parent gametes • What do the letters that fill up the inside squares of the Punnett represent? • Possible genotypes in the zygotes • Do the results of a Punnett square tell you the exact outcome of a monohybrid cross? • No! JUST PREDICTION!!! Predicting the Characteristics of the Zygote:

44. Punnett Squares and TWO-TRAIT crosses

47. Resulting phenotypic ratio: • __9___ normal pigment, normal hearing • __3___ normal pigment, abnormal hearing • __3___ abnormal pigment, normal hearing • __1___ abnormal pigment, abnormal hearing Punnett Squares and TWO-TRAIT crosses