Introduction to Mendelian Genetics

1. Introduction to Mendelian Genetics

2. Genetics: • The study of heredity • Heredity: • How traits are passed down generation to generation • History: • Gregor Mendel is known as the father of genetics

3. Gregor Mendel/1850’s: • Austrian monk • Study mathematics and botany at the University of Vienna • Use both of these areas of study to analyze genetic crosses using pea plants.

4. Mendel worked with 7 pea plant traits:

5. Mendel’s experiments:

7. Important terms to know: • Gene: • A segment of DNA that codes for a specific protein/trait. • Allele: • A specific form of a gene • Dominant: • The overpowering form of a gene • Occurs most often in a population • Represented by a capital letter • Recessive: • The weaker form of a gene • Occurs less often in a population • Represented by a lower case letter

8. Important terms to know: • Phenotype: • A physical trait that you can see • Examples in peas: tall, short, wrinkled, smooth • Genotype: • The genetic make up /gene combination • Three types of genotypes: • RR…..Homozygous dominant • Rr……Heterozygous • rr……. Homozygous recessive

9. The law of dominance • Simply stated: • Anytime a dominant allele is present the dominant trait will be seen, it overpowers the recessive allele.

10. The ability to roll your tongue is dominant over the inability to roll your tongue. • Tongue roller …. T • Non tongue roller…t • Homozygous Dominant: • TT • Tongue roller • -Homozygous Recessive • tt • Nontongue roller • -Heterozygous • Tt • Tongue roller

11. Karyotype - A diagram created from a picture of a person’s actual chromosomes.

12. Use of the karyotype: • Used to determine if a person inherited a certain gene or genetic disorder • Used to determine the chance of passing a gene or genetic disorder on to their child • Used to determine the sex of a child.

14. It’s a male: Why? XY

15. It’s a female: Why? XX

16. Down Syndrome

17. Edward’s Syndrome

18. Creating a karyotype: -Look at the length of the chromosome -Look for the position of the centromere -Look at the repeating pattern of light and dark bands representing genes -Look at the specific genes which have been identified and mapped/labeled through the Human Genome Project.

19. Punnett Squares A mathematical method to determine the chance of producing an offspring with a specific trait.

20. 1 Trait Crosses Purple pea blossoms are dominant over white blossoms Heterozygous purple flower crossed with another Heterozygous purple flower Results: Genotypic ratio: - 25% BB - 50% Bb - 25% bb Phenotypic ratio: -75% purple -25% white

21. In rabbits black fur is dominant over tan fur. Cross a Homozygous dominant black fur male with a Homozygous recessive tan fur female.

22. 2 trait crosses Yellow peas (Y) are dominant over green peas (y). Green pea pods (G) are dominant over yellow pods (g). Cross a Heterozygous green pea pod, Heterozygous yellow pea with another Heterozygous green pea pod, Heterozygous yellow pea GgYy x GgYy

23. 2 trait cross In guinea pigs black fur is dominant over white fur and smooth fur is dominant over rough fur. Cross a Homozygous recessive white, Heterozygous smooth fur female with a Heterozygous black fur, Homozygous dominant smooth fur male.