Genetics

1. Genetics

2. Warm-Up • If all of these puppies came from the same two parents and were born in the same litter…why don’t they look identical?

3. Mendel’s Genetics • Genetics • A branch of biology that studies heredity, or the passing of characteristics from parents to offspring

4. Gregor Mendel • Austrian monk that first studied genetics • “Father of Genetics” • Experimented on pea plants • Mendel used plants that had been bred for a specific trait (tallness, shortness) to create hybrids (heterozygotes)

6. Generations are named as follows: • P = original parents • F1 = first generation (children) • F2 = second generation (grandchildren)

7. Mendel’s Conclusions (#1) • There are 2 forms of genes that control each trait called alleles • Example – 2 genes that control height • T = tall • t = short

8. Mendel’s Conclusions (#2) • The Rule of Dominance • Dominant trait = the observed trait • Recessive trait = hidden by the dominant trait unless dominant is not present

9. Mendel’s Conclusions (#3) • Law of Segregation • Because each plant has two alleles for a trait, it can produce two types of gametes • Pure tall (homozygous) = TT • Pure short (homozygous) = tt • Hybrid (heterozygous) = Tt

10. Mendel’s 3 Principles • Principle of Segregation • Principle of Dominance • Principle of Independent Assortment

11. Principle of Segregation • During gamete formation, there is a random segregation (separation) of alleles whereby each gamete receives only one allele from each pair • Tt • T • t

12. Principle of Dominance • The dominant allele (capital letter) are expressed whereas recessive alleles (lowercase letter) are not because they are masked by the dominant allele

13. Principle of Independent Assortment • Each characteristic is inherited independently of every other trait • Dihybrid crosses

14. STOP

15. Monohybrid Crosses • Step 1 • What are the genotypes of the parents? • Step 2 • Draw the Punnett Square • Step 3 • Write in the alleles of the parents • Step 4 • Fill in the square • Step 5 • Write the genotypes and phenotypes of potential offspring

16. Concept 10.3 • There are many variations of inheritance patterns. • Key Terms • Intermediate inheritance • Codominance • Polygenic inheritance

17. Intermediate Inheritance • In a monohybrid cross where neither parent trait is dominant, the hybrids have an intermediate phenotype • Andalusian Chickens

19. Codominance • Both traits are expressed – the phenotype shows the separate traits of both alleles

20. Incomplete Dominance • A cross between a blue blahblah bird and a white blahblah bird produces offspring that are silver. • What are the genotypes of the parent blahblah birds in the original cross? • What is/are the genotypes of the silver offspring? • What would be the phenotypic RATIO of offspring produced by two silver blahblah birds?

21. Codominance • Predict the phenotypic ratios of offspring when a homozygous red cow is crossed with a roan bull. • What should the genotypes and phenotypes for parent cattle be if a farmer wanted only cattle with red fur?

22. A cross between a black cat and a tan cat produces a tabby pattern (black and tan fur together). • What type of inheritance does this illustrate? • What percent of kittens would have tan fur if a tabby cat is cross with a black cat?

23. Polygenic Inheritance • 2 or more genes affect a single character • In humans, height and skin color have polygenic inheritance

24. Dihybrid Cross • In rats, black (B) fur is dominant to white (b) fur and long (L) tails are dominant to short (l) tails. • Cross two heterozygous individuals.

25. The Importance of Environment • Siamese cats • Enzyme responsible for black fur color is only active at the cooler temperatures

26. Concept 10.4 • Meiosis explains Mendel’s principles. • Key Terms • Chromosome theory of inheritance • Gene locus • Genetic linkage

27. Chromosome Theory of Inheritance • Genes are located on chromosomes and the behavior of chromosomes during meiosis and fertilization accounts for inheritance patterns.

28. Genetic Linkage and Crossing Over Genetic linkage continues as homologous chromosomes separate in the formation of sex cells

29. Genetic Linkage and Crossing Over Crossing-over unlinks alleles of genes as homologous chromosomes separate in the formation of sex cells   

30. Concept 10.5 • Sex-linked traits have unique inheritance patterns. • Key Terms • Sex-linked genes

31. Sex-Determination There are 2 types of chromosomes 1. Autosomes : Body chromosomes = 22 pairs (44 total) 2. Sex Chromosomes: 23rd pair (X or Y) Female = XX Male = XY Which parent determines the sex of the offspring?

32. Sex-Linked Inheritance • Traits controlled by genes located on the sex chromosome are called sex-linked traits • Thomas Hunt Morgan discovered sex linkage of traits using Drosophilia (fruit flies)

33. Sex-Linked Traits White eyes in Drosophilia are a recessive trait. Give the genotypes for the following individuals • White-eyed male: • Red-eyed male: • White-eyed female: • Red-eyed female:

34. Cross a white-eyed male and a homozygous red-eyed female. • Offspring Genotype: • Offspring Phenotype:

35. Sex-Linked Practice #1 • When crossing a white-eyed male and a heterozygous red-eyed female - what is the percentage of male children with white eyes?

36. Sex-Linked Practice #2 • Cross a red-eyed male and a white-eyed female. • Give offspring genotypes and phenotypes.

37. Sex-Linked Practice #3 • Cross a homozygous red-eyed male and a heterozygous red-eyed female. What is the percentage that they will produce a red-eyed male?