Introduction to Genetics – Part 1

1. Introduction to Genetics – Part 1 Genetics – Study of heredity is often divided into four major subdisciplines: 1. Transmission genetics, deals with the transmission of genes from generation to generation 2. Molecular genetics deals with the structure and function of genes at the molecular level 3. Population genetics, which deals with heredity in groups of individuals for traits determined by one or only a few genes 4. Quantitative genetics, deals with the heredity of traits in groups of individuals where the traits are determined by many genes simultaneously

2. Meiosis Cell division in diploid cells that results in haploid cells; reduction division Homologous chromosomes – a pair of chromosomes having the same size and shape and carrying information (alleles) for the same traits (Fig. 11-14)

3. Diploid vs Haploid Diploid – having two sets of chromosomes, or all the homologous chromosomes that are characteristic of the species (2n) Haploid – having only one chromosome from each pair of homologous chromosomes (n) How does a cell go from diploid to haploid?

4. Phases of Meiosis During meiosis the chromosomes replicate once, but the cell divides twice – Fig. 11-15 Meiosis results in two haploid daughter cells with half the number of chromosomes as the original cell

5. Phases of Meiosis Prophase I Homologous chromosomes pair (synapsis) to form a tetrad

6. Phases of Meiosis Prophase I Crossing over – exchange of segments between nonsister chromatids; **increases genetic variation**

7. Phases of Meiosis Metaphase I Tetrads line up on equatorial plane

8. Phases of Meiosis Anaphase I Disjunction occurs - homologous chromosomes from each tetrad separate Cytokinesis begins during late anaphase/early telophase

9. Phases of Meiosis Telophase I End of first meiotic division http://www.phschool.com/science/biology_place/biocoach/meiosis/mei1ani.html

10. Phases of Meiosis Prophase II

11. Phases of Meiosis Metaphase II

12. Phases of Meiosis Anaphase II

13. Phases of Meiosis Telophase II http://www.phschool.com/science/biology_place/biocoach/meiosis/mei2ani.html

14. Phases of Meiosis Overview http://www.johnkyrk.com/meiosis.html

15. Meiosis vs Mitosis

16. Meiosis Quizzes http://biology.about.com/library/weekly/blmeios2a.htm http://www.phschool.com/science/biology_place/biocoach/meiosis/quiz.html http://www.cst.cmich.edu/users/benja1dw/bio101/tools/quiz/mitosis.htm THIS SLIDE ENDS PART ONE

17. Introduction to Genetics – Part 2 Gregor Mendel – “father” of modern genetics

18. Gregor Mendel’s Peas

19. Introduction to Genetics – Part 2 Fertilization – the union of a female and male gamete (specialized sex cell formed during meiosis)

20. Pea plants are: - easy to grow - matured quickly - show contrasting traits - control pollination Introduction to Genetics – Part 2 True breeding – pure for a particular trait. If plants with yellow seeds were self pollinated for several generations they would always produce plants with yellow seeds

21. Genes and Dominance Gene – a distinct unit of hereditary material found in chromosomes; a sequence of nucleotides in DNA

22. Allele – the different forms of the gene for a trait Genes and Dominance

23. Principle of Dominance states that some alleles are dominant and others are recessive Homozygous – having two identical alleles TT – homozygous dominant tt - homozygous recessive Heterozygous – having two different forms of a gene - Tt Genes and Dominance

24. Principle of Dominance states that some alleles are dominant and others are recessive Genes and Dominance

25. Principle of Segregation – factors that occur in pairs are separated from each other during gamete formation and recombined at fertilization ( Fig. – 11-5) Genes and Dominance

26. Probability – likelihood that a particular event will occur Principle of Probability – if there are several possible event that might happen, and no one of them is more likely to happen than any other, then they will happen in equal numbers over a large number of trials Example – Coin Toss – Fig. 11-7 Probability & Punnett Squares

27. Punnett Square – a diagram used to show the results of a cross – Fig. 11-7 Phenotype – physical trait that appears as a result of genetic makeup Probability & Punnett Squares Genotype – the genetic makeup of an organism; total set of genes

28. Principle of Independent Assortment – Genes for different traits can segregate independently during the formation of gametes. (Fig. 11-9, 11-10) http://bcs.whfreeman.com/thelifewire/content/chp10/1002001.html Exploring Mendelian Genetics

29. Incomplete Dominance – both alleles contribute to the phenotype and neither is dominant over the other – Fig. 11-11 Exploring Mendelian Genetics

30. Co-Dominance – Two dominant alleles are expressed at the same time Multiple Alleles – 3 or more different alleles of a gene; each combination producing a different phenotype Exploring Mendelian Genetics

31. Polygenic Traits – traits controlled by two or more genes; genes may or may not be on the same chromosome Exploring Mendelian Genetics

32. Genetics and the Environment – environmental factors can influence “genetic potential” Exploring Mendelian Genetics

33. Genes located on the same chromosome tend to be inherited together in genetic crosses because the chromosome is passed along as a unit. Such genes are said to be linked genes. (Fig. 11-19) Linkage and Gene Maps

34. Gene Map – an ordered list of the genes along a particular chromosome. The farther apart two genes are , the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency. The distance between genes is expressed in “map units” and is defined as equivalent to a 1% recombination frequency Linkage and Gene Maps

35. Linkage and Gene Maps

36. Links to Practice Punnett Squares http://biology.clc.uc.edu/courses/bio105/geneprob.htm http://www.zerobio.com/drag_gr11/blood.htm http://www.quia.com/quiz/220564.html?AP_rand=1287615174