Basic Genetics

1. Basic Genetics The information that makes you who you are!!

2. Warm Up • Write 2 to 3 sentences about genetics. What do you think you know?

3. Learning Goals • I can describe the difference between genotype and phenotype. • I can predict the offspring’s genotype and phenotype based on the parents genotypes and phenotypes using various genetic rules. • I can predict offspring using sex linked traits. • I can describe the process of meiosis. • I can describe the difference between mitosis and meiosis. • I can describe the difference between sex cells/gametes and body cells/somatic cells.

4. Genetics – the study of heredity and variation • Heredity – the transmission of traits from one generation to another • Variation – genetic differences btn siblings and members of the same species

5. Genes – segments of DNA, basic units of heredity • Transmitted from one generation to the next • Transmitted from parent to child through gametes (haploid cells) • Organized on chromosomes • Locus – location of a gene on a chromosome • Two homologous chromosomes carry genes that control the same trait • one inherited from each parent • Autosomes

6. Chromosomes • All chromosomes have a homologous pair except sex chromosomes • X – female (inherited from mom or Dad) • Y – male (inherited from dad) • Carry different information • Much more on X • Y only has secondary sex characteristics • Y makes you male • XX = female child • XY = male child

7. Gregor Mendel • First major researcher in genetics • Looked at characters (heritable feature) of peas • Bred for specific traits (forms of characters • Determined if something is “true bred” it will always create the same offspring with itself • All have the same traits • Then Hybridized (mixed) two “true breeds” (P – Generation) • created first filial (F1) generation • then crossed F1 to create F2

8. Mendel Major Discoveries • One individual might have two traits coded in their genes • each form is called an allele (one on each chromosome) • one from each parent • If alleles are different • dominant (R) covers recessive (r) • one cell has two different alleles – heterozygous • one cell that has two of the same alleles - homozygous • each allele separates during meiosis • each gamete has a 50/50 chance of getting either allele • Law of segregation • Law of independent assortment • each pair of alleles will separate independently of each other

9. Genotype v. Phenotype • Phenotype refers to organisms physical traits • What is actually expressed • Genotype refers to organisms genetic information • One organism can have two different alleles • if two different alleles – genotype is heterozygous • if the same alleles – genotype is homozygous

10. Types of crosses • Monohybrid cross • Crossing for only one character • Dihybrid cross • Study of two characters • Determining traits is based on probability • Use Punnett squares

11. Types of Dominance • Complete dominance – one allele completely hides another • Homozygote dominant and heterozygote appear exactly the same • IE: The allele for brown eyes is dominant over the allele for blue eyes. • Someone who is heterozygous for eye color will have brown eyes.

12. Punnett Square Practice • Two pea plants are crossed. One with round seeds (Rr) and one with wrinkled seeds (rr). What percentage of their offspring should have wrinkled seeds?

13. Warm Up • In humans, brown eyes (B) are dominant over blue (b)*. A brown-eyed man marries a blue-eyed woman and they have three children, two of whom are brown-eyed and one of whom is blue-eyed. Draw the Punnett square that illustrates this marriage. What is the man’s genotype? What are the genotypes of the children?

14. Punnett Square Practice A true-bred tall, purple-flowered plant (TTPP) is crossed with a true-breeding dwarf, white-flowered plant (ttpp). What percentage of the offspring will be tall, with white flowers? 0%

15. Punnett Square Practice • A pea plant is heterozygous for both seed shape and seed color. D is the allele for the dominant, spherical shape characteristic; d is the allele for the recessive, dented shape characteristic. G is the allele for the dominant, yellow color characteristic; g is the allele for the recessive, green color characteristic. If this plant is self pollinated, what percentage of the offspring will have spherical, green seeds? • DdGg X DdGg DDGG DDGg DdGG DdGg DDGg DDgg DdGg Ddgg DdGG DdGg ddGG ddGg DdGg Ddgg ddGg ddgg 3/16 = 18.75%

16. Types of Dominance • Co-Dominance – two different dominant alleles which affect the trait in different but equal ways • Ie blood types – A and B are dominant, o is recessive • if genotype is AA or Ao  BT = A • if genotype is BB or Bo  BT= B • but if genotype is AB  BT = AB • Example: A man with blood type A has a child with a woman whose blood type is AB, what is the probability that their child will have blood type A? • Depends on Dad’s blood type • Could be AA or AO

17. Types of Dominance • Incomplete Dominance – heterozygous offspring have a combination of parent traits • Ie flowers – Red parent X white parent = pink offspring • Example: In northeast Kansas there is a creature know as a wildcat. It comes in three colors, blue, red, and purple. This trait is controlled by a single locus gene with incomplete dominance. A homozygous (BB) individual is blue, a homozygous (bb) individual is red, and a heterozygous (Bb) individual is purple. What would be the genotypes and phenotypes of the offspring if a blue wildcat were crossed with a red one? • BB x bb

18. Warm Up • The common grackle is a species of robin-sized blackbirds that are fairly common (hence the name) over most of the United States. Suppose that long tails (L) were dominant to short tails in these birds. A female short-tailed grackle mates with a male long-tailed grackle who had one parent with a long tail and one parent with a short tail. What is the male's genotype?

19. Cell Reproduction Meiosis and Sexual Life Cycles

20. Cell Reproduction • Cells reproduce both sexually and asexually • Asexual Reproduction • Another name for cloning • Making an exact copy • Usually done through mitosis • Sexual Reproduction • Creates more variation • Mixing of two individuals’ DNA • Done through sex cells • AKA gametes

21. Types of Cells • Haploid cells – gametes (sex cells) • only have half of the genetic information the parent cell has • Created by meiosis • In humans – come in two forms sperm and egg • Diploid Cells – Somatic Cells (autosomes) • Contain two copies of the genetic information • Two homologous (similar) chromosomes paired together • All human body cells are Diploid • Except the gametes • Gametes fuse together during Fertilization • Creates a diploid zygote

22. Analysis of Genetics • To begin to analyze someone’s genetics, many physicians begin with a karyotype or an image of their somatic cell chromosomes. • This shows the pairs of chromosomes of similar length and staining pattern called homologous chromosomes • Each member of these pairs carries genes that control the same trait. • The only exception to these pairs are the sex chromosomes • Females have XX combination (in humans) • Males have XY (in humans)

23. Meiosis • The process of meiosis makes gametes (haploid cells) • only occurs in the ovaries or testes in animals. • Resembles Mitosis • Similar phases that just occur twice • Meiosis I and Meiosis II

24. Meiosis I • Phases VERY similar to Mitosis • Interphase • Growth • Prophase I • Homologous Chromosomes pair • Metaphase I • Tetrads (sets of 4 chromosomes) line up down center of cell • Anaphase I • Homologous pairs separate • Telophase I and Cytokinesis • Cytoplasm splits

25. Meosis II • NO DNA replication • No interphase • Goes from cytokinesis directly into Prophase II • Phases • Goes through another round of cell division creating 4 haploid gametes

26. Mitosis Creates two identical cells Identical to parent Prophase – each chromosome is in a pair with its identical twin attached by a centromere Anaphase – each individual chromosome in a identical pair separate So each new cell gets one of each in a homologous pair Meiosis Creates four cells with half the genetic information as parent Genetically different from each other During Prophase I – homologous chromosomes synapse to form a tetrad Anaphase I – tetrad separates sending the identical pair to one new cell Differences between Mitosis and Meiosis

27. Mitosis Meiosis I Metaphase Anaphase Differences between Mitosis and Meiosis

28. Meiosis Can Cause Variation • Variation in the combination of Chromosomes • Each chromosomes contains variations of a gene • Different combinations can occur • Crossing Over • When tetrads are lined up during Metaphase I, genes can switch chromosomes • Creating recombinant chromosomes

29. Warm Up • Draw each of the 9 stages of meiosis. Include 2 pairs of homologous chromosomes in the parent cell (and the appropriate number as the cell goes through meiosis). Be prepared to share your drawings with the class.

30. Chromosomal Theory of Inheritance • Mendelian genes are have a loci on a chromosome • Chromosomes undergo independent assortment and segregation not just genes • During meiosis

31. Non Mendelian TraitsSex Linked Genes • carried on X Chromosome • carries many more genes than Y chromosome • many genes code for more than just sex • tend to inflict men more often • only have one copy of X to carry trait • Females have to be homozygous for the trait • Both parents must be carriers • Passed from fathers to daughters, but not to sons • Sons receive Y chromosome • Examples: Hemophilia and Color Blindness

32. Sex Linked Traits • Example Problem: A boy, whose parents and grandparents had normal vision, is color-blind. What are the genotypes for his mother and his maternal grandparents? • Boy’s genotype? • XbY • Dad’s genotype? • XBY XBX? X?Y XBX? X?Y XBXB XBY XBXb XbY

33. Sex Linked Traits • Can a color blind female have a son that has normal vision? Color blindness is caused by a sex linked recessive allele. • Mom’s Genotype? • XbXb • No they’ll all be color blind XbX? XbY XbX? XbY

34. Genetic Disorders • Many are caused by recessive alleles • Usually code for a non-functional protein, or on that does work the way it should • Parents that are heterozygous for that trait are said to be carriers • Ie, Cystic fibrosis, Tay-Sachs, Sickle-Cell Anemia, • Others are lethal dominant • Much more rare, usually kill offspring before development • Only late-acting lethal dominant are passed on • ie Huntington’s Disease • Not all dominant “disorders” are lethal • dwarfism is a dominant trait

35. Genetic Disorders • There can be errors during meiosis. • Chromatids don’t split like they are supposed to. • nondisjunction • Causes too many copies in one gamete, and not enough in another • IE: • Down syndrome – extra copy of chromosome 21 • Turner syndrome – only one X chromosome • Klinefelter’s syndrome - XXY • http://wps.aw.com/bc_goodenough_boh_3/104/26722/6840898.cw/content/index.html