2. Heredity & Genetics PART ONE Mendel and Genetics I: Mendel and Genetics : A.What are dominant & Recessive traits? B.What is a Punnett Square? C.What is incomplete dominance?

4. Genetics A- Genetics: Similarities and differences among parents and offspring. It studies how offspring inherit characteristics from their parents and how DNA is involved.

5. B- Mendel Mendel: in 1866, this Austrian monk studied traits of pea plants. 1.Mendel studied 7 traits one at a time. Each trait had two forms. Height Tall Vs. Short. 2.Mendel grew short and tall pea plants. 3.Mendel let these plants self-pollinate for several generations to get pure breed seeds. üSelf-pollinate = Pollination within one plant

6. 4.Mendel cross-pollinates the pure tall with the pure short pea plants. üCross-pollination üCross-pollination = Take pollen from one plant and put it on another plant. 5.The seeds Mendel collects are Hybrids. üHybrid üHybrid = combination of two varieties of organisms. 6. Mendel plants the hybrid seeds to see if they will grow tall tall, short, or medium medium. They all grow tall tall.

8. 7.Mendel self-pollinates the hybrid for several generations, and plants the seeds from the hybrids. 3:1 ratio some grew tall some grew short.

9. 8.Conclusion the trait for tallness was visible and the trait for shortness was hidden. üVisible trait = dominant dominant, prevents the expression of recessive trait in organism. üHidden trait = recessive recessive.

10. C-What we learned from Mendel. 1.Traits 1.Traits (characteristics) are determined by Genes. 2.Genes 2.Genes = a section of chromosomes that determines a trait. { eye color, hair color, etc..}

11. 3. 3. Two genes for every trait. Example tallness in pea plants if pure tall two tall genes, if short two short genes, if a hybrid one tall gene and one short gene. 4. ALLELES 4. The different forms of a gene are ALLELES {recessive & dominant}

12. D- P PP Punnett Squares. 1.Genotype 1.Genotype = the genetic make-up of an organism. Homozygous Homozygous: alleles of a gene are the same. Heterozygous Heterozygous: alleles of a gene are different; one allele for tall one for short. Hybrids are heterozygous. 2.Phenotype 2.Phenotype = What the organism looks like.

13. 3.Punnett 3.Punnett Squares Squares: predict the genotypes & phenotypes of offspring. Symbols for different alleles of a gene. Dominant Dominant is capital and recessive is lower case letter. Height = T for dominant & t for recessive. TT or tt= homozygous Tt = heterozygous or hybrid.

14. 4.Offspring receive one allele for each trait from each parent. 5.Heterozygous pass on either T or t.

15. D- D- Incomplete Dominance Dominance: Condition in which the two alleles of a gene are both dominant. 1- 1-It produces a blended phenotype. Blended phenotype = hybrid. Example: Example: cross a pure red snapdragon with a pure white snapdragon, and you get a pink snapdragon. RW is the hybrid note both are dominant.

18. Part Two Genes and Traits: A.In the nuclei of a human cell you find two sets of chromosomes chromosomes 23 pairs. This is a diploid diploid number of chromosomes.

19. 1.One pair of the chromosomes comes from the father father the other set comes from the mother mother. 2.Genes are sections of DNA DNA, each human chromosome may contain 1,000’s 1,000’s of genes. 3.The way chromosomes pair pair up results in different genetic make-ups make-ups in the offspring.

20. B. B. Meiosis Meiosis: is the formation of sex cells or gametes gametes. 1.Eggs are produced in the female sex organ the ovaries ovaries, sperm is produced in the male sex organ the testes testes. 2.Meiosis produces sex cells with only one one set of chromosomes chromosomes these cells are monoploid monoploid. 3.In meiosis the chromosomes separate twice twice as do the cells.

21. 4.Steps of Meiosis: a.1 st everything that occurs in M MM Mitosis happens with Meiosis. Except the 2 22 2nd time the chromosomes D DD DO NOT DOUBLE. b.Sometimes the twin chromosomes that are similar pair with each other. If they exchange DNA this is known as crossing over this increases the differences in the offspring compared to the parent.

22. 3.At the end of meiosis we have 44 44 cells with a monoploid monoploid number of chromosomes. HALF {HALF THAT OF PARENT CELL} 4.When the egg and sperm cells unite the two monoploid monoploid cells combine their DNA forming a diploid zygote zygote.

24. 2n Diploid 4n n Monoploid

25. PART THREE I.How Sex is I II Inherited: Sex of an offspring is determined by a pair of c cc chromosomes. A.The m mm male body cell has X XX XY The f ff female body cell has X XX XX

26. 1.During meiosis meiosis the eggs of the female receive an X chromosome. 2.During meiosis the sperm sperm cell of the male receive either X or YY.YY.

27. B.Twins: ONE ONE ZYGOTE SEX 1.IDENTICAL TWINS: ONE EGG IS FERTILIZED BY ONE SPERM. THE ZYGOTE SPLITS. ALWAYS THE SAME SEX. Sperm Egg Zygote Same Sex Always

28. 2.F RATERNAL TWINS: T TT TWO EGGS AND TWO SPERM CELLS. THEY D DD DO N NN NOT CONTAIN THE SAME D DD DNA. CAN BE DIFFERENT SEX. 2 Egg 2 Sperms 2 Zygote

29. C. X-Linked Traits: are traits determined by genes on the x-chromosome.

32. 1.Several diseases are more more common in males then in females. Women may not not be affected by the disease, but pass it on to their sons. These women are known as carriers carriers. X-chromosomes are larger larger so they carry more genes genes. The ability to see color color is on the x-chromosome x-chromosome.

33. 2)X -chromosomes have genes that tell whether or not you see c cc color. (Red, G GG Green) Women are s ss seldom color-blind because the gene is a r rr recessive gene on the X-chromosome and they have two x-chromosomes. X ’ =recessive gene for c cc color- blindness

34. 3)H emophilia: is another x-linked disease it is a blood disorder that prevents the blood from c cc clotting properly. X’ = recessive trait for hemophilia

37. IV.Source of Gene Variations: When cells divide each DNA molecule in the cell makes e ee exact copies of itself. But sometimes the cell makes a m mm mistake; bases may pair up i ii incorrectly. The codon are changed the a aa altered gene is passed on to the new cell.

38. A- Mutation Mutation is any permanent change in the DNA DNA of a cell. 1.Mutation increases increases with the exposure of DNA DNA to some chemicals chemicals ands radiation that damage damage the DNA molecule.

39. B.Chromosome Mutation: When a piece piece of chromosome breaks breaks and are rearranged rearranged or lost lost. During meiosis chromosomes mutation mutation may occur when chromosomes do not separate evenly evenly.

40. Dystrophy 1.Muscular Dystrophy= Weak muscles. Trisomy 21st chromosomes threechromosomes 2.Down Syndrome or Trisomy 21= is caused as a result of a sex cell having too many 21st chromosomes. The fertilized egg, contains three 21st chromosomes instead of two. newforms 3.Importance of Mutations= are a source of new traits or new forms of traits.