1. Genetics Standard 4: The student should be able to demonstrate an understanding of the molecular basis of heredity. Essential question What is the structure of DNA?

2. KEY CONCEPT DNA was identified as the genetic material through a series of experiments.

3. People to know Gregor Mendel – 1 st to suggest that paired factors carry traits Walter Flemming – 1 st to see chromosomes Thomas Morgan – determined that specific genes are on specific chromosomes Meischer – 1 st to isolate DNA

4. Wilhelm Johannsen – 1 st to use the term gene Walter Sutton – developed the chromosome theory Rosalind Franklin – the first to see DNA structure Watson and Crick-first to describe the double helix of DNA

5. Ervin Chargaff – determined how nucleotides pair in DNA Griffin – determined that there is a “transforming principle” that is passed on Avery- identified DNA as the “transforming principle” Hershey and Chase – proved DNA is the genetic material

6. Watson and Crick determined the three-dimensional structure of DNA by building models. They realized that DNA is a double helix that is made up of a sugar-phosphate backbone on the outside with bases on the inside.

7. Watson and Crick’s discovery built on the work of Rosalind Franklin and Erwin Chargaff. –Franklin’s x-ray images suggested that DNA was a double helix of even width. –Chargaff’s rules stated that A=T and C=G.

8. Griffith finds a ‘transforming principle.’ DNA can change Griffith experimented with the bacteria that cause pneumonia. He used two forms: the S form (deadly) and the R form (not deadly). A transforming material passed from dead S bacteria to live R bacteria, making them deadly.

9. Avery identified DNA as the transforming principle. Avery isolated and purified Griffith’s transforming principle. Avery performed three tests on the transforming principle. –Qualitative tests showed DNA was present. –Chemical tests showed the chemical makeup matched that of DNA. –Enzyme tests showed only DNA-degrading enzymes stopped transformation.

10. Hershey and Chase confirm that DNA is the genetic material. Hershey and Chase studied viruses that infect bacteria, or bacteriophages. Tagged DNA was found inside the bacteria; tagged proteins were not. – They tagged viral DNA with radioactive phosphorus. – They tagged viral proteins with radioactive sulfur.

11. KEY CONCEPT DNA structure is the same in all organisms.

12. DNA 1.Deoxyribonucleic acid 2.Double strand helix 3.Codes for proteins which determine our traits

13. DNA is composed of four types of nucleotides. Each nucleotide has three parts. –a phosphate group –a deoxyribose sugar –a nitrogen-containing base phosphate group deoxyribose (sugar) nitrogen-containing base deoxyribose

14. The nitrogen containing bases are the only difference in the four nucleotides.

15. Nucleotides always pair in the same way. The base-pairing rules show how nucleotides always pair up in DNA. This is also know as Chargaff’s rule – A pairs with T – C pairs with G

16. The backbone is connected by covalent bonds. hydrogen bond covalent bond The bases are connected by hydrogen bonds.

17. Summary Nitrogen bases Pyrimidines -single –Thymine (T) –Cytosine (C) Purines - double –Adenine (A) –Guanine (G) –Thymine pairs Adenine –Cytosine pairs Guanine

18. Essential Question: How does DNA Code for life? KEY CONCEPT DNA replication copies the genetic information of a cell.

19. DNA replication – makes a copy of itself

20. review DNA is replicated during the S (synthesis) stage of the cell cycle. Each body cell gets a complete set of identical DNA.

21. DNA serves only as a template. (pattern) Enzymes and other proteins do the actual work of replication. –Enzymes unzip the double helix. –Free-floating nucleotides form hydrogen bonds with the template strand. nucleotide The DNA molecule unzips in both directions.

22. –Polymerase enzymes form covalent bonds between nucleotides in the new strand. –DNA polymerase enzymes bond the nucleotides together to form the double helix. DNA polymerase new strand nucleotide

23. DNA replication is semiconservative. original strand new strand Two molecules of DNA Two new molecules of DNA are formed, each with an original strand and a newly formed strand.

24. DNA Replication 1.Strands separate between the nitrogen bases (unzips) 2.free nucleotides bond to the exposed bases 3.There are now two complete strands made of one new and one old strand

25. KEY CONCEPT Transcription converts a gene into a single- stranded RNA molecule.

26. The transcription process is similar to replication. Replication Copies all the DNA Makes one copy takes place in the nucleus transcription Copies a gene (part) of the DNA making RNA Can make many copies. moves to different locations

27. RNA is a link between DNA and proteins. Proteins give organisms their traits replication transcription translation RNA carries DNA’s instructions.

28. RNA differs from DNA in three major ways. 1.RNA has a ribose sugar. 2.RNA is a single-stranded structure. 3.RNA has uracil instead of thymine.

29. Transcription –DNA unzips at the start site to the termination site start site nucleotides transcription complex

30. –RNA polymerase bonds the nucleotides together. –The DNA helix winds again as the gene is transcribed. – Nucleotides pair with one strand of the DNA. DNA RNA polymerase moves along the DNA

31. – The RNA strand detaches from the DNA once the gene is transcribed. RNA

32. Transcription makes three types of RNA. 1.Messenger RNA (mRNA) carries the message that will be translated to form a protein to the ribosome from the nucleus. 2.Transfer RNA (tRNA) brings the message from the nucleus to a ribosome in the cytoplasm. 3.Ribosomal RNA (rRNA) found at the ribosomes where proteins are made.

33. Summary of Transcription 1.The DNA unzips only the gene 2.The nucleolus produces mRNA off of the open strand of DNA 3.Uracil replaces thymine 4.tRNA travels to the ribosome 5.The code is read in groups of 3 called codons as rRNA (ribosomal)

34. KEY CONCEPT Translation converts an mRNA message into a polypeptide, or protein.

35. A codon is a sequence of three nucleotides that codes for an amino acid. codon for methionine (Met) codon for leucine (Leu)

36. A change in the order in which codons are read changes the resulting protein. Regardless of the organism, codons code for the same amino acid.

37. Amino acids are linked to become a protein. An anticodon is a set of three nucleotides that is complementary to an mRNA codon. An anticodon is carried by a tRNA.

38. Ribosomes consist of two subunits. –The large subunit has three binding sites for tRNA. –The small subunit binds to mRNA.

39. For translation to begin, tRNA binds to a start codon and signals the ribosome to assemble. –A complementary tRNA molecule binds to the exposed codon, bringing its amino acid close to the first amino acid.

40. –The ribosome helps form a polypeptide bond between the amino acids. –The ribosome pulls the mRNA strand the length of one codon.

41. –The now empty tRNA molecule exits the ribosome. –A complementary tRNA molecule binds to the next exposed codon. –Once the stop codon is reached, the ribosome releases the protein and disassembles.

42. Codons Three nucleotide bases from the rRNA move through the ribosome Called tRNA (transfer) Each code gives a new amino acid 64 combinations Build proteins

43. Summary of translation rRNA moves through the ribosome The sequence is read in blocks of 3 called codons to form amino acids The amino acids are linked to form the proteins The proteins determine the traits of the organism

45. The genetic code matches each codon to its amino acid or function. The genetic code matches each RNA codon with its amino acid or function.

46. Rules for reading codon charts 1.Break into codons 2.Read bases in order 3.Base one gives the row 4.Base two gives the column 5.Base three gives the amino acid

48. Essential Question: How are traits passed from one generation to another?How are traits passed from one generation to another?

49. KEY CONCEPT Gametes have half the number of chromosomes that body cells have.

50. You have body cells and gametes. Body cells are also called somatic cells. Germ cells develop into gametes. –Germ cells are located in the ovaries and testes. –Gametes are sex cells: egg and sperm. –Gametes have DNA that can be passed to offspring. body cells sex cells (sperm) sex cells (egg)

51. Your body cells have 23 pairs of chromosomes. –Homologous pairs of chromosomes have the same structure. –For each homologous pair, one chromosome comes from each parent. Chromosome pairs 1-22 are autosomes (body cells). Sex chromosomes, X and Y, determine gender in mammals. Your cells have autosomes and sex chromosomes.

52. Body cells are diploid; gametes are haploid. Diploid (2n) cells have two copies of every chromosome. –Body cells are diploid. –Half the chromosomes come from each parent.

53. Haploid (n) cells have one copy of every chromosome. –Gametes are haploid. –Gametes have 22 autosomes and 1 sex chromosome.

54. Review Meiosis reduces chromosome number and creates genetic diversity.

55. Meiosis I and meiosis II each have four phases, similar to those in mitosis. homologous chromosomes sister chromatids sister chromatids –Pairs of homologous chromosomes separate in meiosis I. –Homologous chromosomes are similar but not identical. –Sister chromatids divide in meiosis II. –Sister chromatids are copies of the same chromosome.

56. Meiosis I occurs after DNA has been replicated. Meiosis I divides homologous chromosomes in four phases.

57. Meiosis II divides sister chromatids in four phases. DNA is not replicated between meiosis I and meiosis II.

58. Meiosis differs from mitosis in significant ways. –Meiosis has two cell divisions while mitosis has one. –In mitosis, homologous chromosomes never pair up. –Meiosis results in haploid cells; mitosis results in diploid cells.

59. Gametogenesis is the production of gametes and differs between females and males. –Sperm become streamlined and motile. –Sperm primarily contribute DNA to an embryo. –Eggs contribute DNA, cytoplasm, and organelles to an embryo. –During meiosis, the egg gets most of the contents; the other cells form polar bodies. spermatogenesis Oogenesis

60. KEY CONCEPT Mendel’s research

61. Mendel laid the groundwork for genetics. 1.Traits are distinguishing characteristics that are inherited. 2.Genetics is the study of biological inheritance patterns and variation. 3.Gregor Mendel showed that traits are inherited as discrete units.

62. Mendel’s data revealed patterns of inheritance. Mendel made three key decisions in his experiments. –use of purebred plants –control over breeding –observation of seven “either-or” traits

63. Mendel used pollen to fertilize selected pea plants. Mendel controlled the fertilization of his pea plants by removing the male parts, or stamens. He then fertilized the female part, or pistil, with pollen from a different pea plant. –P generation crossed to produce F 1 generation –interrupted the self-pollination process by removing male flower parts

64. Mendel allowed the resulting plants to self-pollinate. –Among the F 1 generation, all plants had purple flowers –F 1 plants are all heterozygous –Among the F 2 generation, some plants had purple flowers and some had white

65. Mendel observed patterns in the first and second generations of his crosses.

66. Mendel drew three important conclusions. 1.Traits are inherited as discrete units. 2.Organisms inherit two copies of each gene, one from each parent. 3.The two copies segregate during gamete formation. purplewhite

67. Terms of Heredity Terms of Heredity Heredity – the passing on of characteristics from parent to offspring Genetics – the study of heredity Traits – characteristics of inherited Genes – carry the traits of inheritance Alleles – a single member of a pair of genes

68. –Each parent donates one allele for every gene. –Homozygous describes two alleles that are the same at a specific locus. –Heterozygous describes two alleles that are different at a specific locus.

69. Laws of heredity Chromosome theory –Chromosomes carry genes that separate Law of segregation –Genes for a trait separate Law of dominance –One gene can hide another Law of Independent Assortment –Genes separate independently of one an other

70. Law of Dominance Genes can be dominant –Observed (stronger) trait –Can be seen with only one –Symbolized by a capital letter –Tt or TT Genes can be recessive –Hidden trait –Only shows when both alleles are recessive –Symbolized by a lower case letter –tt

71. Expression of genes Phenotype –Physical expression of the trait –Tall or short Genotype –The genes being expressed Homozygous –Same –TT or tt Heterozygous –Different –Tt

72. Law of segregation Alleles separate when gametes (sex cells) form The alleles that combine are at random

75. Law of independent assortment Alleles separate independently of one an other This is seen better in dihybrid or trihybrid crosses

76. Predicting outcomes Monohybrid crosses –One pair of alleles –TT Dihybrid crosses –Two pairs of alleles –TtGg Trihybrid crosses –Three pairs of alleles –TtGgWw

77. Punnett Square Developed in 1905 by Reginald Punnett Allows for accurate predictions of outcomes of crosses and calculations of probablity

79. Mendel’s rules of inheritance apply to autosomal genetic disorders. –A heterozygote for a recessive disorder is a carrier. –Disorders caused by dominant alleles are uncommon. (dominant)

81. Exceptions to the rules Incomplete dominance –Blending –Red flower crossed with a white flower and you get pink flowers Codominance –Both trait show –Black chicken crossed with a white chicken and the offspring have both black and white feathers

82. Phenotype can depend on interactions of alleles. In incomplete dominance, neither allele is completely dominant nor completely recessive. –Heterozygous phenotype is intermediate between the two homozygous phenotypes –Homozygous parental phenotypes not seen in F 1 offspring

83. Codominant alleles will both be completely expressed. –Codominant alleles are neither dominant nor recessive. –The ABO blood types result from codominant alleles. Many genes have more than two alleles.

84. Sex Determination –Two different chromosomes work together –XX gives you a female –XY gives you a male Sex-linked traits –Traits on the sex chromosomes –Color blindness is a trait only found on the X chromosomes for humans Polygentic inheritance –Controlled by two or more genes –Skin color is a combination of 3 to 4 genes

85. sex-linked traits. sex-linked traits. –Y chromosome genes in mammals are responsible for male characteristics. –X chromosome genes in mammals affect many traits.

86. . Males (XY) express all of their sex linked genes. Females (XX) can carry sex-linked genetic disorders Expression of the disorder depends on which parent carries the allele and the sex of the child. X Y

87. Male mammals have an XY genotype. –All of a male’s sex-linked genes are expressed. –Males have no second copies of sex-linked genes.

88. Female mammals have an XX genotype. –Expression of sex-linked genes is similar to autosomal genes in females. –X chromosome inactivation randomly “turns off” one X chromosome.

89. Many genes may interact to produce one trait. Polygenic traits are produced by two or more genes. Order of dominance: brown > green > blue.

90. Epistasis Multiple genes giving multiple factors Hair color in mice is a 5 gene phenotype with genes for color shading and spots Albinism in hedgehogs is caused by epistatic genes blocking color

91. Environmental The sex of sea turtles and many reptiles depends on both genes and the temperature of the environment Phenotype can be a combination of genotype and environment.

92. Crossing over is the exchange of chromosome segments between homologous chromosomes.

93. Human genetics follows the patterns seen in other organisms. The basic principles of genetics are the same in all sexually reproducing organisms. –Inheritance of many human traits is complex. –Single-gene traits are important in understanding human genetics.

94. Patterns of heredity Tracing genetics through a family is done using a pedigree chart 1.Seperated by generations 2.Represents the males and females 3.Represents those that have the trait or carry the trait

95. Phenotypes are used to infer genotypes on a pedigree. Autosomal genes show different patterns on a pedigree than sex-linked genes.

97. If the phenotype is more common in males, the gene is likely sex-linked.

98. Several methods help map human chromosomes. A karyotype is a picture of all chromosomes in a cell. X Y

99. Karyotypes can show changes in chromosomes. –deletion of part of a chromosome or loss of a chromosome –large changes in chromosomes –extra chromosomes or duplication of part of a chromosome