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DNA Structure

DNA Structure. Blueprint of Life Standard 5a-c. 5a. DNA & RNA. DNA is a double helix made of a sugar-phosphate backbone with complimentary bases paired in middle Nucleotide (sugar, phosphate, & base) A pairs with T C pairs with G RNA vs. DNA . Questions.

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DNA Structure

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  1. DNA Structure Blueprint of Life Standard 5a-c

  2. 5a. DNA & RNA • DNA is a double helix made of a sugar-phosphate backbone with complimentary bases paired in middle • Nucleotide (sugar, phosphate, & base) • A pairs with T • C pairs with G • RNA vs. DNA

  3. Questions • 1. The monomers that are put together to make nucleic acids are called: • A) Nucleotide • B) Phosphate • C) Base • D) Sugar A. Nucleotides • 2. DNA & RNA are made up of which type of macromolecule? • A) Carbohydrate • B) Lipids • C) Nucleic Acids • D) Proteins C. Nucleic Acids

  4. DNA RNA • ________ stranded - ______ stranded • ____________ (sugar) - _______ (sugar) • thymine (nitrogenous base) - _____ (nitrogenous base)

  5. 1. DNA or RNA? 2. Identify the bases in strand B GTGACC

  6. 5b. DNA Replication • DNA Replication makes a copy of DNA before cell division (mitosis or meiosis) • DNA replication is semi-conservative • Each parent strand is a template for new daughter strand. • DNA has anti-parallel strands • They run in opposite directions

  7. Enzymes carry out replication • 1) Helicase – unzips DNA • 2) Primase – starts replication • 3) Polymerase – matches A-T, C-G to make new strands • 4) Ligase – glues lagging strand fragments together

  8. Question • What does semi-conservative mean? • A) Strands are anti-parallel. • B) The old strands serve as templates for the new DNA. • C) The old strands are lost. B. Old strand is conserved • What enzyme matches DNA base pairs (A-T, C-G)? • A) Helicase • B) Primase • C) Polymerase • D) Ligase C. Polymerase

  9. 5c. Genetic Engineering • Recombinant DNA contains DNA from 2+ organisms. • Restriction enzymes cut out gene from DNA • Vectors (bacteria & viruses) can be used to insert new gene into cell. • Uses: • 1) Make medicines • Ex: insulin, human growth hormone • 2) Food Crops • Ex: pest-resistant, larger fruits/veggies

  10. Protein Synthesis DNA > mRNA > ribosome > protein Standard 4a & b

  11. 4a. Protein Synthesis Protein Synthesis = making proteins • 1. Transcription = DNA > mRNA • DNA is transcribed (copied) into messenger RNA (mRNA) to leave the nucleus • DNA is too big, it does not leave the nucleus • mRNA carries the info in DNA out of the nucleus to the ribosomes in the cytoplasm

  12. 4a. Protein Synthesis • 2. Translation = mRNA > protein • mRNA is translated into a protein by a ribosome • Codon = 3 letter “words” on mRNA • Ex. U G G U C A A U C • Transfer RNA (tRNA) matches each codon and transfers the correct amino acids • Amino acids add together to make a polypeptide chain, which becomes a protein

  13. 4b. Build a Protein • 1. Transcription DNA > mRNA • Base Pairing Rules • DNA: A-T C-G • mRNA: A-U C-G • Transcribe the DNA template strand into mRNA DNA : C T G T A C G G A  template strand mRNA: G A C A U G C C U

  14. A base sequence of DNA is shown below. ACAGTGC How would the base sequence be coded on mRNA? • TGTCACG • GUGACAU • UGUCACG • CACUGUA

  15. 4b. Build a Protein • 2. Translation: mRNA > protein • Use the codon table

  16. Mutations & Proteins Changes in DNA std. 4c-e

  17. 4c. Mutations • Mutation = permanent change in the DNA base sequence • Mutations can be good, neutral, or bad • 1.Single base change – may or may not have an effect (ex: A  C) • What would happen if GGG changed to GGC? • both= Gly so nothing… • What would happen if UAC changed to UAG? • stops protein production so effect could be major…

  18. 2. An insertion or deletion changes the reading “frame” • The fat cat ate the rat • The atcatatet her at • Major effects! • Mutations occurs in sperm or egg – passed to offspring = disease • Tay Sachs disease, sickle-cell anemia, muscular dystrophy • Mutations occurs in regular body cells they may cause cancer

  19. 4d. Cell Specialization • All cells in your body have the SAME DNA • Only genes need by that cell are expressed. • Each cell only expresses the portion of the DNA containing the genetic information for the proteins required by that cell at that time. • The remainder of the DNA is not expressed • Example: • The cells of in your skin have the DNA that codes for your eye color protein. They just don’t use it

  20. 4e. Proteins • 20 amino acids make up all proteins. • Your body creates many different proteins by changing the number and sequence of amino acids • Proteins vary from about 50 to 3,000 amino acids in length. • The types, sequences, and numbers of amino acids used determine the type of protein produced.

  21. Hemoglobin – 574 aa Insulin – 51aa

  22. One human disease is caused by a change in one codon in a gene from GAA to GUA. This disease is the result of: A a mutation. B a meiosis error. C crossing-over. D polyploidy. • Although there are a limited number of amino acids, many different types of proteins exist because the A. size of a given amino acid can vary. B. chemical composition of a given amino acid can vary. C. sequence and number of amino acids is different. D. same amino acid can have many different properties.

  23. Mutations within a DNA sequence are: A. natural processes that produce genetic diversity. B. natural processes that always affect the phenotype. C. unnatural processes that always affect the phenotype. D. unnatural processes that are harmful to genetic diversity.

  24. CHROMOSOMES Wound up DNA Standard 2e-f

  25. 2e. Chromosomes • Write really small!!! • Chromosome - wound-up DNA containing genes • Sister chromatids are identical copies held together by a centromere Draw & label a chromosome on the right margin.

  26. 2e. Homologous Chromosomes • Homologous chromosomes – have the SAME genes at the SAME locations • One came from mom, one from dad

  27. 2f. Sex-determination • Karyotype – chart shows all the homologous pairs • Autosomes - pairs 1-22 • Sex chromosomes - 23rd pair determines sex • XX = girl • XY = boy

  28. Questions • True or False: • 1) Humans have 46 chromosomes • 2) Humans have 23 pairs of chromosomes • 3) Pairs 1-23 are autosomes • 4) XX is male • 5) XY is male • 6) Sister chromatids are copies of each other. • 7) Homologous chromosomes are identical.

  29. Meiosis Making Sex Cells std. 2a-d, 2g

  30. 2a. Chromosome Number Divide Box 2a into 2 columns (5 concepts to write, 3 in left column, 2 in right) 1. Chromosome Number • Diploid (2n) – somatic (body) cells with 2 sets of homologous chromosomes • Humans = 46 chromosomes (23 pairs) • Haploid (n) – gamete sex cells that have 1 set of chromosomes • Humans = 23 single chromosomes

  31. Diploid meiosis meiosis Haploid gamete Haploid gamete Questions • 1) A bug has a haploid number n=5. What is the diploid number (2n)? • 2) A crocodile has a diploid number 2n=50. What is the haploid number (n)? 2n n n

  32. 23 23 Zygote 46 First cell of a new organism 2a. Meiosis Overview 2. Meiosis vs. Mitosis • Meiosis – cell division specific to sexual reproduction that results in 4, genetically different, haploid gamete (sex) cells • Mitosis – asexual cell division that results in 2, genetically identical, diploid cells

  33. Questions • A = Mitosis B = Meiosis C = Both • 1) Type of cell division. • 2) Produces 2 cells • 3) Produces 4 cells • 4) Sexual reproduction • 5) Asexual reproduction • 6) Resulting cells are genetically different • 7) Diploid to haploid • 8) Resulting cells are genetically identical • 9) Diploid to Diploid C A B B A B B A B

  34. 2a. Steps of Meiosis 3. Steps of Meiosis • Steps are mostly the same as Mitosis, but diploid cell divides twice • Meiosis I separates the homologous pairs • Meiosis II separates sister chromatids

  35. Steps of Meiosis

  36. 2a. Crossing Over 4. Crossing Over • Homologous chromosomes pair up and randomly trade piece of DNA during Prophase I • This creates genetic variation (new gene combinations that never existed before) • Draw Crossing Over (middle step in diagram)

  37. 2a. Independent Assortment 5. Independent Assortment • Genes for different traits sort independently into gametes • Genes on different chromosomes are not connected • Ex: The gene for eye color is not connected to the gene for hair color.

  38. Questions • What accounts for so many possible combinations of genes in gametes? • A) Crossing-over • B) Independent Assortment • C) Both of these C. Both • True or False: • Meiosis 1 separates homologous pairs, while Meiosis II separates sister chromatids. True!

  39. 2b. Meiosis in Humans • Only gonads undergo meiosis • MALES = the testis produces 4 sperm (gametes) • FEMALES = the ovaries produces 1 large egg (gamete) and 3 polar bodies

  40. 2c. Random Segregation Law of Segregation • It is random whether the gamete gets the maternal or paternal version of each trait • Each gamete only gets one allele Draw the diagram: • Ex: If a pea plant is tall (Tt), half the gametes will have T and the other half will have t. After fertilization, the offspring will have 2 alleles, one from mom & one from dad

  41. If a corn plant has a genotype of Ttyy, what are the possible genetic combinations that could be present in a single grain of pollen from this plant? • A. Ty, ty • B. TY, ty • C. TY, Ty, ty • D. Ty, ty, tY, TY

  42. 2d. Fertilization • Fertilization: • Sperm + egg = zygote (23) (23) (46) haploid + haploid = diploid n + n = 2n

  43. 2g. Predicting Offspring • Alleles - different versions of a trait • Ex: Blue or brown eyes • Knowing the alleles of the parents allows you to predict the possible traits of the offspring. • Use a Punnett Square

  44. Questions • True or False? • 1) Segregation occurs when genes separate into gametes. • 2) Females produce 4 eggs. • 3) Males produce 4 sperm. • 4) Fertilization occurs when diploid eggs and sperm make a zygote. • 5) Human zygotes have 23 chromosomes. • 6) Alleles are different versions of a trait.

  45. Punnett Squares Predicting InheritanceStandard 3a & b

  46. 3a. Punnett Squares • Vocabulary to know: • Genotype = genes (TT, Tt, tt) • Phenotype = appearance (Tall or short) • Homozygous/Purebred = 2 of the same allele (TT or tt) • Heterozygous/Hybrid = 2 different alleles (Tt)

  47. Types of Inheritance 1. Autosomal – genes on regular body chromosomes (#1-22) • Dominant covers up recessive • ex: Bb • The protein created by the dominant gene functions better or is darker/stronger than the recessive protein

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