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2 주차 수업자료

2 주차 수업자료. Chapter 2. Basic Genetics. Mendel: father of classic genetics. Mendelian characters Distinct Definitive Yes or no. Allele. An alternative form of gene Locus on chromosome Homozygous Same genes at the locus Heterozygous Different genes at the locus.

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2 주차 수업자료

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  1. 2주차 수업자료

  2. Chapter 2. Basic Genetics

  3. Mendel: father of classic genetics • Mendelian characters • Distinct • Definitive • Yes or no

  4. Allele • An alternative form of gene • Locus on chromosome • Homozygous • Same genes at the locus • Heterozygous • Different genes at the locus

  5. One gene-one enzyme theory • Enzymes can have multi-subunits • Not true any more • One gene-one enzyme  One gene-one protein

  6. Wild type vs. mutant • Wild type: • Typical • Common • Adapted • Normal (not always true) • Mutant: • Genetically altered • Null: • No protein

  7. Genotype and phenotype • Genotype  phenotype • Epistasis • Interaction between genes to control a single phenotype • One gene suppresses the expression of another • Mutation in one gene masks the effect of mutation in another gene

  8. Genes and chromosomes (1) • Homologous chromosomes • Duplicate genes

  9. Genes and chromosomes (2) • Chromosome number: n • Haploid (e.g., bacteria): n=1 x 1 copy = 1 • Diploid (e.g., human): n=23 x 2 copies = 46 • Polyploid (e.g., wheat): n=7 x 2, 4, 6 copies = 14, 28, 42 • Aneuploid: abnormal number of chromosomes • Down syndrome (Trisomy)

  10. Dominant and recessive alleles • Dominant • Recessive • Homozygous • Heterozygous

  11. Partial- or co-dominant alleles • Partial dominant • (e.g., r0.5 vs. R) • Co-dominant • (e.g., R and B vs. r)

  12. Penetrance: phenotypic effect • Variable penetrance: due to modifier genes (e.g., epistatic interaction)

  13. Germ cells: progenitor of gametes • Germ cells vs. somatic cells • Meiosis vs. mitosis

  14. Genotype determination (1) • F0  F1 • Homozygous dominant X • Homozygous recessive • Offspring (progeny): All heterozygous

  15. Genotype determination (2) • F1  F2 • Heterozygous X • Heterozygous • Offspring (progeny): Mendelian ratio, 1:2:1 (3:1)

  16. Sex determination and X/Y chromosomes

  17. Pedigree: inheritance of sex-linked genes XY XX X-linked

  18. Meiotic recombination (1) • Crossing over • For genetic diversity • Unequal crossing over possible when chromosomes are not properly aligned

  19. Meiotic recombination (2) • Tetrad • Synapsis (synaptonemal complex) • Chiasmata

  20. Linkage group • Always on the same chromosome • Should be <50%

  21. Chapter 3. DNA, RNA and protein

  22. Nucleic acids (1) Base + sugar = nucleoside (deoxy- or ribo-) + phosphate = nucleotide (deoxy- or ribo-)

  23. Nucleic acids (2) Phosphodiester linkage

  24. Nucleic acids (3) See Table 3.01

  25. dsDNA: double helix • RNA • Single-stranded • DNA • Double-stranded • Antiparallel • Double-helix, right-handed (clockwise)

  26. Base paring and complementary strands • Base paring • Hydrogen bond • Complementary strands • To inherit genetic information • For gene duplication

  27. Melting and annealing of DNA • Melting (denaturation): temp ↑ • Annealing (renaturation): temp↓, slowly, 20-25 °C below Tm • GC ratio or GC content ↑  Tm ↑

  28. Chromosome (1) • Chromosome • Large DNA containing genes • Chromatin • DNA + protein (histone) • Prokaryotic chromosome • No intron • Operon: gene cluster

  29. Chromosome (2) • Eukaryotic chromosome • Contains centromere and telomere • Replication of chromosome • Kinetochore: binds to centromere and microtubule during cell division • Role of telomerase Kinetochore (red) Chromosome (blue) Microtubule (green) From Google image

  30. Central dogma • Flow of genetic information • Transcription pattern • Prokaryote vs. eukaryote

  31. Translation (1) • Bacterial ribosome (70S) • Large subunit (50S) • 5S, 23S rRNA • Small subunit (30S) • 16S rRNA S = sedimentation coefficient, Svedberg unit

  32. Codon and anticodon • Genetic code: 64 codons  20 amino acids • tRNA: contains anticodon

  33. Translation (2) • Charged tRNA: with amino acid • Ribosome elongates polypeptide chain

  34. Non-translated RNA • rRNA: ribosomal • tRNA: transfer (amino acid  ribosome) • snRNA: small nuclear, processing of mRNA, RNA splicing • gRNA: guide, for RNA editing (insertion/deletion of U) • aRNA: antisense, single-stranded RNA complementary to mRNA, inhibit translation • Ribozyme: ribonucleic acid enzyme • Regulatory RNA: regulation of gene expression • Recognition RNA: recognition of short DNA sequence

  35. Amino acid to polypeptide (alpha carbon) N-terminus (amino) C-terminus (carboxy)

  36. Four organization levels of protein structure • Primary: • Linear • Secondary: • Initial folding due to hydrogen bonding (α-helix, β-sheet) • Tertiary: • 3-D conformation • Quaternary: • Assembly of several polypeptide chains

  37. Protein function (1) • Folding  generation of active site • Enzyme

  38. Protein function (2) • Structural protein: e.g., microtubule • Enzyme • Regulatory protein • Transport protein: e.g., ion channel

  39. X-ray crystallography • Hanging drop method

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