Scientific Basis of Genetics

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Scientific Basis of Genetics

• Janice S. Dorman, PhD
• University of Pittsburgh
• School of Nursing

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Lessons

• Cell cycle
• Chromosomes
• DNA and RNA
• Structure of a gene

• Transcription
• Translation
• Mutations

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Lesson One

• Cell Cycle

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Mitosis

• Somatic cells divide by mitosis
• Involves 1 cell cycle / division
• Parental and 2 daughter cells are genetically
  identical
• Parental cells are diploid
  (46 chromosomes)
• 2 daughter cells are diploid
  (46 chromosomes)

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Meiosis

• Germ cell precursors (parental cells) divide by
  meiosis
• Involves 2 cell cycles / divisions instead of 1
• Germ cells precursors and 4 gametes (daughter
  cells either egg or sperm) are NOT genetically
  identical
• Germ cell precursors are diploid (46 chromosomes)
• 4 gametes are haploid (23 chromosomes)

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The stages of meiosis in an animal cell
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The stages of meiosis in an animal cell
Recombination occurs here
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The stages of meiosis in an animal cell
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Lesson Two

• Chromosomes

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Chromosome Structure

• Chromosomes have 2 arms that are separated by the
  centromere
• p arm for petite
• q arm long arm
• Ends of chromosomes are called telomeres

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Chromosome Types

• Autosomes the numbered chromosomes
• All individuals have 2 copies of each type of
  autosome (homologous chromosomes 1 maternal, 1
  paternal)
• Sex chromosomes the X and Y chromosomes
• All individuals have 2 sex chromosomes
• XX female
• XY male

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Karyotype

• An organized picture of the chromosomes found in
  a cell
• Captured during mitosis, just before cell divides
• Generally demonstrates the normal complement of
  chromosomes
• 46,XX for females and 46,XY for males
• Can point out gross chromosomal abnormalities
  (such as extra or missing chromosomes)

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Lesson Three
DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic
Acid)
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Components of DNA / RNA

• Phosphate group
• Sugar group
• Deoxyribose in DNA
• Ribose in RNA
• Bases
• Adenine, guanine, cytosine, thymine in DNA
• Adenine, guanine, cytosine, uracil in RNA

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RNA Structure

• RNA is generally single stranded
• Can fold and create complicated structure
• Multiple types of RNA, each with a different
  function
• Sugar-phosphate groups form the backbone of the
  molecule
• Nucleotides are organized 5 to 3
• Bases form the center of the molecule

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5 end
3 end
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Double stranded RNA Possible secondary
structures of RNA molecules. The double-stranded
regions are depicted by connecting hydrogen
bonds. Loops are noncomplementary regions that
are not hydrogen bonded with complementary bases.
Double-stranded RNA structures can form within a
single RNA molecule or between two separate RNA
molecules
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DNA Structure

• DNA is a double helix
• Sugar-phosphate groups form the backbone
• Two DNA strands are anti-parallel
• One strand, nucleotides are organized 5 to 3
• Other strand, nucleotides are organized 3 to 5
• Bases are held together by hydrogen bonds and are
  complementary
• A is complementary to T
• C is complementary to G

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3 end
5 end
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DNA Replication

• Uncoil DNA
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• Strand Separation 
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• Templates are Single Stranded 
• ? 
• RNA Primers Needed For New Strands 
• ? 
• Both DNA Strands Extended From the RNA Primer (5
  to 3)
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• One Strand is the Leading Strand
• Other Strand is the Lagging Strand

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