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Scientific Basis of Genetics. Janice S. Dorman, PhD University of Pittsburgh School of Nursing. Cell cycle Chromosomes DNA and RNA Structure of a gene. Transcription Translation Mutations. Lessons. Lesson One. Cell Cycle. Mitosis. Somatic cells divide by mitosis

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scientific basis of genetics

Scientific Basis of Genetics

Janice S. Dorman, PhD

University of Pittsburgh

School of Nursing

Cell cycle



Structure of a gene




lesson one

Lesson One

Cell Cycle

  • 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)
  • 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)
lesson two

Lesson Two


chromosome structure
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
chromosome types
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
  • 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)

Lesson Three

DNA (Deoxyribonucleic Acid) and

RNA (Ribonucleic Acid)

components of dna rna
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
rna structure
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

5’ end

3’ end


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

dna structure
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

3’ end

5’ end

dna replication
DNA Replication

Uncoil DNA

Strand Separation 

Templates are Single Stranded 

RNA Primers Needed For New Strands 

Both DNA Strands Extended From the RNA Primer (5’ to 3’)

One Strand is the Leading Strand

Other Strand is the Lagging Strand