Chapter 4 Genetics and Cellular Function

							             Chapter 4
   Genetics and Cellular Function
• What makes us, how we
  maintain us and how we
  pass it on.
• (DNA, protein synthesis
  and genetics, respectively)




                                    1
      The Nucleic Acids (history)
• Discovery of the DNA
  double helix
  – 1953: x-ray diffraction
    determined geometry of
    DNA molecule made by
    Rosalind Franklin
  – Nobel Prize awarded in
    1962 to 3 men: Watson,
    Crick and Wilkins but not
    to Rosalind Franklin who
    died of cancer at 37 from
    the x-ray data that
    provided the answers.
                                    2
           Organization of DNA
• Forever trapped in the
  _____, that’s why it is
  called _____
• DNA uncoiled is called
  chromatin
• Chromatin is
  compacted DNA
• Chromatin is composed
  of DNA wound around
  protein

                                 3
               Structure of DNA
• DNA is made form a             A
  pair of nucleotides        Nucleotide
• A Nucleotide consist of:
  – 1. base
     • G, C, A, T
  – 2. phosphate
  – 3. sugar
     • deoxyribose



                                          4
                DNA Structure:
                A Double Helix




 DNA can be likened to a ladder. The sides of the ladder
are composed of phosphates and sugar (deoxyribose), the
     rungs or steps of the ladder are composed of two
                                                      5
                  complementary bases.
      Complementary Base Pairing
• The bases form
  hydrogen bonds




                      Sugar-phosphate backbone




                                                                    Sugar-phosphate backbone
• Base pairs
  –   Gee C A T
  –   Gee = Guanine
  –   C = Cytosine
  –   A = Adenine
  –   T = Thymine

                                                 Segment of DNA 6
              DNA Function
• Serves as code for protein
• Put a bunch of amino acids together and you get
  a _____
• Gene - sequence of DNA that codes for one
  amino acid pair
• Genome - all the genes of one person
  – humans have estimated 35,000 genes
  – human genome project completed in 2000
  – Genome by Matt Ridley
                                              7
                   RNA
• 3 types of RNA
  – messenger RNA (m-RNA)
  – ribosomal RNA (r-RNA)
  – transfer RNA (t-RNA)
• RNA has G, C, A, and “U” but no “T”




                                        8
             Protein Synthesis
• Transcription = DNA transcribed to m-RNA
• Translation = m-RNA translated by t-RNA on
  rough ER into a protein
  – (rough ER contains ribosomes, ribosomes are also
    called r-RNA)


• Remember: “C” comes before “L”




                                                   9
                    Mutations

• Mutations - changes in DNA structure due to
  replication errors or environmental factors
  – some cause no effect or cause genetic defects in
    future generations for good or bad




                                                       10
    Inborn Errors of Metabolism
• PKU- phenylketouria
  – Lacks an enzyme to convert the amino acid tyrosine
    to phenylalanine
• Albinism- no melanin produced
  – Lacks an enzyme to make melanin




                                                  11
                       Cell Cycle
• 1. INTERPHASE:
  – G1 phase, the first growth phase
     • normal cellular functions
  – S phase, synthesis phase
     • DNA replication
  – G2 phase, second growth phase
     • preparation for mitosis
• 2. MITOSIS (Not part of interphase)
  – M phase, mitotic phase
     • nuclear and cytoplasmic division
• 3. CYTOKINESIS (Not part of interphase OR
  mitosis)                                 12
                 DNA Replication
• Law of complimentary base pairing allows building
  of one DNA strand based on the bases in 2nd strand
• Steps of replication process
  – DNA opens
     • point of separation called replication fork
  – DNA polymerase
     • enzyme that does the job




                                                     13
                          Mitosis
• Body cell ( somatic cell) creation
  is called mitosis, sex cell (germ
  cell) creation is called meiosis
• Interphase (G1, S, G2)
• Mitosis
   –   PROphase
   –   METapahse
   –   ANAphase
   –   TELophase
        • PRO MET ANA on the TELephone
• Cytokinesis
                                         14
         Mitosis: Metaphase




• Chromosomes meet in the middle


                                   15
            Mitosis: Anaphase




• Chromosomes move towards opposite sides of cell

                                            16
           Mitosis: Telophase




• Cleavage furrow forms

                                17
                Cytokinesis
•   Not part of _____ OR _______
•   Total division of cytoplasm
•   Completed separation at cleavage furrow
•   Cell pinches in two
•   Interphase begins in the two new cells




                                              18
      Chromosomes and Heredity
• We have 23 pairs of chromosomes
   – 1 chromosome inherited from each parent
• 22 chromosomes are called autosomes
• One pair is called the sex chromosomes
• X from mom, Y or X from dad, so dad determines the
  sex of the child (Lost your head, Henry?)
• XX= female, XY= male
• We all start off as _______ until seven weeks
• If the SRY switch is pulled on the Y we become a male
  if not we remain a female
• SRY is the Sex-determining Region of the “Y”
  chromosome                                       19
                     Genetics
•   The study of the passage of genes
•   Terms:
•   Allele- an alternate form of a gene
•   Dominant/ recessive alleles




                                          20
         More Inheritance Terms
• Genotype- genetic make up
  – Dominate trait is a capital letter, recessive is a small
    letter, P= purple, p= white
• Phenotype- the outward expression of the gene,
  like a photo
• Homozygous- the same trait, PP or pp
  – This term is combined with dominate or recessive
• Heterozygous- different alleles, Pp
• Lethal allele (lethal gene)- causes death, usually
  homozygous recessive                          21
              Punnett Square
• Punnett square- a helpful way to determine
  genotype
• Draw a punnett square. This is called a test cross
• The first generation is called P1, next generation
  is called F1, the next F2
• The Punnett square will determine the genotype
  of P1


                                               22
           Sex-Linked Inheritance




• Recessive allele on X, no gene for trait on Y, so color
  blindness is more common in males. When can a female
  get color blindness?                                 23
           Variations on Inheritance
• Codominance
   –   Both Heterozygous alleles are equally dominant
   –   Both sexes are represented equally in a coed college
   –   Blood type: Ma has A and Pa has B, kid is AB
   –   Sickle Cell anemia
• Incomplete dominance
   – Both Heterozygous alleles are expressed incompletely (not
     equally)
   – A ______ and ______ flowers create a pINk flower
• Polygenic Inheritance
   – Continuous gradation of gene expression
   – Kids skin color of dark and light skinned parents
                                                              24
    Cancer- Mitosis Gone Wrong
• Uncontrolled cell proliferation
• Malignant vs. Benign
• Metastasis- cancer that has moved from it’s
  origin
• -OMA= tumor
• Angiogenesis- Cancerprotocol.com



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