Objectives
•  Describe the structure of a generalized cell
the
and function of DNA
•  Describe DNA replication
•  Understand how proteins are made
•  Explain function of gene
•  Understand how mutations occur
•  Recognize & understand importance of chromosomes
•  Explain karotype and why it is useful
•  Understand mitosis and meiosis
•  Recognize the evolutionary significance of meiosis
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BIOLOGICAL BASIS OF LIFE
Gregor Mendel
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Cell Biology
• In-take of nutrients
• Substances for cell growth and repair
• Reproduction
• Excretion
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Cell Types
Prokaryotic Cell
Eukaryotic Cell
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Cells Features
Cell membrane
Nucleus (nuclear membrane)
Cytoplasm
Organelles:
ribosomes, mitochondria, endoplasmic reticulum, centrioles, etc.
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Chromosomes
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Number of Chromosomes
•
•
•
•
Humans: 46 (23 pair)
Chimp and gorilla: 48
Chickens: 78
One fern specoes
1,260
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Anatomy of a Chromosome
çcentromere
Chromatid
Chromosome
(46 in humans)
1) Chromatid
(2) Centromere
(3) Short arm
(4) Long arm
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Karyotype
22 pairs of autosomes +
1 pair of sex chromosomes
XX = Female
XY = Male
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Sex Chromosomes
SRY (sex-determining region Y) gene
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Inactivated X chromosome in females
Genes and Chromosomes
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Somatic Cells &
Sex Cells
Males: sperm (testes)
Females: ova or eggs (ovaries)
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Two Types Cell Division
•  Meiosis
•  Mitosis
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Mitosis
Zygote: fertilized egg
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Meiosis
Diploid (2N)
Haploid (N)
Production of sex cells or
gametes
Two divisions/reduction
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Reproduction
•  Gametogenesis: production of sex cells or
gametes that have one-half the normal
chromosomal content or haploid (N)
condition; spermatogenesis; oogenesis
•  Fertilization: fusion of sex cells that
restores the normal chromosomal content
(diploid (2N) condition)
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DNA
Gene: basic unit of inheritance
DNA = deoxyribonucleic
RNA = ribonucleic acid
Functions:
1. transmission of genetic information from one
generation to the next
2. maintains genetic integrity of individual through
duplication/replication
3. instructs cells to make proteins (enzymes)
Nucleotides
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Nucleotide
•  Sugar molecule: pentose
(RNA) or deoxyribose (DNA)
•  Phosphoric acid
•  Nitrogenous base
•  4 kinds of bases in the DNA
molecule:
–  adenine (A)
–  guanine (G)
–  thymine (T)
–  cytosine (C)
A & G are purines
T & C are pyrimidines
•  RNA: uracil (U) in place of
thymine
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DNA: Double Helix
Protein Synthesis
20 amino acids
3-letter words: triplets or
codons (64)
UUU = phenlalanine
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RNA
mRNA (messenger RNA)
rRNA (ribosomal RNA
tRNA (transfer RNA e.g.,
UUU= phenylalanine, CAA=
glutamine etc.)
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Point Mutation
E.g., Sickle cell hemoglobin
molecule: 2 α (alpha) and 2 β
(beta) polypeptide chains
6th amino acid in the β chain:
instead of glutamic acid
(found in normal
hemoglobin), valine is
substituted in the HbS
molecule; the genetic word,
CTT (HbA) mutated to CAT
(HbS)
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Sickle-cell Anemia
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Types of Gene Mutation
•  Substitution of a
base pair
•  Deletion or insertion
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Causes of Mutation
•  Higher temperatures, high energy
radiation (x-rays, ultraviolet radiation),
mustard gas, caffeine etc.
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Definition of Gene
•  Gene is that section of the DNA molecule
(sequence of codons on the DNA template)
responsible for the ultimate synthesis of a
specific polypeptide chain of amino acid
•
Gene is that portion of the DNA molecule
that specifies the manufacture of a protein
that will produce or assist in the production
of one or more physical traits. Not a discrete
unit but part of a large DNA molecule.
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Next Class
Heredity & Evolution
Read Chapter 4: 402-407
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