Introduction to Genetics

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Chapter 1

• Introduction to Genetics

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From Mendel to DNA

• Mendel studied garden peas from parents to
  offspring in quantitative and predictable ways
• Became the foundation for genetics as he
  determined several key concepts in terms of his
  heritable traits which we know are genes

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Chromosome Theory of Inheritance

• Mendel was before we knew about chromosomes
• Found chromosomes and knew that they were diploid
  or 2n
• Chromosomes exist in pairs called homologous
  pairs identical in size and location of
  centromere

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2 Types of Cell Division

• Mitosis chromosomes copied and distributed to
  each of 2 new daughter cells
• both get full set
• Meiosis process of gamete and spore formation
• results in haploid number of chromosomes in each
  gamete
• fertilization will result in a 2n zygote

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Genes and Chromosomes

• Act the same in that they come in pairs and they
  separate during meiosis
• Genes carried on chromosomes thru the gametes
• genetic continuity from generation to generation

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Genetic Variation

• See in studies of Drosophila melanogaster found
  white eye flies in with wild-type red eye flies
• Mutation causes a change in the gene for eye
  color can pass on to the next generation
• source of all genetic variation, each variant
  gene is the called an allele
• responsible for changes in observable features
  called the phenotype
• a set of alleles is the genotype

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Chemical Nature of Genes

• Knew chromosomes where the cause of the red or
  white eye but what part of DNA was responsible
  DNA or protein
• Bacteriophage work showed that it is DNA and not
  the protein as it is left outside the cell and
  get new viruses

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Discovery of DNA

• After learning DNA was basis of genetic info
  need to decipher the structure and how expressed
  in an observable phenotype
• DNA is a double stranded helix with each strand
  made of nucleotides 4 different bases of A, G,
  T and C
• make up the genetic code or alphabet that will
  ultimately make up protein

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DNA

• Strands complement one another
• Each rung of the ladder is either AT or GC
• Critical to gene function
• Serves in DNA replication and gene expression

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RNA

• Similar to DNA but different sugar
• Different sugar and U instead of T
• Usually single stranded but can also form
  complementary structure with DNA

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Gene Expression

• Begins in the nucleus with transcription into RNA
  sequence complimentary to DNA
• RNA moves to the cytoplasm and directs protein
  synthesis on ribosomes by translation
• mRNA is made up of codons which is 3 adjacent
  nucleotides that dictates the amino acid
• accomplished by adaptor molecule of tRNA that
  brings in the amino acid
• Central Dogma is DNA?RNA?protein

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Proteins and Biological Function

• A protein with 100 amino acids, 20 different
  amino acids so a vast arrangement to make any one
  protein
• 20100 a bunch
• Enzymes are the largest protein biological
  catalyst, allow reactions to occur
• Diverse array of different types of proteins
  all determined by linear sequence that will
  dictate structure

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Genotype to Phenotype

• Normal hemoglobin is made up of 4 subunits 2
  copies of 2 different polypeptides
• carries O2 in the blood
• Mutation in the ?-chain changes one amino acid
  into a different one
• Under low O2 tension the red cells change shape
  which plug up capillaries and small vessels in
  the body
• can break and cause anemia

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Genomics Recombinant DNA Technology

• Discover restriction enzymes in 1970 enzymes
  bacteria use to protect themselves from viruses
• Allowed for cloning and placing our favorite gene
  into a vector to make more or express it as a
  protein
• Acts as a small DNA or protein factory
• Genomic library was used to determine the human
  sequence contains all the DNA of organism

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Sequencing

• 1995 first genome published from bacteria
  Haemophilus influenza
• 2003 human genome is 96 reported
• Many organisms sequenced since then
• Genomics study of genomes use databases of
  sequences to study structure, function and
  evolution of genes and genomes

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Genetic Engineering

• Used recombinant DNA to altered plants that
  resist insects, pesticides, viruses and
  additional products
• Used to clone Dolly the sheep

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Genetics in Medicine
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DNA Microarray

• Use microarrays to study 1000s of genes at a
  time can determine if genetic disease or to see
  changes in gene expression

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Model Organisms and Genetic Studies