BS 162 1nd Edition Lecture 4 Looking at Genetics More Gene Structure A small section of the DNA molecule containing a specific nucleotide sequence Can be as short as a few hundred pairs Average human genes contain 3 000 bases but vary in size The largest known human gene is dystrophin at 2 4 million bases Why is Genetic Information Transferred To make new somatic cells Somatic cells allow to make gametes eggs and sperm to pass on to next generation Mitosis Process by which a cell duplicates the chromosomes in its cell nucleus in order to generate two identical daughter cells How Do Organisms Grow Repair They must make new cells Need to have same blueprint in all cells therefore DNA needs to replicate so that each daughter cell can have the entire blueprint in it Cell Cycle Overview G1 cells DNA is unduplicated 1 maternal 1 paternal chromosome G2 cells DNA is duplicated 1 maternal 1 paternal chromosome 2 identical sister chromatids attached in the middle by the centromere Metaphase sister chromatids line up down the center Anaphase sister chromatids separate 1 copy to each daughter cell Genes Purpose Genes code for proteins These proteins affect how an organism looks and functions They allow the cell to make identical daughter cells that will produce the same proteins through mitosis Information Flow These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute Expression of a gene to form a protein involves 2 processes Transcription copies information from gene to a sequence of RNA Translation converts RNA sequence to an amino acid sequence Messenger RNA mRNA forms as a complementary copy of DNA and carries information to the cytoplasm This is transcription Transfer RNA tRNA molecules that carry amino acids line up on mRNA in proper sequence and form the polypeptide chain This is translation The Genetic Code specifies which amino acids will be used to build a protein Codon a sequence of three bases Each codon specifies a certain amino acid Start Codon AUG initiation signal for translation Stop Codon stops translation and polypeptide is released Each codon specifies only one amino acid A change in a single nucleotide can cause a change in the amino acid and then result in a change in the protein This is a single nucleotide polymorphism SNPs