Molecular+Genetics

DNA Replication DNA-> RNA->Protein mRNA, tRNA, rRNA Transcription (participating molecules, location, enzymes)
 * Molecular Genetics **

Transcription
 * Occurs in the nucleus
 * Enzyme (RNA polymerase) catalyzed assembly of making an mRNA molecule complementary to a strand of DNA
 * Each nucleotide triplet in DNA directs a particular triplet to be formed in mRNA
 * During splicing: Non-encoding introns are removed and coding exons are left

[|Transcription Video] [|mRNA Splicing Video] [|mRNA Processing Video] Translation (products, location, enzymes) Translation
 * Occurs in cytoplasm on ribosomes
 * mRNA determines the order the amino acids are added to the protein being made
 * a triplet in mRNA (codon) pairs with a triplet on a tRNA molecule (anticodon) carrying the correct amino acid
 * ribosome moves along mRNA one codon at a time forming a polypeptide chain
 * 3 stages
 * 1. Initiation- ribosome attaches to start codon (AUG) on mRNA
 * 2. Elongation- amino acids added on one at a time, as ribosome moves along mRNA
 * 3. Termination- mRNA has stop codons (UAA, UAG, UGA) for which tRNA has no anticodon, thus ending translation

[|Translation Video]

the life cycle of a healthy cell which contains the following stages: G1 (gap 1): the cell grows in size, happens simultaniously with G0 G0 (gap 0): the cell is used for its specified functions S (synthesis): the synthesis of sister chromatids G2 (gap 2): the cell prepares for mitosis M (mitosis): the cell divides into two daughter cells Cytokinesis: the process by which the cytoplasm of the original cell is divided between the two daughter cells Interphase: G1/G0, S, G2
 * __Cell Cycle__**


 * __Mitosis vs. Meiosis__**

 **Mitosis:** -the process of sorting and distributing chromosomes, in order to create 2 identical cells -made up of 4 distinct steps: 1. Prophase: -chromatin condenses to from chromosomes (2 identical chromosomes = sister chromatids, held together by a centromere) -the nuclear membrane disintegrates -centrioles move to poles -spindle fibers are formed 2. Metaphase: -the chromosomes line up in the middle of the cell 3. Anaphase: -the sister chromatids are pulled apart along spindle fibers towards the poles of the cells 4. Telophase: -chromosomes reach the poles of the cells and begin to decondense, two new nuclear membranes begin to form ** **Meiosis:** -the process of gamete production -made up of two sequences of cell division: 1. Meiosis I: -follows steps similar to mitosis: Prophase I, Metaphase I, Anaphase I, and Telophase I - major difference = homologous chromosomes, not sister chromatids, line up in the center of the cell in Metaphase I (homologous chromosomes = chromosomes that are similar in length and centromere location & control the same genes; one from each parent) -crossing over occurs during Metaphase I – genes on ends of homologus chomosomes switch positions to create genetic variation in offspring 2. Meiosis II: -identical to mitosis: Prophase II, Metaphase II, Anaphase II, and Telophase II
 * final product = 2 new genetically identical daughter cells
 * final product = 4 haploid gametes**

-Mitosis creates 2 daughter cells, Meiosis creates 4 -Mitosis occurs in somatic (body) cells, Meiosis only occurs during gamete production in the ovaries/testes -Mitosis creates cells that are genetically identical, Meoisis creates cells with varied genetic information (causes diversity in offspring) -Mitosis creates diploid cells, Meiosis creates haploid cells
 * //Major Differences between Mitosis and Meiosis//:**



**DNA Replication**
 * DNA is separated into 2 strands. Each strand creates a template where base pairs match up creating 2 new DNA strands


 * Base pairs: Aà T Cà G


 * DNA polymerase is the enzyme used to duplicate and unwind the DNA strand


 * DNA replication occurs during the S phase of mitosis


 * The unzipping of the double helix breaks the hydrogen bonds


 * Proof reading copy cuts out miss paired nucleotides DNA polymerase is the enzyme that “proof reads” the new strand

Ex: DNA Replication


 * 3 Kinds of RNA**
 * Messenger RNA (mRNA)-Carries DNA message from the nucleus to the ribosomes.


 * Ribosomal RNA (rRNA)- makes up the ribosomes=ribosome


 * Transfer RNA (tRNA)- Carries amino acids to the ribosomes


 * 1) Transcription mRNAß from DNA
 * 2) Translation mRNAà amino acid chain