DNA – Deoxyribonucleic Acid

Nucleic Acids Nucleotides DNA & RNA

Deoxyribonucleic Acid Double Helix connected by N-bases.

DNA Replication …Resulting in two molecules, each identical to the parent, and to each other.

DNA Information is contained in the Sequence of N-bases found along the DNA molecule – GENES! Transferring that information into an Amino Acid Sequence (a PROTEIN) is the trick. A G C C T A G G G A T A G T C G G A T C C C T A T C

A 2-step Process 1.Transcription DNA RNA

A 2-step Process 2.Translation RNA Protein

Ok, Lets take a step back…

Cell Division Cells come from pre-existing cells… Cells need to reproduce! –Single-celled organisms -- asexual reproduction. –Multi-celled organisms – growth. Cell Division = Cytokinesis Nuclear Division = Karyokinesis

Prokaryotes – Binary Fission Simple

Eukaryotes – more complex Chromosomes Chromosome Structure –Chromatin + Histones –Unduplicated –Duplicated Chromosome Number –Diploid Somatic cells (body cells) –Haploid Germ cells (sex cells)

Cell Cycle

Chromosome Duplication During S-phase = “Synthesis” Why?.... So that later, the sister chromatids can separate into different (new) cells!

Karyokinesis Mitosis –Somatic cells (body cells) –“Cloning” of genetic information – exact copies made and distributed to new cells. –Chromosome # is retained (stays the same). Meiosis –Germ cells (sex cells) –Genetic information is shuffled – new cells are each different. –Chromosome # is cut in half.

Mitosis Prophase Metaphase Anaphase Telophase

Prophase Nuclear Envelope Disappears Nucleolus Disappears Chromosomes Condense Chromatin  Chromosomes Spindle Fibers (Microtubules) Attach to Centromeres Attach to M.T.O.C.s

Metaphase Chromosomes line up on the ‘Metaphase Plate’ pushed & pulled by the spindle fibers Spindle Apparatus well developed.

Anaphase Chromosomes each broken at their centromeres spindle fibers on each side shorten New (unduplicated) chromosomes move toward the M.T.O.C.s

Telophase Chromosomes stop moving when they reach the spindle poles (at the M.T.O.C.s) Nuclear Envelope re-forms (2x) Nucleolus re-forms (2x) Spindle fibers disappear Cytokinesis

Cleavage Furrow divides the cells Cell Plate divides the cells

Meiosis Associated with Sex! Sexual Reproduction involves –2 parents –Mixing of genetic information –Life cycles, with MEIOSIS & FERTILIZATION

Life Cycles DIPLOID HAPLOID GAMETIC

Meiosis Mixing of Genetic Information Germ Cells (Sex Cells) Reduction in Chromosome Number –Diploid  Haploid 2 Divisions –Meiosis I --- P,M,A,T –Meiosis II --- P,M,A,T Results in 4 cells

Meiosis I Prophase I Metaphase I Anaphase I Telophase I Pairing and separation of Homologous Chromosomes Crossing Over Independent Assortment 2n  1n VARIATION!

Meiosis I

Meiosis II Prophase II Metaphase II Anaphase II Telophase II Separation of sister chromatids 1n  1n Results in 4 DIFFERENT cells.

Meiosis II

MEIOSIS -- Spermatogenesis

MEIOSIS -- Oogenesis Stimulated by Fertilization

MITOSIS vs MEIOSIS

Ok,…back to the molecular level…

1. Transcription Complimentary Base Pairing. DNA RNA G - C C - G T - A A - U

3 Types of RNA mRNA = Messenger RNA –The “blueprint” rRNA = Ribosomal RNA –The “workbench” tRNA = Transfer RNA –The “truck”

mRNA – messenger RNA The “message” – the blueprint for the production of a polypeptide – a protein.

2. Translation Problem: there are only 4 N-bases, and 20 amino acids to make a protein! We need a TRANSLATION! What’s the code?

The Genetic Code Triplet Base Code. Every 3-letter word in the RNA Transcript is a CODON.

The Genetic Code Each CODON codes for a single Amino Acid.

The Genetic Code See p. 207

2. Translation A meeting of ALL 3 types of RNA: –mRNA – the blueprint. –rRNA – the workbench. –tRNA – the supply truck.

2. Translation Initiation - All 3 types of RNA come together: mRNA, rRNA, & tRNA

2. Translation Elongation – Amino Acids are added with the help of elongation factors (proteins). 1.Codon meets Anticodon at the ‘A’ binding site. 2. A Peptide Bond Forms between adjacent Amino Acids

Summary