Topic: Modern Genetics What are the components of nucleic acids? How do we replicate DNA?

Looking at DNA and RNA owthanddevelopment/dna/ owthanddevelopment/dna/ double-helixhttp:// double-helix PHHI_0http:// PHHI_0

What are nucleic acids? Biochemical molecules that hold hereditary information Two types –DNA= deoxyribonucleic acid –RNA=ribonucleic acid

DNA Composition Phosphate group, sugar, nitrogeneous base  NUCLEOTIDE Bunches of nucleotides come together to make……the DNA molecule

Components of DNA- What type of shape does DNA take on?

DNA Composition Backbone (legs) made from sugar (deoxyribose) and phosphate 4 possible nitrogen bases hold the two strands together – adenine, guanine  classified as purines – thymine, cytosine  classified as pyrimidines bases held together by hydrogen bonding double helix shape

Base Pairing Rules A—T and C—G purine to pyrimidine

The 4 nitrogeneous bases adenine guanine cytosine thymine phosphate sugar

Chargaff’s Rule In a sequence of DNA, approximately –The percentage of A present is the same as T –The percentage of C present is the same as G

Chargaff’s rule Ai_chargaff_ratio.htmlhttp:// Ai_chargaff_ratio.html

Composition of RNA RNA contains the same sugar and phosphate backbone BUT… –The sugar is called RIBOSE –Bases of RNA are: adenine, uracil, cytosine, and guanine –No thymine in RNA uracil is in place of thymine

RNA mRNA, t-RNA, r-RNA RNA= Ribonucleic Acid Ribonucleic Acid takes the information from DNA and converts a message to our cell for different instructions (traits). Ex: hair color, eye color, body type by making proteins from amino acids linking together RNA is located in the nucleus(m-RNA), t- RNA, r-RNA( associated with ribosome) All types of RNA are single stranded

DNA Replication Purpose of DNA replication –Mitotic division for cell growth of new somatic cells –We replicate DNA in the S- phase of the cell cycle in order to prepare for mitosis

DNA Replication w1PdUhttp:// w1PdU

DNA Replication

More More More DNA- DNA Replication Double stranded DNA unwinds using the enzyme helicase (unzips), H- bonds are broken. EACH STRAND IS NOW A TEMPLATE STRAND!!.. A short RNA piece initiates the synthesis A series of enzymes (helicase, polymerase) help to separate the DNA strand Free nucleotides present in nucleus attach themselves by forming new H- bonds (DNA polymerase is the enzyme involved) Enzymes work to create new base pairing with a complementary strand of DNA. The enzyme ligase helps to bind the new strands of DNA together Each strand results in an exact copy DNA replication occurs on the opposite strand in the same way, but in the opposite direction.

Each strand is a template

Watch this tutorial to visualize the process imat/molgenetics/dna-rna2.swf _replication_vo1.html