Topic: Modern Genetics

What are the components of nucleic acids?

How do we replicate DNA?

Looking at DNA and RNA

• http://www.brainpop.com/health/geneticsgrowthanddevelopment/dna/

• http://www.dnatube.com/video/3447/DNA-double-helix

• http://www.youtube.com/watch?v=EqBB8PHHI_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 baseNUCLEOTIDE

• 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, cytosineclassified as pyrimidines

• bases held together by hydrogen bonding• double helix shape

Base Pairing Rules

A—T and C—Gpurine 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

• http://www.hhmi.org/biointeractive/dna/DNAi_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

RNAmRNA, 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 ReplicationPurpose 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

• http://www.youtube.com/watch?v=zdDkiRw1PdU

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

http://www.stolaf.edu/people/giannini/flashanimat/molgenetics/dna-rna2.swf

http://www.hhmi.org/biointeractive/dna/DNAi_replication_vo1.html