Nucleic Acids

Big Idea 3: Living systems store, retrieve, transmit, and respond to

info essential to life processes.

Essential Knowledge

• 3A1: DNA, and in some cases RNA, is the primary source of heritable information.

Nucleic Acids

• Store and transmit hereditary information• Amino acid sequence of a polypeptide is

programmed by a unit of inheritance called a gene• Genes are found on chromosomes.

Nucleic Acids

•Large, complex molecules composed of C, O, H, N, and P.

•2 types are RNA, ribonucleic acid and DNA, deoxyribonucleic acid.

DNA

RNA

Prokaryotes

• Earliest cells

• Smaller than Eukaryotes!

• No nucleus (home for DNA)

Prokaryotic DNA

• Is housed in a region called the nucleoid

Prok. DNA

• Is usually small and circular

• Has plasmids: small, extra-chromosomal, double stranded, and circular DNA

Viruses and Eukaryotes can have plasmids too…

Herstory• Rosalind Franklin: British

scientist (working in Maurice Wilkins lab) who took an X ray

diffraction image of DNA, 1952

• Led to double helix shape discovery by Watson and Crick

Photo 51

HIStory• Watson and Crick

used Franklin’s image to create the double helix DNA model in 1953.

• Won Nobel Prize in 1962,w/ Wilkins.

Double Helix Structure

Nucleic Acid Structure

• Made of nucleotides; both RNA and DNA.

Each nucleotide contains:

• 1 Phosphate Group

• 1 Sugar

• 1 Nitrogen Base

Phosphate

• PO4

• Makes up a part of the DNA/RNA backbone

Sugar• In DNA, sugar is

deoxyribose• In RNA, sugar is

ribose• Binds to

Nitrogen Base• Is in backbone

of DNA/RNA

Fig. 5-27c-2

Ribose (in RNA)Deoxyribose (in DNA)

Sugars

(c) Nucleoside components: sugars

DNA Nitrogen Bases

• Adenine• Thymine• Guanine• Cytosine

Conserved Through Evolution!

DNA Base Pairing Rules (Chargaff’s Rules)

• A only binds with T• C only binds with G

• H bonds hold Nitrogen bases together

RNA Nitrogen Bases

• Adenine• Cytosine• Guanine• Uracil• NO

Thymine!

Fig. 5-27c-1

(c) Nucleoside components: nitrogenous bases

Purines

Guanine (G)Adenine (A)

Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)

Nitrogenous bases

Pyrimidines

Purines: Double Ring Structure, GA

Pyrimidines: Single Ring Structure: CTU

DNA: Double Stranded, RNA Single Stranded

DNA is AntiParallel

Fig. 5-27ab5' end

5'C

3'C

5'C

3'C

3' end

(a) Polynucleotide, or nucleic acid

(b) Nucleotide

Nucleoside

Nitrogenousbase

3'C

5'C

Phosphategroup Sugar

(pentose)

3’ carbon and 5’ carbon bind to PO4 phosphodiester linkage

DNA Replication

• DNA provides directions for its own replication ensure continuous

inheritance of DNA

DNA Replication• Before a cell divides must duplicate its DNA.

• Each strand of DNA will serve as a template/model for a new strand of DNA (semiconservative).

• Enzyme called DNA helicase unzips and unwinds a portion of DNA.

• Enzyme helps breaks apart H connect N bases. (A,T,C,G)

DNA Replication 1st Step

DNA Helicase

DNA Replication: 2nd Step

• 2nd enzyme called DNA polymerase III comes along and begins to add complementary base pairs to nitrogen bases.

• Works in 5’ to 3’ fashion…

• Video Clip!

DNA ReplicationOther Enzymes

Involved:Ligase: Glues back

sugar-phosphate backbone

Topoisomerase: Regulates

overwinding/ underwinding of DNA by cutting

backbone

http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter14/

dna_replication.html

Practice!

• If one side of DNA reads CTCT, what would the

complement side of DNA read? Write down on paper!

GAGA!

Then, The Cell Divides…

• Mitosis: Makes 2 identical diploid (2 copies of chromosomes) cells from 1

parent cell: IPMAT