NUCLEIC ACIDS STRUCTURE AND FUNCTION RNADNA

MONONUCLEOTIDE PHOSPHATE PENTOSE SUGAR ORGANIC BASE

PHOSPHATE

PENTOSE SUGAR RIBOSEDEOXYRIBOSE

ORGANIC BASES PURINESPYRIMIDINES GUANINE G ADENINE A CYTOSINE C URACIL U THYMINE T

NUCEIC ACIDS Found in all cells:- DNA (Deoxyribonucleic Acid) in nucleus. RNA (Ribonucleic Acid) in cytoplasm. Building blocks =NUCLEOTIDES Mononucleotide = Condensation product of:- Phosphate Pentose sugar (Ribose/Deoxyribose) Organic/Nitrogenous base (A T G C U) Nucleic acids = Polynucleotides = condensation products of many mononucleotides (i.e. polymers)

RIBONUCLEIC ACID (RNA) A POLYNUCLEOTIDE

PHOSPHATE RIBOSE ADENINE

PHOSPHATE GUANINE RIBOSE

PHOSPHATE RIBOSE CYTOSINE

PHOSPHATE RIBOSE URACIL

POLYNUCLEOTIDE RNA

ribosomal RNA (rRNA) Makes up the bulk of the ribosome. Large folded molecule.

messenger RNA (mRNA) Carries the genetic message from DNA in the nucleus to the ribosomes where proteins are synthesised (made) accordingly. Long molecule, not folded. Variable in length and base sequence. Readily broken down and remade.

Collects amino acids and takes them to the ribosomes for assembly into proteins. Small molecule. Winds back on itself to form a “clover-leaf” shape. One end carries an amino acid. One loop has a special triplet of bases (ANTICODON) which determines the amino acid carried. transfer RNA (tRNA) AMINO ACID ANTICODON

RIBONUCLEIC ACID (RNA) Single stranded polynucleotide. Sugar is always ribose. Organic bases are always A, G, C, and U, NEVER T. 3 types :- ribosomal RNA (rRNA) messenger RNA (mRNA) transfer RNA (tRNA) Back

DEOXYRIBONUCLEIC ACID (DNA) A POLYNUCLEOTIDE

PHOSPHATE DEOXYRIBOSE ADENINE

PHOSPHATE DEOXYRIBOSE GUANINE

PHOSPHATE DEOXYRIBOSE CYTOSINE

PHOSPHATE DEOXYRIBOSE THYMINE

HYDROGEN BONDS ANTIPARALLEL

What is the difference between deoxyribose and ribose? What type of spiral is DNA? How many bases are there to each turn of the DNA molecule? What three forms of evidence were used to derive the structure of DNA? How many nucleotides (on average) does it take to make a human chromosome set? What are chromosomes made of as well as DNA?

SPECIFIC BASE PAIRING PURINES PYRIMIDINES GUANINE ADENINE CYTOSINE THYMINE COMPLEMENTARY SHAPE

SPECIFIC BASE PAIRING HYDROGEN BONDS

THE DOUBLE HELIX

Double stranded helix - “THE DOUBLE HELIX” Sugar (Deoxyribose) / Phosphate backbone. Antiparallel Bases are A, G, C and T, NEVER U. Chains are held together by “H” bonds between base pairs. Specific base pairing A:T and G:C (i.e. purine:pyrimidine) 10 base pairs per turn of the helix. DEOXYRIBONUCLEIC ACID (DNA) Back

THE FUNCTION OF DNA

DNA REPLICATION GENE EXPRESSION/ PROTEIN SYNTHESIS PROTEIN m RNA Translation Transcription

DNA REPLICATION

SEMI-CONSERVATIVE HYPOTHESIS

Takes place during interphase of the cell cycle (S phase). The DNA helix is unwound and unzipped by the enzyme HELICASE which breaks the weak “H” bonds between the base pairs. The exposed, unpaired bases form a template. Free nucleotides are specifically base paired to the exposed bases by the enzyme DNA POLYMERASE. ATP is required as a source of energy. Since each new DNA molecule retains half an old one, this is known as the “SEMI-CONSERVATIVE HYPOTHESIS”. Two identical DNA molecules are produced. DNA REPLICATION

QUIZ Give 3 differences between DNA and RNA. What is the difference in chemical structure between ribose and deoxyribose? What is meant by complementary? Give the two complementary base pairs. Name the three different types of RNA. What is meant by a “condensation” reaction? Name the three components of a mononucleotide? Name the scientists credited with discovering the structure of DNA? What is meant by antiparallel? What is meant by the “Semi-conservative Hypothesis”?

ANSWERS DNA is double stranded, has deoxyribose sugar, and bases G, C, A & T. RNA is single stranded, has ribose sugar and the bases G, C, A & U. Ribose has a hydroxyl group (OH) on C atom 2, deoxyribose has a H atom. To fit together perfectly, to make a complete whole. A T and C G. rRNA, mRNA and tRNA. Joining molecules together with the production of water. Phosphate, pentose sugar and organic,nitrogenous base. James Watson and Francis Crick (1953), though many others paved the way. To run along side each other but in opposite directions. Each new DNA molecule partially consists of (conserves) the old one.

WANT TO KNOW MORE ? “DNA From the Beginning” THEN VISIT:-

THE END J.Minton SWGS 2002