SC-100 Class 25 Molecular Genetics Molecular genetics is the study of the actual hereditary material: Nucleic Acids The Two Nucleic Acids: DNA, Deoxyribonucleic acid RNA, Ribonucleic acid

Natural Polymers Previously we saw: Chains of Amino Acids form Proteins Chains of Sugars form Carbohydrates Now we observe: Chains of Nucleotides form Nucleic Acids

ATP - Adenosine Triphosphate (Adenine) (Ribose) ATP - Adenosine Triphosphate

A Nucleotide Adenosine Phosphate (Ribose) (Adenine)

RNA Each nucleotide in RNA consists of The Sugar Ribose A Phosphate group One of FOUR bases: Adenine (A) Uracil (U) Guanine (G) Cytosine (C)

DNA Each nucleotide in DNA consists of The Sugar Deoxyribose A Phosphate group One of FOUR bases: Adenine (A) Thymine (T) <<< Guanine (G) Cytosine (C)

DNA The DNA Molecule is a double strand of nucleotides held together by hydrogen bonds between the bases of each strand. Geometry and charge distribution determine that the possible base pairing are A-T and G-C Ladder shape twists to a double helix.

DNA REPLICATION DNA Molecule unzips DNA nucleotides become exposed Complementary free nucleotides attracted to open sites New bonds formed with free nucleotides Identical DNA molecules produced

DNA REPLICATION

Three Types of RNA in Protein Synthesis mRNA-messenger RNA- Has a copy of the base sequence for one gene tRNA- transfer RNA-Three Base sequence (Codon) that attracts a specific amino acid rRNA-ribosomal RNA- form ribosome where protein synthesis occurs Base Pairings for RNA A-U and G-C

Transcription of DNA into mRNA

Protein Synthesis Segment of DNA unzips Three kinds of RNA produced mRNA rRNA tRNA carries genetic message produces ribosomes transports amino acids New polypeptide chain produced Further processing by organelles produces protein

Genetic Code Number of tRNA molecules: 3 bases 4 x 4 x 4 = 64 Number of combinations needed: = Number of Amino Acids + “stop” = 20 + 1 = 21 21 < 64 so we have enough combinations with three bases. (Note two is not enough.)

UCAG UUU UAU CUU CAU AUU AAU GUU GAU UUC UAC CUC CAC AUC AAC GUC GAC UUA UAA CUA CAA AUA AAA GUA GAA UUG UAG CUG CAG AUG AAG GUG GAG UCU UGU CCU CGU ACU AGU GCU GGU UCC UGC CCC CGC ACC AGC GCC GGC UCA UGA CCA CGA ACA AGA GCA GGA UCG UGG CCG CGG ACG AGG GCG GGG

The sequence of bases in the mRNA maps to the sequence of amino acids assembled by the tRNA.

Genes and the Genetic Code Gene: The unit of biological inheritance. A section of the DNA molecule The information to make one protein All living things on Earth us the same Genetic Code.