GENETICS Part 3 Contents: Review, DNA Song, A-T & C-G, RNA: transcription, translation, codons, amino acids Video: 29 min. Codon Wst Website: How Does DNA Work?

REVIEW:

REVIEW: Most human cell have a nucleus that contains 23 pairs of chromosomes which are made of DNA.

Nucleic acids – DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) p. 194 Nucleic acids – DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) Nucleotides – 3 parts: a sugar (deoxyribose), a phosphate group and a nitrogen base. In DNA these form a series of units called genes = encoded information about how the organism will grow and develop.

Oh! Deoxyribonucleic acid, RNA is ribonucleic acid  DNA SONG: (sung to Row, Row, Row Your Boat) We love DNA made of nucleotides, sugar, phosphate, and a nitrogen base bonded down each side. Oh! Deoxyribonucleic acid, RNA is ribonucleic acid

DNA – double helix that encodes the sequences of all the cell’s DNA – double helix that encodes the sequences of all the cell’s proteins, as well as information that determines when each protein is to be made.

Bundles of protein – DNA are called chromosomes. Made up of 4 bases: (p.195) Purines – adenine and guanine (2 larger bases) Pyrimidines – cytosine and thymine (2 smaller bases)   Adenine + Thymine (A = T) Cytosine + Guanine (C = G)

DNA SONG: (sung to Row, Row, Row Your Boat) We love DNA made of nucleotides, sugar, phosphate, and a nitrogen base bonded down each side. Oh! Deoxyribonucleic acid, RNA is ribonucleic acid Adenine and Thymine make a lovely pair, Cytosine without Guanine would feel very bare.

Printout from a DNA sequencer showing the peaks and valleys of a portion of a sequenced gene that correspond to the color-coded bases adenine A, thymine T, guanine G and cytosine C. In this particular section of 34 bases, there are 434 = 2.951479 X 1020 or about 295 quintillion different possible sequences. In the San Diego trial of David Westerfield, the probability of a blood sample in his motor home matching the murder victim's DNA was 25 quadrillion to one.

Replication – process of copying DNA before the cell can divide Replication – process of copying DNA before the cell can divide. The DNA will “unzip” to separate the bases, and then the exposed base will find its complimentary partner. p. 198 A - T T - A T - G - C C - A - A - T T - A G - C C - G

The difference between deoxyribose (DNA) and ribose (RNA)?

In RNA uracil (U) replaces thymine as a base.

RNA – (ribonucleic acid) makes the protein. p. 208 Made of 4 bases: adenine, guanine, cytosine, and uracil (U). A – U C – G T – A G - A – T - A – U C – G T – A G - C T - A

For a cell to make protein, the information from a gene is copied, base by base, from DNA into new strands of messenger RNA (mRNA). Then mRNA travels out of the nucleus into the cytoplasm, to cell organelles called ribosomes. There, mRNA directs the assembly of amino acids that fold into completed protein molecule.

Gene expression – use of genetic information in DNA to make. proteins Gene expression – use of genetic information in DNA to make proteins – 2 stages - 1. transcription – a RNA copy of the gene is made. Information encoded in DNA is transferred to mRNA (messenger RNA – p. 212) molecule. * It must be copied because the DNA cannot leave the nucleus.

2. translation – three different kinds of RNA work together to assemble amino acids into a protein molecule. Every 3 nucleotides in mRNA specify a particular amino acid = codon. The order of bases in the codon determines which amino acids will be added to a growing protein chain. The order of amino acids will determine the structure and function of a protein. EX. UUU = amino acid phenylalanine.

Codons (groups of 3 nucleotides) make amino acids (p. 211)

The final protein molecule may consist of several hundred amino acids linked together according to the instructions encoded in the mRNA.

For example, the mutation toward sickle cell anemia is based upon the production of one different amino acid, which in turn affects the polypeptide strands produced, etc. Mutations are usually non-beneficial to an organism, however, they are almost always recessive and unless two mutations are coupled together the mutation will not be expressed.

Protein or DNA? It was not until 1944 that scientist proved DNA was the genetic material in our cells. Many scientist found it hard to believe the DNA was the hereditary material instead of protein. Protein has 20 different amino acids that can be combined in a variety of ways. DNA consists of basically 4 nucleotide bases. Scientist reasoned that the complex processes involved in heredity would be controlled by something complex.

Proteins help determine the structure of cells and increase the rates of chemical reactions, such as those that occur during metabolism and photosynthesis. There are 20 amino acids that combine to make all the protein in your body.

Deoxyribonucleic acid, RNA is ribonucleic acid  DNA SONG: (sung to Row, Row, Row Your Boat) We love DNA made of nucleotides, sugar, phosphate, and a nitrogen base bonded down each side. Oh! Deoxyribonucleic acid, RNA is ribonucleic acid Adenine and Thymine make a lovely pair, Cytosine without Guanine would feel very bare. Worksheet: Central Dogma and Codons Video: DNA / RNA / Protein Synthesis 29 min.

Worksheet: How Does DNA Work? http://www2.edc.org/weblabs/WebLabDirectory1.html