Lab #5: DNA, RNA & Protein Synthesis Heredity & Human Affairs (Biology 1605) Spring 2012
DNA Stands for : Deoxyribonucleic Acid Double-stranded helix Made up of nucleotides Each nucleotide= 1. 5-carbon sugar deoxyribose 2. Phosphate backbone 3. Nitrogenous base (e.g. A,T,C,G)
DNA: Nitrogenous Bases Purines: Adenine (A) Pyrimidines: Thymine (T) The Principle of Base Pairing Guanine (G) Cytosine (C) Adenine always bonds with its complimentary base Thymine. Guanine always bonds with its complimentary base Cytosine.
DNA: Nitrogenous Bases Bases (A-T, G-C) join via WEAK HYDROGEN bonds. Bases account for variability within a DNA molecule.
Making DNA Existing double-stranded DNA molecule can synthesize new DNA by SEMI-CONSERVATIVE REPLICATION.
STATION #1 USING THE MODEL PROVIDED, ASSEMBLE A DOUBLE-HELIX DNA MOLECULE. BE SURE TO ANSWER QUESTION #1 (a,b,c, & d) IN YOUR LAB MANUAL (PAGE 35).
STATION #1- What does DNA look like? Extract DNA from a Strawberry! Strawberries are polyploidy. So, they have extra sets of chromosomes (lots of DNA!) to extract. BE SURE TO RECORD OBSERVATIONS & ANSWER QUESTIONS IN YOUR LAB PACKET (PAGE 47).
RNA Stands for : Ribonucleic Acid Single-strand of ribonucleotides Each nucleotide 1. 5-carbon sugar ribose 2. Phosphate unit 3. Nitrogenous base (e.g. A,U,C,G)
RNA: Nitrogenous Bases The Principle of Base Pairing Purines: Adenine (A) Guanine (G) Pyrimidines: Uracil (U) takes the place of thymine in RNA \ Cytosine (C) Adenine always bonds with its complimentary base Uracil. Guanine always bonds with its complimentary base Cytosine.
TRANSCRIPTION Process: DNA to mrna Takes place in the NUCLEUS (where DNA is located!)
TRANSCRIPTION Example: DNA STRAND = A T G C G T C A T mrna produced= U A C G C A G U A
STATION #2 USING THE PAPER MODEL PROVIDED, ASSEMBLE A MOLECULE OF RNA, COMPLEMENTARY TO THE DNA STRAND GIVEN. BE SURE TO ANSWER QUESTION #2 (a,b,c, & d) IN YOUR LAB PACKET (PAGE 35).
TRANSLATION Process: mrna to Protein Proteins are made up of amino acids joined together. Takes place in the CYTOPLASM of the cell (specifically, on ribosomes [RER]) RNA message (produced in transcription) is read & converted (translated) into amino acids.
TRANSLATION
In the Cytoplasm trna molecule picks up message from mrna.
RNA to AMINO ACIDS RNA strand is read 3 bases at a time = CODON Example: RNA strand = U A C G C A G U A Amino acids produced = Tyrosine Alanine Valine
RNA to AMINO ACIDS How do you know what 3 bases code for a particular amino acid? USE AN mrna Codon table!
Amino Acid Structure
Amino Acid Structure Bonds the join 2 or more amino acids are STRONG PEPTIDE BONDS. Polypeptide chains are formed.
STATION #4 USING THE A.A. MODELS PROVIDED, ASSEMBLE A POLYPEPTIDE. BE SURE TO ANSWER QUESTION #4 (a,b,c, & d) IN YOUR LAB PACKET (PAGE 36).
GENES Each somatic cell contains 46 chromosomes, each with many genes. There are an estimated 30,000-40,000 genes per human cell (total on all chromosomes). The size of a gene is LARGE, but varies widely could be 1000 b.p., 10,000 b.p., 100,000 b.p. etc.
For Example: Genes on the X Chromosome Contains over 1400 genes Contains over 150 million base pairs, of which approximately 95% have been determined http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=gnd.section.295&ref=sidebar
Making a Gene. STATION #3 USE THE PAPER MODEL PROVIDED TO CONSTRUCT A GENE SIMPLY BY LINING UP THE SEQUENCE END-TO- END. Note: the model here is only a single strand due to limited space. Be sure to note that DNA found in genes is always found as a double-strand.
Meiotic Recombination Maternal Synapsis: pairing of homologous chromosomes Examples: Hair color & Eye color new combos of genotypes/ phenotypes are possible! Paternal http://faculty.uca.edu/~johnc/meiosis.jpg
Meiotic Recombination Crossing over occurs during Prophase I of Meiosis Four cells produced. 2 are identical to parent chromosomes 2 are recombinant cells, each with a new combination of traits (but, not new traits!). http://faculty.uca.edu/~johnc/meiosis.jpg
STATION #5 USING THE CLAY & DIRECTIONS PROVIDED, MAKE HOMOLOGOUS CHROMOSOMES & SIMULATE CROSSING OVER. BE SURE TO ANSWER QUESTION #5 (a, b, & c) IN YOUR LAB PACKET (PAGE 37).
STATION #6 The Secret DNA Code Read the directions at this station carefully. (1) Transcribe the DNA sequence provided (found on ribosomes 1 11). (2) Translate the mrna using the Codon Key provided. (3) Put your answers on the board. Record your answers on page 37, under Question #6.
STATION #6 The Secret DNA Code It s truly amazing how normal we all are! From transcription to translation how many opportunities are there for errors to be made? How many errors will you make during this lab exercise?
Need additional help? See the following interactive website: http://www.dnai.org
Today: Work through STATIONS 1-6, any order. Answer related questions in lab packet. Have instructor sign off. Check with TA: *If flies are ready, count F 2 generations (the 2 vials started on January 24 th ) and submit results to TA. If not ready, you will count during next week s lab.