Molecular Genetics Molecular Genetics

Question??????? What IS a gene or trait? In the case above, what are freckles? What IS a gene or trait? In the case above, what are freckles? Freckles are PROTEINS!!!! Freckles are PROTEINS!!!! One gene = One protein!!!!! One gene = One protein!!!!!

Let’s Review Protein: Protein: Made up of amino acids Made up of amino acids Made in the ribosomes Made in the ribosomes Examples of Proteins: HormonesAntibodiesEnzymes

A. Structure of DNA DNA – Deoxyribonucleic Acid DNA – Deoxyribonucleic Acid * discovered in 1953 by Watson and Crick * Double Stranded molecule that forms a double helix double helix * Basic Unit of DNA is a nucleotide

A Nucleotide

The nucleotide symbols for DNA are: = Phosphate Group = Deoxyribose (5 carbon sugar) = Nitrogenous Base

The bases in DNA always pair according to the following rules: A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T) A with T: the purine adenine (A) always pairs with the pyrimidine thymine (T) C with G: the pyrimidine cytosine (C) always pairs with the purine guanine (G) C with G: the pyrimidine cytosine (C) always pairs with the purine guanine (G)

Function of DNA Instructs the cell to Instructs the cell to make new proteins Passed down to Passed down tooffspring

B. DNA Replication Replication – Process in which DNA makes an exact copy of itself Replication – Process in which DNA makes an exact copy of itself This occurs prior to mitosis (cell division) for growth or repair This occurs prior to mitosis (cell division) for growth or repair

Steps: 1. Occurs in the nucleus 2.DNA must “untwist and unzip” 3.Free nucleotides pair up to the 2 new single stranded DNA (complementary pairing A-T, C-G)

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DNA Replication Review….. What is it? What is it? Making an exact of itself Where does it occur? Where does it occur?Nucleus Why? Why? Mitosis and Meiosis When? When? Growth, Repair and Reproduction Growth, Repair and Reproduction

Steps of Replication DNA untwists and unzips DNA untwists and unzips - Bases are held together by HYDROGEN BONDS - Each single strand becomes a template, or pattern, for a new strand of DNA

A – TA - T A- T T – AT - A T- A G – CG - C G- C C – GC - G C- G T – A T - A T- A Nucleotides are brought to the “unzipped” section and attach following the base pairing rules Original DNA2 Replicated DNA

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How does DNA direct the production of proteins??? The function of DNA is to tell the cells what proteins to make The function of DNA is to tell the cells what proteins to make Where are the proteins made? Where are the proteins made? at the ribosomes in the cytoplasm Dilemma!!! DNA IS TRAPPED INSIDE OF THE NUCLEUS Dilemma!!! DNA IS TRAPPED INSIDE OF THE NUCLEUS SOLUTION – RNA (Ribonucleic Acid) SOLUTION – RNA (Ribonucleic Acid)

RNA - Ribonucleic Acid A Nucleic Acid made up of a long chain of nucleotides A Nucleic Acid made up of a long chain of nucleotides contains the sugar RIBOSE (NOT deoxyribose) contains the sugar RIBOSE (NOT deoxyribose) Bases – Cytosine pairs with Guanine Bases – Cytosine pairs with Guanine Adenine pairs with URACIL (NOT Thymine) Adenine pairs with URACIL (NOT Thymine) RNA is capable of copying the DNA and bringing the genetic message to the ribosome where proteins are produced RNA is capable of copying the DNA and bringing the genetic message to the ribosome where proteins are produced

RNA Structure Phosphate Group Ribose Sugar Nitrogenous Base

Comparison of DNA and RNA DNARNA Structure Double stranded Single stranded Bases A-T, C-G A-U, G-C Location in the cell Nucleus Nucleus and cytoplasm SugarDeoxyriboseRibose

3 Types of RNA mRNA – Messenger RNA – brings genetic code from DNA to ribosomes to synthesize protein (from nucleus to cytoplasm) mRNA – Messenger RNA – brings genetic code from DNA to ribosomes to synthesize protein (from nucleus to cytoplasm) tRNA – Transfer RNA - carries amino acids to ribosome tRNA – Transfer RNA - carries amino acids to ribosome rRNA – Ribosomal RNA – makes up ribosomes rRNA – Ribosomal RNA – makes up ribosomes

Protein synthesis begins in the nucleus by….. 1. The DNA must untwist and unzip. One strand will serve as a TEMPLATE or pattern T - AT A - TA THIS SINGLE T - ATSTRAND IS T - ATUSED AS A C - GCTEMPLATE G - CG

2. Transcription of the gene (DNA to RNA) - how the DNA code gets to the ribosomes Messenger RNA (mRNA) is formed. RNA nucleotides attach to DNA strand Ex. T - A A - UCodon - group of 3 nucleotides A - UCodon - group of 3 nucleotides T - A on mRNA. Codes for a T - A on mRNA. Codes for a T - A specific amino acid T - A specific amino acid C - GTranscription - “to make a copy of” C - GTranscription - “to make a copy of” G - C how the DNA code gets to the G - C how the DNA code gets to theribosomes

3. The mRNA strand is now a copy of the DNA strand 4. Strand of mRNA detaches from DNA and travels to the ribosome in the cytoplasm A U A A G C. A U A A G C. RIBOSOME

REVIEW OF TRANSCRIPTION Transcribe means to make a copy of Steps: Steps: 1. DNA untwists and unzips 2. Free nucleotides are brought to the unzipped DNA following the base pair ruling 3. mRNA strand is formed to be carried out of the nucleus

DNA Base RNA Complimentary Pair AU TA CG GC GC TA AU TA CG GC AU

Now that we have the genetic code at the ribosome, we are ready to synthesize (make) proteins (enzymes, hemoglobin, etc.) 5. Translation of the Gene. Transfer RNA (tRNA) - shuttles the correct amino acid to the ribosome and the correct protein begins to be assembled

Anticodon - 3 nucleotides on the tRNA that match the codon. Anticodon - 3 nucleotides on the tRNA that match the codon. If the codon is CUA the anticodon must be.. GAU Translation - message from mRNA is translated to tRNA to bring the specific amino acid to the ribosome Translation - message from mRNA is translated to tRNA to bring the specific amino acid to the ribosome

Practice Protein Synthesis DNA:TAGGCATTA mRNA AUCCGUAAU tRNAUAGGCAUUA AminoIle ArgAsn Acid

Amino Acids are based on the codon NOT the anticodon

Review Steps 1. Transcription occurs in nucleus (DNA to mRNA) 2. Single stranded mRNA moves OUTSIDE the nucleus to the ribosome 3. mRNA attaches to the RIBOSOME, which reads the codon 4. tRNA’s anticodon matches to the codon and brings Amino Acids to the ribosomes (translation) 5. Amino acids bond together to make a protein

Every 3 bases code for an amino acid Every 3 bases code for an amino acid This code is “universal” = same for all organisms This code is “universal” = same for all organisms Codon - group of 3 bases (nucleotides) Codon - group of 3 bases (nucleotides) Total # of amino acids known = 20 Total # of amino acids known = 20

Protein Synthesis DNA Code mRNAtRNA Amino Acid AAA ATC GAC CTG AGT TTA GGA CCA

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E. Nature vs. Nurture The environment and Heredity There is an interaction with the environment and certain genes are expressed while others are hidden