SB 2 The learner will analyze how biological

SB 2. The learner will analyze how biological traits are passed on to successive generations. b. Explain the role of DNA in storing and transmitting cellular information

LEQ 2: What is the role of DNA in storing and transmitting cellular information?

Try this………. • • • On a sheet of paper, draw a curving line that divides the paper into two halves. Without tracing, copy the line on a second sheet of paper. Hold the papers side by side, and compare the lines. – Do they look the same? • Now, stack the papers, one on top of the other, and hold the papers up to the light. – Are the lines the same?

THINK: How could you use the original paper to draw exact copies of the line without tracing it? Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?

Role of DNA • Stores the code of life in a sequence of nucleotides. – The code is then used to make proteins and determine traits • The role of DNA is explained through the three processes included in the central dogma of biology.

Role of DNA Central Dogma of Biology • The central dogma includes three process. – Replication – Transcription – Translation replication transcription translation

DNA Replication • DNA replication copies the genetic information of a cell • DNA replication is fast and accurate.

DNA Replication • A single strand of DNA serves as a template for a new strand. • The rules of complementary base pairing direct replication • DNA is replicated during the S stage of the cell cycle • Each body cell gets a complete set of identical DNA S (Synthesis) Stage G 2 checkpoint checks for errors in DNA replication

DNA Replication • DNA serves only as the template. • Enzymes and other proteins help carry out the process of replication (do the actual work of replication) – Enzymes unzip the double helix – Free-floating nucleotides form hydrogen bonds with the template strand. nucleotide DNA molecule unzips in both directions The DNA molecule unzips in both directions.

DNA Replication • DNA polymerase enzymes bond the nucleotides together to form the double helix new strand nucleotide DNA polymerase

DNA Replication • Two new molecules of DNA are formed, each with an original strand a newly formed strand • DNA replication is semi-conservative original strand new strand Two molecules of DNA

Concept Check Describe the function of DNA replication and explain how cells help ensure that DNA replication is accurate?

Transcription • Transcription converts a gene into a single stranded RNA molecule. DNA RNA Can you remember the 3 differences between DNA and RNA?

REVEIW • RNA differs from DNA in three major ways: – RNA has ribose sugar – RNA has uracil instead of thymine – RNA is a single stranded structure

Transcription • RNA carries the DNA’s instructions for protein synthesis. • The central dogma states that information flows in one direction from DNA to RNA to proteins. • RNA is the link between DNA and proteins. replication transcription translation

Transcription • Transcription make three types of RNA. – Messenger RNA (m. RNA) • carries the message that will be translated to form a protein • Like the mailman – Ribosomal RNA (r. RNA) • forms part of the ribosome where proteins are made – Transfer RNA (t. RNA) • brings amino acids from the cytoplasm to ribosome.

Transcription • Transcription is catalyzed by RNA polymerase • RNA polymerase helps recognize the start gene and unwinds a segment of DNA. start site transcription complex nucleotides

Transcription • Nucleotides pair with one strand of the DNA • RNA polymerase bonds the nucleotides together • The DNA helix winds back as the gene is transcribed. DNA

Transcription • The RNA strand detaches from the DNA once the gene is transcribed. RNA

Did you know… • RNA can be found in your blood? • If forensic scientists find RNA, they can determine a time line of when a person was injured or killed.

Transcription Complete the Venn Diagram below comparing and contrasting Replication vs. Transcription: Rep. Trans.

Concept Check If the DNA sequence had the nucleotides AGCCTA what would be the nucleotide sequence of the complementary DNA and the complementary RNA strand? What process creates DNA? What process creates RNA?

Translation • Translation is the last processes involved in protein synthesis. • Translation converts an m. RNA message into a protein, or polypeptide. • This process consists of three repeating steps. m. RNA Protein

Translation • Amino acids are coded by m. RNA base sequences. • Translation converts m. RNA message into proteins by decoding the base sequence. • A codon (m. RNA) is a sequence of three nucleotides that codes for a specific amino acid. codon for methionine codon for leucine

Translation • The genetic code matches each codon (m. RNA) to its amino acid or function. – Three stop codons • UGA, UAG – One start codon, codes for methionine. • AUG

The genetic code matches each m. RNA Codon with its amino acid or function

Translation • A change in the order in which codons (m. RNA) are read changes the resulting protein. • Regardless of the organism, codons code for the same amino acids – Unity of life

Translation • Amino acids are linked to become a protein or polypeptide. • An anticodon (t. RNA) is a set of three nucleotides that is complementary to a codon (m. RNA). • An anticodon is carried by a t. RNA

Translation 3 Steps For translation to begin: 1. anticodon (t. RNA) binds to its complementary start codon (m. RNA) and signals the ribosome to assemble. The complementary t. RNA bring its specific amino acid to the ribosome.

Translation 2. The ribosome helps form a polypeptide bond between the amino acids. The ribosome pulls the m. RNA strand the length of one codon.

Translation 3. The now empty t. RNA molecule exits the ribosome. The next complementary t. RNA (anticodon) molecule binds to the next exposed m. RNA (codon). – Processes are repeated for each codon (m. RNA). • Once the stop codon is reached, the ribosome releases the protein and disables.

Concept Check What would happen to the protein formed during translation if m. RNA was copied incorrectly?

Concept Check Put the following in order as they would occur in protein synthesis. A. B. Transcription of m. RNA in the nucleus of the cell. The ribosome helps form a polypeptide bond between amino acids C. The codon (m. RNA) and the complementary anticodon (t. RNA) bringing the specific amino acid to the ribosome. D. The now empty t. RNA leaves the ribosome and the process is repeated for each codon until the stop codon is reached. E. The polypeptide is released from the ribosome

Proteins Why do we need proteins?

Importance of Proteins • They are key to almost everything that living cells do – Transport materials – Fight off viruses/bacteria – Form muscles – Catalysts (enzymes) • speed up chemical reactions – Regulation of hormones – Communication between cells

Proteins • All proteins are built from only 20 amino acids • Only 12 are made by the human body other 8 are found in certain foods • Essential Amino Acids (8) – Found in meat, eggs, cheese, soy products, and combinations of rice and beans

Did you know… • Proteins can be tested in a blood sample to find cancer in the body? • The picture shows a tumor in the lungs. Such a tumor can be found by looking for specific proteins.