C11- DNA and Genes Chapter 11

Contents 11-1 DNA: The Molecule of Heredity 11-2 From DNA to Protein Protein Synthesis video 11-3 Genetic Changes

11-1 DNA: The Molecule of Heredity Genetic info in DNA controls organism’s traits

11-1 DNA: The Molecule of Heredity Genetic info in DNA controls organism’s traits Determines structure of proteins built

11-1 DNA: The Molecule of Heredity Genetic info in DNA controls organism’s traits Determines structure of proteins built Hershey & Chase (1952) used radioactively tagged viruses to infect bacteria and proved DNA is genetic material

11-1 DNA: The Molecule of Heredity Genetic info in DNA controls organism’s traits Determines structure of proteins built Hershey & Chase (1952) used radioactively tagged viruses to infect bacteria and proved DNA is genetic material

Nucleotide Structure DNA polymer of repeating units called nucleotides.

Nucleotide Structure DNA polymer of repeating units called nucleotides. 3 parts Simple sugar Phosphate Phosphorus w/ 4 O Nitrogenous base

Nucleotide Structure DNA polymer of repeating units called nucleotides. 3 parts Simple sugar Phosphate Phosphorus w/ 4 O Nitrogenous base C ring w/ 1 or more N & a base Adenine (A) Cytosine (C) Guanine (G) Thymine (T)

Nucleotides Join in long chains with phosphates connecting to sugar of next unit to form a backbone

Nucleotides Join in long chains with phosphates connecting to sugar of next unit to form a backbone with the bases sticking out like the teeth of a zipper. Adenine = Thymine Guanine = Cytosine

Structure of DNA James Watson & Francis Crick (1953) unraveled the structure of DNA. Double Helix structure

Nucleotide Sequence Forms unique genetic information of organism

Nucleotide Sequence Forms unique genetic information of organism Can be used to determine evolutionary relationships between organisms

Nucleotide Sequence Forms unique genetic information of organism Can be used to determine evolutionary relationships between organisms Or familial relationships DNA can identify victims or criminals

Replication of DNA Copies DNA in chromosome during interphase

Replication of DNA Copies DNA in chromosome during interphase Enzyme breaks the hydrogen bond between bases

Replication of DNA Copies DNA in chromosome during interphase Enzyme breaks the hydrogen bond between bases Complimentary base pairing allows duplication

Replication of DNA Copies DNA in chromosome during interphase Enzyme breaks the hydrogen bond between bases Complimentary base pairing allows duplication Each strand is a template

11-2 From DNA to Protein DNA controls the production of proteins. Proteins are key cell structures & regulators of cell functions.

11-2 From DNA to Protein DNA controls the production of proteins. Proteins are key cell structures & regulators of cell functions. RNA, another nucleic acid carries out DNA’s instructions

11-2 From DNA to Protein DNA controls the production of proteins. Proteins are key cell structures & regulators of cell functions. RNA, another nucleic acid carries out DNA’s instructions Structure differs 3 ways Single-stranded Sugar is ribose Uracil replaces thymine

Three Types of RNA Protein assembly line: Messenger RNA (m-RNA) Ribosomal RNA (r-RNA) Transfer-RNA (t-RNA)

Three Types of RNA Protein assembly line: Messenger RNA (m-RNA) Brings instructions from DNA to ribosome in the cytoplasm Ribosomal RNA (r-RNA) Transfer-RNA (t-RNA)

Three Types of RNA Protein assembly line: Messenger RNA (m-RNA) Brings instructions from DNA to ribosome in the cytoplasm Ribosomal RNA (r-RNA) Reads instructions to assemble protein by binding to m-RNA Transfer-RNA (t-RNA)

Three Types of RNA Protein assembly line: Messenger RNA (m-RNA) Brings instructions from DNA to ribosome in the cytoplasm Ribosomal RNA (r-RNA) Reads instructions to assemble protein by binding to m-RNA Transfer-RNA (t-RNA) Delivers amino acids for assembly to ribosome

Transcription Occurs in the nucleus by enzymes copying part of the DNA Enzyme unzips DNA Assembles single-strand copy

Transcription Occurs in the nucleus by enzymes copying part of the DNA Enzyme unzips DNA Assembles single-strand copy DNA rezips after m-RNA detaches

Transcription Occurs in the nucleus by enzymes copying part of the DNA Enzyme unzips DNA Assembles single-strand copy DNA rezips after m-RNA detaches m-RNA leaves nucleus by nuclear pore to enter cytoplasm

Transcription Occurs in the nucleus by enzymes copying part of the DNA Enzyme unzips DNA Assembles single-strand copy DNA rezips after m-RNA detaches m-RNA leaves nucleus by nuclear pore to enter cytoplasm Carries instructions to ribosome

Translation Occurs in the ribosome Process of converting series of bases into chain of amino acids forming a protein

Translation Occurs in the ribosome Process of converting series of bases into chain of amino acids forming a protein r-RNA reads sequence of 3 bases (codon)

Translation Occurs in the ribosome Process of converting series of bases into chain of amino acids forming a protein r-RNA reads sequence of 3 bases (codon) t-RNA anticodon matches up with the codon from m-RNA and supplies the amino acid needed

Translation Occurs in the ribosome Process of converting series of bases into chain of amino acids forming a protein r-RNA reads sequence of 3 bases (codon) t-RNA anticodon matches up with the codon from m-RNA and supplies the amino acid needed Ribosome translates the next codon until finished assembling the protein

RNA & Protein Synthesis

RNA Processing Introns- noncoding nucleotide sequences Exons- expressed sections of nucleotides Enzymes cut out the introns & paste the exons together

Genetic Code Amino acids are the building blocks of proteins. A sequence of 3 nucleotide bases code for each of the 20 amino acids. 64 different codons in m-RNA AUG start codon UAA stop codon All organisms use the same genetic code.

Translating the m-RNA Code T-RNA leaves amino acid in position to form peptide bond with previous amino acid

Translating the m-RNA Code T-RNA leaves amino acid in position to form peptide bond with previous amino acid The ribosome continues to assemble amino acids until stop codon is reached.

Translating the m-RNA Code T-RNA leaves amino acid in position to form peptide bond with previous amino acid The ribosome continues to assemble amino acids until stop codon is reached. Translation is complete

Translating the m-RNA Code T-RNA leaves amino acid in position to form peptide bond with previous amino acid The ribosome continues to assemble amino acids until stop codon is reached. Translation is complete Amino acid chain is released & twists into complex folded shape of protein

Translating the m-RNA Code T-RNA leaves amino acid in position to form peptide bond with previous amino acid The ribosome continues to assemble amino acids until stop codon is reached. Translation is complete Amino acid chain is released & twists into complex folded shape of protein Become enzymes & structures

11-3 Genetic Changes Mutation- any change in DNA sequence Caused by errors in Replication Translation Cell division Or by external agents such as UV or chemical exposure

Mutations in Reproductive Cells Changes in the sequence of nucleotides can cause: Altered gene in offspring New traits Nonfunctional protein with structural or functional problems in cells Embryo may not survive Positive effect

Mutations in Body Cells Does not pass on to offspring May cause problems for the individual Impair function of the cell Contributes to aging Can cause cancer by making cells reproduce rapidly

Effects of Point Mutations Point mutation - Change in a single base pair in DNA Can change entire structure of the protein Error may or may not affect protein function Ex. Sickle cell anemia

Frameshift Mutations A single base is added to or deleted from DNA Shifts the reading of the codons by one base Nearly every amino acid after the insertion or deletion will be changed

Chromosomal Alterations Chromosomal mutations Deletions -Parts break & are lost during mitosis or meiosis Insertions- Parts rejoin incorrectly Inversions- Rejoin backwards Translocations- Join other chromosomes Common in plants

Causes of Mutations Mutagens- agents that cause change in DNA Radiation X-rays Gamma rays Ultraviolet light Nuclear radiation Chemicals Dioxins Asbestos Benzene Formaldehyde High temperatures 6-legged frog aflatoxin

Repairing DNA Repair mechanisms have evolved: Enzymes proofread DNA & replace incorrect nucleotides. The greater the exposure to the mutation, the less likely it can be corrected. Limit exposure to mutagens.