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Cumulative review dna rna-protein synthesis-mutations
 

Cumulative review dna rna-protein synthesis-mutations

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    Cumulative review dna rna-protein synthesis-mutations Cumulative review dna rna-protein synthesis-mutations Presentation Transcript

      • What You’ll Learn
      • You will relate the structure of DNA to its function.
      • You will explain the role of DNA in protein production.
      • You will distinguish among different types of mutations.
      • Analyze the structure of DNA
      • Determine how the structure of DNA enables it to reproduce itself accurately.
      Section Objectives
    • What is DNA?
      • Although the environment influences how an organism develops, the genetic information that is held in the molecules of DNA ultimately determines an organism’s traits.
      • DNA achieves its control by determining the structure of proteins.
      • Within the structure of DNA is the information for life— the complete instructions for manufacturing all the proteins for an organism.
    • DNA as the genetic material
      • Hershey and Chase labeled the virus DNA with a radioactive isotope and the virus protein with a different isotope.
      • By following the infection of bacterial cells by the labeled viruses, they demonstrated that DNA, rather than protein, entered the cells and caused the bacteria to produce new viruses.
    • The structure of nucleotides
      • DNA is a polymer made of repeating subunits called nucleotides .
      • Nucleotides have three parts: a simple sugar, a phosphate group, and a nitrogenous base.
      Sugar (deoxyribose ) Nitrogenous base Phosphate group
    • The structure of nucleotides
      • The simple sugar in DNA, called deoxyribose (dee ahk sih RI bos) , gives DNA its name—deoxyribonucleic acid.
      • The phosphate group is composed of one atom of phosphorus surrounded by four oxygen atoms.
      • A nitrogenous base is a carbon ring structure that contains one or more atoms of nitrogen.
      • In DNA, there are four possible nitrogenous bases: adenine (A), guanine (G), cytosine (C), and thymine (T).
      Thymine (T) Cytosine (C) Adenine (A) Guanine (G)
    • The structure of nucleotides
      • in DNA there are four possible nucleotides, each containing one of these four bases.
      • The phosphate groups and deoxyribose molecules form the backbone of the chain, and the nitrogenous bases stick out like the teeth of a zipper.
      Nucleotide Sugar-phosphate backbone Phosphate group Sugar (deoxyribose) DNA nucleotide Nitrogenous base (A, G, C, or T) Thymine (T)
    • The structure of nucleotides
      • Base pairing rule:
      • A always pairs with T
      • G always pairs with C
      • A-T
      • G-C
    • The structure of DNA
      • James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin
      • (1953)
    • The structure of DNA
      • Watson and Crick also proposed that DNA is shaped like a long zipper that is twisted into a coil like a spring.
      • Because DNA is composed of two strands twisted together, its shape is called double helix .
    • The importance of nucleotide sequences
      • The sequence of nucleotides forms the unique genetic information of an organism. The closer the relationship is between two organisms, the more similar their DNA nucleotide sequences will be.
      • Scientists use nucleotide sequences to determine evolutionary relationships among organisms, to determine whether two people are related, and to identify bodies of crime victims.
      Chromosome
    • Replication of DNA
      • Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes.
      • The DNA in the chromosomes is copied in a process called DNA replication .
      • Without DNA replication, new cells would have only half the DNA of their parents.
      • DNA is copied during interphase prior to mitosis and meiosis.
      • It is important that the new copies are exactly like the original molecules.
    • Replication of DNA
      • DNA replication depends on specific base pairing
      • In DNA replication, the strands separate
        • Enzymes use each strand as a template to assemble the new strands
      Parental molecule of DNA Nucleotides Both parental strands serve as templates Two identical daughter molecules of DNA
    • Replication of DNA
      • Untwisting and replication of DNA
      • Section Objectives
      • Relate the concept of the gene to the sequence of nucleotides in DNA.
      • Sequence the steps involved in protein synthesis.
    • Genes and Proteins
      • The sequence of nucleotides in DNA contain information.
      • This information is put to work through the production of proteins.
      • Proteins fold into complex, three- dimensional shapes to become key cell structures and regulators of cell functions.
      • Thus, by encoding the instructions for making proteins, DNA controls cells.
    • Genes and Proteins
      • You learned earlier that proteins are polymers of amino acids.
      • The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein.
    • RNA
      • RNA like DNA, is a nucleic acid
      • RNA structure differs from DNA structure in three ways.
        • 1. Has ribose sugar instead of deoxyribose (DNA)
        • 2. Replaces thymine (T) with uracil (U)
        • 3. Single stranded as opposed to double stranded DNA
      Sugar (ribose) Phosphate group Uracil (U) Nitrogenous base (A, G, C, or U)
    • RNA
      • RNA has a different function than DNA
      • Whereas DNA provides the instructions for protein synthesis, RNA does the actual work of protein synthesis.
      • They take from DNA the instructions on how the protein should be assembled, then—amino acid by amino acid—they assemble the protein.
    • RNA
      • 3 types of RNA
        • 1. Messenger RNA (mRNA), single, uncoiled strand which brings instructions from DNA in the nucleus to the site of protein synthesis.
        • 2. Ribosomal RNA (rRNA), globular form, makes up the ribosome –the construction site of proteins binds ( site of protein synthesis); binds to the mRNA and uses the instructions to assemble the amino acids in the correct order.
        • 3. Transfer RNA (tRNA) single, folded strand that delivers the proper amino acid to the site at the right time
    • Protein Synthesis: 2 step process 1. Transcription 2. translation
      • Transcription: DNA -> mRNA
      • In the nucleus, enzymes make an RNA copy of a portion of a DNA strand in a process called transcription .
      • The main difference between transcription and DNA replication is that transcription results in the formation of one single-stranded RNA molecule rather than a double-stranded DNA molecule.
    • RNA Processing
      • Not all the nucleotides in the DNA of eukaryotic cells carry instructions — or code — for making proteins.
      • Genes usually contain many long noncoding nucleotide sequences, called introns , that are scattered among the coding sequences.
      • Regions that contain information are called exons because they are ex pressed.
      • When mRNA is transcribed from DNA, both introns and exons are copied.
      • The introns must be removed from the mRNA before it can function to make a protein.
      • Enzymes in the nucleus cut out the intron segments and paste the mRNA back together.
      • The mRNA then leaves the nucleus and travels to the ribosome.
    • RNA Processing:simplified
      • Noncoding segments called introns are spliced out ( coding segment = exons )
    • Genetic information written in codons is translated into amino acid sequences
      • Transfer of DNA to mRNA uses “language” of nucleotides
        • Letters : nitrogen bases of nucleotides (A,T,G,C)
        • Words : codons ~ triplets of bases
        • ( ex. AGC)
        • Sentences : polypeptide chain
        • The codons in a gene specify the amino acid sequence of a polypeptide
    • The Genetic Code
      • The nucleotide sequence transcribed from DNA to a strand of messenger RNA acts as a genetic message, the complete information for the building of a protein. .
      • Virtually all organisms share the same genetic code
    • Translation: From mRNA to Protein
      • process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of amino acids in protein is known as translation .
      • takes place at the ribosomes in the cytoplasm.
        • Involves 3 types of RNA
        • 1. Messenger RNA (mRNA ) =carries
        • the blueprint for construction of a protein
        • 2. Ribosomal RNA (rRNA) =
        • the construction site where the protein is made
        • 3. Transfer RNA (tRNA) =
        • the truck delivering the proper amino acid to the site at the right time
    • Transfer RNA molecules serve as interpreters during translation
      • In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a polypeptide
      • The process is aided by transfer RNAs
      • Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other
      • Anticodon base pairs with codon of mRNA
      • Section Objectives:
      • Categorize the different kinds of mutations that can occur in DNA.
      • Compare the effects of different kinds of mutations on cells and organisms.
    • Mutations
      • Any change in DNA sequence is called a mutation .
      • can be caused by errors in replication, transcription, cell division, or by external agents.
      • If mutation occurs in gametes it will be passed on to offspring
      • may produce a new trait or it may result in a protein that does not work correctly.
        • the mutation results in a protein that is nonfunctional, and the embryo may not survive
        • In some rare cases a gene mutation may have positive effects.
    • Mutations
      • If mutation takes place in a body cell, it is not passed on to offspring
        • Damage to a gene may impair the function of the cell
        • When that cell divides, the new cells also will have the same mutation
        • Some mutations of DNA in body cells affect genes that control cell division.
        • This can result in the cells growing and dividing rapidly, producing cancer.
    • Types of Mutations
      • A point mutation is a change in a single base pair in DNA.
        • A change in a single nitrogenous base can change the entire structure of a protein
        • Normal
      Point mutation Replace G with A mRNA mRNA Protein Protein
    • Frameshift mutations
      • A mutation in which a single base is added or deleted from DNA is called a frameshift mutation because it shifts the reading of codons by one base.
      • This mutation would cause nearly every amino acid in the protein after the deletion to be changed.
      Deletion of U mRNA Protein
    • Chromosomal Mutations
      • Chromosome breakage can lead to rearrangements that can produce genetic disorders or cancer
        • Four types of rearrangement are deletion, duplication, inversion, and translocation
    • Causes of Mutations
      • sometimes a mistake in base pairing during DNA replication.
      • many mutations are caused by factors in the environment
      • Any agent that can cause a change in DNA is called a mutagen .
        • Mutagens include radiation, chemicals, and even high temperatures
    • Repairing DNA
      • Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides.
      • These repair mechanisms work extremely well, but they are not perfect.