* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download BDOL Interactive Chalkboard - Broken Arrow Public Schools
Genetic engineering wikipedia , lookup
Epigenetics of human development wikipedia , lookup
Human genome wikipedia , lookup
Bisulfite sequencing wikipedia , lookup
Site-specific recombinase technology wikipedia , lookup
United Kingdom National DNA Database wikipedia , lookup
DNA polymerase wikipedia , lookup
Genealogical DNA test wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
Cancer epigenetics wikipedia , lookup
Polyadenylation wikipedia , lookup
RNA silencing wikipedia , lookup
DNA damage theory of aging wikipedia , lookup
No-SCAR (Scarless Cas9 Assisted Recombineering) Genome Editing wikipedia , lookup
Epigenomics wikipedia , lookup
Molecular cloning wikipedia , lookup
DNA vaccination wikipedia , lookup
Nucleic acid tertiary structure wikipedia , lookup
Cell-free fetal DNA wikipedia , lookup
Messenger RNA wikipedia , lookup
Expanded genetic code wikipedia , lookup
DNA supercoil wikipedia , lookup
Nucleic acid double helix wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
Vectors in gene therapy wikipedia , lookup
History of genetic engineering wikipedia , lookup
Non-coding DNA wikipedia , lookup
Microevolution wikipedia , lookup
Frameshift mutation wikipedia , lookup
History of RNA biology wikipedia , lookup
Non-coding RNA wikipedia , lookup
Helitron (biology) wikipedia , lookup
Therapeutic gene modulation wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Epitranscriptome wikipedia , lookup
Genetic code wikipedia , lookup
Primary transcript wikipedia , lookup
Deoxyribozyme wikipedia , lookup
P 287 Griffith and Transformation • In 1928, British scientist Fredrick Griffith was trying to figure out how bacteria made people sick. • Griffith had isolated two slightly different strains, or types, of pneumonia bacteria from mice. • The disease-causing strain of bacteria grew into smooth colonies on culture plates, whereas the harmless stain produced colonies with rough edges. P 288 Griffith’s Experiment • Griffith injected mice with the disease-causing strain of bacteria and the mice developed pneumonia and died. • When they were injected with the harmless stain they didn’t get sick at all. • Then he decided to heat the bacteria and inject it into the mice and they lived. P 288 Griffith’s Experiment • Griffith then decided to mix the heat-killed, disease-causing bacteria with live, harmless ones and injected it into the mice. Many developed pneumonia and died. • After examining the lungs of the dead mice he discovered the disease-causing strain of bacteria. Somehow the heat-killed bacteria had passed their disease ability to the harmless strain. • Griffith called this process transformation. P 289 Avery and DNA • In 1944, a group of scientist led by Canadian biologist Oswald Avery at the Rockefeller Institute in New York decided to repeat Griffith’s work. • Avery and other scientists discovered that the nucleic acid DNA stores and transmits the genetic information from one generation of an organism to the next. P 291 Components and Structure of DNA • DNA is a long molecule made up of units called nucleotides. • Nucleotides are made up of three basic components: P 291 Components and Structure of DNA 1. A 5-carbon sugar called deoxyribose, 2. A phosphate group, and 3. A nitrogenous base 1. Adenine 2. Guanine 3. Cytosine 4. Thymine P 291 Components and Structure of DNA • The backbone of a DNA chain is formed by sugar and phosphate groups of each nucleotide. • The nitrogenous bases stick out sideways from the chain. • The nucleotides can be joined together in any order, meaning that any sequence bases is possible. P 294 Components and Structure of DNA • Watson and Crick’s model of DNA was a double helix, in which two strands were wound around each other. • A double helix looks like a twisted ladder or a spiral staircase. • Hydrogen bonds can form only between certain base pairs—A and T, G and C; which is the principle of base pairing. P 296 Chromosome Structure • Eukaryotic chromosomes contain both DNA and protein, tightly packed together to form a substance called chromatin. • Chromatin consists of DNA that is tightly coiled around proteins called histones. P 297 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. P 298 Replication of DNA Click this image to view movie P 299 Copying DNA • DNA is copied during interphase prior to mitosis and meiosis. • It is important that the new copies are exactly like the original molecules. P 298 Copying DNA New DNA molecule Original DNA Strand New DNA Strand Free Nucleotides Original DNA Strand Original DNA New DNA molecule 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, threedimensional shapes to become key cell structures and regulators of cell functions. Genes and Proteins • Some proteins become important structures, such as the filaments in muscle tissue. • Other proteins, such as enzymes, control chemical reactions that perform key life functions—breaking down glucose molecules in cellular respiration, digesting food, or making spindle fibers during mitosis. Genes and Proteins • In fact, enzymes control all the chemical reactions of an organism. • Thus, by encoding the instructions for making proteins, DNA controls cells. Genes and Proteins • The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein. P 300 RNA • DNA provides workers with the instructions for making the proteins, and workers build the proteins. • The workers for protein synthesis are RNA molecules. P 300 RNA • RNA like DNA, is a nucleic acid. RNA structure differs from DNA structure in three ways. • First, RNA is single stranded—it looks like one-half of a zipper —whereas DNA is double stranded. P 300 RNA • The sugar in RNA is ribose; DNA’s sugar is deoxyribose. Ribose P 300 RNA • Both DNA and RNA contain four nitrogenous bases, but rather than thymine, RNA contains a similar base called uracil (U). Uracil Hydrogen bonds Adenine • Uracil forms a base pair with adenine in RNA, just as thymine does in DNA. P 300 RNA • DNA provides workers with the instructions for making the proteins, and workers build the proteins. • The workers for protein synthesis are RNA molecules. • They take from DNA the instructions on how the protein should be assembled, then— amino acid by amino acid—they assemble the protein. P 300 RNA • There are three types of RNA that help build proteins. • Messenger RNA (mRNA), brings instructions from DNA in the nucleus to the cell’s factory floor, the cytoplasm. • On the factory floor, mRNA moves to the assembly line, a ribosome. P 301 RNA • The ribosome, made of ribosomal RNA (rRNA), binds to the mRNA and uses the instructions to assemble the amino acids in the correct order. P 301 RNA • Transfer RNA (tRNA) is the supplier. Transfer RNA delivers amino acids to the ribosome to be assembled into a protein. P 301 Transcription • In the nucleus, enzymes make an RNA copy of a portion of a DNA strand in a process called transcription. Click image to view movie P 301 Transcription A DNA strand RNA strand RNA strand C B DNA strand P 301 Transcription • The main difference between transcription and DNA replication is that transcription results in the formation of one singlestranded RNA molecule rather than a doublestranded DNA molecule. P 302 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. P 302 RNA Processing • Regions that contain information are called exons because they are expressed. • 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. P 287 RNA Processing • 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. P 302 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. • As you know, proteins contain chains of amino acids. You could say that the language of proteins uses an alphabet of amino acids. P 302 The Genetic Code • A code is needed to convert the language of mRNA into the language of proteins. • Biochemists began to crack the genetic code when they discovered that a group of three nitrogenous bases in mRNA code for one amino acid. Each group is known as a codon. P 303 The Genetic Code • Sixty-four combinations are possible when a sequence of three bases is used; thus, 64 different mRNA codons are in the genetic code. P 303 The Genetic Code • See Figure 12-17 p303 P 303 The Genetic Code • Some codons do not code for amino acids; they provide instructions for making the protein. • More than one codon can code for the same amino acid. • However, for any one codon, there can be only one amino acid. P 303 The Genetic Code • All organisms use the same genetic code. • This provides evidence that all life on Earth evolved from a common origin. P 303 Translation: From mRNA to Protein • The 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. • Translation takes place at the ribosomes in the cytoplasm. • In prokaryotic cells, which have no nucleus, the mRNA is made in the cytoplasm. P 304 Translation: From mRNA to Protein • In eukaryotic cells, mRNA is made in the nucleus and travels to the cytoplasm. • In cytoplasm, a ribosome attaches to the strand of mRNA like a clothespin clamped onto a clothesline. P 304 The role of transfer RNA • For proteins to be built, the 20 different amino acids dissolved in the cytoplasm must be brought to the ribosomes. • This is the role of transfer RNA. P 304 The role of transfer RNA Amino acid • Each tRNA molecule attaches to only one type of amino acid. Chain of RNA nucleotides Transfer RNA molecule Anticondon P 305 The role of transfer RNA • As translation begins, a ribosome attaches to the starting end of the mRNA strand. Then, tRNA molecules, each carrying a specific amino acid, approach the ribosome. • When a tRNA anticodon pairs with the first mRNA codon, the two molecules temporarily join together. P 305 The role of transfer RNA Ribosome mRNA codon P 305 The role of transfer RNA • Usually, the first codon on mRNA is AUG, which codes for the amino acid methionine. • AUG signals the start of protein synthesis. • When this signal is given, the ribosome slides along the mRNA to the next codon. P 305 The role of transfer RNA Methionine tRNA anticodon P 305 The role of transfer RNA • A new tRNA molecule carrying an amino acid pairs with the second mRNA codon. Alanine P 305 The role of transfer RNA • The amino acids are joined when a peptide bond is formed between them. Methionine Alanine Peptide bond P 305 The role of transfer RNA • A chain of amino acids is formed until the stop codon is reached on the mRNA strand. Stop codon P 301 RNA • Transfer RNA (tRNA) is the supplier. Transfer RNA delivers amino acids to the ribosome to be assembled into a protein. Click image to view movie Question 1 What are the three chemical differences between RNA and DNA? Answer RNA consists of a single strand of nucleotides whereas DNA is a double strand. RNA contains ribose as its sugar and DNA contains deoxyribose as its sugar. Uracil in RNA replaces thymine in DNA as the nitrogenous base. Question 2 What is the role of rRNA in protein synthesis? Answer Ribosomal RNA binds to messenger RNA and assembles the amino acids in the order needed for the protein to be synthesized. Question 3 Which regions of the mRNA travel to the ribosome; introns, exons, or both? Answer Only exons, which contain coding information, travel to the ribosome. Introns, noncoding nucleotide sequences, do not travel to the ribosome. Question 4 What is an anticodon, and what does it represent? Answer An anticodon is a sequence of three nucleotides on the tRNA molecule that binds to a codon of the mRNA strand. P 307 Mutations • Organisms have evolved many ways to protect their DNA from changes. • In spite of these mechanisms, however, changes in the DNA occasionally do occur. • Any change in DNA sequence is called a mutation. • Mutations can be caused by errors in replication, transcription, cell division, or by external agents. P 287 Mutations in reproductive cells • Mutations can affect the reproductive cells of an organism by changing the sequence of nucleotides within a gene in a sperm or an egg cell. • If this cell takes part in fertilization, the altered gene would become part of the genetic makeup of the offspring. P 287 Mutations in reproductive cells • The mutation may produce a new trait or it may result in a protein that does not work correctly. • Sometimes, 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. P 287 Mutations in body cells • What happens if powerful radiation, such as gamma radiation, hits the DNA of a nonreproductive cell, a cell of the body such as in skin, muscle, or bone? • If the cell’s DNA is changed, this mutation would not be passed on to offspring. • However, the mutation may cause problems for the individual. P 287 Mutations in body cells • 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. P 287 The effects of point 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 because a change in a single amino acid can affect the shape of the protein. P 287 The effects of point mutations mRNA Normal Protein Stop Replace G with A mRNA Point mutation Protein Stop P 287 Frameshift mutations • What would happen if a single base were lost from a DNA strand? • This new sequence with the deleted base would be transcribed into mRNA. But then, the mRNA would be out of position by one base. • As a result, every codon after the deleted base would be different. P 287 Frameshift mutations Deletion of U Frameshift mutation mRNA Protein P 287 Frameshift mutations • This mutation would cause nearly every amino acid in the protein after the deletion to be changed. • 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. P 287 Chromosomal Alterations • Changes may occur in chromosomes as well as in genes. • Alterations to chromosomes may occur in a variety of ways. • Structural changes in chromosomes are called chromosomal mutations. P 287 Chromosomal Alterations • Chromosomal mutations occur in all living organisms, but they are especially common in plants. • Few chromosomal mutations are passed on to the next generation because the zygote usually dies. P 287 Chromosomal Alterations • In cases where the zygote lives and develops, the mature organism is often sterile and thus incapable of producing offspring. • When a part of a chromosome is left out, a deletion occurs. A B C D E F G H A B C E Deletion F G H P 287 Chromosomal Alterations • When part of a chromatid breaks off and attaches to its sister chromatid, an insertion occurs. • The result is a duplication of genes on the same chromosome. A B C D E F G H A B C B C D E Insertion F G H P 287 Chromosomal Alterations • When part of a chromosome breaks off and reattaches backwards, an inversion occurs. A B C D E F G H A D C B E FGH Inversion P 287 Chromosomal Alterations • When part of one chromosome breaks off and is added to a different chromosome, a translocation occurs. AB C D E F GH WX Y Z W X AB C DE F GH Translocation Y Z P 287 Causes of Mutations • Some mutations seem to just happen, perhaps as a mistake in base pairing during DNA replication. • These mutations are said to be spontaneous. • However, many mutations are caused by factors in the environment. P 287 Causes of Mutations • Any agent that can cause a change in DNA is called a mutagen. • Mutagens include radiation, chemicals, and even high temperatures. • Forms of radiation, such as X rays, cosmic rays, ultraviolet light, and nuclear radiation, are dangerous mutagens because the energy they contain can damage or break apart DNA. P 287 Causes of Mutations • The breaking and reforming of a doublestranded DNA molecule can result in deletions. • Chemical mutagens include dioxins, asbestos, benzene, and formaldehyde, substances that are commonly found in buildings and in the environment. • Chemical mutagens usually cause substitution mutations. P 287 Repairing DNA • Repair mechanisms that fix mutations in cells have evolved. • Enzymes proofread the DNA and replace incorrect nucleotides with correct nucleotides. • These repair mechanisms work extremely well, but they are not perfect. • The greater the exposure to a mutagen such as UV light, the more likely is the chance that a mistake will not be corrected. P 287 Question 1 Any change in DNA sequences is called a _______. A. replication B. mutation C. transcription D. translation The answer is B. P 287 Question 2 Which is more serious, a point mutation or a frameshift mutation? Why? Answer A frameshift mutation is more serious than a point mutation because it disrupts more codons than a point mutation. P 287 Question 3 Why are chromosomal mutations rarely passed on to the next generation? Answer Few chromosomal changes are passed on to the next generation because the zygote usually dies. If the zygote survives, it is often sterile and incapable of producing offspring. P 287 DNA: The Molecule of Heredity • Alfred Hershey and Martha Chase demonstrated that DNA is the genetic material. • Because adenine can pair only with thymine, and guanine can pair only with cytosine, DNA can replicate itself with great accuracy. P 287 DNA: The Molecule of Heredity • DNA, the genetic material of organisms, is composed of four kinds of nucleotides. A DNA molecule consists of two strands of nucleotides with sugars and phosphates on the outside and bases paired by hydrogen bonding on the inside. The paired strands form a twisted-zipper shape called a double helix. P 287 From DNA to Protein • Genes are small sections of DNA. Most sequences of three bases in the DNA of a gene code for a single amino acid in a protein. • Messenger RNA is made in a process called transcription. The order of nucleotides in DNA determines the order of nucleotides in messenger RNA. P 287 From DNA to Protein • Translation is a process through which the order of bases in messenger RNA codes for the order of amino acids in a protein. P 287 Genetic Changes • A mutation is a change in the base sequence of DNA. Mutations may affect only one gene, or they may affect whole chromosomes. • Mutations in eggs or sperm affect future generations by producing offspring with new characteristics. Mutations in body cells affect only the individual and may result in cancer. P 287 Question 1 The process through which the order of bases in messenger RNA codes for the order of amino acids in a protein is: A. transcription B. translation C. replication D. point mutation The answer is B. P 287 Question 2 Why would scientists use nucleotide sequences to identify bodies of crime victims? Answer In comparing nucleotide sequences in the DNA of a crime victim with nucleotide sequences from a possible close relative of the crime victim, scientists can determine if the two are related. P 287 Question 3 What happens when a stop codon is reached during translation? Answer When a stop codon is reached, translation ends and the amino acid strand is released from the ribosome. P 287 Question 4 A ________ bond forms between adjacent amino acids during translation. A. nucleotide B. phosphate C. hydrogen D. peptide The answer is D. P 287 Question 5 What is the difference between a purine and a pyrimidine? Answer A purine is a double-ringed nitrogenous base. A pyrimidine is a single-ringed nitrogenous base. P 287 Question 6 Why is DNA replication important to cell division? Answer Without DNA replication, new cells would have only half the DNA of their parents. Species could not survive and individuals could not grow or reproduce successfully. P 287 Question 7 At the beginning and end of replication, which of the following are instrumental in breaking and bonding the hydrogen bonds between bases? A. pyrimidines B. purines C. nucleotides D. enzymes The answer is D. P 287 Question 8 What is the role of mRNA in protein synthesis? Answer The messenger RNA acts as a genetic message, providing the complete information, in sequences of codons, for the building of a protein.