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RNA: ribonucleic acid • Large nucleic acid built from many nucleotides bonded together • Remember a nucleotide consists of a phosphate group, 5 carbon sugar and nitrogen containing base RNA nucleotide • The 5-Carbon sugar is ribose • The 4 nitrogen containing bases: – Adenine – Uracil – Cytosine – Guanine 3 types of RNA • mRNA: messenger RNA: carries the genetic code from the nucleus to the ribosome • rRNA: ribosomal RNA: builds ribosomes • tRNA: transfer RNA: carries amino acids to the synthesizing polypeptide Wednesday 4/3/13 • AIM: How is mRNA translated? • DO NOW: Explain the importance of messenger RNA. Where does the message come from? • HOMEWORK: Text read page 306 answer the reading check question Modification of RNA • The rough draft is called the primary transcript • Before it leaves the nucleus it gets modified • Addition of 5’cap and Poly-A tail • The most important is RNA splicing RNA modification • 5’ cap and Poly A tail protect the RNA from being broken down by cellular enzymes • They also help the ribosome recognize the RNA RNA splicing • Introns: junk DNA that does not code for proteins • Exons: good DNA codes for protein • Splicesome: enzymes that catalyze the removal of introns and the connection of exons • Allows the human genome to produce a variety of polypeptides • One gene codes for one polypeptide • How do your cells know which amino acids it wants or needs? • ANSWER: the genetic code determines the polypeptide (sequence of amino acids) Now the mRNA is ready to leave the nucleus and enter the cytoplasm Quick Review • What are the 3 major events that occur during transcription? • Why is it important to modify the primary RNA before leaving the nucleus? The Genetic code • Codon: sequence of 3 nucleotides that specify an amino acid • There are 20 amino acids that build ALL polypeptides • It is the unique sequence of amino acids that build polypeptide chains • It is the unique folding of polypeptides that build proteins Codon: sequence of 3 nucleotides that specify an amino acid Period 7 Thursday 4/4/13 Friday 4/5/13 • AIM: How is the mRNA molecule translated? • DO NOW: In your own words explain how the primary transcript is modified before it leaves the nucleus. • Why is it modified? Codons to know • • • • AUG UAA UAG UGA • So we know DNA can replicate and transcribe. But what happens next? Translation: RNA to amino acid sequence • Involves mRNA, tRNA, rRNA and ribosomes • Before mRNA leaves the nucleus, proteins called splicesomes cut out and paste together coding regions of the primary mRNA transcript • Plays a major role in polypeptide diversity • Now it is ready for translation RNA:ribonucleic acid • Polymer made up of small subunits called nucleotides • Each nucleotide has a 5 C sugar, nitrogenous base and phosphate group • The 5 carbon sugar in RNA is ribose • The four possible nitrogenous bases are • Adenine, uracil, cytosine and guanine • Instead of thymine, adenine attracts a uracil nitrogenous base mRNA: messenger RNA tRNA: Transfer RNA carries amino acids to the mRNA-ribosome complex mRNA: messenger RNA mRNA: codon tRNA anticodon • 3 base pair sequence complementary to the mRNA codon • Anticodon-codon complex allows amino acids to bond in proper sequence Ribosomal RNA builds ribosomes • AIM: How are codons translated into polypeptides? • DO NOW: Handout. Label 1-10 • Homework: Handout Translation- mRNA and tRNA interact at a ribosome Translation continued Translation Stage of Protein Synthesis • Rectangles = amino acids • Crooked Cross = transfer RNA with an amino acid on top and anticodon at bottom • X = messenger RNA molecule with codons • Double oval = ribosome What I want you to know about translation • Process that builds a polypeptide chain from a mRNA molecule • The original message comes from the DNA template • tRNA anticodon bonds to mRNA codon bringing an amino acid into its proper place • Translation occurs in the ribosome Translation • There is a specific start AUG codon • There are 3 possible stop codons that terminate UAA,UAG or UGA Reading frame • Each codon specifies an amino acid • The reading frame is the sequence of codons in a gene • If the reading frame is changed, the amino acid sequence may be changed • Possibly resulting in a dis-functional protein Lets build a protein DNA : mRNA: tRNA: aa: TACCCTCAACTCTCAACT AUGGGAGUUGAGAGUUGA UACCCUCAACUCUCAACU met - gly- val- glu- ser Amino acid sequence • MET-GLY-VAL-GLU-SER • We got a polypeptide but is this a functional protein? • NO! Remember it is the unique shape of a protein that gives it a specific function Assessment • Handout 1-5 and A-E Wednesday 4/27/2011 • AIM: How is the reading frame effected if the base pair sequence changed? • DO NOW: How would mRNA and amino acid sequence change if the following DNA template changed? Original DNA: TACCCTCAACTCTCAACT Changed DNA: TACCCTCATTCTCAAC DO NOW ANSWER • If the gene sequence is changed and causes a change in the amino acid sequence (polypeptide), the physical characteristic changes Homework • Textbook Read Page 266. Using Science graphics questions 1-3 Are all genes in each cell expressed in every cell? NO! All of the 30,000 genes are in each body cell but only specific genes are expressed in specific cells Differentiation • The regulation of gene expression • Different genes are expressed in different cells • Different cells build different proteins Thursday 4/28/11 • AIM: How is human phenotype effected by genetic mutations? DO NOW: 1- How many base pairs make up a single codon? 2- How many amino acids build all human proteins? Homework: Read 267-269. Reading Check pages 267 and 269 DO NOW ANSWER • 3 nitrogen bases=codon • 64 codons in total • 20 amino acids build all proteins • More than one codon for a single amino acid • This is why some mutations have NO effect on the polypeptide chain How do you make a polypeptide? Gene-mRNA-ribosomecodon/anticodon bonding which makes a long chain of amino acids How are polypeptides related to physical characteristics? Polypeptides build proteins which lead to chemical reactions that cause physical traits Functional protein • Polypeptide: Long chain of amino acids – Combine with other polypeptides – Folds into a unique shape – This makes a functional protein – The shape of a protein is unique to its function – If you change the shape, you change the function Denaturing a protein • Changes the shape of the protein • If the shape of the protein changes the function changes or it does not function at all. • How would a protein get denatured? – Gene mutation – Mistake in mRNA modification – Mistake in translation – Mistake in polypeptide folding • If my DNA makes a mistake, how will the protein behave? – The protein will have a different shape, and without its shape, it cannot function properly – Proteins are shape specific – Denature: changes the shape of a protein GENE Mutations • Change in nucleotide sequence of bases in a DNA molecule (gene) • May or may not change the amino acid sequence • Nonsense mutation: gene sequence changes but amino acid does not • EX: normal DNA CTT mutated DNA: CTC Assessment How many amino acids build all of the human proteins? 20 How many nitrogen bases build RNA? 4 How many nitrogen bases make up a codon? 3 How many codons are there? 64 Gene Mutations • Nucleotide substitutions: single base pair is replaced with a different incorrect pair • Insertion: addition of 1 or more base pairs • Deletion: removal of one or more base pairs Mutations • How is the polypeptide changed if the reading frame of an mRNA molecule is changes from GGC to AGC? • amino acid in the polypeptide chain is changed from SER to GLY • Mutation in reading frame of a gene could result in protein dysfunction Sources of mutations • Mutagen: any chemical that causes a change is nucleotide sequence of a gene – Chemicals – Medication – Vaccine – Radiation – carcinogens How are mutations inherited? • If a mutation is in a gamete (sperm or egg), it will be inherited by the zygote Wednesday 3/10/10 • AIM: How can a genetic mutation effect the phenotype of a human being? • DO NOW: How is the human genome organized? Autosomes: 1-22 23 pair sex chromosomes XX=female XY=male Sex genetic disorders Found on Y chromosome • Deletion of SRY • Deletion of DAZ Found on X chromosome • Red-green colorblindness • Hemophilia Deletion of the SRY gene can lead to XY females • SRY: sex determining region Deletion of DAZ gene leads to infertility in males Sex-linked disorder • found on the X chromosome • female can have one copy of the allele and be a carrier • a male with one copy always display the trait Red Green Colorblindness Hemophilia: on the X chromosome • Inability for blood to clot • People do not produce one of the proteins necessary for proper blood clotting Autosomal Genetic Disorders • Found within Chromosomes 1-22 • If you mutate a gene, it may change the shape of the protein that it codes for Human Recessive Autosomal Genetic disorders • Homozygote Recessive is the only way to display • Heterozygotes are carriers • Ex: Achondroplasia (Dwarfism) Sickle cell anemia Cystic fibrosis Albinism PKU Tay Sachs Achondroplasia • Dwarfism • “without cartilage formation” • the defect is not in forming cartilage but in converting it to bone Sickle cell anemia Sickle cell anemia Sickle cell anemia Sickle Cell Anemia • Effects mostly South African Descendants • Hemoglobin: protein in the red blood cell that carries oxygen • People with Sickle Cell Anemia make a sickled shape hemoglobin protein • Symptoms: – Inability to carry oxygen – Shortness of Breath – Pain in Joints – Coagulation of RBC’s Cystic Fibrosis • European descent • 1:2500 • Lack of a cell membrane protein • Causes cells to produce a thick sticky mucous Renal (kidney) cystic fibrosis Albinism • Albinism: homozygous recessive allele for the enzyme tyrosine which builds melanin • Melanin: protein that gives skin pigment Phenylketonuria (PKU) • Base substitution( G-A) – Changes amino acid from ARG-GLU Changes the shape of hydrooxylase enzyme Enzyme cannot break down the amino acid PHE (Phenylalanine) • increases the levels of a substance called phenylalanine in the blood – Causes mental retardation and other serious health problems • If detected early, it can be treated by dieting Phenylketonoria PKU • Accumulation of the amino acid phenylaline in the blood • Mental Retardation • Abnormal skin color Tay Sachs disease • Lipid accumulation in brain cells • Mental deficiency • Blindness • Death in childhood • Blue stain shows swollen neurons Period 2 Friday 3/12/10 • AIM: How do chromosomal disorders differ from genetic disorders? • DO NOW: Explain why a heterozygote does not display albinism but could have a child with albinism. • HOMEWORK: • Textbook read pages 650-651. Observe fig 22.13. Is that child a male or female? How do you know? Human Dominant Disorders: Huntington disease • Genetic duplication: repeat of CAG codon • Causes string of glutamines (glu) in the polypeptide chain of the huntington protein • Causes change in shape of huntington protein • Slow deterioration of brain and nervous system Huntington’s disease Huntington Disease • People usually have symptoms for up to 10 years before they find out they have Huntington's disease. • Most people are diagnosed between the ages of 30 and 50, although this can happen much earlier or later. • Symptoms are often overlooked, as they are mild and commonly experienced by well people • mild tremor • clumsiness • lack of concentration • difficulty remembering things • mood changes, including depression • sometimes, aggressive antisocial behavior per 6 Friday 3/12/10 • AIM: How are gene mutations different from chromosomal mutations? • DO NOW:Explain why a heterozygote does not display albinism but could have a child with albinism. In your own words, explain the relationship between genes and chromosomes. Gene vs chromosome • Genes are on chromosomes • Gene mutations: occur at the single gene • Chromosomal mutations: loss or gain of entire chromosome Hypertrichosis: genetic disorder excessive hair growth over and above the normal for the age, sex and race of an individual Exact cause is unknown but has been linked to a spontaneous mutation Nondisjunction: • Uneven distribution of chromosomes during gamete formation • Usually leads to spontaneous abortion or severe disorders Autosomal Disorders • • • • Trisomy 21 Trisomy 8 Trisomy 13 These are the only trisomy’s that will lead to full term fetal development • Any other trisomy will cause spontaneous abortion (miscarriage) Nondisjunction and Down’s syndrome • • one gamete has two 21st the resulting fertilized egg has three 21st chromosomes. • 90% of the abnormal cells are the eggs • Trisomy 21 Mental retardation Physical abnormalities Down’s syndrome Trisomy 8 and 13 Trisomy 8 • low-set or abnormally shaped ears and a bulbous-tipped nose, eye abnormalities • bone and tissue abnormalities, • various structural heart problems, • palate abnormalities • mild to moderate mental delays • deep hand and feet creases. Trisomy 13 • • • • • • • • • • • • • • • • Cleft lip or palate Close-set eyes -- eyes may actually fuse together into one Decreased muscle tone Extra fingers or toes (polydactyly) Hernias: umbilical hernia, inguinal hernia Hole, split, or cleft in the iris (coloboma) Low-set ears Mental retardation, severe Scalp defects (absent skin) Seizures Single palmar crease Skeletal (limb) abnormalities Small eyes Small head (microcephaly) Small lower jaw (micrognathia) Undescended testicle (cryptorchidism) Nondisjunction of sex chromosomes • Turner’s syndrome: • XO: no sex hormones lead to no menstruation and no secondary sex characteristics • Infertility • Short stature, folds on neck, more X linked recessive disorders, color blindness, hemophilia etc. Trisomy X • 1 in every 1000 woman have 3 X chromosomes • Very tall • Below normal intelligence Klinefelter syndrome • 1 in every 1000 males have XXY • Most never even know they have it • partial breast development, widening of the hips and small testis • These men are usually infertile XYY males • • • • High levels of testosterone Severe acne More than 6 feet tall Lower IQ Per 7 • AIM: How can pregnant woman get tested for genetic and chromosomal disorders? • DO NOW: In your own words, explain what would happen to a zygote if it contained 3 autosome 3’s. How are genetic disorders different from chromosomal disorders? Fetal Testing • • • • • Ultrasound Amniocentesis Chorionic Villus Sampling Fetoscopy Newborn Screening Ultrasound • Sounds waves are used to produce an image Fetoscopy • Viewing scope is placed into the uterus creating an image • Enables blood samples to be taken • Detects Spina bifida • Only done if there is a history of birth defects Amniocentesis • 14th-16th week • 10 mL of amniotic fluid • Looks at chemicals and molecules present • chromosomal disorders, including Down’s syndrome, trisomy 13,18,Turner’s syndrome, Kleinfelter’s syndrome • Sickle Cell, Tay Sachs • spina bifida and anencephaly Chorionic Villus Sampling 8th-10th week • Insert through the cervix into the uterus • Take a tissue sample from the placenta • Contain fetal cells which divide more rapidly than amniotic cells New born Screening • Examines newborn blood to detect genetic disorders • PKU: phenylketonoria • Tay Sacs • Treated with diet regulation End Friday notes Viruses: Genes in packages • Basically is a piece of nucleic acid surrounded by a protein • Survives by infecting other cells with its nucleic acid and taking over the cell • Using the cells organelles to produce new viral cells Animal viruses • Such as influenza or the mumps • Surrounded by protein coat • Protein coat attaches to cell membrane and injects its nucleic acid in to the cell cytoplasm • New viral proteins and mRNA are synthesized and often the animal cell is destroyed HIV: Human Immunodeficiency virus • Virus that causes AIDS: autoimmunodeficiency syndrome • Similar to the flu and mumps in that it is surrounded by a protein coat • Its nucleic acid is RNA: it is called a retrovirus • An RNA virus that reproduces by means of a DNA molecule HIV a retrovirus • Carry molecules of RNA and a specific enzyme called reverse transcriptase • Reverse transcriptase: cause the synthesis of a DNA strand from an RNA template Steps in HIV infection • Reverse transcriptase makes a single strand of DNA from an RNA template • The new strand of DNA then builds a second complementary strand • The resulting double strand then enters the nucleus and inserts itself into the genome: provirus • NOW EVERY TIME THE CELL DIVIDES THE VIRAL DNA IS REPLICATED AND TRANSCRIBED HIV • Infects and eventually kills several kinds of white blood cells • Causing the body to become susceptible to many diseases • SECONDARY infections cause the development of AIDS • AIDS: collection of symptoms Treatment for HIV and AIDS • Drugs interfere with the reproduction of the virus • AZT: blocks the synthesis of the HIV DNA by binding to reverse transcriptase during transcription. – Structurally similar to Thymine • Proteases: inhibit the synthesis of HIV proteins making the virus unable to be transmitted