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IB Biology 3.1 genes

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IB Biology 3.1 genes

  1. 1. 3.1 Genes • Essential idea: Every living organism inherits a blueprint for life from its parents. http://pixabay.com/static/uploads/photo/2014/05/11/14/25/elephants-341981_640.jpg
  2. 2. Understandings Statement Guidance 3.1.U1 A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic 3.1.U2 A gene occupies a specific position on a chromosome. 3.1.U3 The various specific forms of a gene are alleles. 3.1.U4 Alleles differ from each other by one or only a few bases. 3.1.U5 New alleles are formed by mutation. [Deletions, insertions and frame shift mutations do not need to be included.] 3.1 U6 The genome is the whole of the genetic information of an organism. 3.1 U7 The entire base sequence of human genes was sequenced in the Human Genome Project.
  3. 3. Applications and Skills Statement Guidance 3.1.A1 The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin. [Students should be able to recall one specific base substitution that causes glutamic acid to be substituted by valine as the sixth amino acid in the hemoglobin polypeptide.] 3.1.A2 Comparison of the number of genes in humans with other species. [The number of genes in a species should not be referred to as genome size as this term is used for the total amount of DNA. At least one plant and one bacterium should be included in the comparison and at least one species with more genes and one with fewer genes than a human.] 3.1.S1 Use of a database to determine differences in the base sequence of a gene in two species. [The Genbank® database can be used to search for DNA base sequences. The cytochrome C gene sequence is available for many different organisms and is of particular interest because of its use in reclassifying organisms into three domains.]
  4. 4. 3.1.U1 A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic Eukaryotic Chromosomes • The Photograph shows a human chromosome. The picture show two chromatids joined at the centromere.Each Eukaryotic chromosomes is composed of •DNA •Protein (Histones)
  5. 5. Chromosome Histones DNA double helix 3.1 U.1 A gene is a heritable factor that consists of a length of DNA and influences a specific characteristic Chromosome is a length of DNA with associated proteins (histones).
  6. 6. Homologous Pair of Chromosomes: One Comes From Each Parent •Gene loci is the position of the gene on a chromosome. Alleles have the same gene loci.
  7. 7. 3.1 U.2 A gene occupies a specific position on a chromosome. http://www.daviddarlin g.info/images/gene.jpg •Gene is a heritable factor that controls a specific characteristic. There are over 20,000 genes that make up a human. One gene codes for one polypeptide.
  8. 8. Allele is one specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene. 3.1 U.3 The various specific forms of a gene are alleles.
  9. 9. 3.1 U.4 Alleles differ from each other by one or only a few bases. This may cause: •Change in the base sequence of the gene •Change in the mRNA made in transcription •Change in the amino acids sequence / primary structure of the protein •Change in the secondary/ tertiary or quaternary structure of the protein •Change the shape of the protein •Change the function of the protein. http://evolution.berkeley.edu/evolibrary/images/interviews/pax_mouse_fly.gif
  10. 10. Examples of the mutations to the gene Deletion Duplication Inversion Translocation 3.1 U.5 New alleles are formed by mutation. [Deletions, insertions and frameshift mutations do not need to be included.] http://www.goldiesroom.org/Multimedia/Bio_Images/19%20Applie d%20Genetics/05%20Chromosome%20Mutations.jpg
  11. 11. 3.1 U.6 The genome is the whole of the genetic information of an organism. Allows for: • Physical mapping of chromosomes • Used to screen for genetic diseases • Lead to a better understanding of genetic diseases. • May lead to the development of better drugs to fight diseases. • Maybe be used for comparison of genomes with other species.
  12. 12. 3.1 U.6 The genome is the whole of the genetic information of an organism. Genome Size and Number of Genes
  13. 13. Chromosome 16 3.1 U.6 The genome is the whole of the genetic information of an organism. http://physrev.physiology.org/content/physrev/91/1/151/F11.large.jpg
  14. 14. 3.1 U.6 The genome is the whole of the genetic information of an organism. Advantages from the project Advantage 1 • Screening can also be done for adults, to see if they may be carriers of potential genetic conditions. Certain Jewish and Canadian populations regularly obtain voluntary screening for Tay- Sachs disease, a known child-killer. This information has been used to help make decisions about future marriage partners. Advantage 2 Perhaps the greatest benefit will come from what is called gene-based therapy. Understanding the molecular workings of genes and the proteins they encode will lead to more precise drug treatments. The more precise the drug treatment, the fewer and milder will be the side effects.
  15. 15. 3.1 U.7 The entire base sequence of human genes was sequenced in the Human Genome Project. http://www.bioscience.heacademy.ac.uk/imagebank/search/Fullimage.aspx?IDvalues=6513 • The project began in 1990 and was completed in 2003. • It is now know which base sequences are protein coded genes • There about 23,000 genes • Much of the genome is highly repetitive base sequences that are not translated in proteins originally called “junk DNA”. Now referred to as satellite DNA
  16. 16. 3.1 A.1 The causes of sickle cell anemia, including a base substitution mutation, a change to the base sequence of mRNA transcribed from it and a change to the sequence of a polypeptide in hemoglobin. [Students should be able to recall one specific base substitution that causes glutamic acid to be substituted by valine as the sixth amino acid in the hemoglobin polypeptide.]
  17. 17. 3.1 A.1 The causes of sickle cell anemia The Disease: •Sickle cell anemia is an inherited disorder that affects hemoglobin, a protein that enables red blood cells to carry oxygen to all parts of the body. •The disorder produces abnormal hemoglobin, which along with the abnormalities of the cells membrane cause damage from be trapped and freed in the capillaries. This shortens the blood cells life to as little as 4 days. Disease Symptoms: •chronic anemia, •acute chest syndrome, •stroke, •spleen and renal dysfunction, •pain crises and susceptibility to bacterial infections, particularly in children. •Sickle cell disease is also associated with significant mortality.
  18. 18. 3.1 A.1 The causes of sickle cell anemia •The HBA gene carries the instructions for the manufacture of a protein that is a component of hemoglobin. •Hemoglobin is the protein containing a sequence GAG which codes for the amino acid glutamic acid. •In a base substitution mutation of Hemoglobin proteins in Sickle Cell Anemia. GAG has been changed into GTG which codes for the amino acid valine. It is given the symbol HBs for the gene. http://upload.wikimedia.org/wikipedia/commons/a/ac/Sickle_cell_01.jpg
  19. 19. Alleles, genotypes and Phenotypes of Sickle Cell: HbA Normal allele producing normal protein using the amino acid glutamic acid Hbs Sickle allele which is the abnormal mutation of the normal allele. Is produced using the replacement amino acid valine. 3.1 A.1 The causes of sickle cell anemia http://www.zo.utexas.edu/faculty/sjasper/images/17.23.gif
  20. 20. 3.1.A2 Comparison of the number of genes in humans with other species. [The number of genes in a species should not be referred to as genome size as this term is used for the total amount of DNA. At least one plant and one bacterium should be included in the comparison and at least one species with more genes and one with fewer genes than a human.]

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