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Genetics

Genetics. Ms. Carballosa Biology. 14.1 Human Chromosomes. The genome is the full set of genetic information that an organism carries in its DNA A karyotype shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size.

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Genetics

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  1. Genetics Ms. Carballosa Biology

  2. 14.1 Human Chromosomes • The genome is the full set of genetic information that an organism carries in its DNA • A karyotype shows the complete diploid set of chromosomes grouped together in pairs, arranged in order of decreasing size

  3. 14.1 Human Chromosomes • A human has 2 sets of 23 chromosomes – 46 in total • 2 of which are sex chromosomes – XX in females and XY in males (Y is much smaller) • Autosomal chromosomes or autosomes are the other 44

  4. 14.1 Human Chromosomes • Many human traits follow a pattern of simple dominance • Rh blood group (+ or -)

  5. 14.1 Human Chromosomes • Other human genes display codominant inheritance • ABO blood group (A & B being codominant)

  6. 14.1 Human Chromosomes • Other genes may be located on the X or Y sex chromosomes, making them sex-linked genes • If it involves only the Y, the disease is present in males • If it involves the X, the disease is present in males, females may be carriers or have the disease

  7. 14.1 Human Chromosomes • How is a female a carrier and not affected? X chromosomes inactivation • One of the X’s in females (usually the bad one) is turned off • Males cannot do this because they only have one X which is important for normal development

  8. 14.1 Human Chromosomes • You can use a pedigree (chart that shows relationships within the family) to figure out a traits pattern of inheritance • Inferring the genotypes helps to explain how the disease is transmitted

  9. 12.1 Identifying The Substance of Genes • Frederick Griffith wanted to figure out how bacteria makes people sick – particular pneumonia • Experimented with something called transformation the passing of DNA from one bacteria to another • Came to this conclusion because the harmless bacteria (heat-killed were transformed into harmful bacteria (disease-causing) if placed in the same area: even if heat killed!

  10. 12.1 Identifying The Substance of Genes • By observing bacteria transformation, Avery and other scientists discovered that the nucleic acid DNA stores and transmits genetic information from one generation of bacteria to the next • Hershey & Chase later experimented with bacteriophages – a virus that infects bacteria

  11. 12.1 Identifying The Substance of Genes • Hershey & Chase studied the bacteriophage and looked at whether the virus injected its protein or DNA – they confirmed that DNA was the genetic material found in all living cells

  12. 12.1 Identifying The Substance of Genes • The DNA that makes up genes must be capable of storing, copying, and transmitting genetic information in a cell • Very important that during meiosis, there is no loss of DNA – that would be losing valuable information!

  13. 12.2 The Structure of DNA • DNA is a nucleic acid made up of nucleotides joined into long strands or chains by covalent bonds • Nucleotides are the building blocks of nucleic acids and are made up of a sugar, a phosphate group, and a nitrogenous base

  14. 12.2 The Structure of DNA • DNA has 4 kinds of nitrogenous bases: • Adenine • Thymine • Cytosine • Guanine • A==T ; C==G (Chargaff’s rule) • These bases can be strung together in many different sequences to give different information

  15. 12.2 The Structure of DNA • The clues in Franklin’s X-Ray pattern enabled Watson and Crick to build a model that explained the specific structure and properties of DNA • DNA is a twisted ladder (double-helix) that runs anti-parallel and has specific base pairing (A==T, C==G)

  16. 12.3 DNA Replication • Each strand of DNA is complementary to the other – therefore, it has all the info needed to reconstruct the other half during replication (late interphase)

  17. 12.3 DNA Replication

  18. 12.3 DNA Replication • Steps for DNA Replication: • DNA strand unzips • DNA Polymerase (an enzyme) joins individual nucleotides according to base pairing to produce a new strand of DNA on both strands • DNA Polymerase checks for errors “proofreads” • 2 new identical DNA strands are created

  19. 12.3 DNA Replication • Telomeres (tips of chromosomes) are particularly hard to replicate • Telomerase help to prevent genes from being damaged or lost during replication by being in charge of the ends • In adult cells, telomerase barely works. In new stem cells or cancer cells, telomerase is on overdrive

  20. 12.3 DNA Replication Prokaryotes Eukaryotes DNA in chromosomes in nucleus Replication can start at hundreds of places, proceeding in both directions until completed copied • Circular DNA in cytoplasm • Replication starts from a single point and proceeds in 2 directions until it’s all copied

  21. 12.3 DNA Replication • Sometimes, DNA Polymerase doesn’t catch all of the errors and damaged regions of DNA are copied – leads to cancer or cell death

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