BIO_SC 1010 1st Edition Lecture 6Outline of Current Lecture I. What is DNA?II. Where is DNA found?III. DNA and GenesIV. What is a Chromosome?V. EpigeneticsVI. Humans have 23 pairs of chromosomes: this is their genomeVII. The structure of DNAVIII. DNA ReplicationIX. Chromosomes at cell division have unique propertiesX. What makes DNA a great molecule for hereditary information?Current LectureWhat is DNA?• DNA stands for deoxyribonucleic acid-DNA is a hereditary molecule that is passed from parents to offspring -DNA is common to all living organisms-DNA serves as the instruction manual for how to build an individual• Nucleic acid- large macromolecules essential for living things, made up of nucleotide monomersWhere is DNA found?• DNA is found in the nucleus of eukaryotic cells• Inside the nucleus, the chromosomal DNA is wound around proteins; together they formchromatin-most of the time chromosomes are unraveled as loose chromatinDNA and Genes• All life on Earth uses DNA as the genetic materialThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.• The nucleus contains long strands of DNA called chromosomes • Each chromosome contains genetic information in genes• A gene is a length of DNA that codes for the proteins that make up our bodies-genes are the unit of inheritanceWhat is a Chromosome?• A chromosome consists of a single DNA molecule wrapped around proteins• If a single DNA molecule was stretched out it would be 2 to 3 inches long Epigenetics • This winding and unwinding and how “tight” the molecules wind around histones may influence function-DNA is unwound in order to be read-DNA is wound for cellular replicationHumans have 23 pairs of chromosomes: this is their genome• Genome: one complete set of genetic instructions encoded in the DNA of an organism• One chromosome from each pair is inherited from the biological mother• One chromosome from each pair I inherited from the biological father • The 23rd chromosome pair determines a person’s sex-XX = female-XY = male• Chromosome number: every human body cell has 46 chromosomesThe structure of DNA• Double Helix-the two strands of nucleotides -paired strands twist around each other-form a spiral-shaped helix-double helix because there are two strands-the sugars and phosphates from the outside “backbone” of the helix-the bases form the internal “rungs” like steps on a twisting ladder• complementary base pairing-each strand of DNA is held together by base pairing-hydrogen bonds between the bases of each strand• Nucleotides -nucleotides have one of the four bases: adenine (A), thymine (T), guanine (G), cytosine (C)-the complementary base pairing rule: A always pairs with T, C always pairs with G• Nucleotide Sequences-the specific sequence of nucleotides along a strand of DNA is unique to each individualDNA Replication• Cells make an identical copy of a DNA molecule through DNA replication• The hydrogen bods that hold base pairs together are broken and the helix is unwound• DNA polymerase adds complementary nucleotides using the rules of base pairing• Semi-Conservative• At the end of DNA replication, two copies of the original DNA molecule exist-each molecule consists of an original and a new strand• The polymerase chain reaction-PCR is a laboratory technique used to replicate a specific DNA segment -PCR can make billions of copies from a starting sample of just a few molecules of DNA-during each round of PCR-each strand is used as a template for complementary base pairing Chromosomes at cell division have unique properties• At cell division chromosomes:-become tightly packed-duplicate • Pairs of duplicated chromosomes are called sister chromatids -are joined at the centromere-formation means the cell is preparing to divide What makes DNA a great molecule for hereditary information?• DNA strands are complementary -if you know ½ of the molecule, you can build the other• To replicate, the DNA molecule unzips• Each strand serves as a template to build a new strand following the base-pairing rules -genetic instructions are passed down via DNA