Chapter 9 Molecules of Heredity Chapter 9 Molecules of Heredity

Chapter 9 Outline 9.1 How Did Scientists Discover That Genes Are Made of DNA? 9.2 What Is the Structure of DNA? 9.3 How Does DNA Encode Information? 9.4 How Does DNA Replication Ensure Genetic Constancy During Cell Division? 9.5 How Do Mutations Occur?

9.1 Genes Are Made of DNA Known since the late 1800s: 1.Heritable information is carried in discrete units called ________ 2.Genes are parts of structures called __________________ 3.Chromosomes are made of ________________________ and ___________

Genes Are Made of DNA Transformed bacteria revealed the link between ________ and ________

Genes Are Made of DNA F. Griffith worked with two strains of Streptococcus pneumoniae bacteria –_______ caused pneumonia when injected into mice, __________ them –____ strain _______ cause pneumonia when injected

Genes Are Made of DNA Griffith made a sample of heat-killed S strain and mixed it with R strain –Injection of combination into mice caused ____________________

Genes Are Made of DNA Deductions from Griffith’s experiment (1920s) –Living safe bacteria (R strain) were __________ by something in the dead (but normally disease-causing) S strain –The living R strain bacteria were _________________________________ ________________________________

Genes Are Made of DNA Later findings by Avery, MacLeod, and McCarty (1940s) –The transforming molecule from the S strain was ________

9.2 DNA Structure DNA is made of chains of small subunits called _________________

DNA Is Composed of Four Nucleotides Each nucleotide has three components: 1.__________________ 2.____________________ 3.One of four nitrogen-containing bases –______________

DNA Is Composed of Four Nucleotides In 1940, biochemist E. Chargaff determined that: –In a DNA molecule, amounts of ______________________ –“Chargaff’s Rule”

DNA Is a Double Helix In the 1940s several other scientists investigated the structure of DNA Rosalind Franklin and Maurice Wilkins studied DNA structure _____________________

DNA Is a Double Helix From X-ray diffraction patterns they deduced that DNA –Is ___________ –Has a uniform diameter of ___________ –Is _____, and is _________ like a corkscrew –Consists of repeating subunits

DNA Is a Double Helix James Watson and Francis Crick combined the X-ray data with bonding theory to deduce DNA structure: –DNA is made of ____ _______ of nucleotides –The deoxyribose and phosphate portions make up the ______________ backbone

Hydrogen Bonds Nitrogen-containing bases protrude __________ from sugar-phosphate backbone

Hydrogen Bonds ______________ hold certain nitrogenous base pairs together –A bonds with __, G bonds with ___ –Bonding bases called _________________ base pairs

Hydrogen Bonds Ladder-like structure of the two DNA strands are twisted into a _____________

9.3 How Does DNA Encode Information? How can a molecule with only 4 simple parts be the carrier of genetic information? The key lies in the _________________, of subunits Within a DNA strand, the four types of bases can be arranged in any ____________, and this sequence is what encodes genetic information

How Does DNA Encode Information? The genetic code is analogous to languages, where small sets of letters combine in various ways to make up many different words – English has 26 letters –The binary language of computers uses only two “letters” (0 and 1, or “on” and “off”)

How Does DNA Encode Information? The sequence of only _______________ can produce many different combinations –A 10 nucleotide sequence can code for greater than ___________ different combinations

9.4 DNA Replication All cells come from __________ cells Cells reproduce by _______________ Each of two daughter cells gets an exact copy of parent cell’s genetic information Duplication of the parent cell DNA is called ___________________

DNA Replication DNA replication begins when _______________ separate the two strands –Hydrogen bonds between_______ are broken

DNA Replication A second strand of new DNA is synthesized along each separated strand by __________________, which position ______ nucleotides across from ______________ nucleotides

DNA Replication Base pairing is the foundation of DNA replication –An adenine on one strand pairs with a _______ on the other strand; a cytosine pairs with ___________ –If one strand reads ATG, the other reads _______

DNA Replication The two resulting DNA molecules have one ___ ___________ strand and one ______________ (________________ replication)

9.5 How Do Mutations Occur? Replication And Proofreading During replication, DNA polymerase mismatches nucleotides once every __________________ DNA repair enzymes _________” each new daughter strand, replacing mismatched nucleotides However…

Mistakes Do Happen DNA is damaged in a number of ways ___________ chemical breakdown at body temperature Certain chemicals (some components of _______________)

Mistakes Do Happen UV light from the sun causes DNA damage –DNA damage leads to uncontrollable _________ and ____________

Types of Mutations ___________ - individual nucleotide in the DNA sequence is changed

Types of Mutations __________ mutation - one or more nucleotide pairs are inserted into the DNA double helix

Types of Mutations __________ mutation - one or more nucleotide pairs are removed from the double helix

Types of Mutations ____________ - piece of DNA is cut out of a chromosome, turned around, and re-inserted into the gap

Types of Mutations _______________ - chunk of DNA (often very large) is removed from one chromosome and attached to another