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Biology Final Exam (chapter 8)
Terms in this set (16)
studies of biological molecules (DNA, RNA, and proteins)
deals with the genetic inheritance at the gene level
What is DNA?
Deoxyribonucleic acid, instructional molecules, genetic material, polymers of nucleotides, compromise all the genes that code for specific phenotypic expressions
Who is Miescher?
Discovered DNA in 1868, organic acid high in phosphorus that he called nuclein
Who is Griffith?
Discovered transformation in 1928
Who is Avery and McCarty?
Confirmed Griffith's finding, concluded that DNA, not protein, nor carbohydrates, nor lipids, transformed the R cells bacteria
Who is Hershey and Chase?
Confirmed Griffiths finding
Who is Chargaff?
Determined the proportions of Adenine, Thymine, Guanine, and Cytosine in DNA; found A=T and C=G; bases in DNA can only pair one way according to his rule
Who is Rosalind Franklin?
determined that DNA was helical, composed of 2 sub-units; was the first to discover the molecular structure of DNA; died of cancer at age 37, possibly related to extensive exposure to x-rays
Who is Watson and Crick?
Proposed a structure of DNA based on the work of Rosalind Franklin (1953)
Structure of DNA
DNA is a polymer of nucleotides; nucleotides: consisting of five-carbon sugar; there are 4 different nucleotides in DNA: two pyrimidines: thymine and cytosine and two purines: adenine and guanine
DNA replication and repair
A cell copies its DNA before mitosis ( a cell duplicates its chromosomes before M-stage)
Semiconservative DNA replication
Each strand of a DNA is uses a template synthesis of a complementary strand of DNA; one template builds DNA continuously (leading strand);the other builds it discontinuously (lagging strand); each new DNA molecule consists of one old strand and one new strand
Enzymes responsible for DNA replication
DNA helicase: breaks hydrogen bonds between DNA strands
DNA polymerase: synthesizes nucleotides
DNA ligase: joins DNA segments on discontinuous strand
Topoisomerase: prevents DNA from over-twisting
Mistakes occur during replication; DNA polymerase proof-reads and corrects mistakes. When a mistake is detected endonuclease excises the mistake and DNA polymerase synthesizes a correct sequence, then DNA ligase stitches the DNA; when proofreading and repair mechanisms fail, the error becomes permanent; mutation: a permanent change in DNA
reproductive cloning: a reproductive intervention that results in an exact genetic copy of an adult individual
Clones: exact copy of a cell or individual; occurs in nature by asexual reproduction or embryo splitting (identical twins)
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