isolated DNA nuclei, discovered that chromosomes are 50% protein and 50% nucleic acid
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Frederick Griffith
while attempting to make a vaccine to prevent pneumonia using 2 strands of bacterium, found that something was transferred from heat killed to harmless bacteria - discovered bacterial transformations
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Avery, McCarthy, and MacLeod
concluded that DNA is what holds genetic information, NOT protein - coined the term “DNA”
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Hershey and Chase
used radioactive labels to discover that DNA is what transfers genetic information to offspring
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Wilkins and Franklin
discovered double helix structure of DNA first but did not publish work
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Watson and Crick
published work about double helix structure first
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nucleotide
contains 5-carbon sugar (deoxyribose), phosphate group, a nitrogen-containing base
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Erwin Chargaff
discovered bases, A=T and G=C
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base pairs
adenine and thymine, cytosine and guanine
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purines
2 rings, adenine and guanine
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pyrimidines
1 ring, thymine and cytosine
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DNA structure
antiparallel, double helix, composed of 2 antiparallel strands of nucleotides - nucleotides are held together by hydrogen bonds
width of 2nm
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DNA Helicase
opens up the double helix, breaks the hydrogen bonds
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DNA Polymerase
reads from 3’ to 5’ ends and assembles the nucleotides - matches up the bases
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DNA Ligase
joins the phosphodiester bonds of the Okazaki fragments on the lagging strand
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Semi-conservative DNA replication
produces two identical molecules of DNA
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RNA
nucleic acid, messenger between DNA and ribosomes, involved in protein production
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RNA vs. DNA differences
3 types: mRNA, tRNA, rRNA, ribose sugar (not deoxyribose), single stranded (not double), uracil replaces thymine (the base in DNA) and binds with adenine
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Transcription (nucleus)
1. DNA molecule is split by RNA Polymerase enzyme 2. DNA molecule is copied onto complimentary strand of mRNA 3. DNA transfers genetic material to messenger RNA (DNA does NOT leave the nucleus)
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Translation (ribosome)
1. ribosomal RNA (matchmaker) brings transfer RNA to mRNA (messenger) at ribosome 2. codons on mRNA bind to 3 anticodons on tRNA 3. peptide bonds form between the amino acids on tRNA 4. polypeptide chains are formed