Biology Genetics Unit

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Frederick Miescler

isolated DNA nuclei, discovered that chromosomes are 50% protein and 50% nucleic acid

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

Avery, McCarthy, and MacLeod

concluded that DNA is what holds genetic information, NOT protein - coined the term “DNA”

Hershey and Chase

used radioactive labels to discover that DNA is what transfers genetic information to offspring

Wilkins and Franklin

discovered double helix structure of DNA first but did not publish work

Watson and Crick

published work about double helix structure first

nucleotide

contains 5-carbon sugar (deoxyribose), phosphate group, a nitrogen-containing base

Erwin Chargaff

discovered bases, A=T and G=C

base pairs

adenine and thymine, cytosine and guanine

purines

2 rings, adenine and guanine

pyrimidines

1 ring, thymine and cytosine

DNA structure

antiparallel, double helix, composed of 2 antiparallel strands of nucleotides - nucleotides are held together by hydrogen bonds

width of 2nm

DNA Helicase

opens up the double helix, breaks the hydrogen bonds

DNA Polymerase

reads from 3’ to 5’ ends and assembles the nucleotides - matches up the bases

DNA Ligase

joins the phosphodiester bonds of the Okazaki fragments on the lagging strand

Semi-conservative DNA replication

produces two identical molecules of DNA

RNA

nucleic acid, messenger between DNA and ribosomes, involved in protein production

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

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)

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