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What did Frederick Griffith learn?
how certain types of bacteria caused pneumonia
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Griffith made 2 observations, what were they?
- 1. The disease-causing S-strain (virulent) strain of bacteria grew into smooth colonies o nculture
- 2. The harmless strain (R-strain) grew into colonies with rough strains
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How many experiments did Griffith do?
four
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What did Griffith do in experiment 1?
mice injected with disease-causing (virulent) strain of bacteria, mice got pneumonia= mice died
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What did Griffith do in experiment 2?
mice injected with harmless strain of bacteria= mice live
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What did Griffith do in experiment 3?
Griffith heated the disease-causing bacteria, injected the heat-killed bacteria into the mice= mice lived
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What did Griffith do in experiment 4?
heat-killed, isease-causing bacteria + live, harmless bacteria; injected the mixture into the mice = mice got pneumonia and died
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What was Griffith's transformation?
one strain of vacteria (harmless) had changed pemanently into another (disease)
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What did Griffith hypothesize?
a factor must contain info that could change harmless bacteria into disease-causing ones
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Who repeated Griffiths work in 1944?
Oswald Avery
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What was the first stage in Avery's experiment, and what was the result?
destroyed all macromolecules except DNA; transformation still occured
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What did Griffith conclude?
that heat killed bacteria passed their disease causing ability to the harmless strand
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What happened whaen Avery destroyed the DNA?
no transformation occurred
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What was Avery's conclusion?
transfomrming factor in bacteria= DNA
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In 1952, who worked with T2 bacteriophages, and what were they? What were the bacteriophages composed of?
Hershey and Chase; virus that infects and kills bacteria; composed of DNA core with a protein coat
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What did Hershey and Chase do in their experiment?
attaches to bacterium and injects its DNA(viral genes)- makes bacterium a virus factory- "hijacks" cell- produces new T2 bacteriophages and gradually destroys bacterial cells
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What was the result of Hershey and Chase experiment?
the bacterial cell splits open and hundreds of new viruses burst out of host cell
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What did Hershey and Chase determine?
it was the DNA that entered and infected the cell by using radioactive isotopes
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What is DNA made up of?
nucleotides
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What are the parts of DNA?
- sugar (deoxyribose)
- phosphate
- nitrogen base
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What are the four nucleotides of DNA?
- adenine
- guanine
- thymine
- cytosine
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What are Chargaff's Rules (base pairing rules)?
- 1. A is found in equal amount to T and C is found in equal amount to G
- 2.therefore, A=T and C=G
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What did Rosalind Franklin do?
used x-ray diffractioin to take a picture of DNA
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What did Watson and Crick do?
the used Franklins picture of DNA, and found out DNA is a double helix (twisted ladder)
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Where are prokaryotes DNA located?
cytoplasm
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What is single circular DNA?
one chromosome with several genes
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Where are eukaryotes DNA located?
nucleus
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What are DNA and protein (histones)?
chromatin
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Chromatin form bead like structure called____.
nucleosome
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Nucleosomes help do what/
fold long DNA to fit into the tiny spaces
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What are tightly coiled up chromatin?
chromosome
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What is DNA replication?
when the DNA molecule produces two complementary strands
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DNA replication starts at a single poin (replication fork) and _______.
proceeds in two different directions
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What unwinds and "unzips" DNA?
helicase
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What are broken between base pairs?
hydrogen bonds
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What are the differences between RNA and DNA?
- single strand of nucleotides
- sugar is ribose
- base pairing has uracil instead of thymine
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What are the types of RNA?
messenger, ribosomal, and transfer
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What is messenger RNA?
carries instructions for making proteins from DNA into ribosomes
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What is ribosomal RNA?
makes up ribosomes, helps assembal proteins
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What is transfer RNA?
transfers amino acids to the ribosome
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What is transcription?
making mRNA from DNA
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What are the steps of transcription?
- 1. mRNA makes a copy of DNA- RNA polymerse
- 2. starts at promoter site on DNA
- 3. RNA nucleotides pair up with DNA to make mRNA
- 4. mRNA leaves nucleus: goes to ribosome
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what is an exon?
expressed sequence of DNA- codes for protein
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What is an intron?
interrupting noncoding sequences of DNA- does not code for protein
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What are the steps of RNA editing?
- 1. mRNA strand introns cut out, so only exons left
- 2. Final mRNA transcrtipt= exon spliced together, cap and tail are added (prevents degradation/ damage on the way to ribosome)
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Why is this editing important to organisms?
- 1. one gene on DNA can be cut and spliced to make different RNA strands for different versions of a protein
- 2. role in evolution- very small changes in DNA have large effects in gene expresions
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What is a codon?
a sequence of 3 bases on mRNA that codes for a specific amino acid
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What is the genetic code?
3 bases read at a time= a one "word" (one amino acid)
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Four different letters used to code for how many amino acids?
20
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How many codons does one amino acid have?
it can have many
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What is the start codon?
AUG
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What are the stop codons?
UGA, UAA, UAG
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WHAT IS TRANSLATION?
decodin of mRNA into protein (polypeptide chain)
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What does translation begin with?
mRNA attatches to ribosome on start codon
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What are the steps of Translation?
- 1. each codon moves through rivosome and correct amino acid is brought to robosome by tRNA
- 2.anticodon on tRNA pairs with codon on mRNA
- 3.peptide bond forms between amino acids
- 4. mRNA move through until stop codon
- 5. New protein (polypeptide chain) and mRNA are released from ribosome`
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What are anticodon?
sequence of three bases on tRNA
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