bio ch 12
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What did Frederick Griffith learn?
how certain types of bacteria caused pneumonia
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
How many experiments did Griffith do?
What did Griffith do in experiment 1?
mice injected with disease-causing (virulent) strain of bacteria, mice got pneumonia= mice died
What did Griffith do in experiment 2?
mice injected with harmless strain of bacteria= mice live
What did Griffith do in experiment 3?
Griffith heated the disease-causing bacteria, injected the heat-killed bacteria into the mice= mice lived
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
What was Griffith's transformation?
one strain of vacteria (harmless) had changed pemanently into another (disease)
What did Griffith hypothesize?
a factor must contain info that could change harmless bacteria into disease-causing ones
Who repeated Griffiths work in 1944?
What was the first stage in Avery's experiment, and what was the result?
destroyed all macromolecules except DNA; transformation still occured
What did Griffith conclude?
that heat killed bacteria passed their disease causing ability to the harmless strand
What happened whaen Avery destroyed the DNA?
no transformation occurred
What was Avery's conclusion?
transfomrming factor in bacteria= DNA
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
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
What was the result of Hershey and Chase experiment?
the bacterial cell splits open and hundreds of new viruses burst out of host cell
What did Hershey and Chase determine?
it was the DNA that entered and infected the cell by using radioactive isotopes
What is DNA made up of?
What are the parts of DNA?
- sugar (deoxyribose)
- nitrogen base
What are the four nucleotides of DNA?
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
What did Rosalind Franklin do?
used x-ray diffractioin to take a picture of DNA
What did Watson and Crick do?
the used Franklins picture of DNA, and found out DNA is a double helix (twisted ladder)
Where are prokaryotes DNA located?
What is single circular DNA?
one chromosome with several genes
Where are eukaryotes DNA located?
What are DNA and protein (histones)?
Chromatin form bead like structure called____.
Nucleosomes help do what/
fold long DNA to fit into the tiny spaces
What are tightly coiled up chromatin?
What is DNA replication?
when the DNA molecule produces two complementary strands
DNA replication starts at a single poin (replication fork) and _______.
proceeds in two different directions
What unwinds and "unzips" DNA?
What are broken between base pairs?
What are the differences between RNA and DNA?
- single strand of nucleotides
- sugar is ribose
- base pairing has uracil instead of thymine
What are the types of RNA?
messenger, ribosomal, and transfer
What is messenger RNA?
carries instructions for making proteins from DNA into ribosomes
What is ribosomal RNA?
makes up ribosomes, helps assembal proteins
What is transfer RNA?
transfers amino acids to the ribosome
What is transcription?
making mRNA from DNA
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
what is an exon?
expressed sequence of DNA- codes for protein
What is an intron?
interrupting noncoding sequences of DNA- does not code for protein
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)
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
What is a codon?
a sequence of 3 bases on mRNA that codes for a specific amino acid
What is the genetic code?
3 bases read at a time= a one "word" (one amino acid)
Four different letters used to code for how many amino acids?
How many codons does one amino acid have?
it can have many
What is the start codon?
What are the stop codons?
UGA, UAA, UAG
WHAT IS TRANSLATION?
decodin of mRNA into protein (polypeptide chain)
What does translation begin with?
mRNA attatches to ribosome on start codon
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`
What are anticodon?
sequence of three bases on tRNA
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