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Flashcards in Chapter 1-3 Deck (110)
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What are chromosomes made of?

DNA and proteins


What did Frederick Griffith do?

Discovered process of transformation using S and R strains of pneumonia on mice.


Describe Frederick Griffith's experiment, what is the difference between s and r strains?

S strain has a protective and SMOOTH polysaccharide capsule that can cause illness in rats.
R Strain has ROUGH capsule and does not cause illness.
Both strains are true-breeding.

Frederick injected a mouse with live R cells and DEAD S cells, but the mouse still died. Realized that in order for R bacteria can undergo transformation into S bacteria, there was some sort of substance that enabled R Cells to begin to synthesize smooth capsule coats.


Using knowledge of the concentration of base pairs, how could you determine whether the DNA of an organism is single stranded or double stranded?

An organism would have the same concentrations of complimentary base pairs (A)=(T) etc. A single stranded organism would have differing concentrations of bases because the bases on a single strand are not complimentary to each other.


What did Oswald Avery et. al. do?

discovered that transformation was caused by DNA


Describe Oswald Avery's experiments

If mouse was injected with mixture of destroyed SRNA and protein in live R cells, transformation from R to S still occurred and mouse died.

If mouse was injected with mixture of destroyed SDNA in live R cells, transformation from R to S did not occur and mouse still lived.

Concluded that dna of s needed to be present in order for R to transform into S


Who conducted the blender experiment?

Hershey and Chase


What did Hershey and Chase conclude

demonstrated that DNA and not protein directed the production of progeny T2 Phages


Describe Hershey and Chase experiments

tagged either phage DNA with 32P or phage protein with 35S in separate trials, and injected them into e.coli cells.
Ecoli was swirled into a blender to remove phage material from the cell surfaces

When analyzed, they noticed that 32P was integrated into the ecoli, whereas 35S was mainly outside of the cells.
Therefore, the T2 phage transfers most of its DNA into the bacteria in order to replicate, but very little protein.


What is the general structure of DNA that Watson and Crick Proposed?

-proposed the first correct 3D structure of DNA
-2 Long chains of nucleotide subunits, running antiparallel in a polarized fashion


What did Watson and Crick infer about the probable mechanisms of replication, coding, and mutation from their proposed structure?

Replication: one strand can act as a template in order to form a complimentary strand. One DNA duplex can produce two identical duplexes.

Coding: genetic information could be coded by the sequence of bases along the DNA molecule

Mutation: changes in genetic information could results from errors in replication


Why did Hershey and Chase choose to study a bacteria phage?

DNA was stored in the head while the rest of the phage was mostly protein. This compartmentalization allowed for easy tagging because the head contents were transfeered into the bacteria, while majority of the protein would be left outside the cell.


What can you conclude about the equal percentages of A,T,G, and C in an organism

The amount of A=T, and the amount of G=C. Therefore, adenine and thiamine must pair together, and guanine and cytosine must pair together. In order for the bases to pair with each other, the DNA is most likely double stranded.


In vitro, how many reading strands can a DUPLEX of DNA make?
In vivo?

In vitro: 6 reading strands per duplex; 3 reading per single strand. This is because in vitro, hybridization can occur at any point without the need for a start codon.

In Vivo: 2 reading strand; one reading strand per single strand. In vivo/cell, DNA polymerase needs a start methionine codon in order to begin synthesis of the other chain.


Characteristics of Purines

2 rings, adenine and guanine


Characteristics of Pyramidine

1 ring, thiamine, uracil and cytosine


What direction does DNA synthesis occur in? How is the template strand read?

Synthesis in 5'-3'. Therefor, the template strand is read in 3'-5' direction. One strand is therefor made continuously (the one using 3'-5' template), and the other strand is synthesized in fragments (5'-3' template)


What did Archibald Garrod propose

Inborn Errors of Metabolism, studied alkaptonuria


What is the proposal of Inborn Errors of Metabolism?

Any hereditary disease resulting in abnormal cellular metabolism is a result of an INHERITED deficient/defective enzyme


Characteristics of Alkaptonuria

black urine disease caused by excretion of accumulated homogentistic acid. HA cannot be broken down because of defective 1,2, dioxygenase enzyme.


Characteristics of Phenyl Ketonuria

Disease that results in mental retardation because of the accumulation of phenylalanine. Phenylalanine cannot be broken down into tyrosine, due to defective phenylalanine hydroxylase (PAH) enzyme. Phenylalanine then crosses the blood brain barrier and then affects an individuals myelin in neurons.


What did Beadle and Tatum do?

found the connection between genes and enzymes by studying N.Crassa fungus. Each set of mutation, and therefore each individual gene, corresponds to one enzymatic step in a metabolic pathway

Concluded: each block corresponded to a defective enzyme and prevents the metabolic pathway from running to completion. A defective enzyme is a result from a defective gene.


What is a mutant screen?

the isolation of a set of mutants affecting any biological process.


Complementation Test

Process where 2 mutations are mated in order to identify mutations that have defects in the same gene.


Complementation vs non complementation

Complementation (+)= normal offspring from two mutants are produced, and mutations were thus on different genes. Usually produces a 9:7 phenotypic ratio is F2

non Complementation (-)= mutant offspring from two mutants are produced, and thus the mutations from both parents were on the SAME gene.


Define central dogma

the idea that information flows from DNA to the phenotypic effect via DNA--> RNA-->Protein. The sequence of nucleotides in a DNA Gene specifies the sequence of nucleotides in RNA, which specifies the sequence of amino acids in a polypeptide chain

The genetic code for a protein is contained in ONE STRAND, and it is decoded in a linear order 5'-3'



- RNA is single stranded, DNA is double
- In RNA, thiamine is replaced with uracil
- RNA incorporates ribose sugar instead of deoxyribose
- 3 different types of RNA; mRNA, tRNA and rRNA


Which enzyme makes transfer Rna

aminoacyl-tRNA synthetase


Start codon?

Methionine, AUG


Define Wobble Hypothesis

anti-codon of a specific tRNA may recognize 2 or more codons. Base pairing must be between a purine and a pyrimidine