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168 Cards in this Set
- Front
- Back
What is the most common way to examine gene functions? Who discovered this way? |
Using loss of function alleles, or knock out alleles that are defective and don't work. Beadle and Tatum |
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One gene, One Enzyme hypothesis |
Claimed that each gene contains the information needed to make an enzyme |
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Metabolic Pathway |
The steps that organisms synthesize arginine |
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How did Horowitz and Srb test the one gene one enzyme hypothesis? |
They used radiation to create a large number of mutant cells and used a genetic screen to find out the specific gene that knocked out a step in the pathway and documented a correlation between specific genetic defects and defects at a specific point in a metabolic pathway |
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Genetic Screen |
Any technique for picking certain types of mutant out of many randomly generated mutants |
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What do genes do? |
Contain instructions for making proteins |
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The Genetic Code Hypothesis |
Cricks proposal that different combinations of different bases could specify the 20 amino acids, just as different combinations of dots and dashes specify the 26 letters of the alphabet |
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Messenger RNA |
Short lived RNA molecules that act as carriers for genetic information out of the nucleus from the DNA to the site of protein synthesis |
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RNA Polymerase and how does it function? |
Polymerizes ribonucleotides into strands of RNA and does this according to the information provided by the sequence of bases in a particular stretch of RNA |
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The central dogma |
Summarizes the flow of information in cells, so genes basically code for protiens |
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Transcription |
Process of copying hereditary information in DNA to RNA |
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Translation |
The process of using the information in nucleic acids to synthesize proteins |
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Phenotype |
Physical traits that are the result of the proteins produced by the sequence of bases |
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Genotype |
determined by the sequence of bases in DNA |
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Reverse Transcriptase |
A specialized viral polymerase synthesizes a DNA version of RNA genes. Therefore, the information flows from RNA back to DNA. That is "reverse" from the way that DNA flows into RNA according to the central dogma
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Genetic Code |
The rules that specify the relationship between a sequence of nucleotides in DNA or RNA and the sequence of Amino Acids in a protein. |
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Who came up with the Triplet Code Hypothesis? What is the Triplet Code and how many bases different amino acids can it represent? |
George Gamow came up with the hypothesis of the Three base code for an amino acid, allowing for 64 different amino acid to be represented in the sequence. |
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Codon |
Three base code that specifies a particular amino acid |
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Reading Frame |
Sequence of codons |
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Start Codon |
Signalsthat protein synthesis should begin at that point on the mRNA molecule.Thestart codon specifies the amino acid methionine
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Stop Codon |
Called termination codons, signal that the protein iscomplete, they do not code for any amino acid, and they end translation.
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What are the different properties of the genetic code? |
The code is redundant- Amino acids are coded by more than one codon The code is unambiguous- a single codon only codes for one protein The code is non overlapping- once the ribosome locks onto a codon, it reads each separate codon after that The code is nearly universal- All codons specify the same amino acids in all organisms The code is conservative- When two codons specify the same amino acid, the first two bases are almost always identical. |
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Nirenberg and Leder |
They devised a system for synthesizing specific codon, and were able to determine which of the 64 codons coded for each of the 20 amino acids |
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Mutation |
Any permanent changes in an organisms DNA , or a modification to the cells information archive causing a change in its genotype. Mutations create new alleles.
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Whatdoes having the code be conservative serve to do in an organism?
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Ifa DNA error occurs during translation, having the only the third codon affectedit is less likely to change the amino acids in the final protein.
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Whatare the two things that biologists can predict and determine using the geneticcode?-
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Predict the codons and amino acid sequence encoded by aparticular DNA sequence. Determine the set of mRNA and DNA sequences that wouldcode for a specific set of amino acids.
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Alleles |
One or more form of a gene caused by mutations and are found at the same place as a chromosome |
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Point Mutation |
A mistake during DNA synthesis that results in a mutation in which a single based is changed |
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Missense Mutation |
A Point mutation that causes a change the amino acid sequence of a protein |
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Silent Mutation |
A point mutation in which the change of the single base does not affect the sequence of amino acids |
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Frame-shift Mutation |
A point mutation in which the deletion or addition of a single base causes the whole amino acid sequence to be thrown off and alters the meaning of all subsequent codons. |
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What are the three categories that biologists divide mutations into? |
Beneficial, nuetral, and deleterious. Beneficial- Any mutation that increases the fitness of an organism. Nuetral- any mutation that doesn't have an affect on the fitness of an organism. Deleterious- any mutation that lowers the fitness of an organism. |
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what are the four different types of chromosome mutations? |
Inversion, Translocation, Deletion, Duplication |
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Inversion |
A chromosomal mutation in which the segments of a chromosome may be flipped and rejoined |
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Translocation |
A chromosomal mutation in which a segment of a chromosome becomes attached to another chromosome |
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Deletion |
A chromosomal mutation in which a segment of a chromosome is lost |
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Duplication |
A chromosomal mutation in which additional copies of a segment are present |
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aneuploidy |
Addition or deletion of individual chromosomes
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Polyploidy |
The addition in the number of chromosomes |
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Transcription |
The conversion of genetic information from DNA to RNA specifically mRNA |
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Beadle and Tatum proposed the one-gene, one-enzyme hypothesis based on __________.
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Knock out mutants that lacked the ability to synthesize certain compounds |
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Knock Out Allele |
A gene altered so that it no longer produces intended proteins |
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Describe the genetic screen done by Srb and Horowitz to determine the metabolic pathway for arginine synthesis.
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The key design in their study was that they found three different mutants and raised them with different intermediates in the arginine pathway. This allowed them to demonstrate that each mutant (or gene) was responsible for a particular enzyme along the pathwa |
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What is the function of mRNA?
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To carry information from DNA out of the nucleus to the site of protein synthesis |
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What required the rethinking of the central dogma theory? |
The discovery of retroviruses and their mechanism of replication required scientists to rethink the central dogma of molecular biology. Based on this information, RNA → DNA → RNA → protein represents an appropriate adjustment to the central dogma.
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Which enzyme allows RNA to be coded into DNA?
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Reverse Transcriptase |
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What is an exception to the central dogma of molecular biology? |
Single stranded RNA from a virus is used as a template for producing DNA that inserts into the host genome. This uses reverse transcriptase to synthesize the DNA to RNA |
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HIV virus is an example of a virus that uses what polymerase? |
Reverse transcriptase. Several prescribed drugs for AIDs patients fight the infection by poisoning the HIV reverse transcriptase. |
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How many amino acids are represented in the genetic code by just one codon?
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2- Tryptophan and Methionine |
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Nonsense Mutation |
A point Mutation that causes an early termination of protein synthesis because the change causes the sequence for a stop codon. |
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How many types of RNA polymerase do Eukaryotic cells have? |
3 |
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What is RNA Polymerase, does it need a primer? |
It is the enzyme that is responsible for synthesizing mRNA from the template strand, and there is no primer needed, unlike DNA polymerase |
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Template Strand |
The Strand that is read by the enzymes. |
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Coding Strand |
The strand that is not the template strand, whose sequence matches that of the RNA that is transcribed from the template strand to code for the polypeptide |
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Bacteria have how many versions of RNA polymerase? |
1 |
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What base does RNA have that differs from that of DNA |
Uracil |
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Whatdirection does RNA polymerase perform template directed synthesis?
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Always in the 5' to 3' direction |
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What is the initiation phase in bacteria, and it involves what enzyme and group of proteins? |
A stage in transcription in which the RNA polymerase ishelped by a protein that signals where to start transcription. |
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Sigma |
Promoter recognizing protein subunit of bacterial RNA polymerase holoenzyme |
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Whatdoes the Bacterial RNA polymerase and Sigma form?
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Holoenzyme |
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What does a holoenzyme consist of? |
A core enzyme ( RNA polymerase) which contains the activesite for analysis, and then a group of proteins (sigma)
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When does transcription begin in bacteria? What makes initial contact with the promotor? |
When sigma binds to the -35 and -10 boxes.This will determine in which direction the RNA polymerase will start synthesize RNA |
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What happens after the holoenzyme is bound to the promotor? |
The DNA helix is opened by RNA polymerase, creating two separate strands of DNA |
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Elongation phase of transcription- When does it begin and what is it? |
It is the phase that begins once the RNA polymerase begins moving along the DNA template synthesizing RNA
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Termination phase of transcription |
In bacteria, transcription stops when RNA polymerase transcribes a DNA sequence that functions as a transcription-termination signal |
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RNA polymerase II |
The only polymerase that transcribes protein-encoding genes |
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TATA Box |
Eukaryotic promotor sequence centered about 30 base pairs upstream of the transcription start site. |
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Basil Transcription Factors |
The protein used instead of sigma in order for RNA polymerase to recognize promoters |
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How is eukaryotic transcription terminated? |
Using a short sequence called a poly signal. Soon after the signal is transcribes, the RNA is cut down by an enzyme downstream of the poly signal. |
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Primary Transcript |
The initial product of transcription. The RNA needs to undergo multistep processing before it is functional |
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What did Sharp and Roberts discover? |
The presence of introns-sections of genes that are not expressed in the final RNA product. |
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What is Splicing? What protein is involved? |
The process in which the introns within the growing RNA strand are removed.The splicing of introns is catalyzed by RNA's called small nuclear RNA's (nRNA) and works with a complex of proteins called small nuclearribonucleoprotiens (snRNP's). |
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Describe the process of Splicing RNA within the nucleus |
1. snRNPs bind to the start of intron and an A base within the intron 2.snRNP's assemble to form a splicosome ( a complex group of proteins 3.Intron forms a loop 4 The loop is cut, and phosphodiester linkages links the exons on either side, producing a continuous coding sequence- the mRNA |
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What is the step after splicing to complete RNA processing in eukaryotes? How do they help? |
Adding caps and tails. They help to protect from degradation along with enhancing the efficiency of translation. |
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Which end are caps added to, and what are they? |
The caps are added to the 5' end of the pre-mRNA emerges from the RNA polymerase by enzymes, and are composed of a modified guanine nucleotides |
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Which end are poly(A) tails added to, and what are they? |
To being, an enzyme cleaves the 3' end of the pre-mRNA, then another enzyme adds a long row of 100-250 adenine nucleotides downstream of the poly signal. |
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How do the untranslated region help the mRNA? |
The regions help stabilize the mature RNA and regulate its translation. |
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Translation |
The translation of RNA molecules into a sequence of amino acids in a polypeptide. |
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Where does protein synthesis occur? |
They are synthesized at the ribosome and then released |
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Why do transcription and translation occur concurrently in bacteria? |
Because there is no nuclear envelope to separate the two processes |
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Describe translation in Bacteria. |
Ribosomes attach to mRNA's and begin synthesizing proteins even before transcription is complete. Multiple ribosomes attach to each mRNA forming polyribosomes, |
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Describe Translation in Eukaryotes. |
The mature mRNA is exported to the cytoplasm. This means that translation and transcription occur separately in time and space. As in bacteria, polyribosomes form. When mRNA interacts with a ribosome, instructions encoded in nucleic acids are translated into a different chemical language- the amino acid sequences found in proteins. Transfer RNA transfers the amino acids from the RNA to a growing polypeptide. |
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Anticodon |
A set of three nucleotides that forms base pairs with the mRNA codon |
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What is universal of the structure of tRNAs?How do they differ? |
They are shaped like an upsidedown "L". They vary at the anticodon and attached amino acid. |
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How are amino acids attached to RNA's? |
Enzymes called ammoniacal-tRNA syntheses catalyze the addition of amino acids to tRNA's. Each enzyme has a binding sight for a particular amino acid and a particular tRNA. |
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aminoacyl-tRNA |
The combination of a tRNA molecule covalently linked to an amino acid. |
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Wobble Hypothesis |
the hypothesis that states that non standard base pairs like G U are acceptable in the third position of a codon and do not change the amino acid that the codon specifies. |
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Ribosomes, and the three step protein synthesis process. |
Ribosome is a macromolecular machine that synthesizes protein as follows: 1)An ammoniacal tRNA diffuses into the A site; if its anticodon matches a codon on mRNA , it stays in the ribosome. 2.)A peptide bond forms between the amino acid held by the ammoniacal tRNA in the A site and the growing polypeptide, which was held by tRNA in the P site. 3) The ribosome moves down the mRNA by one codon, and all three tRNA's move one position within the ribosome. The tRNA in the E site exits; the tRNA in the P site moves to the E, and the tRNA in the A site switches to the P site. |
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N terminus and C terminus |
The N terminus is the amino end of a polypeptide, and the C terminus is the carbozyl end of the polypeptide |
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How is translation initiated? |
1)The mRNA binds to a small ribosomal subunit 2)the initiator ammoniacal tRNA binds to the start codon 3)The large ribosomal subunit binds, completing the complex |
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When is the invitation phase of translation complete? |
When the large subunit joins the complex |
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Initiation Factors |
Proteins that mediate the interactions between the small sub unit of the ribosome, the mRNA and the tRNA. They help prepare the ribosome for translation and bind the first aminoacyl tRNA |
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Elongation Phase of Translation |
The phase in which the polypeptide is extended. |
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What are the three sites of the large subunit of the ribosome? Which performs which action? |
The A site, the P site, and the E site. A site- Active Site Accepts the new tRNA's where its anticodon base pairs with the mRNA codon P Site-Peptide bonds form E site- Exit Site |
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Describe the process of elongation |
tRNA anticodon pairs with mRNA codon Peptide Bond Forms The polypeptide chain moves one codon down the mRNA |
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What catalyzes the formation of peptide bonds on the active site during translation? |
RNA |
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Translocation |
The process in which thee polypeptide chain is transferred from the tRNA in the P site to the amino acid held by the tRNA in the A site. This opens up the A site, and the tRNA found in the E site is ejected into the cytosol. This is made possible by elongation factors. |
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How is translation terminated? |
When the translocating ribosome reaches one of the stop codons, a protein called a release factor recognizes the stop codon and fills the A site. |
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Post translational Modifications |
This includes the step requires before a protein is functional. This include the folding- which is speeded up by proteins called molecular chaperones, and chemical modifications like phosphorylations, or the addition of sugar or lipid groups. |
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TATA Box |
Eukaryotic promoter sequence centered about 30 base pairs upstream of the transcription start site. |
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What are Amino Acids and what is their common structure? |
The building blocks of proteins- there are twenty. The structure consists of: 1.H- a hydrogen atom 2. NH2- Amino acid functional group 3.COOH-A carboxyl functional group 4.A distinctive R-group |
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What part of an amino acid is acidic? Why is it acidic? |
The carboxyl group- it is acidic because two oxygen atoms are highly electronegative |
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R-groups |
Varying side chains of Amino acids. Each of the 20 R-groups is unique |
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What are the 3 most common structural formulas of side chains? What do they mean? |
Non polar side chains-No charge
Polar Side chains-Partial charges form hydrogen bonds Electrically charged side chains- Charged side chains can form ionic and hydrogen bonds. |
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What do different R- groups affect? |
The reactivity of an amino acid Solubility-some dissolve and and some don't depending on whether they are polar or non polar |
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What are the three questions to determine what type of amino acid it is? |
1)Does the side chain have a negative charge? If so, it has lost a proton and is acidic 2)Does the side chain have a positive charge? if so, it has taken a protein so it must be basic 3)If the side chain is uncharged, does it have an oxygen atom? If so, it is an uncharged polar. If all three questions are no, then the amino acid is non polar. |
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Monomer |
Molecular subunit like an amino acid. |
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Polymer |
When a large number of monomers are bonded together |
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Polymerization |
The process of linking monomers together |
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Macromolecule |
Biologists use this word to denote a very large molecule made up of similar molecules joined together. |
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Proteins |
Macromolecules, or polymers that consist of amino acid monomers. |
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How do monomers polymerize? |
Through condensation or dehydration reactions The newly formed bond between monomers results in the loss of a water molecule |
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Hydrolysis |
Breaks polymers apart by adding a water molecule, which reacts with the bonds, then separates one monomer from the polymer chain |
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Peptide bond |
The C-N covalent bond that forms from a condensation reaction. They are usually stable linkages |
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What are the three key points to note about the peptide bonded backbone |
1)R-group directionality-The side chains extend out from the back bone and make it possible for them to react with each other and with water 2)Directionality- N terminus (Where protein synthesis begins) to C- terminus 3)Flexibility-The single bonds on either side of the peptide bond can rotate, so the structure as a whole is flexible. |
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Polypeptide |
Polymers that contain 50 or more amino acids |
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Protein |
Often used to describe any chain of amino acids, but refers to complete functional form of the molecule. |
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Primary Structure of Proteins |
The unique sequence of amino acids in a protein. The number of combinations of the acids are limitless. |
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Secondary Structure of proteins |
The second level of the hierarchy created by hydrogen bonding between components of the peptide bonded backbones. The hydrogen bonds form alpha helix or beta pleated sheet |
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Ionic Bonding |
Ionic bonds form between groups that have full and opposing charges, such as the ionized acidic and basic side chains |
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Quaternary structure of a protein |
When proteins contain multiple polypeptidess that interact to form a single structure, this combination of polypeptides gives protein a quaternary structure |
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Macromolecular Machines |
Groups of proteins that assemble to carry out a particular function |
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How is protein folding directed? |
By the sequence of amino acids present in the primary structure |
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Denatured (Protein) |
Unfolded- this happens by treating proteins with compounds that break hydrogen bonds and disulfide bonds |
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Molecular Chaperones |
Proteins that help to facilitate protein folding. They belong to a family of proteins called heat-shock proteins |
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Protein function is depended on what? |
A proteins shape, controlling when or where it is folded will regulate the proteins activity |
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Prions |
Proteins that folded into infectious, disease-causing agents. The infectious form propagates by inducing conformational changes in normal proteins that cause them to adopt the alternative, infectious shape. |
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What does the final shape of a protein depend on? |
The proteins folding, or the function of protein |
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Proteins are crucial to most tasks for cells to exist. These 6 are... |
Catalysis Defense Movement Signaling Structure Transport |
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Active Site |
The location where the substrate binds to the enzyme and where catalysis occurs |
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Why are enzymes good catalysts? |
They bring reactant molecules, called substrates, together in precise orientation so he atoms involved in the reaction can interact. |
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Fertilization |
The process of uniting a sperm and an egg |
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Gametes |
Reproductive cells such as sperm and eggs |
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Who hypothesized gamete formation and how did he do it? |
August Weissman proposed that there must be a distinctive type of cell division that leads to the reduction in chromosome numbers |
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Meiosis |
Nuclear division that leads to a halving in of chromosome number and ultimately to the production of the sperm and egg. |
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sex chromosomes |
The X and Y chromosomes that are associated with an individuals sex. |
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Autosomes |
Non sex chromosomes |
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Homologous Chromosomes |
Chromosomes that are the same size and shape, and have the same content or the same genes. They can, however carry different alleles. |
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Gene |
A section of DNA that influences some hereditary trait of an individual |
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Allele |
Different versions of the same gene. For example, the gene for eye color is the same. But homologs can contain different alleles which are blue and green eye color. |
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Karyotype |
The number and types of chromosomes present |
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Diploid |
Organisms that have two alleles of each gene i.e. humans, insects, trees |
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Haploid |
Organisms whose cell contains just one type of each chromosome. ie bacteria, fungi |
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Haploid number |
The letter n that stands for the number of distinct types of chromosomes in a given cell |
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Ploidy |
Combination of sets and n is termed the cells ploidy Diploid cells are designated 2n, because two chromosomes of each type are present-one from the mother and one from the father |
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Polyploidy |
Having three or more of each type of |
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What happens in Meiosis 1? |
The homologs in each chromosome pair separate from each other, and two haploid cells are created |
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What happens in Meiosis 2?
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sister chromatids from each chromosome separate. The cells produced by Meiosis 2 also have one of each type of chromosome, but now the daughter chromosomes are no longer replicated |
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How do chromosomes move during Meiosis? |
By microtubules of the spindle apparatus that attaches to kinetochores located at the centromere of each chromosome. |
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When does meiosis begin? |
after chromosomes have been replicated in the S phase |
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Early Prophase 1 |
The stage in Meiosis one in which the chromosomes condense, spindle apparatus forms, the nuclear envelope starts to break down, and the homologous pairs come together |
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Synapsis |
The pairing of homologous chromosomes that creates a bivalent or a tetrad |
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Late prophase 1 |
The second stage of meiosis 1 in which the nuclear envelope breaks down and microtubules of the spindle apparatus attach to kinetochores. Non sister chromatids begin to separate |
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Chiasmata |
The crossover points where the chromosome stays joined at certain locations |
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Crossing Over |
The reciprocal changes between different homologs that creates non sister chromatids that have both paternal and maternal segments. This increases diversity of genes. |
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Metaphase 1 |
The third stage of meiosis 1 in which the kinetochore microtubules move the pairs of homologous chromosomes to a region called the metaphase plate in the middle of the spindle apparatus |
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Anaphase 1` |
The fourth stage of Meiosis 1 in which the homologs separate and begin moving toward opposite ends of the cell |
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Telophase 1 and Cytokinesis |
Chromosomes move to opposite poles of the spindle apparatus and the spindle apparatus disassembles |
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Prophase 2 |
The first stage of meiosis 2 in which the spindle apparatus forms, nuclear envelope breaks apart |
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Metaphase 2 |
The second stage of Meiosis 2 in which Replicated chromosomes, consisting of two sister chromatids, are lined up at the metaphase plate |
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Anaphase 2 |
The third stage of Meiosis 2 in which the sister chromatids separate and the daughter chromosomes that result begin moving to opposite poles of the spindle apparatus |
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Telophase 2 |
The last phase of Meiosis 2 in which the chromosomes move to opposite poles of the spindle apparatus. A nuclear envelope forms around the haploid chromosomes. |
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Cohesins |
The proteins that hold the sister chromatids together |
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synaptonemal complex |
A network of proteins that holds the two homologs tightly together |
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Asexual Reproduction |
any mechanism of producing offspring that does not involve the production and fusion of gametes. It produces exact clones of the parents. |
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How many pairs of chromosomes does each cell in our bodies contain |
23 pairs, so 46 chromosomes in total |
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Genetic recombination
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The appearance of new combinations of alleles |
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The principle of independent assortment |
The phenomena that each daughter cell gets a random assortment of maternal and paternal chromosomes |