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Which of the following build(s) new strands of DNA? |
DNA polymerases |
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Which statement about DNA replication is CORRECT? |
The leading strand is built continuously, and the lagging strand is built in pieces. |
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The molecule that seals the gaps between the pieces of DNA in the lagging strand is |
DNA ligase. |
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Which of the following events occurs during transcription? |
A molecule of RNA is formed based on the sequence of nucleotides in DNA. |
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mRNA? |
mRNA moves from the nucleus to the cytoplasm following RNA processing. |
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The site of translation is |
ribosomes in the cell cytoplasm. |
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does not play a role in translation? |
dna |
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Virus |
not considered to be alive, studied alongside other microbes such as bacteria |
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Capsid |
the protein coat that surrounds the nucleic acid of a virus |
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lytic cycle |
a viral life cycle that results in bursting of the host cell |
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lysogenic cycle |
a viral life cycle in which the virus inserts its genome into the genome of its host, where it may remain dormant for long periods. |
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Prophage |
a viral genome that has inserted itself into the genome of its host |
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Bacteriophage |
a virus that specifically infects bacteria. |
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In DNA, one nucleotide monomer is linked to the next through _____. |
covalent bonds between the sugar of one nucleotide and the phosphate of the next |
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During replication, the original "parent" DNA _____. |
serves as the template for the creation of two complete sets of DNA |
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central dogma follows the flow of information from _____. |
DNA to protein |
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DNA carries out two basic functions in cells: (1) information storage and transfer (genes can be copied and passed to offspring) and (2) the "blueprint" function (genes provide instructions for building proteins). The key process for information storage and transfer to offspring cells is _____. |
DNA replication |
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A gene is a sequence of DNA nucleotide bases that codes for a single protein. Approximately how many nucleotide bases would be required to code for a protein chain that is 100 amino acids long? |
300 |
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tRNA molecules work to _____. |
translate mRNA to produce a specific amino acid sequence |
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In transcription, _____. |
RNA polymerase links nucleotides to form mRNA. |
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An anticodon is _____. |
a set of triplet bases that is complementary to a codon triplet on mRNA |
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If protein production were an assembly line, a ribosome would be _____. |
the worker who puts all of the pieces together |
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At the start of translation, where does the initiator tRNA bind? |
start codon on the mRNA molecule |
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The translation process in eukaryotes requires all of the following: _____. |
transfer RNA, ribosomes, AUG codons |
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nucleotides |
that nucleic acids are polymers of subunits |
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two main kinds of nucleic acids |
1) DNA stores genetic information. 2) RNA transmits genetic information |
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Nucleotide Structure |
Each nucleotide consists of: a 5-carbon sugar a phosphate group a nitrogenous base |
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DNA nucleotide consists of |
a phosphate group, a 5-carbon sugar called deoxyribose, and one of four nitrogenous bases: Adenine Guanine Cytosine Thymine |
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RNA nucleotide consists of |
a phosphate group, a 5-carbon sugar called ribose, and one of four nitrogenous bases: Adenine Guanine Cytosine Uracil |
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pyrimidines. |
single-ring structures Thymine, cytosine, and uracil |
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purines |
double-ring structures Adenine and guanine |
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Structure of DNA |
DNA is formed of not one, but two parallel polynucleotides. The sugar-phosphate backbones face each other, with the nitrogenous bases pairing up in the middle. The entire molecule then twists, to form a double helix, or "twisted ladder." |
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Origins of Replication |
DNA replication does not proceed from one end of the DNA molecule to the other. DNA replication occurs at many places along the molecule at the same time. |
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Direction of Replication |
Recall that the two DNA strands are oriented in opposite directions. Each strand has a 3′ end and a 5′ end (referring to the number of the carbon on the 5-carbon sugar). |
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DNA polymerases |
enzymes that link the nucleotides together in replication |
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DNA ligase |
An enzyme, essential for DNA Replication, catalyzes the covalent bonding of adjacent DNA polynucleotides strands. It "stiches" DNA together. |
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Accuracy of Replication |
DNA replication is amazingly accurate, but mistakes do occur. Sometimes in base-pairing, the wrong nucleotide is added. Sometimes DNA is damaged by toxic chemicals or by radiation such as ultraviolet light |
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T A C G |
A T G C |
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Structure of RNA |
Like DNA, an RNA molecule consists of nitrogenous bases extending out from a sugar-phosphate backbone. Unlike DNA, RNA is a single-stranded molecule. |
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RNA’s function |
to transmit genetic information,by: Copying DNA (transcription) Turning the information into protein (translation) |
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Messenger RNA (mRNA) |
copies the genetic code on DNA during transcription, and takes it to the cytoplasm. |
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Ribosomal RNA (rRNA) |
forms the ribosomes, which provide a site for the assembly of amino acids into a protein during translation. |
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Transfer RNA (tRNA) |
brings the correct amino acids to the ribosome. |
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Transcription |
In transcription, the information on one gene is copied by one strand of mRNA. |
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RNA polymerase |
base-pairs nucleotides to form the mRNA strand. |
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A Brief Recap |
One gene codes for one protein. The code is copied by messenger RNA. The strand of mRNA leaves the nucleus via the nuclear pores, to be translated into a protein. |
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The Genetic Code |
The sequence of nucleotides in DNA contains the code that directs the order of amino acids in a protein. The genetic code is read in groups of three nucleotides. Each group of three is called a codon. Each codon codes for a specific amino acid. |
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Another Recap! |
One strand of the DNA molecule is transcribed to mRNA by complementary base-pairing. The sequence of codons for a protein begins with the start codon and ends with a stop codon. The protein begins with methionine Then AAG codes for lysine, then UUU codes for phenylalanine. The stop codon indicates that the protein has been completely assembled. |
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Exons |
coding regions of a gene that are actually "expressed," or translated into amino acids. |
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Introns |
Introns, or "intervening sequences," are non-coding regions between exons. These are sometimes called "junk DNA." |
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RNA "Processing" |
Before leaving the nucleus as mRNA, the transcript must undergo modification. Eukaryotic cells are able to edit out introns, and "cut and paste" exons, splicing them together and changing the sequence of nucleotides. RNA splicing of exons enables the cell to produce different kinds of polypeptides from a single gene. |
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Translation |
In the cytoplasm, the codons on mRNA are deciphered and amino acids are assembled to make a protein. |
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Translation requires: |
1) A strand of mRNA 2) Transfer RNA (tRNA) to read the code on mRNA and bring the correct amino acid. 3) Ribosomes (rRNA) to assemble the amino acids. |
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Initiation |
When the mRNA molecule arrives in the cytoplasm, it binds to the binding site on the small subunit of the ribosome. The anticodon of the first tRNA (the "initiator") binds to the start codon, bringing methionine as the first amino acid in the protein. |
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Elongation |
Once initiation is complete, amino acids are added one by one to the first amino acid. |
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Elongation three-step process. |
1) Codon recognition 2) Peptide bond formation 3) Translocation |
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Gene Mutations |
Recall that a chromosome mutation is a change in the number or the structure of an entire chromosome, and can often be detected visually with a karyotype. |
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gene mutation |
a change in the nucleotide sequence of DNA, affecting single genes. |
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Viruses |
non-living intracellular parasites. doesn’t have a metabolism. |
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A virus is a tiny packet of nucleic acid |
"programmed" to invade a living cell and hold it hostage |
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The virus works by |
forcing the host cell to synthesize viral components rather than its own proteins, essentially turning the cell into a "virus factory." |
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capsid |
The outer covering of a virus constructed of individual protein subunits, surrounds a core of nucleic acid |
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lytic cycle |
destroys the host cell. |
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The lysogenic cycle |
allows the host cell to also carry on its own business—at least for awhile. |
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Lytic Cycle |
1. Phage attaches to cell Phage DNA 2. Phage injects DNA 3. Phage DNA circularizes 4. New phage DNA and proteins are synthesized 5. Phages assemble 6. Cell lyses realeasing phages. |
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Lysogenic cycle |
After step three splits off 1.Phage DNA inserts into the bacterial chromosome by recombination. 2.Lysogenic bacterium reproduce normally, replicating the phophage at each cell division 3. Goes back into lytic cycle |
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