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Unit 6B Test AP Bio
Terms in this set (93)
Where do nucleotides add on to during DNA replication?
What holds the 2 strands of DNA together?
What is the difference between the leading strand and the lagging strand in DNA replication?
Leading strand synthesizes continuously, lagging strand synthesizes discontinuously in Okazaki fragments.
What is added to the 5' and 3' end of mRNA to protect it from enzymes in the cytoplasm?
5' cap (GTP) and a 3' poly A tail (AAAAAAAAAAA)
What is the role of DNA polymerase I?
To replace RNA primer with DNA during replication. Also has proofreading capabilities.
What is transcription?
Transcription- going from DNA to RNA
What is translation?
Going from RNA to protein
What is the role of RNA primase?
To create an RNA primer to prime DNA synthesis.
What is a telomere?
Protection sequences on the ends of our chromosomes. Added with the enzyme telomerase.
DNA strands run in____________ directions. They are termed____________.
What does it mean to say there is redundancy in our genetic code?
More than one codon can code for the same amino acid.
What is Chargaff's rule?
A binds with T
G binds with C
DNA is replicated in a ________________ manner, where one parent strand serves as a template for a new daughter strand.
What unwinds the DNA helix in order to begin replication?
What is the enzyme that adds nucleotides to a replicating strand?
DNA polymerase III
What is the central dogma of gene expression?
DNA --> RNA --> Protein
What is the purpose of primer? What is it made of?
To prime DNA synthesis, it is made of RNA.
Why do chromosomes shorten after every replication cycle?
Every replication cycle, RNA primer is not replaced with DNA at the ends of the chromosomes, therefore the chromosomes get shorter with every replication.
What is the role of single stranded binding proteins?
They prevent the double helix from reannealing after the strands are separated.
DNA is synthesized from a________ to_________________direction.
5' --> 3'
What are the 3 main components of a protein-coding gene?
Promoter, RNA coding sequence, and the terminator.
Name three types of RNA.
mRNA (messenger), tRNA (transfer), rRNA (ribosomal)
What is the difference between prokaryotic and eukaryotic transcription/translation?
Eukaryotes- have mRNA processing. Transcription occurs in nucleus, translation occurs in cytoplasm.
Prokaryotes- no mRNA processing. Transcription and translation occur in cytoplasm.
What are the purines and the pyrimidines? Which ones have 2 rings and which ones have a single ring?
Purines- adenine, guanine (2 rings)
Pyrimidines- cytosine, thymine, uracil (1 ring)
What is the enzyme that carries out transcription?
What binds to the promoter?
RNA polymerase II
How does RNA polymerase II recognize promoters in eukaryotes and prokaryotes?
Transcription factors in eukaryotes. Sigma factors in prokaryotes.
The consensus sequence for a promoter region can typically be found in the -_____ and -______ region, relative to the transcriptional start site (+1).
-35 and -10
Eukaryotes have a ________ box in the promoter.
How is transcription terminated?
When RNA polymerase hits the terminator sequence, a hairpin loop forms in the mRNA, which causes RNA polymerase to fall off and stop transcription.
What is the purpose of DNA ligase?
Ligate okazaki fragments together.
What are introns and exons?
Introns are the inbetween sequences that are later excised from mRNA. Exons are the sequences that are spliced together in a mature mRNA.
How are introns excised?
Spliceosomes and snRNP's.
What protein carries out translation?
Where does translation begin? Where does it end?
Ribosome binds to a sequence just upstream of the start codon, which codes for the beginning of the AA sequence. Stop codon stops the translation process.
How does a tRNA recognize an mRNA?
Anticodon recognizes the codon.
RNA is built in the ____________ to____________ direction.
5' --> 3'
TACGCA is the DNA sequence. Transcription occurs. What is the sequence of our mRNA?
What does AUG code for?
Start codon (methionine).
How many stop codons are there? What are they?
3 (UAA, UAG, UGA)
What is a codon?
Groups of 3 nucleotides, how we read genetic sequences.
__________ is attached to the 3' end of the tRNA.
How many subunits make up a ribosome?
What is the A, P, and E site for on a ribosome?
A- waiting period for next tRNA
P- main site for tRNA with growing AA sequence
E- exit site to get rid of tRNA's that have been used
What is the promoter?
A site where RNA polymerase can bind to DNA and begin transcription.
What is the operator?
Controls the access of RNA polymerase to the genes.
What is the regulatory gene?
A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.
What is a repressor?
It inhibits gene transcription.
What is an inducer?
It binds to a bacterial repressor protein and changes the repressor's shape so that it cannot bind to an operator, thus switching an operon on.
What is a corepressor?
It binds to a bacterial repressor protein and changes the protein's shape allowing it to bind to the operator and switch and operon off.
What is the trp operon?
Repressible operon. (usually on)
What is the lac operon?
Inducible operon. (usually off)
What is differential gene expression?
The expression of different genes by cells with the same genome.
At which stages can gene expression be regulated? Which is the most commonly regulated stage?
They can be regulated at any stage. The main control point for many genes is transcription.
Explain how histone acetylation and DNA methylation regulate gene expression.
Histone acetylation loosens the DNA (increases expression). DNA methylation blocks transcription factors (decreases expression).
What is the role of microRNA's in the control center of cellular function?
Capable of binding to complementary sequences in mRNA molecules. miRNA allows the complex to bind to any mRNA molecule with 7-8 nucleotides of complementary sequence.
What is a bacteriophage?
A virus that infects bacteria; composed of DNA and protein.
What did James Watson and Francis Crick discover?
The double helix by building models using Rosalind Franklin's X-ray data.
What are the backbones of the double helix? Rungs?
Sugar and phosphate are the backbone. Nitrogenous bases are the rungs.
What are main features of prokaryotic DNA?
Double stranded, circular, one chromosome, in cytoplasm, supercoiled DNA (nucleoid), and no histones.
What are main features of eukaryotic DNA?
Double stranded, linear, usually 1+ chromosomes, in nucleus, and has chromatin which is DNA wrapped around histones (proteins).
What does semiconservative replication mean?
Daughter DNA molecules each consist of one parental strand and one new strand.
What is the replication bubble?
The space formed by the initiation proteins' separation of the 2 strands.
What is topoisomerase?
Relieves overwinding strain ahead of replication forks by breaking, swiveling, rejoining DNA strands.
What is primase?
Puts down RNA primer to start replication.
What is DNA polymerase III?
Adds complementary bases to leading strand (new DNA is made 5' --> 3').
Which direction does the lagging strand grow?
Grows in the 3' ---> 5' direction by the addition of Okazaki fragments.
What is the purpose of DNA polymerase I in DNA replication?
Replaces RNA primers with DNA.
What does DNA ligase do?
Seals fragments together.
What happens in nucleotide excision repair?
Nucleases cut damaged DNA. DNA polymerase and ligase then fills in the gaps.
What is the terminator?
It is the sequence that specifies the end of the mRNA transcript. The structure:
DNA--Promoter--RNA coding sequence--terminator
What is RNA splicing?
Introns are removed.
What is the 5' cap?
Guanine with 2 additional P groups (GTP). Provides stability to the mRNA and a point of attachment for the small subunit of the ribosome.
What is the poly A tail?
Attached to the 3' end. Consists of ~200 A nucleotides. Provides stability to the mRNA and also controls the movement of the mRNA across the nuclear envelope.
What are the 3 silent point mutations for DNA, mRNA, and proteins?
What are the 3 nonsense point mutations for DNA, mRNA, and Proteins?
What are the 3 non-conservative, missense point mutations for DNA, mRNA, and Proteins?
What are the 3 conservative, missense point mutations for DNA, mRNA, and proteins?
What is frame-shift mutation?
The deletion or insertion of a base, changing the codon sequences.
What is gene regulation?
Instead of blocking enzyme function, block transcription of genes for all enzymes in tryptophan pathway.
What is an example of turning genes off? (repressible)
If bacterium has enough tryptophan then it doesn't need to make enzymes used to build tryptophan.
What is an example of turning genes on? (inducible)
If bacterium encounters new sugar (energy source), like lactose, then it needs to start making enzymes used to digest lactose.
What regulates transcription in eukaryotic DNA?
Degree of packing.
What happens when DNA is tightly wrapped around a histone?
No transcription. Genes turned off.
What is involved with DNA methylation?
Blocks transcription factors. Methyl groups attach to cytosine and that results in nearly permanent inactivation of genes.
What is a Barr Body?
This x-inactivation prevents female mammals from having twice as many x chromosome gene products as males. Methylation.
What is histone acetylation?
Acetylation unwinds DNA, leaving loosely wrapped histones enabling transcription. They have easier access to genes.
What is transcription initiation?
Controls regions on DNA. Promoter is the nearby control sequence on the DNA where the binding of RNA polymerase and transcription factors occur. Enhancer is the distant control sequence on DNA, binding activator proteins, and it enhances the level of transcription.
What is post-transcriptional control?
It is alternative RNA splicing where variable processing of exons creates a family of proteins.
What is the regulation of mRNA degradation?
The life span of mRNA determines the amount of protein synthesis and mRNA can only produce proteins while they are alive. They only last hours to weeks.
What is RNA interfering?
Small interfering RNA's (siRNA) are short segments of RNA that bind to mRNA and create sections of double stranded mRNA. This is a death tag for mRNA because it triggers degradation of mRNA.
What is the control of translation?
Blocks initiation of translation stage. Regulatory proteins attach to the 5' end of the mRNA, preventing attachment of ribosomal subunits and initiator tRNA. Stops the making of proteins from mRNA.
What is protein processing and degradation?
Protein processing is the folding, cleaving, adding sugar groups, and targeting for transport. Then protein degradation is ubiquitin tagging where proteasomes take in the ubiquitin tagged proteins and degrade them.
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