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Review guides for Bio test 4
Terms in this set (69)
What is the definition of a gene?
Region of DNA that carries information for a discrete hereditary characteristic.
What is the flow of information in the central dogma of molecular biology?
What is the name of the process whereby information within a gene is copied in the form of RNA?
What is the name of the process whereby the information contained within a strand of RNA is read to assemble a protein?
What type of RNA is read to assemble a protein? What are some other types of RNA?
mRNA; microRNA, rRNA, tRNA
Can the information in RNA ever be used to make DNA - give an example?
Yes; Reverse Transcription, RNA---->DNA
What is the name of the rules that govern the relationship between DNA/RNA and the sequence of amino acids in a protein?
How many bases are in a codon of mRNA? What does a codon of mRNA correspond to?
3; Each codon specifies 1 amino acid
Why is the genetic code said to be "specific yet redundant"?
61 codons specify 20 amino acids, making it redundant; yet each codon specifies 1 amino acid, making it specific.
Why is the genetic code said to be nearly universal and conservative?
Universal- all codons specify the same amino acids; conservative when several codons specify the same amino acid, the first 2 bases in these codons are almost always identical
What is a change in the normal base sequence of DNA? What cellular process most often leads to this change in the normal base sequence?
Mutation; occurs in the process of replication
What is a point mutation?
A single base mutation
What is a silent mutation? What base position of a codon does it change?
A point mutation-Does not affect final protein- often in 3rd base of codon.
What is a missense mutation? Nonsense mutation?
Missense- Changed sequence of amino acids (replacement); Nonsense- Results in a STOP codon- shortened truncated protein.
What type of mutation results from an insertion or deletion of a base?
Frame Shift- shifts bases over
What is the name of the strand being copied in transcription? What enzyme catalyzes transcription?
Template strand; RNA polymerase
How does the transcription machinery know where the starting place and end of a gene are located?
Promoter region, transcribed region and terminator region.
What sequence in bacterial prokaryotes is recognized by sigma? What does sigma recruit to the start of genes?
-35 and -10 boxes; promoter
How is transcription terminated in prokaryotes?
Terminator point signals RNA to form 'hairpin' shape, which stops transcription.
What sequence does the general transcription machinery bind to in eukaryotic promoters?
How is transcription terminated in eukaryotes?
TATA box; poly a signal terminates transcription
What RNA polymerase catalyzes the formation of mRNA?
RNA Polymerase 2
True or False - translation can begin before a gene is fully transcribed in prokaryotes
True or False - eukaryotic RNA gets processed before leaving the nucleus.
What regions of DNA that often contain regulatory sequences are removed?
What is alternative splicing? How does it lead to the production of multiple proteins from a single gene?
Splice- remove and stick together, introns are cut out and exons stick together
What is added to the 5' end of an mRNA molecule for ribosomal recognition?
5' Cap (modified guanine)
What is found at the 3' end of a mature mRNA? How does it contribute to mRNA stability in the cytoplasm?
3' Poly a tail; Stabilizes for certain amount of time in cytoplasm until poly a tail is shortened to an amount when RNA is destroyed.
What organelle is the site of translation? How many subunits is it composed of? What is it a complex of?
Ribosomes; 2; large subunit and small subunit
What is the function of tRNAs? What is a tRNA's anticodon?
Bring amino acids to ribosomes; it binds to codon on mRNA
True or False. More than one ribosome can be producing a protein from a single strand of mRNA at a given time.
True, more than one ribosome attach to the mRNA. A small single strand of mRNA can make hundreds of proteins
What catalyzes peptide bond formation in the process of translation?
How can only 40 tRNAs bring the correct amino acids to ribosomes for approximately 60 codons?
Sam tRNA anticodon has to bind to several different codons.
List the steps of translation initiation. What is the start codon?
1.mRNA binds to small subunit. 2. Initiator aminoacyl tRNA binds to start codon. 3. Large subunit of ribosome binds, completing ribosome assembly.
Is the starter tRNA found in the A, P or E sites of the large ribosomal subunit?
New tRNAs bring amino acids to ribosome in what ribosomal site - A, P or E?
After a tRNA with a correct amino acid enters the A site and "sticks", what happens between the amino acid chain in the P site and the new amino acid in the A site?
The amino acid is transferred to the amino acid in the a site
What is translocation?
Step 6 of elongation phase; the movement of something from one place to another.
After translocation, what site is empty? What site contains the growing protein chain?
A Site is empty, P Site contains the growing protein chain
From what site do tRNAs who no longer have amino acids leave the ribosome?
What happens when a stop codon enters the A site?
Peptide bonds break away.
What type(s) of mutations would be most harmful if it occurred near the start of a gene?
frameshift and nonsense if they occur near the start of a gene
What is meant when we say a gene is "expressed"? How can you tell if a gene is being expressed in a cell?
Its turned on;
1. Protein of RNA corresponding to the gene.
2. Production of a protein corresponding to the the gene if a protein coding gene
What causes cells to look and act differently from other types of cells?
Differentiated gene expression
What is a "constitutively active" gene?
Always on or expressed.
What are stem cells? Are they fully differentiated? Which type can become a greater number of different types of cells - totipotent stem cells or adult stem cells?
Cells with the ability to become multiple cell types;
Environmental cues activate what type of proteins to influence gene expression?
What are nucleosomes? Chromatin?
Nucleosome- length of DNA coiled around a core of histones.Chromatin is wrapped around proteins it consists of protein, RNA, and DNA.; chromatin is arranged into nucleosomes like beads on a string
Are active genes found in condensed or decondensed regions of chromatin?
What histone modification causes chromatin to relax/decondense? What enzyme adds this modification? What enzyme removes it?
HAT- adds acetyl group; relaxes chromatin
HDAC- removes acetyl group; recondense
What are epigenetic changes? Do they alter the base sequence? Can they alter gene expression? Does the environment alter them?
Change in the structure of DNA without changing base sequence- yes- yes
What do regulatory transcription factors bind to in order to alter the transcription of particular genes?
What are enhancers, promoter proximal elements?
Enhancers- Regulatory sequences far from promoter
Promoter proximal elements- Next to to promoter
Both influence the transcription of a gene.
What does RNAi regulate - transcription or translation? What are the roles of microRNA and RISC in RNAi?
They are complementary and target specific mRNA for destruction.
What activates regulatory proteins such as regulatory transcription factors?
What must a cell have to respond to a particular environmental signal?
A protein receptor
Contrast signal reception between steroid and peptide hormones - which one can diffuse into the cell and which one must bind receptors at the cell membrane?
-Lipid soluble (steroid hormones)- response is direct- bind directly to receptor that act as reg. transcription factor- no intermediate steps
-Lipid insoluble signals( peptide)- signal must be processed
-Info is transduced (form is changed) inside the cell
-Signal is amplified for fast response
-Intracellular signaling molecules then active regulatory transcription factors (and other proteins in the cell)
What is signal transduction? Does this occur with lipid soluble or insoluble hormones?
Form is changed; Insoluble
What is signal amplification?
For fast response (amplifies- multiples)
What do cell signaling pathways activate that can bind to DNA to alter expression of target genes?
Regulatory transcription factors
A _________is a segment of DNA that contains information for or "codes" for a particular RNA molecule or protein.
In eukaryotes, the basal transcription machinery binds to the _____ box within the promoter.
The process of protien production is catalyzed by....
_____ bring the correct amino acdis to the ribosome by complimentary bonding.
Many protein may be produced from a single eukaryotic pre-mRNA due to
Which of the following are true regarding a heart cell and a muscle cell?
different genes are expressed in each cell type
In which type of cells are groups of genes not permanently turned on/off ?
Totipotent stem cells
Which of the following would result in expression of a particular gene?
histone acetylation in the region of the gene
activation of regulatory transcription factors that bind to the promoter of the gene
receipt of a cellular signal to activate the gene
Why do some cells express genes in response to a cellular signal while others do not?
Cells have many different transcription factors
We say the genetic code is ___ because more than one codon codes for an amino acid.
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