AP Bio Unit 6
In what direction is DNA synthesized?
5' to 3'
Which nitrogenous bases are purines?
Adenine and Guanine
How do mutations affect genes?
Alter the gene expression by changing the proteins that are coded for
How do negative regulatory molecule inhibit gene expression?
Blocks RNA polymerase and minimizes gene expression
How is eukaryotic DNA shaped?
Double stranded in chromosomes, in a membrane-bound nucleus
What is the function of RNA polymerase?
Enzyme that makes mRNA from DNA during transcription.
How does the location of translation differ between a prokaryote and a eukaryote?
Eukaryotes: in the nucleus Prokaryotes: in the cytoplasm
Identify two examples of retroviruses
HIV, SIV
What is miRNA?
RNA Interference molecule that targets specific mRNAs
Why does a purine always pair with a pyrimidine?
So they can form hydrogen bonds and has consistent ratios
What is the enhancer region?
Stretch of DNA that alters gene expression by binding transcription factors.
How does the DNA sequence determine the RNA sequence?
The DNA is the template
What happens in the initiation step of translation?
The DNA molecule unwinds and separates to form a small open complex
Describe the process that takes place during transcription
The major steps of transcription are initiation, promoter clearance, elongation, and termination
What is cell differentiation?
The process in which cells become specialized.
How is DNA modified to initiate transcription?
The promoter region of DNA opens up so that the RNA polymerase can begin
How does the repressor interact with the promoter?
The repressor protein works by binding to the gene's promoterregion, preventing the production of mRNA
What is a plasmid?
a small, often circular DNA molecule found in bacteria and other cells—separate from chromosomal DNA
What is a codon?
a three-nucleotide sequence that codes for an amino acid
How does a retrovirus violate the central dogma?
by synthesizing DNA from their RNA genomes, and also by replicating their RNA genomes.
True or false: One codon can code for more than one amino acid
false
What is the function of rRNA?
help hold ribosomal proteins in place and help locate the beginning and end of the mRNA message. They may also carry out the chemical reaction that joins amino acids together.
What is the function of the poly-A tail?
increases mRNA stability in eukaryotes
Is the lac operon repressible or inducible?
inducible
What is the function of the promoter?
initiate transcription
What are the three steps of translation?
initiation, elongation, termination
What is the central dogma?
it is a statement that summarizes how information flows in one direction from DNA to RNA to proteins
Where does translation take place?
ribosomes in the cytoplasm
How is prokaryotic DNA shaped?
single chromosome without a nuclear membrane
Where does translation start?
start codon
What is the function of the GTP cap?
the cap plays a role in the ribosomal recognition of messenger RNA during translation into a protein
What is differential gene expression?
the expression of different genes by cells with the same genome
What is the central dogma?
the process by which the instructions in DNA are converted into a functional product
What happens when tryptophan is absent?
the repressor protein does not bind to the operator and the genes are transcribed
Which nitrogenous bases are pyrimidines?
thymine and cytosine
What is the function of DNA polymerase?
to add nucleotides to the end of a growing DNA strand
Identify two functions of plasmids.
to enhance the survival of an organism by defending the host cell and facilitating replication
What is the function of RNA splicing?
to remove introns and connect the exons
What is the function of helicase?
to separate DNA strands
What is the structure of a purine?
two rings
What is the function of reverse transcriptase?
catalyzing the formation of DNA from a RNA template
What is the function of DNA ligase?
connects okazaki fragments
What is transcription?
synthesis of an RNA molecule from a DNA template
What is the function of tRNA?
transfers each amino acid to the ribosome as it is specified by the coded messages in the mRNA.
What are the nucleotide base pairing rules?
A with T and C with G
What is the function of mRNA?
To bring the instructions to make a protein from the nucleus to the ribosome.
What is the function of RNA primers and primase?
To serve as a starting for DNA synthesis
How is DNA modified to inhibit transcription?
Repressors respond to external stimuli to prevent the binding of activating transcription factors.
What is a promoter?
A sequence of nucleotides on the DNA that designates a start point
What is the TATA box?
A sequence on DNA that signals the beginning of a gene
What are the three sites found on a ribosome and what is their function?
A site: accepts the incoming tRNA P site: holds the tRNA E site: binds a free tRNA
What happens in the termination step of translation?
A stop codon enters the A site
Which direction is the template strand read?
3' to 5' direction
If there is 20% thymine in a DNA strand, how much cytosine is there?
30%
What direction does the DNA polymerase READ the DNA template?
5' to 3'
Which direction does transcription take place (which direction is the RNA synthesized)?
5' to 3'
What are epigenetic changes?
Changes that don't affect DNA sequence, but can effect gene regulation.
What is the primary source of heritable information?
DNA and sometimes RNA
Why is DNA a better hereditary material than RNA?
DNA is more stable
How is genetic information transmitted from one generation to the next?
DNA is organized in chromosomes which are separated and passed down from the parents through meiosis
Why are RNA primers required for DNA replication?
DNA polymerase can only extend a nucleotide chain, not start one
How does the leading and the lagging strand differ?
Leading: 5' to 3' and continuous Lagging: 3' to 5' and in fragments
How do transcription factors affect the binding at the promoter?
Makes it either easier or harder for RNA polymerase to bind to the promoter
What is DNA?
Molecule that encodes the genetic instructions used in all known living organisms
What happens when tryptophan is present for the trp operon?
RNA polymerase is blocked
What happens in the elongation step of translation?
RNA polymerase moves along the template strand, synthesising an mRNA molecule
What are regulatory sequences?
Regions that impact how genes are used (gene switches, promoters, leader/trailer, etc.)
How does the genetic code demonstrate common ancestry?
Similarities can be tracked back
What is siRNA?
Small interfering RNA. They block expression of a gene with the same sequence as the RNA
Describe the process of DNA replication using the enzymes described above (helicase, topoisomerase, DNA polymerase, primase, RNA primers, and DNA ligase)
The strands of DNA are separated using the helicase, the topoisomerase gets rid of the knots at the replication fork so that the strands can separate, then primers and primase act as a starting point so that the polymerase can add on nucleotides, then the ligase connects the okazaki fragments
How do siRNA and miRNA affect gene expression?
They inhibit gene expression
How is DNA stored?
Tightly packed as chromosomes in the nucleus
True of False: All somatic cells have the same DNA
True
What is a repressor?
a protein that binds to the operator and prevents transcription
What is the promoter region?
a region of DNA that initiates transcription of a particular gene
What is an operon?
a unit made up of linked genes that is thought to regulate other genes responsible for protein synthesis.
How do new phenotypes arise?
environment
How can multiple proteins be synthesized from the same mRNA transcription?
multiple codons can code for the same amino acid
What are other names of the template strand?
noncoding strand
How does the mRNA, tRNA, and rRNA all interact?
rRNA forms ribosomes which physically move along an mRNA molecule to catalyze the assembly of amino acids into protein chains. They also bind tRNAs and various accessory molecules necessary for protein synthesis.
What is the function of transcription factors?
recognition of sequences within the enhancer and promoter and activation of transcription, and control expression
What is the function of topoisomerase?
relieving strain in the DNA ahead of the replication fork
Is the trp operon inducible or repressible?
repressible
What are the three types of substitution point mutations?
silent, missense, and nonsense mutations
What is the structure of a pyrimidine?
single ring
Which strand is the template strand?
template strand
How does a virus incorporate its viral genome into a host genome?
the RNA of the retrovirus is reverse-transcribed into DNA by reverse transcriptase, then inserted into the host genome by an integrase
Identify three post-transcriptional modifications that alter the pre-mRNA prior to its release from the nucleus
the addition of a 5' cap, the addition of a 3' polyadenylated tail, and RNA splicing
What happens when lactose is absent for the lac operon?
the lac repressor binds tightly to the operator, preventing transcription by RNA polymerase
What happens when lactose is present for the lac operon?
the lac repressor loses its ability to bind DNA