1
What is the name of the enzyme responsible for the creation of the RNA strand in transcription?
RNA Polymerase
In prokaryotes, gene expression is often regulated at the level of transcription initiation through:
A) Ribosomal binding
B) Operons
C) mRNA splicing
D) DNA replication
B) Operons
1) Where does transcription occur in a prokaryotic cell?
2) Where does transcription occur in a eukaryotic cell?
1) Cytoplasm
2) Nucleus
1) Where does translation occur in a prokaryotic cell?
2) Where does translation occur in a eukaryotic cell?
1) Cytoplasm
2) Cytoplasm
1) What is a gene?
2) What is an allele?
1) A gene is a segment of DNA that codes for a specific protein or trait; "eye color"
2) An allele is a variation of a gene; "green eyes" or "blue eyes"
Which of the following is NOT needed for transcription to occur?
A) DNA
B) RNA polymerase
C) tRNA
D) Nucleotides (A, U, C, G)
c) tRNA
What are the four tissue types?
2) Nervous Tissue
3) Connective Tissue
4) Muscle Tissue
The promotor is essential for transcription of gene expression to begin. Why???
A promoter is a region of DNA that signals the start of a gene. It dictates which DNA strand is the template strand AND acts as the docking site for RNA polymerase to sit on.
The ribosome consists of a large and small subunit.
The small subunit is in charge of ____________.
The large subunit is in charge of ____________.
- scanning mRNA to find start codon "AUG"
- breaking bonds between polypeptide chain & tRNA AND catalyzing the peptide bonds between amino acids
What is the difference between homozygous and heterozygous?
Homozygous means having two identical alleles for a trait, while heterozygous means having two different alleles for a trait.
State the functions of the following types of RNA:
1) mRNA
2) tRNA
3) rRNA
1) mRNA (messenger RNA): Carries genetic information from DNA in the nucleus to the ribosome for protein synthesis.
2) tRNA (transfer RNA): Delivers specific amino acids to the ribosome during translation, helping to assemble the polypeptide.
3) rRNA (ribosomal RNA): Form ribosomes, where protein synthesis occurs.
In the regulation of gene expression in prokaryotes, the operator, repressor, and co-repressor are involved in:
A) Controlling the initiation of transcription in operons
B) Splicing mRNA transcripts
C) Modifying histones to affect transcription
D) Transcribing genes into mRNA
A) Controlling the initiation of transcription in operons
*Specifically the Trp Operon Model in prokaryotes
1) Operator is located on the promotor; may be turned on or off
2) Repressor is a protein receptor made when products (Tryptophan) are in high []
3) Corepressor is Tryptophan (the product) which binds to the repressor to turn off the operator and thus during off gene expression for Tryptophan
The mRNA strand will always run in the ___ to ___ direction; therefore, the DNA template strand will always run in the ___ to ___ direction.
5' to 3'
3' to 5'
Explain the interaction between the codon and anticodon. Where does this interaction occur, and why is it crucial for protein synthesis?
The codon-anticodon interaction occurs in the ribosome's A site, where the mRNA codon pairs with the complementary tRNA anticodon to ensure the correct amino acid is added during protein synthesis.
Albinism is caused by a recessive allele (a), while the allele for normal pigmentation is dominant (A). A man with normal pigmentation who is heterozygous (Aa) marries a woman who is also a carrier for albinism (Aa). What are the possible genotypes of their offspring?
Sally inherits two alleles for the "eye color" gene: one from her mother and one from her father. Her mother's allele codes for brown eyes (B), while her father's allele codes for blue eyes (b). What is Sally's phenotype for eye color, and why?
Sally's phenotype would be brown eyes because the brown allele (B) is dominant over the blue allele (b). With a genotype of Bb, the dominant brown allele determines her eye color.
*she is heterozygous (Bb)
In the trp operon of E. coli, the operon is repressed (turned off) when:
A) Tryptophan levels are low
B) Tryptophan binds to the repressor protein, activating it
C) The RNA polymerase binds to the promoter without any regulation
D) Tryptophan levels are high, and it binds to the repressor protein, which then inhibits transcription
D) Tryptophan levels are high, and it binds to the repressor protein, which then inhibits transcription
How is transcription terminated in prokaryotes and eukaryotes, and what are the key differences?
In prokaryotes, transcription stops when RNA polymerase reaches the termination signal causing the RNA polymerase to dissociate from the DNA. In eukaryotes, transcription stops when RNA Polymerase reaches a polyadenylation signal, after which RNA polymerase dissociates from the DNA.
What is the "shifting frame" mutation in translation, and how does it impact protein synthesis?
A frameshift mutation occurs when nucleotides are inserted or deleted in a way that shifts the reading frame of the mRNA. This causes the ribosome to read the codons incorrectly, often resulting in a nonfunctional protein. These mutations can be particularly VERY damaging because they change the entire amino acid sequence.
How does epistasis affect the expression of genetic traits, and provide an example where one gene can mask the expression of another.
Epistasis occurs when one gene masks or modifies the expression of another gene. An example is the coat color in mice, where the E gene controls the expression of the B gene. If the mouse has two recessive alleles for the E gene (ee) it does NOT have the gene that allows pigmentation, and therefore, it will be albino, regardless of the alleles for the B gene.
Explain why a carrier of Sickle Cell Anemia would be at an advantage if exposed to Malaria. What is this phenomenon called?
The recessive allele for SCA provides "selective advantage" ONLY if the organism is heterozygous.
"AA" = no protection against Malaria
"Aa" = protection against Malaria
"aa" = protection against Malaria; would die to SCA though.
Pleiotropy
At which of the following stages is gene expression NOT typically regulated in eukaryotic cells?
A) Transitioning from chromatin to chromosomes
B) mRNA transport from the nucleus to the cytoplasm
C) Protein degradation
D) DNA replication during cell division
D) DNA replication during cell division
What is the significance of RNA splicing, and how does it contribute to protein diversity?
RNA splicing is the process by which non-coding sequences (introns) are removed from the pre-mRNA transcript and the remaining coding sequences (exons) are joined together. This process allows for alternative splicing, where different combinations of exons can be joined together to produce multiple protein isoforms from a single gene, contributing to protein diversity.
How does post-translational modification of proteins influence their final structure and function?
Post-translational modifications such as phosphorylation, glycosylation, and proteolysis occurs AFTER translation. It may alter a protein’s function, stability, and interactions with other molecules. These modifications are critical for regulating cellular processes and ensuring that proteins function correctly in response to environmental.
Explain the difference between incomplete dominance and codominance with examples.
In incomplete dominance, the heterozygous phenotype is a "in-between" of the two alleles (e.g., red and white flowers produce pink offspring). In codominance, both alleles are fully expressed (e.g., "A" blood type allele is equal to the "B" blood type allele which produces an "AB" blood type).