Chapter 12
What is the difference between mitosis and meiosis?
Mitosis is the genetic material copied and divided equally between two cells.
Meiosis produces daughter cells genetically different from each other.
What is the difference between a haploid and diploid number?
Haploid (n): Indicates the number of distinct types of chromosomes present.
Diploid (2n): Involves a maternal chromosome from mother and paternal from the father.
What are the three alternative hypotheses for DNA Replication?
1.Semiconservative replication
2.Conservative replication
3.Dispersive replication
Who proposed sequence of bases in DNA acted as a code?
Francis Crick
What is Negative Feedback?
Form of control where final product inhibits production of product
- Trp repressor binds to operator only when bound by its regulator-tryptophan
-When tryptophan levels are low, repressor no longer binds operator
- Trp operon genes are now transcribed; mRNA is translated and tryptophan is restored.
What is RNA Processing?
Unique to eukaryotes
Produces mature, processed mRNA
Alternative splicing
Plasmids can serve as cloning vector
Piece of foreign DNA spliced into plasmid
Plasmid is inserted into bacteria cell
Plasmid is replicated and transmitted to daughter cells as host cell grows and divides
Produces billions of identical copies of DNA
What are the events that occur during mitosis?
Two sister chromatids separate to form independent daughter chromosomes.
One copy of each chromosome goes to each of the two daughter cells.
Each daughter cell receives copy of genetic information contained in each chromosome.
What are the two cell divisions of Meiosis and explain the difference?
Meiosis I: The two homologs of each chromosome pair separate into two daughter cells.
- Each daughter cell has one set of chromosome
- A diploid parent produces two haploid daughter cells
Meiosis II: The sister chromatids of each chromosome separate into two daughter cells.
- Each of the two daughter cells from meiosis I divides
- Result is 4 haploid cells
What kind of helix does the antiparallel strands twist to form? What are the Complemetary base pairing?
Double Helix
–Guanine (G) hydrogen-bonds with cytosine (C)
–Adenine (A) hydrogen-bonds with thymine (T)
What is the central dogma? What is transcription and translation?
Summarizes the flow of information in cells
Transcription: DNA------> mRNA
Translation: mRNA-------> Proteins
What are the three classes of lactose metabolism mutants that were identified?
LacZ- mutants could not cleave lactose because they lack functional beta-galactosidase
LacY- mutants do not accumulate lactose in their cells because they lack galactoside permease
LacI- mutants produce beta-galactosidase and galactoside permease even when lactose is absent called constitutive mutants
What are Silencers?
Similar to enhancers
Except they repress gene expression
When regulatory proteins called repressors bind to silencers, transcription shut down
What is PCR and what are the steps done?
Quicker way to clone DNAs
Millions of copies obtained in hours
Using Plasmid takes days or weeks
PCR involves three steps repeated over:
- Denaturation
- Annealing
- Extension
What are the subphases in Mitosis?
Mitosis: Prophase, Prometaphase, Metaphase, Anaphase, Telophase
What are the Phases of Meiosis I and II?
Meiosis I: There are 5 distinct phases which are early prophase I, late prophase I, Metaphase I, Anaphase I, Telophase I
Meiosis II: Prophase II, Metaphase II, Anaphase II, Telophase II
What was the Hershey and Chase Experiment about? Describe it and tell me what isotopes were used?
-Phage was produced in a medium containing s35 radioactively-labeled amino acids. This resulted with s35 labeled proteins, but np radioactive label in the DNA.
-The phage was then given permission to infect the bacteria. The phage attached to the bacterial cell and injected their DNA, but the radioactively- labeled protein coat remained on the outside of the cell.
-The phage produced in these cells contained no radioactivity.
-Shaking caused the empty protein coats to be taken out, but it did not get involved with the production of new phage in the cell.
-In the second part of experiment, phage were introduced in a medium containing p32 labeled DNA. This resulted in a phage population with p32 labeled DNA, but no label was seen in the protein.
-Conclusion: DNA, not protein, is the hereditary material (New Generation of Phage)
What are the types of point mutations and what is the function of them all?
–Missense mutations change an amino acid in protein
–Silent mutations do not change amino acid sequence due to redundancy in the code
–Frameshift mutations shift reading frame, altering meaning of all subsequent codons
–Nonsense mutations change codon that specifies an amino acid into stop codon
Transcription can be regulated with what two controls?
What do both controls do?
Negative control: Regulatory protein-repressor-binds to DNA and shuts down transcription.
Positive control: Regulatory protein- activator- binds to DNA and triggers transcription
The model for transcription initiation in eukaryotes
Step 1: Activators bind to DNA and recruit chromatin remodeling complexes and HATs
Step 2: Chromatin remodeling opens chromatin, exposing core promoter and regulatory sequences
Step 3: Other activators bind enhancers and promoter-proximal elemendts; DNA loops, so mediator and activators interact
Step 4: General transcription factors and RNA polymerase assemble on mediator and associate with core promoter so that transcription can begin.
Genes can be under what?
Transcriptional control: mRNA only made for proteins needed
Translational control: Not all mRNAs are translated
Post-translational control: Proteins must be activated by chemical modification