Exam 3 Review Flashcards
What is the inducer molecule of the lactose operon:
allolactose
Catabolite repression is utilized by E. coli to:
- ensure glucose is metabolized first
- increase metabolic efficiency
- increase rates of transcription
An operon is controlled by an activator protein protein. When the activator binds to an allosteric effector, it binds to DNA near the operon. Control of this operon is:
positive inducible
Which of the following statements is true about the tryptophan.
a. the trp operon is negative repressible operon
b. in the presence of tryptophan, the genes of the trp operon are not expressed
c. in the presence of tryptophan, the genes of the trp operon are expressed
a and b
Mutations passed to the next generation only occur in ______ cells.
germline cells
Fragile-X syndrome is an example of _____, which are caused by _____.
an expanding trinucleotide repeat mutation; polymerase slippage.
Deletion of 2 base pairs will most likely lead to which kind of mutation.
frameshift mutation
The nuclear membrane breaks down during:
prometaphase
During prophase 1 of meiosis:
homologous chromosomes pair and crossover begins
In a meiotic cell, ______ hold sister chromatids together through anaphase I due to the presence of ______/
cohesion, shigosin
An elephant has a total of 56 chromosomes (2n=56). An egg of a female elephant will have ____ chromosomes.
28
Meiosis increases genetic variation through __________ and _________.
crossing over: anaphase 1
Spindle fibers attach to the __________ in order to separate sister chromatids during ________.
kinetochores; anaphase and anaphase II
Homologous pair separate during _____.
anaphase 1
Spermatogenesis produces ___ #sperm cells, while oogenesis produces ____ # egg cells.
4; 1
One mechanism of epigenetics is histone acetylation, which _____ the rate of transcription.
increases
Codon specifies new amino acid, but does not change protein function
neutral mutation
Reversal of a phenotypic change by a second mutation in the same gene
intragenic suppressor
reversal of a phenotype change by a mutation in a second gene
intergenic supressor
causes premature death
lethal mutation
amino acid sequence unchanged
silent mutation
causes the appearance of a new trait
gain-of-function mutation
codon becomes a stop codon
nonsense mutation
list four ways meiosis is different than mitosis.
- meiosis goes through two rounds of separation while mitosis goes through one.
- meiosis produces haploid gametes and mitosis produces diploids
- Mitosis produces daughter cells identical to the parent cell and meiosis produces cells that genetically vary from the parent cell and daughter cells.
- mitosis produces two cells with the same number of chromosomes as the parent cell and meiosis produces 4 daughter cells with half the number or parent chromosomes.
What is happening at G1?
cell growth and development is occurring
What is happening at S?
DNA is synthesizing
What is happening at G2?
Biochemical preparation for cell division is occurring
Why is the G2/M checkpoint important?
The G2/M checkpoint is important because it is only passed if the DNA is fully replicated and undamaged. This is important so that damaged or not fully replicated DNA is not passed into more cells.
Why do prokaryotic cells organize their genes into operons?
Prokaryotic cells organize their genes into operons for efficiency so that it takes less energy to get more proteins. This way they can get multiple proteins form one operon instead of doing transcription for 3 separate genes which would take more energy.
Describe the cellular conditions required to transcribe the lac operon at a high rate. Describe how these conditions regulate transcription of the operon through the lac repressor and catabolite repression.
To transcribe the operon at a high rate there needs to be low levels of glucose, high levels of lactose, high levels of CAP, and high levels of cAMP.
Glucose needs to be low because due to catabolite repression the cell would rather metabolize glucose the lactose . Lactose needs to be high to induce the operon by producing allolactose to inhibit the repressor protein. CAP needs to be high because it binds to the promoter sequence to initiate transcription and cAMP concentration inversely relates to the concentration of glucose and cAMP binds to the CAP. The CAP is also bound to the polymerase.
I-
recessive mutation
I^s
repressor no longer binds allolactose
O^c
repressor no longer binds DNA
I^-d
repressor no longer binds DNA
explain O^c mutation
the sequence of the operator is changed which makes the repressor unable to bind to it. This results in transcription always being on in the presence and absence of lactose.
explain I^s mutation
there is a mutation in the repressor protein and allolactose is unable to bind to the repressor. This makes transcription uninducible and transcription is always off in the presence and absence of lactose.
a single bond is replaced with another base and the frameshift is not altered
base frameshift
when there is an insertion or deletion of one or more bases causing a shift in the reading frame of a gene
frameshift mutation
likely to cause a gain of function becasue changing the base could change the codon which could change on of the amino acids in a protein giving it a new function
base substitution
List three causes of DNA damage.
- UV light: UV light can cause thymine dimers and bend the DNA helix both of which block DNA polymerase
- mutagens
- Depurination; deprivation occurs when water removes a purine group form a nucleotide
