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Flashcards in HYPS Biology Deck (9)
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1

Bacterial genetic recombination can result in enhanced resistance to antibiotics. What bacterial genetic recombination process(es) is/are most likely to quickly convert entire bacterial colonies from being sensitive to a given antibiotic to being resistant to that antibiotic

Conjugation is a deliberate and specific transferal of genetic material from one bacterium to another. Further, in many cases of conjugation, the recipient cell acquires the necessary sex factor to carry out conjugation with other cells; that is, the recipient is converted into a donor. This would allow rapid, exponential spread of genetic material between bacterial organisms. If the sex factor were located on the same plasmid as an antibiotic resistance gene, then this would allow the rapid conversion of an entire preexisting colony from being antibiotic sensitive to being antibiotic resistant.
Transformation and Transduction could result in resistance, but these colonies would have to be descened from an individual cell that underwent recombination. Transformation = foreign dna from environment. Transduction- bacteriophage intermediate.

2

A pharmaceutical company would like to induce the production of a target protein by a particular strain of e.coli. What would be the required characteristics of the plasmid in order to create large colonies of E. coli that produce the target protein?

Think about the characteristics required to induce the transcription of the DNA encoded on the plasmid. In order for bac to transcribe the genetic sequence, an appropriate promotor must be present. The genetic material to be transcribed must be close enough to the promotor to facilitate effective transcription. In order to ensure efficient conversion of all the bacteria in the colony to bacteria able to produce this protein, the plasmid should also encode a sex factor so that the plasmid can be efficiently transferred between cells.

3

A researcher discovers that a type of bacteriophage removes the exact same sequence of DNA from each bacterium infected. What does this info likely indicate about the bacteriophage's ability to feed into either the lytic or lysogenic cycle.

The fact that the same sequence is transferred each time this bacteriophage infects a bacterium implies that the process of transduction is not random. This is likely the case if the phage genome integrates into the bacterial genome, and when the phage genome is later released from the bacterial genome, it takes a small segment of bacterial DNA with it. This implies that the bacteriophage must enter the lysogenic cycle. To replicate and subsequently infect other bacteria, the bacteriophage will also have to reenter the lytic cycle at some point.

4

It is noted by a researcher that a certain colony of bacteria has developed an extremely high rate of recombination, acquiring multiple phenotypic changes in a very short period of time. What mechanism related to conjugation would most likely explain this finding.

Sometimes, the sex factor becomes incorporated into the bacterial genome. this information is generally carried on a plasmid, but, by the process of transformation, it may become part of the bacterial genome itself. When this occurs, the entire genome will be replicated and the bacterium will attempt to transfer the entire genome during conjugation. The conjugation bridge is usually not stable enough to permit transfer of te entire bacterial genome, but sizable portions of it are often still transferred. This results in high frequency recombination. Cells that have undergone this particular change are known as Hfr or high frequency of recombination cells.

5

During the follicular phase of the menstrual cycle, a dominant follicle is produced that secrets estrogen. If this follicle produces normal amounts of estrogen during the early days of its maturity but declines in estrogen production by day 10 of menstrual cycle, what would be the result?

During the follicular phase, the hypothalamus secretes gnrh, which acts on ant pit to promote release of FSH. FSH acts on ovary and promotes development of several ovarian follicles. The mature follicle begins secreting estrogen. Estrogen has + and - feedback effects in menstrual cycle. Early in the follicular phase, estrogen acts on the uterus, causing vascularization of the endometrium. It also acts in a negative feedback to inhibit the release of FSH to prevent the development of multiple eggs. Because the question stem states that early levels of estrogen are normal, vascularization of the uterus and inhibition of FSH will both occur normally. The question states that estrogen declines after day 10. The normal role of estrogen after this point would be to increase rapidly around day 12 of the cycle, and this burst of estrogen surpasses a threshold to begin having a + feedback effect on the secretion of FSH and LH. this results in the LH surge, which is responsible for ovulation (releasing the egg). SO if estrogen decreases after day 10, there would be no ovulation.

6

Estrogen has both negative and positive feedback effects on FSH and LH at different times in the menstrual cycle.

Estrogen levels fall dramatically after the LH surge but rise again during the luteal phase. During this phase, however, both estrogen and progesterone are now produced by the corpus luteum and both have a negative feedback effect.

7

At what point in the follicular phase is FSH inhibited.

FSH is inhibited early in the follicular phase to prevent the development of multiple follicles. While some FSH is necessary for the development of a follicle at all, the body prevents te formation of many follicles by negative feedback of estrogen on the hypothalamus and ant pit. Later in the follicular phase, FSH levels rise in parallel with LH levels as estrogens feedback mechanism switches from - to + feedback.

8

How do the levels of progesterone change during the menstrual cycle? what is the function of progesterone?

Progesterone levels are very low during the follicular phase of the menstrual cycle, and do not begin to rise until the luteal phase. The corpus luteum, which does not exist until the secondary oocyte has been released from the ovary, secretes progesterone to develop and maintain the endometrium. Thus, progesterone levels rise during the luteal phase. It is the drop in the level of progesterone that ultimately stimulates menses, which- by definition- begins on day 0 of the cycle.

9

How could ovulation be prevented during the menstrual cycle through biochemical means?

By manipulating the hormones involved in the menstrual cycle. OCP keep estrogen and progesterone levels elevated so that FSH and LH are constantly inhibited. Because of the inhibition, a follicle does not develop and the LH surge does not occur, thereby preventing ovulation.