Answer:
The correct answer is "There are several mechanisms that explain why a hormone have different effects in different cells. These mechanisms include: multiple receptors for the same hormone, a single receptor coupled to different pathways and hormones interacting with receptors for other molecules".
Explanation:
Hormones are among the most versatile molecules of the body, responsible for different biological processes such as human growth, sex development and metabolisms. Hormones are responsible of these complex biological processes because they have drastically different effects in different cells. There are several mechanisms that explain why a hormone have different effects in different cells. These mechanisms include:
- Multiple receptors for the same hormone. For instance, there are multiple receptor for dopamine, a hormone and neurotransmitter responsible for different functions such as movement, memory, sleep and motivation.
- A single receptor coupled to different pathways. Most hormone receptors act with a cascade of signaling. This in consequence results in a single receptor interacting with different molecules having multiple effects.
- Hormones interacting with receptors for other molecules. One example is the action of one metabolite of progesterone named allopregnanolone. This metabolite interacts with GABA-A receptor, which gives it anxiolitic properties.
Answer:
10 chromosomes/sister chromatids
Explanation:
Prophase is the first stage of cell division (mitosis). Prior to the cell entering the actual division stage, it undergoes a phase where it prepares its content and most importantly undergo the duplication of its genetic material (DNA). This DNA are found as chromosomes. It undergoes replication of its DNA in the S-phase of interphase stage.
Since Arabidopsis thaliana has 10 chromosomes, and each chromosome holds one DNA molecule, 10 molecules of DNA will be present in the mustard plant's genome. These 10 molecules of DNA will be replicated on another copy of chromosome which is identical to the template. This chromosomes are called SISTER chromatids i.e. replicated chromosome. Each sister chromatids are held together at the centromere and are considered one individual chromosome until they separate during anaphase stage.
Hence, at the Prophase stage, before separation, each sister chromatid (replicated chromosome) is considered as one chromosome. Thus, in the mustard plant with 10 chromosomes, it will possess 10 sister chromatids or chromosomes at the Prophase stage.
N.B: When sister chromatids separate during anaphase stage, they will be regarded as individual chromosomes.
Answer:
DNA may be taken up by bacterial cells and be active.
Explanation:
To understand Avery, MacLeod, and McCarty's experiment, it is important to know Frederick Griffith's precursor experiment. The microbiologist worked at the British Ministry of Health's Pathology Laboratory with pneumococci (commonly known as the bacterium Streptococcus pneumoniae, then known as Pneumococcus, which causes pneumonia), which were previously classified into several types. When cultured in petri dishes in the laboratory, the pneumococci that synthesize their capsules generate 'smooth' colonies. Subcutaneous injection of liquid culture of these pneumococci into mice causes their death. However, in vitro culture also allows the emergence of rough colonies', whose bacteria have lost the ability to synthesize mucopolysaccharide (and therefore have no capsules). Rough mutants could no longer be classified with sera and, moreover, lost their virulence: mice inoculated with them remained alive, unlike inoculated with smooth pneumococci.
The nature of Griffith's transforming principle remained unclear until the work of Avery, MacLeod, and McCarty. They repeated the in vitro transformation of pneumococci at the Rockfeller Institute for Medical Research, but replaced heat-dead cells with a purified fraction of smooth bacterial extract (unable to cause disease alone) and treated the material with different enzymes, each capable of destroying a specific type of macromolecule. Experience has shown that this fraction retained its transforming capacity when treated with protein or RNA degrading enzymes, but lost that ability when treated with DNA degrading enzymes. These results indicated that the chemical nature of the 'transforming principle' was DNA.
Thus, we can conclude that in addition to identifying genetic material, Avery, MacLeod and McCarty experiments with different strains of Streptococcus pneumoniae demonstrated that DNA can be absorbed by bacterial cells and be active.
About 97.5% of the earth's water is saltwater and about 2.5% is fresh.
