Answer:
In 1928, Fred Griffith performed an experiment revealing that genetic material can be passed between two different stains of the bacteria.
Explanation:
In 1928, Frederick Griffith, a British bacteriologist conducted some experiments to develop a pneumonia vaccine. He used mice and two strains of Streptococcus pneumoniae bacteria, known as R and S in his experiments.
The live R strain bacteria had a rough appearance and were nonvirulent. When he injected R bacteria into mice, they did not cause pneumonia. The live S strain bacteria had a smooth appearance due to their polysaccharide coating and were virulent. When injected into mice, the mice died as a result of pneumonia. The polysaccharide coating protected the S bacteria from the immune system of the mice.
Griffith then injected mice with heat-killed S bacteria (the heat killed the bacterial cells) and they did not cause pneumonia in mice. But when he injected a combination of non-lethal R bacteria and non-lethal heat-killed S bacteria into mice, the mice died from pneumonia. When he examined the blood sample from the dead mice, he found that the blood sample contained live S bacteria. This finding leads him to the conclusion that the nonvirulent R-strain bacteria had been "transformed" into virulent and lethal S-strain bacteria by taking up a "transforming principle" from the heat-killed S bacteria.
This experiment was then used for additional experiments conducted by Avery, McCarty, McLeod and then by Hershey and Chase. They found the evidence that the transforming principle from Griffith's experiment was actually the hereditary material, DNA. The DNA of the S strain bacteria had survived the heating process. This DNA that contains the genes for the production of the protective polysaccharide coating was taken up by the R strain bacteria. The transformed R strain bacteria were now protected from their host's immune system and this process of transferring genetic information between different bacterial strains is known as transformation.
Answer:
macroevolution
Evolution that occurs over a long period of time is called macroevolution. It might take place over millions of years. This scale of evolution occurs above the level of the species.
Air temperature: When temperatures (and the humidity) soar, the heart pumps a little more blood, so your pulse rate may increase, but usually no more than five to 10 beats a minute.<span>Body position: Resting, sitting or standing, your pulse is usually the same. Sometimes as you stand for the first 15 to 20 seconds, your pulse may go up a little bit, but after a couple of minutes it should settle down. Emotions: If you’re stressed, anxious or “extraordinarily happy or sad” your emotions can raise your pulse. </span><span>Body size: Body size usually doesn’t change pulse. If you’re very obese, you might see a higher resting pulse than normal, but usually not more than 100. </span><span>Medication use: Meds that block your adrenaline (beta blockers) tend to slow your pulse, while too much thyroid medication or too high of a dosage will raise it.
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Answer:
Helicase
Explanation:
The DNA double helix is unzipped by the enzyme *HELICASE*. The enzyme breaks the hydrogen bond between the bases thereby causing the strands of the double helicase to unzip. The action of the helicase enzyme uses energy from ATP. The unzipping of the double helix does not occur in a swift move. One end of the DNA molecule with 5'-3' is opened up showing the antiparallel single strands. The end that is opened is termed INITIATION SITE of replication. The opening look like someone standing with legs wide open. The wide opening is called REPLICATION FORK. The single strands of the fork are usually unstable but their stability is maintained by the DNA-binding-proteins. Having opened the double helix, the replication would then continue in the 5'-3' direction of one of the two antiparallel single strands.
