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.
They rarely tact with any other elements
Answer:
Xylem cells have no cytoplasm or end walls, meaning they form a tube through which water can pass freely to allow water transport. Lignin strengthens the cell walls, helping to support the plant.
Answer:
Part 1:
The mother’s genotype is ii, rr, MN
The father’s genotype is IAIA/IAi, Rr, MM
Part 2:
Approximately 1/32 (3.125%) of children can be expected to have the stated blood types.
Explanation:
Part 1:
The mother has blood types 0, Rh- and MN. Therefore, her genotype has to be ii, rr, MN.
The father has ABO type A. His ABO genotype may therefore be either IAIA or IAi, as both are compatible with type A offspring with a type 0 mother. His Rh genotype must be rr, since his Rh- child necessarily has to have inherited one r allele from each parent. Finally, his MN genotype has to be MM since both alleles are codominant.
Part 2:
Using the given data, we build the following Punnett chart:
IA R N IA r N i R N i r N
IA R M
IA R N
IA r M
IA r N
IB R M
IB R N
IB r M X
IB r N
Note that, of all 32 possible combinations, only a single one of them (marked with “X” produces a genotype which matches the desired blood type, as follows:
genotype: IBi, rr, MN
blood type: B, Rh-, MN
The two richest ecosystems lie in tropical rainforests and coral reefs. On land, tropical rainforests contain many species variation with an abundance of species in bird, mammals, amphibians, and plants. While tropical rainforests occupy only 7 percent of the Earth’s land area, they contain over half of the world’s species. This may be because species richness tends to increase with decreased elevation, increasing solar exposure, and increased precipitation; that is, hot, rainy low-land areas have the most species. In contrast, deserts have low species variation because of low precipitation. On earth, water is majorly important the equation for life. Many of the species are genetically isolated because of habitat size and variation in the build of the land (mountains, equator location, etc) such as seen in the Galapagos islands and the Amazon rainforest, both near and in South America.
Hope this helps!
