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3 years ago

Which pressure is associated with blood flow to organs?

Biology

1 answer:

oee [108]3 years ago

6 0

Answer:

In humans, blood pressure is usually measured indirectly with a special cuff over the brachial artery (in the arm) or the femoral artery (in the leg). There are two pressures measured: (1) the systolic pressure (the higher pressure and the first number recorded), which is the force that blood exerts on the artery walls as the heart contracts to pump the blood to the peripheral organs and tissues, and (2) the diastolic pressure (the lower pressure and the second number recorded), which is residual pressure exerted on the arteries as the heart relaxes between beats. In healthy individuals, systolic pressure is normally between 90 and 120 millimetres of mercury (mmHg).

Explanation:

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Why might a phylogeny based only on molecular data show a different pattern of relationships than a phylogeny of the same taxa b

Kitty [74]

A phylogeny of the same taxa based only on morphological traits:

Some highly conserved genetic sequences can result in unrelated species appearing closely related in a molecular phylogeny, and not reflect the same pattern as the morphologic phylogeny.

Gene sequence changes may not result in morphological changes.

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Morphological analyses always provide more data because each morphological trait is the result of the expression of many genes.

The molecular data may be based on the analysis of introns, which aren't expressed and don't contribute to the evolutionary history of a group of taxa.

Why is molecular data more accurate?

Phylogenetic trees reconstructed from molecular sequences are often considered more reliable than those reconstructed from morphological characters, in part because convergent evolution, which confounds phylogenetic reconstruction, is believed to be rarer for molecular sequences than for morphologies

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2 years ago

I need some help with an environmental science question.

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3 years ago

A gene is involved in promoting limb development in humans. The gene is initially weakly activated during the limb induction pha

Anna [14]

Answer:

1. If the gene is weakly activated, it likely lacks repressive histone modifications, but may also lack the presence of histone marks associated with strong transcriptional activation such as acetylation.

When the gene is strongly activated, it likely lacks repressive marks (such as H3K9me2/3 and H3K27me3 - both examples of repressive histone methylation) and might possess some activating histone acetylation marks, such as H3K4ac, and active histone methylation such as H3K4me3

An aside: The pattern and presence of different histone modifications would depend on the gene, but based on the fact that it is a developmental gene, I would assume that H3K27me3 and H3K4me3 are at play (these are part of the Polycomb/Trithorax system)

After limb growth is complete, the gene is turned off. Repressive histone methylation marks would be associated with this state, such as the aforementioned H3K9me2/3 or H3K27me3.

2. Histone modifications are tightly linked to genome organisation. Histone methylation marks associated with repression such as H3K27me3 and H3K9me3 are associated with compact chromatin structures, which restrict the access of transcriptional machinery and other positive regulators. Conversely, histone marks associated with gene activation are associated with a more permissive chromatin environment that facilitates the binding of factors associated with gene expression. In the case of histone acetylation, the acetyl mark directly removes the positive charge of chromatin, relaxing its interaction with negatively charged DNA.

3. If the inappropriate activation of this gene caused a cancerous tumor, this gene would be referred to as an oncogene (or a proto-oncogene for the term before it is inappropriately activated).

Typically, there are two classes of genes that lead to cancer: tumor-suppressor genes and oncogenes. Tumor suppressor genes lead to cancer when their protective activity is reduced or demolished, leading to the production of cancer cells. Oncogenes lead to cancer when they become over active. Oncogenes are often genes associated positively with growth and proliferation, consistent with the gene in this example.

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3 years ago

Please answer 5&6. Thank you.

erastovalidia [21]

Answer:

5. The correct answer would be an option A. ova

Note: I assume that all the samples are of human origin.

DNA (deoxyribonucleic acid) content of somatic cells of humans consists of 46 chromosomes or 23 pairs of chromosomes. Gametes (sperm or ova) are haploid cells produced by the process of meiosis and contain half the number of chromosomes found in parent cell. Hence, they contain 23 chromosomes.

6. The correct answer would be an option J.

Sperm formation or spermatogenesis is the process by which spermatozoa (haploid gamete) is produced from germ cell with the help of meiotic division.

Meiosis results in the formation of four haploid (n) cells from single diploid (2n) parent cell. Here, 2n is given as 8 so, n would be equal to 4.

Meiosis I results in the formation of two secondary spermatocyte cells (both haploid or 4 chromosomes in this case) from single primary spermatocyte (diploid or 8 chromosome in this case).

Both the secondary spermatocytes undergo meiosis II to produce 4 spermatids (each haploid or 4 chromosome in this case). Spermatids differentiate and mature into spermatozoa.

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