How is blood flow in the placenta maintained so that there is maximum opportunity for the exchange of materials while still keeping the blood of the mother and the baby separate?
What will be an ideal response?
The mother's capillaries break down so that the chorionic villi are bathed in the mother's blood to allow maximum exposure, but the baby's blood remains in capillaries inside the chorionic villi to maintain separation.
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Transcription in prokaryotes is carried out by ______, which unwind(s) and transcribe(s) the gene.
A. RNA synthetase B. RNA polymerase II C. RNA polymerase III D. transcription factors E. RNA polymerase
Teratogens affect the ____ more than any other part of the fetal body
a. central nervous system b. upper limbs c. heart d. lower limbs e. external genitalia
Below is a pedigree of a human genetic disease in which solid color indicates affected individuals. Assume that the disease is caused by a gene that can have the alleles A or a. What is/are the possible genotype(s) of person 3?
A) AA
B) Aa
C) Either AA or Aa
D) aa
E) Cannot be determined
During meiosis, pairs of homologous chromosomes line up at the metaphase plate where they attach to kinetochore microtubules and are drawn to opposite poles of the cell. The selection of chromosomes from each pair is essentially random and accounts for much of the immense variety of traits displayed by sexually reproductive organisms, as illustrated in this diagram. Despite a similar division of genetic material between daughter cells in mitosis, no shuffling of chromosomes occurs. What accounts for this difference between meiosis and mitosis?
a. During mitosis, only a single combination of chromosomes is possible due to a slight polar charge that is absent during meiosis.
b. During mitosis, only a single combination of chromosomes is possible due to enzymes that arrange chromosomes in order.
c. During mitosis, only a single combination of chromosomes is possible because no recombination occurs and the homologs are never separated.
d. During mitosis, only a single combination of chromosomes is possible because nonconforming cells trigger an immune response.