The central nervous system first forms during
A. fertilization.
B. cleavage.
C. neurulation.
D. gastrulation.
E. organogenesis.
C. neurulation.
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In the tryptophan operon, the repressor actively binds to the operator when:a
tryptophan binds to an allosteric site on the repressor protein, thereby activating it. b. tryptophan levels are low. c. lactose levels are low. d. there is a great need for proteins. e. allotryptophan levels are low.
Which of the following structures allow bacteria to transfer genetic information through conjugation?
A) slime layer B) pili C) capsule D) fimbriae E) glycocalyx
Which of the following statements about the globin gene family is true?
(a) The globin protein, which can carry oxygen molecules throughout an organism's body, was first seen in ancient vertebrate species about 500 million years ago. (b) The gene duplication that led to the expansion of the globin gene family led to the separation and distribution of globin on many chromosomes in mammals, such that no chromosome has more than a single functional member of the globin gene family. (c) As globin gene family members diverged over the course of evolution, all the DNA sequence variations that have accumulated between family members are within the regulatory DNA sequences that affect when and how strongly each globin gene is expressed. (d) Some of the duplicated globin genes that arose during vertebrate evolution acquired inactivating mutations and became pseudogenes in modern vertebrates.
In the treatment of ADA deficiency and SCID, which cell type was targeted for gene therapy?
A. Fibroblasts B. Embryonic stem cells C. Hematopoietic stem cells D. Lymphocytes E. Neutrophils