Answer the following statements true (T) or false (F)
1. The fast block to polyspermy occurs through a rapid increase in cytosolic calcium within the egg.
2. The sperm and its DNA enters the egg through simple diffusion through the egg plasma membrane.
3. The cortical reaction prevents multiple sperm from contributing their chromosomes to the egg.
4. The endoderm is a germ cell layer that tends to cover the embryo.
1. FALSE
2. FALSE
3. TRUE
4. FALSE
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In humans, males are the ____ sex, and females are the ____ sex
a. autosomal, maternal b. recessive, dominant c. dominant, recessive d. homogametic, heterogametic e. heterogametic, homogametic
Answer the following statements true (T) or false (F)
1, Antigen-presenting dendritic cells are found in the skin and in the linings of the respiratory and digestive tracts. 2. The function of dendritic cells is to signal T cells, starting an immune response. 3. Experimental gene therapy can be used to treat a form of severe combined immune deficiency, SCID-X1. 4. People homozygous recessive for a 32-base deletion in the CCR5 gene do not become infected with HIV. 5. Mutation of the CCR5 coreceptor may have enabled people to survive various European plagues during the Middle Ages.
All steroids have
a. the same number of double bonds. b. one or more fatty acids. c. four rings of carbon to which other atoms are attached. d. the same functional groups. e. the same number and positions of double bonds.
For a species with a diploid number of 10 chromosomes, how many different combinations of maternal and paternal chromosomes are possible for the gametes?
A) 5 B) 25 C) 32 D) 100 E) about 10,000