Nearly half of the pregnancies that end in miscarriage have:a
trisomy of chromosome 21.
b. homozygosity for a recessive lethal allele.
c. major chromosomal abnormalities.
d. Klinefelter syndrome.
e. Down syndrome.
c
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The tertiary structure of a protein is the _____
A) bonding together of several polypeptide chains by weak bonds B) order in which amino acids are joined in a polypeptide chain C) unique three-dimensional shape of the fully folded polypeptide D) organization of a polypeptide chain into an ?-helix or ?-pleated sheet E) overall protein structure resulting from the aggregation of two or more polypeptide subunits
Scientists have used the fossil record to estimate the average length of time that a species inhabits the Earth. How can this estimate be useful for assessing the impact of humans on the Earth's biological diversity?
A) It can help determine how long the human species might survive. B) It can determine which species might become extinct soon, even if humans aren't involved. C) It can estimate how many species extinctions are caused by human activity. D) It can assure us that human activity is not the cause of most species extinctions.
What do we mean when we use the terms monohybrid cross and dihybrid cross?
A) A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents. B) A dihybrid cross involves organisms that are heterozygous for two characters that are being studied, and a monohybrid cross involves organisms that are heterozygous for only one character being studied. C) A monohybrid cross is performed for one generation, whereas a dihybrid cross is performed for two generations. D) A monohybrid cross results in a 9:3:3:1 ratio whereas a dihybrid cross gives a 3:1 ratio.
For a pathogen to cause an infection, which of the following must be present?
a. There must be an open wound in the skin. b. The host must be able to fight off the infection. c. If the pathogen must be very strong. d. The pathogen must be able to resist the defenses of the host.