1. Chromosomes, colored bodies, are composed of proteins and DNA. In human body
ID: 10302 • Letter: 1
Question
1. Chromosomes, colored bodies, are composed of proteins and DNA. In human body or somatic cells there are 23 chromosome pairs. In mature human sperm cells there are _____ nuclear DNA molecules. a. 23 b.1023 c. 46 d.1046 e. 922. Mendel's Law of Independent Assortment basically states that the alleles of two or more genes segregate independently within and between loci; the chromosomal explanation of this observation is alignment of nonhomologous chromosomes at metaphase I. If alleles at two loci are in linkage disequilibrium, the disequilibrium breaks down at a rate determined by r the recombination rate between the loci. For alleles at loci on different chromosomes, r is equal to
a. 1.0 b. 0.5 c. 0.25 d. 0.33 e. none of these is correct
3. Watson and Crick used model building and the data of other workers to propose a double helical model for DNA. The data of Erwin Chargaff on purine-pyrimidine ratios was critical and showed that
a. phosphodiester linkages are covalent b. base pairing is A-T & G-C
c. the two chains are held by hydrogen bonds
d. the DNA molecule is a double helix e. bases face the axis
Explanation / Answer
Hello, 1. In human sperm cells (gametes) there are half the number of chromosomes as in somatic cells (normal body cells). The answer is 23. 2. Alleles on different chromosomes have a rate of 50% or 0.5. 3. Chargaff showed that A/T and G/C always pair. The answer is B. Hope this helps!
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