biochemistry and genetics pretest

[...]... of double-stranded DNA is semiconservative, meaning that each strand separates and serves as a template for synthesis of a new complementary strand The first round of replication of a labeled DNA helix in a cold (unlabeled) solution will yield two daughter double-stranded molecules, each with one labeled and one unlabeled strand The second round of replication will yield four double-stranded DNA molecules... for one daughter strand and 3′ to 5′ for the other daughter strand at the replication fork Despite the apparent need for 3′ to 5′ synthesis, all DNA polymerases and repair enzymes can only synthesize DNA in the 5′ to 3′ direction The apparent contradiction is solved by understanding that one strand of DNA is synthesized continuously in the 5′ to 3′ direction while the other strand is made up of small... lines) between A and T, and three bonds between C and G (Reproduced, with permission, from Murray RK, Granner DK, Mayes PA, Rodwell VW: Harper’s Biochemistry, 25/e New York, McGraw-Hill, 2000: 404.) 2 The answer is b (Murray, pp 412–434 Scriver, pp 3–45 Sack, pp 3–29 Wilson, pp 99–121.) In the classic double-helical model of DNA proposed by Watson and Crick, the purine (adenosine and guanine) and pyrimidine... diagnosis and management Their first two children, a boy and a girl, have a complete form of albinism (203100) with pink irides, blond hair, and pale skin Which of the following represents your correct advice concerning the newborn child? a b c d e A 1/8 risk for albinism and skin cancer from DNA deletions A 1/8 risk for albinism and skin cancer from DNA cross-linkage A 1/4 risk for albinism and skin... DNA between adenine methylated bases within a GATC sequence 8320 Wilson_01_k.qxd 28 11/14/01 10:36 AM Page 28 Biochemistry and Genetics Mismatches are removed and replaced First, a GATC endonuclease nicks the faulty strand at a site complementary to GATC, then an exonuclease digests the strand from the GATC site beyond the mutation Finally, the excised faulty DNA is replaced In HNPCC, the unrecognized... pyrimidine (cytosine and thymine) bases (see the figure above) attached to the sugar backbone are perpendicular to the axis and parallel to each other They are paired (A to G or T to C) and held together by hydrogen bonds The DNA strands (nucleotide polymers) are joined by linkages between the 3′-hydroxyl of each pentose (deoxyribose) and the 5′-phosphate of its deoxyribose neighbor Each strand composing... bonding in doublestranded DNA is important to allow each strand to act as a template for the other complementary strand, with adenine bonding to thiamine and cytosine bonding to guanine Hydrophobic stacking between bases in the hydrophobic interior of the double strand actually makes a greater contribution to the stability of the DNA double helix than does hydrogen bonding DNA and protein helices are... synthesize first a single strand and then a doublestranded DNA from a single-strand RNA template It was originally found in animal retroviruses Primase is a DNA-dependent RNA polymerase enzyme that synthesizes an RNA molecule 10 to 200 nucleotides in length that initiates or “primes” DNA synthesis DNA ligase joins DNA fragments and DNA gyrase winds or unwinds DNA Transfer RNA, 5SRNA, and other small RNAs are... of Use 8320 Wilson_02_k.qxd 38 11/14/01 10:37 AM Page 38 Biochemistry and Genetics 35 The DNA sequence M, shown below, is the sense strand from a coding region known to be a mutational “hot spot” for a gene It encodes amino acids 21 to 25 Given the genetic and amino acid codes CCC = proline (P), GCC = alanine (A), TTC = phenylalanine (F), and TAG = stop codon, which of the following sequences is a... nucleosides (Reproduced, with permission, from Murray RK, Granner DK, Mayes PA, Rodwell VW: Harper’s Biochemistry, 25/e New York, McGraw-Hill, 2000: 376.) 21 8320 Wilson_01_k.qxd 22 11/14/01 10:36 AM Page 22 Biochemistry and Genetics (a) (b) (a) Structure of DNA (B form) showing the double helix with antiparallel strands (arrows) One complete turn (3.4 nm) includes 10 base pairs (bp) A, adenine; C, cytosine; . should contain radioactivity in both strands d. One should contain radioactivity in both strands e. None should contain radioactivity 14 Biochemistry and Genetics 8320 Wilson_01_k.qxd 11/14/01. diseases include a horizontal pedi- gree pattern, affliction of males and females, frequent consanguinity 2 Biochemistry and Genetics Pathway Fed Fasted Diabetes Glycogen synthesis +− − Glycolysis. mutant allele detection by 8320 Wilson_hyf_k.qxd 11/14/01 10:35 AM Page 3 4 Biochemistry and Genetics Pedigree symbols and pedigree patterns. 8320 Wilson_hyf_k.qxd 11/14/01 10:35 AM Page 4 hybridization