How do recombination signal sequences ensure that gene segment rearrangement occurs in the right order?
What will be an ideal response?
Gene rearrangement by somatic recombination involves recombination signal sequences (RSSs) that flank V, D, and J segments and are recognized by the enzymes involved in cutting and rejoining the gene segments. An RSS is composed of a conserved nonamer sequence and heptamer sequence separated by a spacer region. There are two types of RSS, one with a spacer of 12 bp and one with a spacer of 23 bp. To ensure that segments are brought together in the right order, an RSS with a 12-bp spacer is always brought together with one with a 23-bp spacer. This is called the 12/23 rule. This ensures that in the heavy-chain locus, V rearranges to DJ and not directly to J or another V, and in the light-chain locus, V rearranges to J and not to another V.
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a. They exercise more. b. They are more often obese. c. They are less likely to smoke. d. They consume less fat in their diet.
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Indicate whether the statement is true or false
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a. Direct instruction b. Task style c. Mastery learning d. Cooperative learning