Biology DNA Structure and Replication Flashcards
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Read the first 7 Biology DNA Structure and Replication flashcards as text
The end-replication problem refers to the inability of DNA polymerase to fully replicate:
Answer: The lagging strand at the 3' end of linear chromosomes, causing telomere shortening
After the final RNA primer on the lagging strand is removed from the 5' end, there is no upstream 3'-OH to fill in the gap, causing progressive shortening of linear chromosome ends.
Which of the following nucleotides is found in DNA but NOT in RNA?
Answer: Deoxythymidine monophosphate (dTMP)
Thymine (as deoxythymidine) is found only in DNA; RNA uses uracil instead of thymine and contains ribose instead of deoxyribose.
A DNA molecule is described as B-form. This means it is:
Answer: The standard right-handed double helix with approximately 10.5 base pairs per turn
B-form DNA is the most common form under physiological conditions: a right-handed double helix with about 10.5 base pairs per helical turn.
If one strand of a DNA molecule has the sequence 5'-ATCGGC-3', what is the sequence of the complementary strand?
Answer: 5'-GCCGAT-3'
The complement of 5'-ATCGGC-3' is written antiparallel as 3'-TAGCCG-5', which is the same as 5'-GCCGAT-3'.
Which of the following correctly describes semi-conservative replication?
Answer: Each daughter molecule contains one original parental strand and one newly synthesized strand
In semi-conservative replication, the double helix unwinds and each original strand serves as a template for a new complementary strand, so each daughter molecule is a hybrid.
What would happen if a cell lacked functional DNA ligase during replication?
Answer: Okazaki fragments on the lagging strand would remain unjoined
Without ligase, the nicks between Okazaki fragments on the lagging strand after primer replacement could not be sealed, leaving a broken lagging strand.
The major and minor grooves of the DNA double helix are important because they:
Answer: Allow proteins to access and read the base sequence without fully unwinding DNA
Proteins such as transcription factors and restriction enzymes can insert into the grooves and make contact with specific base pairs to read the genetic sequence.