DNA Replication & Transcription Practice
PSI Biology
Name__________________________
Background
Cells must reproduce many times. In complex organisms, trillions of copies are made
from one original cell. When cells reproduce, they must replicate (or copy) their DNA.
The structure of DNA reveals how trillions of copies of the DNA in one of your cells can be
reproduced accurately. Each strand of DNA has two ends: a 5’ end and a 3’ end. The two
strands of DNA always run in opposite directions. They are said to be anti-parallel to
each other. The 5’ end has a phosphate group at the end, and the 3’ end has an - OH group
at the end. Replication of DNA begins when the strands separate. The original strand is
termed the parent or template strand and the new strand is the daughter strand. With
the help of enzymes, new nucleotides are added to the - OH end. Each new nucleotide
attaches to the parent strand according to base pairing rules.
For example:
3' ATCGGGTTAACGCGTAAA
5' TAGCCCAATTGCGATTT 3'
5'
template (parent) strand
new daughter strand
Part 1
Question 1: What would be the daughter strand produced from this parent strand?
3' GCT TAC TTG TCG AGG ACC
5' template (parent) strand
5' _____________________________________________ 3'
new daughter strand
Question 2: What would be the parent strand that produced this daughter strand?
3' _______________________________________________5' template (parent) strand
5'
AAA TTC GCG GCC TTA
3'
new daughter strand
Question 3: Fill in the missing pieces in the DNA molecule. Each piece is 15 base pairs long.
Each dash represents one missing base.
3' TT_
AGC GC_
5' _ _T T_ _
www.njctl.org
___
_GC CGT
AAT 5' template (parent) strand
_ _ A 3' new daughter strand
PSI Biology
Genes
Part 2
RNA is essential for bringing the genetic information stored in the DNA to where it can be
used in the cell. Transcription is the process by which RNA strands are synthesized from
DNA strands. This is the first step in the transport of the genetic information contained in
DNA. The process of transcription is very similar to that of DNA replication.
Note: the non-template strand of DNA matches the new RNA strand
except that U replaces T in RNA.
Question 4: What messenger RNA molecule would be produced from this DNA template
strand?
3' TAC TTG TCG AGG ACC ACT
5' template (parent) strand
5' __________________________________
3'
new messenger RNA molecule
Question 5: What is the DNA template strand that produced this messenger RNA
molecule?
3' ____________________________________
5' template (parent) strand
5' AUG UUG UCC GGU CAC UAA
3'
new messenger RNA molecule
Question 6: From the DNA daughter strand, synthesize both the template strand and the
corresponding messenger RNA molecule:
3' ______________________________________ 5' template (parent) strand
5' TAC TTC AGG TCG AGC ATC
5' _____________________________________
www.njctl.org
3'
daughter DNA strand
3'
new messenger RNA molecule
PSI Biology
Genes