DNA
DNA, or ______________________, contains information that helps an organism develop and function. It is made
up of _____________, which consist of a 5-carbon sugar (deoxyribose), a nitrogen-containing base (attached to the
sugar), and a phosphate group.
DNA, or deoxyribonucleic acid, is a nucleic acid that contains the information that is needed to help an organism
develop and function. Segments of DNA which are located in the _____________ and carry information for certain
traits are called _________. When a gene is expressed, a protein is synthesized and produces a _________.
DNA is composed of two polymers, which can be found in a __________ structure, giving DNA the nickname
"_______________________". The backbone of the DNA polymers is made of sugars and phosphate groups,
which are bonded together. The two polymers are linked by nitrogen bases, which attach to the sugars. The bases
on one DNA polymer pair with complementary bases on the other polymer in order to link the polymers together.
The four nitrogen bases are:
1. _____________(A)
2. _____________ (C)
3.______________ (G)
4. ______________ (T)
Three bases (in a row) make up a ___________. On an mRNA molecule, codons are read during _______________
and symbolize specific amino acids. When all of the codons have been read, the amino acids group together to form
________________.
During DNA Replication...
1. The two original strands of DNA separate.
2. DNA polymerases add complementary nucleotides to each strand.
(adenine bonds with thymine; cytosine bonds with guanine)
3. Two DNA molecules form, which are identical to the original DNA molecule.
The process of
____________________ begins with one double-stranded molecule of DNA. The two strands of this molecule
separate during replication, and DNA polymerases add __________________nucleotides to each strand. The end
results of DNA replication are two identical DNA molecules.
During Transcription...
1. Initiation: Enzymes bind to a DNA sequence and unzip the molecule.
2. Elongation: As the molecule unzips, RNA nucleotides pair to complementary DNA nucleotides on one of
the DNA strands. (If the DNA strand reads AGT, the new RNA strand would read UCA.)
3. Termination: Once base pairing is complete, the new RNA molecule (mRNA) breaks away from the DNA
strands and the DNA strands re-attach.
The process of _______________ occurs in the _____________of a cell, but the ______________ that is created
travels into the cytoplasm once it is made.
During Translation...
1. A codon on the mRNA molecule attaches to a _________________.
2. tRNA molecules, which each carry a specific ________ __________, approach the ribosome.
3. The tRNA molecule that corresponds to the codon (called the tRNA ___________) attaches to the mRNA
codon.
4. The ribosome slides to the next codon on the mRNA molecule and repeats the process.
5. As amino acids are added next to each other, peptide bonds link the amino acids together.
6. The ___________ of amino acids continues to grow until the ribosome reaches a __________ codon on the
mRNA strand. This signals that no more amino acids should be added and the ____________ is completed.
The first codon that is read on the mRNA molecule is usually a start codon (AUG), which codes for the amino acid
methionine.
Gene expression occurs as follows:
The instructions for building a protein are found in a ________ and are "rewritten" to a molecule of RNA during
________________. The RNA is then "deciphered" during translation.
DNA → ________________ → RNA → ___________________→ _________________
[Key: yellow-A, green-T, red-G, blue-C, purple-uracil]
Ribonucleic acid (RNA)
Uracil
Transcription
Translation
A change of a gene is called a ________________. Mutations can be harmful and cause genetic
______________such as cystic fibrosis and some forms of ________________. Mutations can be caused by
____________, exposure to toxic chemicals, through natural means during DNA replication, and so on.
Next
DNA Replication
After a molecule of DNA replicates, two ________________double-stranded molecules are formed. Each new
molecule contains one DNA strand from the _______________ molecule.
Process of DNA Replication
Before DNA can be _____________, initiator proteins must find origins of replication, or specific DNA sequences,
in the DNA. The initiator proteins then recruit other proteins, which help ______________the DNA molecule. The
enzyme DNA _____________ helps to unravel the strands of DNA by breaking hydrogen bonds between the
strands.
Then, an ___________primer attaches to the template to begin a new strand of _________. DNA polymerases add
nucleotides to the exposed nitrogen bases of the old DNA and check the new DNA molecule for errors. Nucleotides
are added to the 3' end of the strand. The repeated units of nucleotides form what is called a sugar-phosphate
backbone of the molecule.
Once the DNA polymerase is finished constructing the new strand, it will be _______________ to the template
strand but exactly the same as the original. In this way, one molecule of DNA can become two molecules.
Base-pairing Rules
The type of nucleotide that is added to a growing strand of DNA is determined __________________ rules. The
base-pairing rules are listed below.
Adenine (A) pairs with ______________ (T).
Cytosine (C) pairs with ______________ (G).