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Biotechnology Study Guide

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1. DNA Replication-DNA is made up of a double helix of two complementary strands. During
replication, these strands are separated. Each strand of the original DNA molecule then serves as
a template for the production of its counterpart, a process referred to as semiconservative
replication. As a result of semi-conservative replication, the new helix will be composed of an
original DNA strand as well as a newly synthesized strand.
2. The leading strand is the strand of nascent DNA which is being synthesized in the same
direction as the growing replication fork. This sort of DNA replication is continuous. The lagging
strand is the strand of nascent DNA whose direction of synthesis is opposite to the direction of
the growing replication fork.
3. DNA polymerase adds a new strand of DNA by extending the 3' end of an existing nucleotide
chain, adding new nucleotides matched to the template strand one at a time via the creation of
phosphodiester bonds.
4. A primer is a short single strand of RNA or DNA (generally about 18-22 bases) that serves as a
starting point for DNA synthesis. It is required for DNA replication because the enzymes that
catalyze this process.
5. Nucleotide excision repair is a DNA repair mechanism. DNA damage occurs constantly because
of chemicals, radiation and other mutagens. Three excision repair pathways exist to repair single
stranded DNA damage.
6. DNA ligase is a specific type of enzyme, a ligase, that facilitates the joining of DNA strands
together by catalyzing the formation of a phosphodiester bond. It plays a role in repairing single-
strand breaks in duplex DNA in living organisms.
7. Transcription is the first step of gene expression, in which a particular segment of DNA is
copied into RNA by the enzyme RNA polymerase.
8. Initiation is the beginning of transcription. It occurs when the enzyme RNA polymerase binds to
a region of a gene called the promoter. This signals the DNA to unwind so the enzyme can
‘‘read’’ the bases in one of the DNA strands.
9. Elongation is the addition of nucleotides to the mRNA strand. RNA polymerase reads the
unwound DNA strand and builds the mRNA molecule, using complementary base pairs.
10. Termination is the ending of transcription, and occurs when RNA polymerase crosses a stop
(termination) sequence in the gene
11. RNA processing- The splicing of pre-mRNAs is conducted by complexes of proteins and RNA
molecules called spliceosomes. Pre-mRNA splicing: Pre-mRNA splicing involves the precise
removal of introns from the primary RNA transcript. The splicing process is catalyzed by large
complexes called spliceosomes.
12. Exons can be termed as DNA bases which are translated into mRNA. Introns are also DNA
bases that are found in-between
13. Each spliceosome is composed of five small nuclear RNAs (snRNA) and a range of associated
protein factors. ... The snRNAs that make up the major spliceosome are named U1, U2, U4, U5,
and U6.
14. Exon shuffling is a molecular mechanism for the formation of new genes. It is a process through
which two or more exons from different genes can be brought together ectopically, or the same
exon can be duplicated, to create a new exon-intron structure.

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15. Translation is a step in protein biosynthesis wherein the genetic code carried by mRNA is
decoded to produce the specific sequence of amino acids in a polypeptide chain. The process
follows transcription in which the DNA sequence is copied (or transcribed) into an mRNA.
16. An aminoacyl-tRNA synthetase is an enzyme that attaches the appropriate amino acid onto its
tRNA. It does so by catalyzing the esterification of a specific cognate amino acid or its precursor
to one of all its compatible cognate tRNAs to form an aminoacyl-tRNA.
17. Ribosomes consist of two major components: the small ribosomal subunits, which read the RNA,
and the large subunits, which join amino acids to form a polypeptide chain.
18. A polyribosome is a complex of an mRNA molecule and two or more ribosomes that act to
translate mRNA instructions into polypeptides.
19. Codon- a sequence of three nucleotides which together form a unit of genetic code in a DNA or
RNA molecule.
20. Substitution. A substitution mutation occurs when one base pair is substituted for another.
Insertion and Deletion. An insertion mutation occurs when an extra base pair is added to a
sequence of bases.
21. A frameshift mutation is a genetic mutation caused by a deletion or insertion in a DNA
sequence that shifts the way the sequence is read.
22. An operon is a segment of DNA containing adjacent genes including structural genes, an
operator gene, and a regulatory gene. An operon is thus a functional unit of transcription and
genetic regulation.
23. The lac operon is a negatively controlled inducible operon, where the inducer molecule is
allolactose. In negative repressible operons, transcription of the operon normally takes place.
Repressor proteins are produced by a regulator gene, but they are unable to bind to the operator in
their normal conformation.
24. A repressor is a negatively acting regulatory protein. It binds to the operator region of a
promoter and thereby negatively influences the ability of RNA polymerase to transcribe the gene
or operon. In the absence of the inducer, the repressor binds to its operator. The other type of
effector is called a corepressor.
25. Gel electrophoresis is a laboratory method used to separate mixtures of DNA, RNA, or proteins
according to molecular size. In gel electrophoresis, the molecules to be separated are pushed by
an electrical field through a gel that contains small pores.
26. A plasmid is a small DNA molecule within a cell that is physically separated from a
chromosomal DNA and can replicate independently.
27. A restriction enzyme or restriction endonuclease is an enzyme that cleaves DNA into
fragments at or near specific recognition sites within the molecule known as restriction sites.
Restrictions enzymes are one class of the broader endonuclease group of enzymes.
28. Recombinant DNA molecules are DNA molecules formed by laboratory methods of genetic
recombination to bring together genetic material from multiple sources, creating sequences that
would not otherwise be found in the genome
29. Sticky end-an end of a DNA double helix at which a few unpaired nucleotides of one strand
extend beyond the other.
30. Restriction enzymes are DNA-cutting enzymes. Each enzyme recognizes one or a few target
sequences and cuts DNA at or near those sequences.

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1. DNA Replication-DNA is made up of a double helix of two complementary strands. During replication, these strands are separated. Each strand of the original DNA molecule then serves as a template for the production of its counterpart, a process referred to as semiconservative replication. As a result of semi-conservative replication, the new helix will be composed of an original DNA strand as well as a newly synthesized strand. 2. The leading strand is the strand of nascent DNA which is being synthesized in the same direction as the growing replication fork. This sort of DNA replication is continuous. The lagging strand is the strand of nascent DNA whose direction of synthesis is opposite to the direction of the growing replication fork. 3. DNA polymerase adds a new strand of DNA by extending the 3' end of an existing nucleotide chain, adding new nucleotides matched to the template str ...
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