09/12 09 Molecular Genetics and Gene Expression Free Online FlashCards

What are the three components of a DNA nucleotide?

A nucleotide contains a deoxyribose sugar, a phosphate group, and one nitrogen-containing base: adenine, thymine, cytosine, or guanine.

What are DNA’s complementary base pairs?

Adenine pairs with thymine, and cytosine pairs with guanine. These complementary pairings are stabilized by hydrogen bonds.

What does semiconservative DNA replication mean?

Semiconservative replication produces daughter DNA molecules that each contain one parental strand and one newly synthesized strand.

How do leading and lagging strand synthesis differ?

The leading strand is synthesized continuously toward the replication fork; the lagging strand is synthesized discontinuously as Okazaki fragments.

What distinguishes transcription from translation?

Transcription makes RNA from a DNA template, whereas translation uses mRNA information to assemble a polypeptide.

How is eukaryotic pre-mRNA processed?

Eukaryotic pre-mRNA receives a 5′ cap and 3′ poly-A tail, while introns are removed and exons are joined by a spliceosome.

What is the role of tRNA in translation?

tRNA carries a specific amino acid to the ribosome and uses its anticodon to pair with a complementary mRNA codon.

What is a codon, and how many codons are in the genetic code?

A codon is a sequence of three mRNA nucleotides. The genetic code has 64 codons: 61 specify amino acids and three are stop codons.

When is lac operon transcription increased?

When lactose is available and glucose is scarce, bacteria increase lac operon transcription to produce proteins for lactose transport and digestion.

What is epigenetic regulation?

Epigenetic regulation changes gene activity without changing the DNA base sequence. DNA methylation is often associated with gene silencing.

What causes a frameshift mutation?

A frameshift results when an insertion or deletion changes the reading-frame grouping and is not a multiple of three nucleotides.

What are the three steps of a PCR cycle?

PCR repeatedly denatures DNA, anneals primers, and extends them with heat-stable DNA polymerase, amplifying a selected segment.