Chapter 4: DNA & Gene Expression- Calista Velasquez

What is DNA?

The molecular script of life.

What is DNA made up of?

Two chains of nucleotides that wind around each other to form a double-helix.

What shape is DNA?

Double-helix.

What is each nucleotide made up of?

A phosphate group, deoxyribose sugar, and nitrogenous base.

What is the backbone of DNA?

The sugar and phosphate.

How are the rungs of the ladder connected together?

The rungs are the nitrogenous bases connected through hydrogen bonds.

What are the four nitrogen bases?

Adenine, Thymine, Cytosine, Guanine.

How do the nitrogenous bases of DNA pair?

A+T, C+G

What do the sequence of bases code?

Instructions for building proteins.

How does biotechnology use DNA’s stability and reproducibility?

PCR, gene sequencing, and genetic engineering.

What does understanding the structure of DNA allow?

The foundation of modern biotechnology and genetic medicine.

When does DNA replication occur?

S phase.

What is semiconservative replication?

When in DNA replication, each new molecule contains one old strand and one new strand.

How does the DNA double helix unwind?

With the help of enzymes that separate the strands.

What is the replication fork?

Region where DNA is actively unwound and copied.

What is the leading strand?

Synthesized continuously, away from the fork. Requires one primer.

What is the lagging strand?

Synthesized discontinuously, away from the fork. Has Okazaki fragments.

What type of DNA does bacteria have?

Double-stranded circular DNA.

What is DNA polymerase?

Attaches to the Origin of Replication, building new complementary strands.

What is the Origin Replication Complex?

Detects and binds to the Origin of Replication, marks where replication begins.

What is Helicase?

Unwinds the DNA double-helix by breaking the hydrogen bonds.

What is the purpose of the template DNA?

Serves as guides to build complementary new strands.

What is the Replication bubble?

Formed where strands separate, expands as replication proceeds.

What is the replication fork?

Region where DNA is actively unwound and copied.

What are topoisomerases?

Prevents DNA from unwinding ahead of the fork by making cuts. Relieves stress during replication.

What are single-strand binding proteins?

Keeps unpaired DNA strands from reattaching by binding to them. Stabilizes the replication fork.

What are RNA primers?

Short RNA sequences synthesized to start DNA synthesis.

What is primase?

Enzyme that synthesizes RNA primers on both strands.

What are Okazaki fragments?

Stretches of newly synthesized DNA joined later into a continuous strand.

What is DNA ligase?

Enzyme that joins Okazaki fragments. It is the final step ensuring a complete strand.

What are histone proteins?

Eight histones form a core around which DNA unwinds.

What are histones?

Small, positively charged proteins that bind to DNA, allowing it to coil tightly.

What are nucleosomes?

Basic unit of chromatin, consists of DNA wrapped around histones.

What is chromatin?

The entire DNA-protein complex visible in the nucleus.

What are euchromatin?

Loosely-packed, active.

What are heterochromatin?

Tightly-packed, inactive.

Who discovered transformation?

Oswald Avery.

When was transformation discovered?

1944.

What was the end conclusion of DNA transformation?

Today it is used to insert genes into bacteria, making up basic genetic engineering and recombinant DNA technology.

What is transcription?

Makes DNA into mRNA.

What is mRNA?

A single-stranded copy of DNA that carries genetic information to ribosomes. Formed through transcription.

What is a ribose phosphate backbone?

RNA’s sugar-phosphate sturcture (ribose instead of deoxyribose)

What is a codon?

A sequence of three RNA bases coding for a specific amino acid.

What is a polypeptide?

Chain of amino acids linked by peptide bonds. Becomes functional protein.

What is an enzyme?

A biological catalyst formed from polypeptide.

What is the central dogma of molecular biology?

DNA → mRNA → Protein → Trait.