Unit 7 honors bio

Bacteriophage (phage)

A virus that infects bacteria, important in studies of genetic material transmission.

Base pairing rules (complementary pairing)

The principle that adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G) in DNA.

DNA polymerase

Enzyme that adds complementary nucleotides to a growing DNA strand during replication; it also checks for mistakes and corrects them.

Double helix

The twisted ladder structure of DNA, formed by two complementary strands of nucleotides.

Helicase

An enzyme that unwinds the DNA double helix ahead of the replication fork.

Lagging strand

The DNA strand that is replicated in small segments (Okazaki fragments) in the direction opposite to the replication fork.

Leading strand

The DNA strand that is synthesized continuously in the direction of the replication fork.

Nucleotide

The monomer unit of DNA, consisting of a phosphate group, a sugar (deoxyribose), and a nitrogenous base (A, T, C, or G).

Okazaki fragments

Short DNA fragments formed on the lagging strand during DNA replication.

Purine

A type of nitrogenous base that has a two-ring structure, examples include adenine (A) and guanine (G).

Pyrimidine

A type of nitrogenous base with a single ring, examples include cytosine (C) and thymine (T).

Replication

The process by which DNA makes a copy of itself.

Replication origins (bubbles)

Sites where DNA replication begins; the DNA is unwound into a bubble-like structure.

Semiconservative replication

A model of DNA replication where each new DNA molecule consists of one original strand and one newly synthesized strand.

Frederick Griffith

Discovered the process of bacterial transformation using Streptococcus pneumoniae.

Oswald Avery

Showed that DNA is the substance responsible for transformation, not proteins.

Martha Hershey and Alfred Chase

Conducted the famous experiment with bacteriophages to demonstrate that DNA, not protein, is the genetic material.

Rosalind Franklin & Maurice Wilkins

Used X-ray crystallography to capture images of DNA, leading to the understanding of its double helix structure.

James Watson & Francis Crick

Proposed the double-helix model of DNA, integrating Franklin’s X-ray data.

Erwin Chargaff

Discovered that the amount of adenine equals thymine, and the amount of cytosine equals guanine in a DNA molecule (Chargaff’s rules).

Monomer of DNA

A nucleotide, which consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base (A, T, C, or G).

Differences between DNA and RNA

DNA has deoxyribose sugar and thymine (T), RNA has ribose sugar and uracil (U). DNA is double-stranded; RNA is single-stranded.

Protein Synthesis Process

Includes transcription (coping DNA code onto mRNA) and translation (using mRNA to create proteins at the ribosome).

Mutations

Changes in the DNA sequence that can alter the amino acid sequence of proteins.

Silent mutation

No effect on the protein.

Missense mutation

A single amino acid is changed.

Nonsense mutation

The change creates a stop codon, shortening the protein.

Frameshift mutation

Insertion or deletion of nucleotides shifts the reading frame, altering subsequent amino acids.

tRNA

Transfers amino acids to the ribosome based on the mRNA codon sequence.

rRNA

Makes up the structure of the ribosome.

Splicing

The process of removing introns and joining exons in pre-mRNA to form mature mRNA.