Cell Biology Lecture 6: Protein Structure, DNA, and Chromosomes

Practice vocabulary flashcards covering protein identification and determination methods, DNA structural discovery and composition, and eukaryotic chromosome organization and regulation.

Mass spectrometry

A technique that allows proteins to be identified based on its digestion fingerprint and amino acid sequence information through comparisons with predicted genomic sequences.

X-ray crystallography

A technique used to determine the three-dimensional structure of a protein molecule by analyzing the diffraction pattern produced when a beam of x-rays is passed through a crystal.

Nuclear magnetic resonance (NMR) spectroscopy

A technique used for determining the three-dimensional structure of a protein in solution.

Cryo-electron microscopy (cryo-EM)

A technique for observing the detailed structure of a macromolecule at very low temperatures after freezing native structures in ice.

Protein families

Groups of proteins that share specific “sequence-patterns” – stretches of amino acids that fold into distinct structural domains.

Alphafold

An AI database developed by DeepMind to predict protein structures.

Transformation

The taking up of extraneous genetic material by an organism, first observed by Frederick Griffith in Streptococcus pneumoniae.

T2 phage

A virus that infects and destroys bacteria, containing only DNA and protein; used by Hershey and Chase to prove DNA is the genetic material.

Antiparallel

A term describing the opposite orientation of the two polynucleotide chains in a DNA double helix.

Purines

The bulky nitrogenous bases in DNA, which are Guanine (G) and Adenine (A).

Pyrimidines

The smaller nitrogenous bases in DNA, which are Cytosine (C) and Thymine (T).

Chromatin

Long linear DNA molecules associated with proteins that fold the DNA into a compact structure.

Homologous chromosomes

The two copies of each chromosome present in most human cells, with one copy inherited from each parent.

Genome

The total genetic information carried by all the chromosomes in a cell, which in humans is approximately $3.1 \times 10^9$ nucleotide pairs.

Replication origin

The specialized DNA sequence where DNA replication begins.

Telomeres

DNA sequences that mark the ends of a chromosome and prevent misidentification as broken DNA needing repair.

Centromere

The DNA sequence used for separating duplicated chromosomes during Mitosis.

Nucleolus

The region where parts of different chromosomes carrying ribosomal genes cluster to make ribosomal RNA and form ribosomes.

Histones

Abundant, highly conserved, and positively charged chromosomal proteins (containing high proportions of arginine and lysine) around which DNA wraps.

Nucleosome

The beadlike structural unit of a eukaryotic chromosome composed of a short length of DNA wrapped around an octameric core of histone proteins.

Histone octamer

The core of a nucleosome consisting of two molecules each of H2A, H2B, H3, and H4.

SMC ring complex

A large ring-shaped structure containing Structural Maintenance of Chromosome protein subunits that uses ATP-hydrolysis to form DNA loops.

Cohesions

Ring-shaped SMC protein complexes that organize interphase chromosomes into chromatin loops and hold sister chromatids together after DNA replication.

ATP-dependent chromatin remodeling complexes

Complexes that utilize ATP hydrolysis to loosen DNA around nucleosomes and move it to expose the DNA to other factors.

Heterochromatin

The most highly compacted form of chromatin, visible with a light microscope and concentrated in centromeres and telomeres.

Euchromatin

The less condensed form of chromatin that is typically the region being actively transcribed.

X-inactivation

The formation of heterochromatin on one of two X chromosomes in females, ensuring only one X is expressed in that cell and its progeny.

Epigenetic inheritance

The transmission of a heritable pattern of gene expression from a cell to its progeny that does not involve altering the nucleotide sequence of the DNA.