Chapter 24 Definitions/Concepts Flashcards
(23 cards)
Genome
Nucleic acid sequence as genetic material that almost every cell contains.
Chromosome Definition
Segments of DNA that hold parts of the genome
Gene
Segment of DNA that encodes the primary sequence of a final product (either a polypeptide or RNA).
Intergenic Regions
Regions of DNA between genes. Serve structural and regulatory functions.
Codons
Set of three successive nucleotides required to code an amino acid in a polypeptide.
Human Genome
Consists of 23 chromosomes of variable length.
Diploid
Most human cells contain a pair of each chromosome.
Exons
Coding segments in genes.
Introns
Non-coding segments in genes. Make up a higher percent of nucleotides in high order eukaryotes.
Transposons
Sequences which can move from one location in the genome to another.
Centromere
Location of attachment of the mitotic spindle during cell division and contains thousands of copies of 5-10 base pair simple repeats.
Telomere
The sequence at the ends of the chromosomes that help stabilize the chromosomes and contain repeat sequences with 4 stranded tetraplex structures.
DNA Supercoiling
A result of structural strain. Helps compact DNA. Highly regulated by intracellular enzymes.
DNA Topology
The study of the properties of an object under continuous deformations (thermal motion, interactions with proteins or molecules) rather then discontinuous deformations (strand breakage without reattachment).
Plectonemic Supercoiling
Form extended right-handed coiled coils which typically contain many branches.
Solenoidal Supercoiling
Form tight left-handed turns which are compact and are typically stabilized but protein binding.
Chromatin Definition
In non-dividing eukaryotic cells the chromosomal material is amorphous (appears to have no structure) and is dispersed throughout the nucleus.
Chromatin Structure
Fibers containing DNA tightly associated with histone proteins. Can contain non-histone proteins for gene regulation and structure.
Nucleosome
Each histone bound DNA structural unit containing;
-8 Histone proteins
-146 base pairs of DNA, wrap 1.8 turns left-handed
-linker DNA to like to next nucleosome
-additional protein to bind linker
Facilitates solenoidal supercoiling and compaction.
Histones
Small proteins containing a lot of lysine and argenine which interact and neutralize the phosphate backbone of DNA. Amino acid sequence is highly conserved.
30 nm Fiber
Structure containing successive nucleosomes.
Rosette
Further DNA compaction in which related genes cluster into loops.
Nucleoid
Found in bacteria. High concentration of DNA without the physical bounds of a nucleus. Forms attachments to the plasma membrane, organizes a series of loops, binds histone like proteins. Thought to facilitate higher rates in RNA production, cell division (replicates every 20 min.) and metabolism.
