CH 1 book terms Flashcards
alleles
One of several alternative forms of a gene occupying a given
locus on a chromosome.
annealing/hybridization
The renaturation of a duplex structure from single strands that were obtained by denaturing duplex DNA.
antiparallel
two polynucleotide chains running in opposite directions
antisense/template strand
the sequence of mRNA is complementary to the sequence of one strand of DNA
back mutations
A mutation that reverses the effect of a mutation that had inactivated a gene; thus, it restores the original sequence or function of the gene product.
base pairing
hydrogen bonding between bases
bivalent
The structure containing all four chromatids (two representing each homologue) at the start of meiosis.
causes of point mutations
- Chemical modification of DNA directly changes one base into a different base.
- An error during the replication of DNA causes the wrong base to be inserted into a polynucleotide.
central dogma
DNA to RNA to polypeptide
chiasma
The point of synapsis between homologs
chromatid
Either of the two threadlike strands formed when a
chromosome duplicates during the early stages of cell division. The two strands are held together at the centromere and separate into daughter chromosomes during anaphase.
chromosome
A discrete unit of the genome carrying many genes. Each
consists of a very long molecule of duplex DNA and an
approximately equal mass of proteins (in eukaryotes).
cis-acting
A site that affects the activity only of sequences on its own molecule of DNA (or RNA); this property usually implies that the site does not code for protein.
coding/sense strand
the sequence of mRNA is identical (apart from the replacement of T with U) to the other strand of DNA
codon
Each trinucleotide sequence
colinear
The relationship that describes the 1:1 correspondence of a sequence of triplet nucleotides to a sequence of amino acids.
denaturation
A molecule’s conversion from the physiological conformation to some other (inactive) conformation. In DNA, this involves the separation of the two strands due to breaking of hydrogen bonds between bases.
DNA polymerases
An enzyme that synthesizes a daughter strand(s) of DNA (under direction from a DNA template). Any particular enzyme may be involved in repair or replication (or both).
DNases
degrade DNA
endonucleases
break individual phosphodiester linkages within RNA or DNA molecules, generating discrete fragments
exons
The sequences that are transcribed, retained, and joined in the mature mRNA
exonucleases
remove nucleotide residues one at a time from the end of the molecule, generating mononucleotides
forward mutations
A mutation that inactivates a functional gene
frameshift mutation
A genetic mutation formed through the addition or deletion of nucleotide bases such that the reading frame is thrown off. The resulting polypeptide formed is usually abnormally short or abnormally long and most likely nonfunctional.