Chapter 16: The Molecular Basis Of Inheritance Flashcards
Structure of DNA
Double helix
Antiparallel
Chargaff’s Rules
DNA composition varies between species
For each species percentages of A/T are roughly equal as are the C and G bases
DNA Composition
Deoxyribose - 5 carbon sugar
Nitrogenous base
Phosphorus group
Complimentary nucleotides are held together by hydrogen bonds
Bacteriophage
A virus that infects bacteria.
Infects genetic material into a cell that turns it into a phage producing factory
Evidence that DNA is the genetic material
Radioactive sulfur was added to proteins and radioactive phosphorus was added to the DNA in the chromatin of a phage
Only the phosphorus was transferred to the daughter phages
Chromatin
The complex of DNA and proteins that makes up eukaryotic chromosomes.
When the cell is not dividing it exists in its dispersed form, as a mass of long, thin fibers that are not visible with a light microscope
Euchromatin
The less condensed form of eukaryotic chromatin that is available for transcription
Heterochromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed
Replication Fork
A Y-shaped region on a replicating DNA molecule where the parental strands are being unwound and the new strands are being synthesized
Helicase
Unwinds parental double helix at replication fork
Single-strand binding protein
Binds to and stabilizes single-stranded DNA until it is used as a template
topoisomerase
Relieves overwinding strain ahead of replication fork by breaking, swiveling, and rejoining DNA strands
DNA pol I
Removes RNA nucleotides of primer from 5’ end and replaces them with DNA nucleotides added to the e’ end of the adjacent fragment
DNA pol II
Using parental DNA as a template, synthesizes new DNA strand by adding nucleotides to an RNA primer or pre-existing DNA strand.
Okazaki Fragment
A short segment of DNA synthesized away Fromm the replication fork on a template strand during DNA replication
DNA ligand
Joins Okazaki fragment of lagging strand
On leading strand, joins 3rd end of DNA that replaces primer to rest of leading strand DNA
Telomere
Tandemly repetitive DNA at the end of eukaryotic chromosome’s DNA molecule. Telomeres protect the organism’s genes from being eroded during successive rounds of replication
Telomerase
Catalyzes the lengthening of telomeres in eukaryotic germ cells, thus restoring their original length
Leading Strand
The new complementary DNA strand synthesized continuously along the template strand towards the replication fork in the 5 to 3 direction
Lagging strand
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5 to 3 direction away from the replication fork.
Semiconservative model
A type of DNA replication in which the replicated double helix consists of one old strand, derived from the parent molecule, and one newly made strand.
