Chapter 16 Flashcards
Genes exist as parts of chromosomes. What are the 2 chemical components of chromosomes?
DNA and protein
Transformation
Change in genotype and phenotype (observable characteristics of an organism) due to the absorption of external DNA by cell.
Bacteriophages aka phages
Viruses that infect bacteria
Virus 🦠
Little more than DNA or RNA enclosed by a protective coat
What are the 2 rules of chargaffs findings? You can use to predict % of nucleotide bases
1) DNA bases varies between species 2) the % of A and T bases are roughly equal and G and C are roughly equal
Antiparallel
Subunit run in opposite directions
In nitrogenous base pairing what pairs go together in the DNA double helix?
A with T G with C
DNA replication
The copying of DNA
What are the 3 alternative models of DNA replication?
Conservative model: 2 parental cells reassociate after acting as templates ***Semi conservative: 2 strands of parental molecule separate and each become part of a new pair **confirmed method** Dispersive model: each strand of birth parent and daughter molecules mix into each new template
Origins of replication
Short stretches of DNA that have specific sequence of nucleotides Proteins that initiate DNA replication recognize this sequence and attach to the DNA separating the 2 strands and opening up a replication bubble
Replication fork
A Y shaped region where the parental strands of DNA are being unwound
Helicases
Enzymes that untwist the double helix at replication forks, separating the two parental strands and making them available as template strands
Single strand binding proteins
Bind to unpaired DNA strands keeping them from re pairing
Topoisomerase
Enzyme that helps relieve the strain of untwisting the helix ahead of the replication fork. Relieves strain by breaking, swiveling and rejoining DNA strands
Primer
Short stretch of RNA that is an initial nucleotide chain and is synthesized by primase
Primase
Synthesized an RNA primer at 5’ end of leading strand and 5’ end of each Okazaki fragments of lagging strand
DNA polymerases
Catalyze the ynthesis of new DNA by adding nucleotides to the 3’ end of a pre existing chain
DNA polymerases can only add nucleotides to what end of a primer?
The free 3’ end The new DNA strand can elongate only in the 5’-3’ direction
Leading strand
Being made toward 5’ to 3’ direction toward the replication fork Elongates continuously
Lagging strand
Made away from the replication fork Synthesized in a series of segments called Okazaki fragments
Okazaki fragments
Series of lagging strand segments
Nuclease
DNA cutting enzyme Cuts out damaged strands of DNA
Nucleotide excision repair
DNA repair system
DNA pol III
Using parental DNA as a template, synthesis new DNA strand by adding nucleotides to an RNA primer or a preexisting DNA strand
