Ch 16: The Molecular Basis of Inheritance Flashcards
What is transfromation?
a change in genotype and phenotype due to assimilation of foreign DNA
What are bacteriophages (or phages)?
viruses that infect bacteria
What is a virus?
DNA (sometimes RNA) enclosed by a protective coat, often simply protein
Who discovered the genetic role of DNA?
Frederick Griffith
What is the first Chargaffs rule?
the base composition of DNA varies between species
Who was involved in discovering the role of DNA in inheritance?
Maurice Wilkins and Rosalind Franklin came up with the first image of DNA and then James Watson stole the image and deduced his findings off of it
What is the second Chargaffs rule?
in any species the number of A and T bases is equal and the number of G and C bases is equal
What were the findings from Watson and Crick?
DNA has a structure of a double helix and the backbones are antiparallel
What type of unit is adenine and guanine?
they are both purine
What type of unit is cytisine and thymine?
they are both pyrimidine
What is DNA replication?
the copying of DNA
What is a semiconservative model?
it predicts that when a double helix replicates, each daughter molecule will have one old strand (derived or “conserved” from the parent molecule) and one newly made strand
What are origins of replication on DNA?
where the two DNA strands ae separated, opening up a replication “bubble”
What is a replication fork?
a Y-shaped region where parental DNA strands are being unwound
What are helicases?
enzymes that untwist the double helix at the replication forks
What are single-strand binding proteins?
proteins that bind to and stabilize single-stranded DNA
What is topoisomerase?
it relieves the strain of twisting of the double helix by breaking, swiveling, and rejoining DNA strands
What are DNA polymerases?
they are enzymes that catalyze the synthesis of new DNA at a replication fork
What is the function of a primer?
DNA polymerases require a primer so they can add nucleotides
What is the function of a primase?
to synthesize the short RNA primer
What do DNA polymerases require?
they require a primer and a DNA template strand
What is the difference between dATP and ATP?
dATP has deoxyribose while ATP has ribose
Which way does DNA polymerases add nucleotides?
DNA polymerases add nucleotides only to the free 3’ end of a growing strand, therefore a new DNA strand can elongate only in the 5’ –> 3’ direction
What does the DNA polymerase synthesize?
the DNA polymerase synthesizes a leading strand continuously, moving toward the replication fork
Besides the leading strand, what is the other strand called?
the lagging strand
How is the lagging strand elongated?
the DNA polymerase must work in the direction away from the replication fork
What are Okazaki fragments?
the series of fragments that are synthesized for the lagging strand
What are Okazaki fragments joined by?
they are joined together by DNA ligase
What occurs during mismatch repair?
repair enzymes replace incorrectly paired nucleotides that have evaded the proofreading process
What happens during nucleotide excision repair?
a nuclease cuts out and replaces damaged stretches of DNA
What is the function of telomeres?
telomeres do not prevent the shortening of DNA molecules, but they do postpone the erosion fo genes near the ends of DNA molecules
What are chromatin?
in the eukaryotic cell, DNA is precisely combined with proteins in a complex
What are histones responsible for?
these proteins are responsible for the main level of DNA packing in interphase chromatin
What are nucleosomes?
the unfolded chromatin which resembles beads on a string, the bead being the nucleosomes
What are nucleosomes composed of?
they are composed of DNA wound twice around a core of eight histones
What is euchromatin?
loosely packed chromatin
What is heterochromatin?
highly condensed chromatin
