Exam 3 - Lecture 14 Flashcards
what is a genome?
all of the DNA present in a cell or virus
what is a genotype?
a specific set of genes an organism possesses
what is a phenotype?
collection of observable characteristics
how many sets of DNA do prokaryotes have? what about eukaryotes?
- prokaryotes: haploid (1N)
- eukaryotes: diploid (2N)
who did the first experiments proving DNA is the genetic material?
Fred Griffith
what was the bacteria used in the transformation experiments?
Streptococcus pneumoniae
explain the transformation experiment done with smooth and rough strains.
- smooth cells (S strain) have capsules and kill the host mouse
- rough cells (R strain) have no capsule and do not kill the host
- heat-killed S strains do not kill the host
- live R strain with heat-killed S strain kills the host because the unharmful R strain transformed with the DNA of the lethal S strain
what is a nucleoside? what is a nucleotide?
- nucleoside: nitrogenous base + 5 carbon sugar (ribose)
- nucleotide: nucleoside + phosphate
which strand of the DNA does the mRNA resemble?
the plus (+) strand
can RNA be double stranded?
yeap (folded in on itself)
what are the four major types of RNA?
- messenger (mRNA)
- ribosomal (rRNA)
- transfer (tRNA)
- small regulatory (sRNA)
where does replication complete in circular bacterial DNA?
the terminus
DNA synthesis only occurs in what direction?
5’ to 3’
DNA polymerase adds new bases to what end of the DNA?
the 3’ end
what are the three things DNA polymerase requires?
- template
- primer
- dNTPs
how many DNA polymerases does E. coli have?
5
which DNA polymerase plays the major role in replication in E. coli?
DNA polymerase III
which DNA polymerase is involved in lagging strand synthesis in E. coli?
DNA polymerase I
what is the role of helicase?
unwinding DNA strands
what is the role of single-stranded binding proteins?
keeping the DNA strands apart for replication to occur
what is the role of DNA gyrase & topoisomerases?
alter DNA supercoiling to relieve tension from rapid unwinding of double helix
what is the role of primase?
synthesizes short complementary strands of RNA (~10 nucleotides) to serve as primers needed by DNA pol I
what is the role of ligase?
attaching two pieces of single stranded DNA together
which strand of the DNA is synthesized non-continuously? how about continuously?
- lagging strand: non-continuously
- leading strand: continuously
how many primers does the lagging strand need?
a primer is needed for every Okazaki fragment
which DNA polymerase removes and replaces the RNA primers with DNA?
DNA pol I
DNA ligase forms a bond between what in the lagging strand?
between the 3’-hydroxyl of the growing strand and the 5’-phosphate of an Okazaki fragment
minor mistakes in DNA synthesis can be corrected by __________ activity
exonuclease
which direction does exonuclease work in?
3’ to 5’
do all polymerases have exonuclease activity?
nah
which DNA polymerase(s) has/have exonuclease activity?
DNA pol III
what is catenation?
when two circular chromosomes do not fully separate after replication
how is catenation solved?
topoisomerases temporarily break DNA molecules so that the strands can separate and then are ligated back into circular formation
what is the end replication problem?
shortening of chromosomes after each round of replication