Chapter 13 Molecular Basis Of Inheritance Flashcards
In_______, Watson and Crick introduced a model for _______
1953, DNA
Hereditary information is encoded in
DNA
The role of DNA was worked out by studying_______ and the _______ that infected them
Bacteria, viruses
Discovery of genetic of DNA began with research by _______ in _______
Frederick Griffith, 1928
Griffith mixed heat heat killers remains of pathogenic strain with harmless strain and some living cells became pathogenic. He called this_____
Transformation
Chargaff’s Rules
The base composition of DNA varies between species
In any species the percentages of A and T bases are equal and the percentages of G and C bases are equal
Franklin used ______ to determine the molecular structure of DNA
X-ray crystallography
Watson and Crick SemiConservative Model of Replication
Predicts that when a double helix replicates, each daughter molecule will have one old strand derived from the parent molecule and one newly made strand.
Conservative model
Two parent strands rejoin
Dispersive model
Each strand is a mix of old and new
Replication begins at sites called _________, where the two DNA strands are separated, opening up a replication bubble
Origin of replication
At each end of the bubble is a _________, a Y shaped region where the parents strands of DNA are being unwound
Replication fork
Helicases
Are enzymes that untwist the double helix at the replication forks
Single strand binding proteins
Bind to and stabilize single stranded DNA
Topoisomerase
Relieves the strain caused by tight twisting ahead of the replication fork by breaking, swiveling, and rejoining DNA strands
The initial strand is a short RNA
Primer
DNA polymerase cannot initiate_______ of a polynucleotide, they can only add nucleotides to an already existing chain base paired with the template
Synthesis
The enzyme_______, starts an RNA chain with a single RNA nucleotide and adds RNA nucleotides one at a time using the parent DNA as a template
Primase
The new DNA strand will start from the
3’ end of the RNA primer
Enzymes called_________, catalyze the elongation of new DNA at a replication fork
DNA polymerases
The rate of elongation is about _____ nucleotides per second I’m bacteria and ______ per second in human cells
500,50
dATP is
Used to make DNA and is similar to the ATP of energy metabolism
The difference is in the sugars: dATP has deoxyribose and ATP has ribose
As each monomer nucleotide joins the DNA strand,
It loses two phosphate groups as a molecule of pyrophosphate
Newly formed DNA strands must be formed _______ to the template strand
Antiparallel
DNA polymerase add nucleotides only in the free 3’ end of a growing strand. Therefore a new DNA strand can only elongate in the
5’ to 3’ direction
Leading strand
DNA polymerase synthesizes moving toward the replication fork
To elongate the other new strand, the ___________, DNA polymerase must work in the direction away from the replication fork
Lagging strand
The lagging strand is synthesized as a series of segments called
Okazaki fragments
After formation of Okazaki fragments, DNA polymerase removes
The RNA primers and replaces the nucleotides with DNA
The remaining gaps are joined together by
DNA ligase
The proteins that participate in DNA replication form a large complex
DNA replication machine
__________ proofread newly made DNA, replacing any incorrect nucleotides
DNA polymerase
In________ of DNA, other enzymes correct errors in base pairing
Mismatch repair
For linear DNA, the usual replication machinery cannot complete
The 5’ ends of daughter strands
Repeated rounds of replication produce shorter DNA molecules with
Uneven ends
Eukaryotic chromosomal DNA molecules have special nucleotide sequences at their ends called
Telomeres
Telomeres typically consist of
Multiple repetitions of one short nucleotide sequence
Telomeres do not prevent the shortening of DNA molecules but they do postpone it
An enzyme called_________ catalyzes the lengthening of telomeres in __________
Telomerase, germ cells
Telomerase is not active in most
Human somatic cells
In a bacterium, the DNA is supercoiled and found in a region of the cell called the
Nucleoid
A complex of DNA and protein found in the nucleus of eukaryotic cells
Chromatin
Proteins called________ are responsible for the first level of DNA packing in ________
Histones, chromatin
Four common types of histones
H2A, H2B, H3 and H4
A__________ consists of DNA wound twice around a protein core of eight histones, two of each of the main histone types
Nucleosome
The condensed chromatin is called___________, leas compacted chromatin is called
Heterochromatin, euchromatin
Nucleic Acid Hybridization
The base pairing of one strand of a nucleic Acid to another complementary sequence
Genetic Engineering
The direct manipulation of genes for practical purposes
Plasmids
Small circular DNA molecules that replicate separately from the bacterial chromosome
Recombinant DNA
Result of inserting foreign DNA into a plasmid
Production of multiple copies of a single gene
Gene cloning
The plasmid that carries the cloned DNA is called
Cloning vector
Bacterial Restriction Enzymes
Cut DNA molecules at specific DNA sequences called restriction sites
A restriction enzyme usually makes many cuts yielding
Restriction fragments
Sticky ends
Cleaves DNA in a staggered manner. Sticky ends can bind with other complementary sticky ends
Gel electrophoresis
Separates a mixture of nucleic Acid fragments based on length
Polymerase Chain Reaction
Can produce many copies of a specific target segment of DNA
The key to Polymerase Chain Reaction is an unusual heat stable DNA polymerase called
Taq Polymerase
Once a gene is cloned, complementary base pairing can be used to determine the genes complete nucleotide sequence in a process called
DNA sequencing
Purines
Two carbon nitrogen ring bases
Adenine and Guanine
Pyrimidines
One carbon nitrogen ring bases
Thymine and Cytosine
