Test 4. Chapter 17 Flashcards
Miescher was the first person to
see DNA
Mendel was the first ___________-
genectisist
He established the following foundation:
Inheritance involves the passing of discrete units of inheritance, or genes, from parents to offspring.
The inherited factors must separate into reproductive cells.
Genes located on different chromosomes will be inherited independently of each other.
Levene was first to discover?
order of the three major components of a single nucleotide (phosphate-sugar-base)
carbohydrate component of RNA (ribose) and DNA (deoxyribose)
what is chargarff’s rule?
nucleotide compostion of DNA varies among species
in DNA, purines=pyrimidines
what are the purines?
adenine guanine
what are the pyrimidines?
cytosine uracil thymine
describe the hershey and chase experiment
Bacteriophages are viruses that infect bacteria; they consist of a protein coat surrounding a nucleic acid.
- Radioactively label components
Label DNA with 32P
Label protein with 35S
Infect unlabeled bacteria
Separate bacteria from virus
each DNA nucleotide monomer is composed of __________,_________,___________-
nitrogenous base, deoxyribose sugar, phosphate
nucleotides are linked by 3’ 5’ _______ bond
phosphodiester bonds
these bonds join the 3’ hydroxyl of one nucleotide to hte 5’ phosphate of another
dna molecules consist of two chains of ____________ directionality intertwined to form a right-handed double helix
opposite directionality
the sugar-phosphate back bones are ___________ the helix, whereas the bases are ________ the helix
outside
inside
The bases are ___________ to the axis of the helix with adjacent bases separated by 3.4 A
perpendicular
the dna helix is approximately ________ wide
20 A wide
guanine and cytosine have how many hydrogen bonds?
3
adenine and thymine have how many hydrogen bonds
2
DNA is a relatively stable molecule with several ____________ interactions adding to its stability
noncovalent
“DNA”
hydrophobic interaction
internal base clustering
“DNA”
hydrogen bonds
formation of preferred bonds; three between CG base pairs and two between AT base pairs
“DNA”
base stacking
bases are nearly planar and stacked, allowing for weak van der Waals forces between rings
“DNA”
hydration
water interactions with the structure of DNA to stabilize structure
“DNA”
electrostatic interactions
destabilization by negatively charged phosphates of sugar phosphate backbone are minimized by the shielding of effect of water on Mg+2
semiconservative replication
Hypothesis proposed by Watson and Crick
Two strands of DNA separate
Each strand acts as template for synthesis of new strand
conservative
entire DNA molecule acts a stemplate for synthesis of entirely new one
dispersive
the original DNA double helix breaks apart into fragments, and each fragment then serves as a template for a new DNA fragment
semiconservative
two original strands seperate and each strand then serves as a template for a new DNA strand
during replication or transcription the two strands of DNA double helix must be separated
in the lab, DNA can be separated by heating in a solution, this is called ___________-
denaturation or melting
the temperature at which half of the DNA molecules are denatured is called the _____________-
melting temperature
upon cooling, the two strands can bind to one another to reform the double helix, a process called __________-
reannealing
what forms can DNA double helix adopt?
B form, A form, Z form
Watson and Crick discovery is referred to as ________ for DNA
B formed DNA (sodium salt)
another form is the _________ which forms when RNA/DNA duplexes form
A DNA form
__________ (zigzag conformation) is left handed DNA that can form as a result of torsion during transcription
Z DNA
DNA can form other structures, including cruciforms, which are cross like structures, probably a result of palindromes (___________)
inverted repeats
packaging large DNA molecule to fit inside a cell or nucleus requires a process termed __________–
supercoiling
The major and minor grooves are lined by sequence specific _____________ groups
hydrogen bonding groups
DNA super cooling faciliates several biological processes including :
packaging of DNA, replication, and transcription
Linear and circular DNA can be in a relaxed or supercoiled shape
when DNA is underwound, it twist to the right to relieved strain, causing __________-
negative supercoiling
supercoiling that forms during strand separation can be relieved by a class of enzymes called ________-
topoisomerases
they make reversible cuts that allow the supercoiled segments to unwind
nucleosomes are complexes of _______ and ________–
DNA and histones
histone ______ binds to the nucleosome where the DNA enters and acts as a clamp that prevents unraveling
H1
approximately _________ bp are in contact with the histone octamer (1.8 helical turns)
145 np
connections between nucleosomes requires approximately _________ bp of linker DNA (may vary between 20 and 70 depending on the speices and tissue)
60 bp
each of the highly conserved histone core proteins contains a common structure feature called _______ fold
histone fold
the N- terminal tails of histones protrude from the nucleosomes and can be covalently modfied (___________ and ___________)
methylation and acetylation
in anticipaiton of cell division chromatin must be compacted into ________—
chromosomes
nucleosomes are coiled into _______nm fiber which is further coiled to form _________ filament
30nm fiber
200 nm filaments
200 nm fibers have numerous supercoiled loops attached to a central nuclear scaffold
during interphase, chromatin can be in one of two forms?
heterochromatin (more condensed)
euchromatin
less condense
investigation of E. Coli revealed the following prokaryotic features?
- Genome size—usually considerably less DNA and fewer genes (E. coli 4.6 megabases) than eukaryotic genomes
- Coding capacity—compact and continuous genes
- Gene expression—genes organized into operons
prokaryotes often contain ________ which are usually small and circular DNA with additional genes
plasmids
What are unique eukaryotic genome features?
- Genome size—eukaryotic genome size does not necessarily indicate complexity
- Coding capacity—enormous protein coding capacity; 80% of human DNA sequences have biological functions
- Coding continuity—genes are interrupted by noncoding introns, which can be removed by splicing from the primary RNA transcript
about _______ of the human genome is intergenic or __________-
noncoding sequences
what are some differences between DNA and RNA primary structure?
- Ribose vs deoxyribose
- Uracil vs thymine
- RNA exists as a single strand that can form complex 3D structures by base pairing with itself
- Some RNA molecules have catalytic properties, or ribozymes (e.g., self-cleavages or cleave other RNA)
T/F in RNA non Watson Crick base pairs occur frequently?
True making 3D structure harder to predict
In RNA more elaborate structures may form, often stabilized by ______ ions
Mg+2
What do the following types of RNA do?
tRNA: brings aa to ribosome
rRNA: translates mRNA
mRNA: encodes aa seq
name types of ncRNA (noncoding)
miRNA: regulate gene expression
siRNA: RNA degradation (siRNA)
snoRNA: chemical modification
snRNA: mRNA processing
__________ transport amino acids to ribosomes for assembly (15% of cellular RNA)
TRNA
average length 75 bases
At least one tRNA for each amino acid
Structurally look like a warped cloverleaf due to extensive intrachain base pairing
amino acids are attached via specific ___________ to the end opposite of the three nucleotide anticodon
aminoacy-tRNA synthetase
Anticodon allows the tRNA to recognize the correct mRNA codon and properly align its amino acid for protein synthesis
The tRNA loops help facilitate interactions with the correct aminoacyl-tRNA synthetases
___________ is the most abundant RNA in the living cells with a complex secondary structure
rRNA
Components of ribosomes (eukaryotes and prokaryotes)
Scaffolding &
Enzymatic roles
compare eukaryotic rRNA with prokaryotic
Similar in shape and function, both have a small and large subunit, but differ in size and chemical composition
Eukaryotic are larger (80S) with a 60S and 40S subunit, while prokaryotic are smaller (70S) with 50S and 30S subunits
rRNA plays a role in scaffolding as well as enzymatic functions
Ribosomes also have proteins that interact with rRNA for structure and function
what is a ribosome made out of?
RNA and protien
_________ mediate modifications of other RNA nucleotides
Sno RNAS
Sno RNAs direct __________ and _________ enzymes to the appropriate rRNA nucleotide
methyltransferase
pseudouridine synthase
