Chapter 8 Flashcards
Gene
A segment of a DNA molecule that contains the information required
for the synthesis of a functional biological product, whether protein or RNA
________ are components of ribosomes, the complexes that carry out the synthesis of proteins.
Ribosomal RNAs (rRNAs)
_________ are intermediaries, carrying information for the synthesis of a
protein from one or a few genes to a ribosome
Messenger RNAs (mRNAs)
___________ adapter molecules that faithfully translate the information in mRNA into a specific sequence of amino acids
Transfer RNAs (tRNAs)
___________ and Nucleic Acids Have Characteristic Bases and Pentoses
Nucleotides
A nucleotide has 3 characteristic, what are they?
- A nitrogenous base
- A pentose
- One or more phosphates
________ is a molecule without a phosphate group but has a nitrogenous base & pentose is what?
Nucleoside
The nitrogenous bases are derivatives of what two parent compounds?
- Pyrimidine
- Purine
Nucleobase is a ________ nitrogenous base
Heterocylic
The base of a nucleotide is joined covalently at _______ of pyrimidines & ______ of purines
N-1, N-9 & in pentose at C1 & in phosphate at C5
Both DNA & RNA both contain the purines bases such as _______ & _____
Adenine (A) & Guanine (G)
Both DNA & RNA contain the pyrimidines base _______
Cytosine (C)
Thymine is also a pyrimidine base but found in _____
DNA
Uracil is also a pyrimidine base but found in ______
RNA
2’-deoxy-D-ribose is the pentose for _______
DNA
D-ribose is the pentose for _____
RNA
Both DNA & RNA have pentose in a _________ form
β-furanose (closed five-membered ring) form
Both DNA & RNA have pentose in a _________ form
β-furanose (closed five-membered ring) form & they are “puckered”
Prime numbers distinguish _____________ numbering
sugar & base
Nucleobases are derivatives of _________ & ___________
Pyrimidine or purine
___________ Bonds Link Successive Nucleotides in Nucleic Acids
Phosphodiester
The successive nucleotides of both DNA and RNA are covalently linked
through phosphate-group “bridges,” in which the 5′-phosphate group of one
nucleotide unit is joined to the 3′-hydroxyl group of the next nucleotide,
creating a ________________
phosphodiester linkage
The properties of nucleotide bases affect the 3-D structure of __________
Nucleic Acids
Nucleobases are planar structures which asborb UV light around __________
250-270nm
Nucleobases vary in polar groups which is based on their tautomeric form where you have to identify their ______ & _______
Hydrogen bond donors & acceptors
Chargaff’s rule
Was a key to establishing
the three-dimensional structure of DNA and yielded clues to how genetic
information is encoded in DNA and passed from one generation to the next
What is chargaff rule?
- The base composition of DNA generally varies from one species to
another. - DNA specimens isolated from different tissues of the same species
have the same base composition. - The base composition of DNA in a given species does not change
with an organism’s age, nutritional state, or changing environment. - In all cellular DNAs, regardless of the species, the number of
adenosine residues is equal to the number of thymidine residues (that
is, A = T), and the number of guanosine residues is equal to the
number of cytidine residues (G = C). From these relationships it
follows that the sum of the purine residues equals the sum of the
pyrimidine residues; that is, A + G = T + C.
Describe DNA structure in a 2D sense
DNA molecules are helical, with two periodicities along their long axis, a primary one of 3.4 Å and a secondary one of 34 Å.
Describe the 3D structure of DNA
- It consists of two helical DNA chains wound around the same axis to form a right-handed double helix
- The hydrophilic
backbones of alternating deoxyribose and phosphate groups are on the
outside of the double helix, facing the surrounding water. - The furanose ring
of each deoxyribose is in the C-2′ endo conformation. - The purine and
pyrimidine bases of both strands are stacked inside the double helix, with
their hydrophobic and nearly planar ring structures very close together and
perpendicular to the long axis.
The offset pairing of the two DNA strands forms ________ & ________ groove
Major groove & minor groove
G & C has ____ H-bonds & A & T has ____ H bonds
3,2
DNA strands run ____________ to each other in a 3’, 5’, - phoshodiester
Antiparallel
The two DNA strands are ______________ to each other
Complementary
The DNA double helix is held together by ________ between complementarybase pairs
H bonds
The double helix is primarily stabilized by ____________, which shield the negative charges of backbone phosphates, and by base-stacking interactions between complementary base pairs.
metal cations
Base-stacking interactions between adjacent G≡C pairs are stronger than those between adjacent A=T pairs or adjacent pairs including all four bases. Because of this, DNA duplexes with higher G≡C content are more __________.
stable
What is the equation verison of Chargaff rule?
A + G = C + T (A-U are base pairs in RNA)
What is the equation verison of Chargaff rule?
A + G = C + T (A-U are base pairs in RNA) (purine pairs with pyrimidine)
A-T and G-C base pair are_________ to helix axis
perpendicular
In the watson & crick model of B form DNA it shows that the bases are stack on top of each other & that they are distance by _____ angstroms & the strands are _____ angrtsom long with a heical turn of _____ angstrom
3.4, 20, 10.5
__________________ of DNA Strands allows each strand to serve as a template for the synthesis of new strands
Complementarity
Pyrimidines are generally restricted to the _______________ because of steric interference between the sugar and the carbonyl oxygen at C-2 of the pyrimidine
anti-conformation
The Watson & crick structure of DNA is referred to as _________ DNA
B-Form DNA (most stable form of DNA)
What are the 3 forms of DNA?
A form, B form, Z form
A common type of DNA sequence is a _____________
palindrome
A _____________ is a word, phrase, or sentence that is spelled identically when read either forward or backward; two examples are ROTATOR and NURSES RUN
palindrome
In DNA palindrome is a term applied to regions of DNA with _________, such that an inverted, self-complementary sequence in one strand is repeated in the opposite orientation in the paired strand
inverted repeats
The self-complementarity within each strand confers the potential to form __________ or cruciform (cross-shaped) structures
hairpin
Mirror repeat
When the inverted repeat
occurs within each individual strand of the DNA
____________ do not have complementary sequences within the same strand and thus cannot form hairpin or cruciform structures
Mirror repeats
Messenger RNAs Code for _______________ Chains
Polypeptide
In eukaryotes, most mRNAs are _______________
monocistronic
Monocistronic mRNA
Carries the code for only one polypeptide
Double helical DNA & RNA can be ______________-
Denatured
DNA ______________ occurs when hydrogen bonds are broken and strands separate
Denaturation
During DNA denaturation the genetic doe remains intact & base stacking is lost, UV absorbance _________ due to the hyperchromic effect
Increase
DNA denaturation is induced by _______________________
high temperatures or pH
Denaturation of a double-stranded
nucleic acid produces the opposite result: an increase in absorption which is called the ____________ effect
Hyperchromic
__________________ is the process where a denature DNA reforms to its double stranded DNA
Annealing
What is the process of annealing?
Seperated strand of DNA are associated by base pairs to form a partially denature DNA into a double helical DNA
The midpoint of melting (Tm) depends on base _______________ & DNA length (longer DNA higher Tm), & on pH & ionic strength (high salt increase Tm)
Composition (high CG increases Tm)
At rich regions ______ at a lower temp than GC rich regions
Melt
Nucleotides and Nucleic Acids Undergo ____________________
Nonenzymatic Transformations
Mutations
Alterations in DNA structure that produce permanent changes in the genetic information encoded
Deamination
Nucleotide bases undergo spontaneous loss of their exocyclic
amino groups
