Characteristics of the genetic material:
1.) Genetic material must contain complex information, capable of storing large amounts of information with the capacity to vary (mutations) but still stable
2.) Genetic material must replicate faithfully, can be copied accurately
3.) Genetic material mus
Why was the discovery of the structure of DNA so important for understanding genetics?
Without knowledge of the structure of DNA, an understanding of how genetic information was encoded or expressed was impossible.
The genetic material must be capable of...
carrying large amounts of information, replicating faithfully, and translating its coding instructions into phenotypes
nucleotides
repeating unit of DNA, contains a sugar, a phosphate, and a nitrogen containing base
Chargaff's rules
Ratios of the bases in DNA, amount of adenine is always equal to the amount of thymine (A=T), and the amount of guanine is always equal to the amount of cytosine (G=C)
Griffith's Experiments:
-injected bacteria into mice (streptococcus pneumoniae)
- virulent (smooth) into mice = mouse death, always, virulent bacteria recovered in blood of mice
-nonvirulent (rough) into diff mice = mouse lived, no bacteria recovered in autopsy
-heat killed viru
What did Griffith's experiments demonstrate?
Transformation in bacteria, discovery of the transforming principle
Identification of the transforming principle:
Avery, MacLeod, McCarty: identified DNA as transforming principle
Experiment:
1.) took virulent (smooth) bacteria, heat killed it, homoginized and filtered it
2.) took filtrate and added RNase to one sample, Protease to another, and DNase to last one
3.)
If Avery, MacLeod, and McCarty had found that samples of heat killed bacteria treated with RNase and DNase transformed bacteria, but samples treated with protease did not, what conclusion would they have made?
Protein is the genetic material
Hershey-Chase experiment:
Tested to find out which part of a phage (DNA or protein) serves as the genetic material and is transmitted to phage progeny (E.coli and phage T2)
1.) Radio label DNA (phosphorus) or some virus, and Protein (sulfur) of others by growing e.coli in two diff
Could Hershey and Chase have used a radioactive isotope of carbon instead of P32? Why or why not?
No because carbon is found in both protein and nucleic acid
What did Watson and Crick use to help solve the structure of DNA?
X-ray diffraction, models of DNA, and laws of structural chemistry
Frankel-Conrat and Singer's experiment:
Demonstrated that RNA in the tobacco mosaic virus carries the genetic information
1.) removed protein coats from two diff strains of TMV
2.) mixed RNA of each with opposite protein creating to hybrid viruses
3.) Infect the tobacco with the new Hybrids
4.)
Three levels of DNA structure:
Primary: nucleotide structure of DNA
Secondary: DNA's stable three dimensional configuration, helical structure
Tertiary: complex packing arrangements of double stranded DNA in chromosomes
Two sugars of nuclei acids:
pentose sugars, with five carbon atoms, ribose in RNA, and deoxyribose in DNA
primary structure of DNA
consists of a string of nucleotides joined together by phosphodiester linkages, sequence of bases
Simple structure of DNA:
a polymer- chain made up of many repeating units linked together
ribose
RNA's sugar, has a hydroxyl group (-OH) attached to the 2' carbon atom, makes RNA more reactive and less chemically stable than DNA
deoxyribose
DNA's sugar, has a hydrogen atom (-H) at the 2' carbon instead of an (-OH)
nitrogenous base
second component of a nucleotide, may be a purine or pyrimidine
purine
consists of a six-sided ring attached to a five-sided ring, adenine and guanine
pyrimidine
consists of a six-sided ring only, cytosine, thymine (only DNA), uracil (only RNA)
nucleoside
a deoxyribose or a ribose sugar and a base together
phosphate group
third component of a nucleotide, consists of a phosphorus atom bonded to four oxygen atoms, carries a negative charge making DNA acidic, bonds to 5' carbon atom of the sugar in a nucleotide
deoxyribonucleotides
deoxyribonucleoside 5'-monophosphates, DNA nucleotide, there is one phosphate group attached to 5' carbon of the sugar
ribonucleotides
ribonucleoside 5'-monphosphates, RNA nucleotide
What are the two different types of DNA bases?
purines (adenine and guanine) and pyrimidines (thymine and cytosine)
How do sugars of RNA and DNA differ?
The sugar of RNA has a hydroxyl group that is not found in the sugar of DNA
List the four types of DNA nucleotides:
dAMP-Deoxyadenosine 5'-monophosphate
dGMP-Deoxyguanosine 5'-monophosphate
dTMP-Deoxythymidine 5'-monophosphate
dCMP-Deoxycytidine 5'-monophosphate
phosphodiester linkages
strong covalent bonds that link nucleotides together, joining the 5'-phosphate group of one nucleotide to the 3' -carbon atom of the next nucleotide
polynucleotide strand
series of nucleotides linked by phosphodiester linkages
backbone of the polynucleotide strand:
composed of alternating sugars and phosphates
What are the differences between the two ends of a DNA strand?
5' end: a free phosphate group is attached to the 5'- carbon atom of the sugar in the nucleotide
3' end: has free OH group attached to the 3' -carbon atom of the sugar
DNA secondary structure
double helix- two polynucleotide strands wound around each other
antiparallele nucleotide strands
two strands in DNA run in opposite directions of one another, the 5' end of one strand is opposite the 3' end of the other strand
What holds the two strands of a double helix together?
Two different types of molecular forces:
Hydrogen bonds: link the bases on opposite strands, weak compared to covalent phosphodiester bonds that connect the sugar and phosphate groups of adjoining nucleotides of a strand
Interaction between stacked base p
What is the cause of the specificity of base pairing in DNA?
Hydrogen bonding, which imposes a limitation on the types of bases that can pair. Adenine pairs with thymine through two hydrogen bonds. Cytosine pairs with guanine through three hydrogen bonds. C-G pairing is stronger than A-T pairing.
complementary DNA strands
two polynucleotide strands of a DNA molecule are not identical but complementary due to base pairing
The antiparallel nature of DNA refers to?
the opposite direction of the two strands of nucleotides
B-DNA
traditional structure of DNA, exists in the presence of plenty of water with no unusual base sequence in the DNA, most stable configuration, it is an alpha helix, with right handed (clockwise) spiral
- 10bp per 360 deg turn, has major and minor groves
A-DNA
structure occurs when there is less water present, it is an alpha (rich-handed) helix, shorter and wider than B-DNA
Z-DNA
forms a left handed helix, the sugar-phosphate backbone zig-zags back and forth, results if the molecules contains particular base sequences (eg. stretches of alternating C and G nucleotides)
How does Z-DNA differ from B-DNA?
Z-DNA has a left-handed helix; B-DNA has a right handed helix. The sugar-phosphate backbone of Z-DNA zigzags back and forth, whereas the sugar-phosphate backbone of B-DNA forms a smooth continuous ribbon
hairpin
common type of secondary structure found in single strands of nucleotides, forms when sequences of nucleotides on the same strand are inverted complements, consists of a region of paired bases (the stem) and sometimes a region includes intervening unpaire
Hairpins are formed in DNA as a result of:
sequences on the same strand that are inverted and complementary
DNA methylation
process in which methyl groups (-CH3) are added to certain positions on the nucleotide bases, modifies DNA
5-methylcytosine
formed commonly in eukaryotic DNA by methylation of cytosine bases
key characteristics of the genetic material:
-store information
-replicate faithfully
-encode the phenotype
-stable
-undergo change (mutations)
-RNA also has these features but it is not as stable as DNA due to 2'-OH group, it is the genetic material in some viruses and plants
nuclein
first discovery of nucleic acid
Who is responsible for the discovery of the transforming principle?
Griffith
Who is responsible for the identification of the transforming principle?
Avery, MacLeod, and McCarty
Who proved DNA is the genetic material?
Hershey-Chase
Who found that RNA can act as genetic material in viruses?
Frankel-Conrat and Singer
What connects the 5'-phosphate group and the 3'-OH group of adjoining nucleotides?
a phosphodiester linkage
How many hydrogen bonds pair A and T?
two
What replaces thymine in RNA?
uracil
How many hydrogen bonds pari G and C?
three
reverse transcription
transfers information from RNA to DNA in some viruses
What is the DNA backbone composed of?
deoxyribose sugars linked by phosphate
transcription
information is transferred from DNA to an RNA molecule
DNA replication
information is transferred from one DNA molecule to another
translation
information is transferred from RNA to a protein through a code that specifies the amino acid sequence
special information pathways in some viruses:
information is transferred from RNA to DNA (RNA transcription), or to another RNA molecule (RNA replication)
What keeps helix width uniform?
Pairing of purines with pyrimidines, Chargaffs rules
Polarity of DNA?
single stranded DNA is polar, double stranded is not
Which carbon of the pentose sugar does the nitrogenous base in a nucleotide bond to?
covalently bonds with the 1'-C of the sugar
major groove:
allows proteins to bind and identify DNA while in the helix form
central dogma
states that genetic information passes from DNA to protein in a one-way information pathway
What three general characteristics must the genetic material posses?
1.) must contain complex information that encodes phenotype
2.) must replicate or be replicated faithfully
3.) must be able to mutate to generate diversity
What experiments demonstrated that DNA is the genetic material?
Hershey-Chase experiment using bacteriophage T2 demonstrated that DNA is the genetic material of the bacteriophage. Avery, Macleod, and McCarty demonstrated that the transforming material initially identified by Giffith was DNA
What is transformation? How did Avery and his colleagues demonstrate that the transforming principle is DNA?
Transformation occurs when a transforming material (DNA) genetically alters the bacterium that absorbs the transforming material. Avery and his colleagues demonstrated that DNA is the transforming material by using enzymes that destroyed the different cla
How did Hershey-Chase show that DNA is passed to new phages in phage reproduction?
Hershey and Chase used the radioactive isotope P32 to and S 35 to demonstrate that DNA is passed to new phage particles during phage reproduction. The progeny phage released from bacteria infected with P32-labedled phages emitted radioactivity from P32. T
Why was Watson and Crick's discovery so important?
By deciphering the structure of DNA molecule, they provided the foundation for molecular studies of the genetic material (DNA), allowing scientist to discern how genes function to produce phenotypes. Their model also suggested a possible mechanism for the
How does a purine differ from a pyrimidine? What purines and pyrimidines are found in DNA and RNA?
A purine consists of a six sided ring attached to a five sided ring. A pyrimidine consists of only a six sided ring. In both DNA and RNA, the purines are adenine and guanine. Pyrimidine cytosine is found in both RNA and DNA, DNA alone contains the pyrimid
Which bases are capable of forming hydrogen bonds with each other?
A-T (2), C-G (3)
What different types of chemical bonds are found in DNA and where do they occur?
Covalent bonds: called phosphodiester linkages hold together the deoxyribonucleotides in a single chain(strand) of DNA between the 3' end of the deoxyribose sugar of a nucleotide and the 5' end of the deoxyribose sugar of the next nucleotide in the chain.
What are some of the important genetic implications of the DNA structure?
Gives insight into the three fundamental genetic processes. It suggests that genetic information is encoded in the nucleotide sequences. The complementary polynucleotide strands indicate how faithful repletion of the genetic material is possible. The arra
What are the major transfers of genetic information?
replication, transcription, and translation (part of central dogma)
What are hairpins and how do they form?
Hairpins are a type of secondary structure found in single strands of nucleotides. The formation of hairpins occurs when sequences of nucleotides on the single strand are inverted complementary repeats of one another