Ch. 1 Genes, DNA, RNA, & Polypeptides (Exam 1) Flashcards
Genes, Genetic Material
1
Q
Which molecule is the basis of heredity?
A
DNA
2
Q
Define heredity.
A
The passing of genetic information from one generation to the next
3
Q
What is the relationship between DNA, genes, and chromosomes?
A
Genes consist of DNA and are located on chromosomes, which are very long DNA molecules
4
Q
What is the central dogma of molecular biology?
A
DNA encodes RNA, which translates into proteins/polypeptides
5
Q
What exactly do genes do?
A
Code for proteins
6
Q
What aspects of a species do genes dictate?
A
Its inherent properties
7
Q
What macro-molecule do most genes produce?
A
Specific proteins
8
Q
What is the main macro-molecule in an organism that is translated from RNA?
A
Protein
9
Q
Genes are a functional unit of this…
A
Heredity
10
Q
What are alleles?
A
Different forms of the same gene
11
Q
What is a genetic locus?
A
The particular location of a gene
12
Q
What are the 3 main properties that define a gene’s nature?
A
- Replication
- Generation of Form
- Mutation
13
Q
Describe generation of form and what it requires.
A
Working organismal structure is form, and DNA is needed to create and maintain that form
14
Q
What is responsible for offspring resembling their parents?
A
The transmission of genetic material
15
Q
What are 5 requirements of genetic material?
A
- Must carry genetic info/code
- Must self-replicate
- Must allow for mutation
- Must govern phenotype expression (gene function)
- Must be stable
16
Q
Who was the first to evidence DNA as the genetic material of organisms?
A
Frederick Griffith
17
Q
What did Hershey & Chase conclude?
A
DNA is the genetic material of phages
18
Q
What was the conclusion of Griffith’s transformation experiment?
A
The live R-Strain was transformed by S-Strain via inheritance of some “transforming principle” from heat-killed S-Strain
19
Q
What was the purpose of Avery, McLeod, and McCarty’s project?
A
To understand Griffith’s “transforming principle”
20
Q
Why did the DNAase in Avery, McLeod, and McCarty’s experiment prevent the transformation of the live R-Strain into S-Strain?
A
The DNAase dissolved the heat-killed S-Strain’s DNA
21
Q
What was Avery, McLeod, and McCarty’s conclusion?
A
DNA was Griffith’s “transforming principle”
22
Q
What did Hershey and Chase want to know?
A
How phages reprogrammed bacterial cells to create more phages
23
Q
How did Hershey and Chase set up their experiment?
A
They used 2 sets of phages. One set’s DNA was irradiated with P-32, and the other set’s protein was irradiated with S-35
24
Q
What was the result of Hershey and Chase’s experiment?
A
The P-32 phages were no longer radioactive, but the S-35 phages were still radioactive. The P-32-infected bacteria were found to contain the P-32 radio-label
25
What did Hershey and Chase conclude?
DNA is the genetic material for the genome of a cell or virus
26
What is the eukaryotic analog of bacterial transformation?
Transfection
27
Define DNA in terms of it being a polymer.
Linear, unbranched polymer with monomeric subunits
28
What are the 3 parts of a nucleotide?
Pentose sugar, phosphate group, & nitrogenous base
29
How does deoxyribose differ from ribose?
Deoxyribose has 2 H's at C2 while ribose has an H and an OH group at C2
30
Why is ribose less stable than deoxyribose?
The OH group is very reactable
31
What are the 4 DNA bases?
Adenine, guanine, cytosine, & thymine
32
How does a nitrogenous base bond with pentose?
Via an N-glycosidic bond
33
Which DNA bases are purines?
Adenine and guanine
34
Which DNA bases are pyrimidines?
Cytosine & thymine
35
Is uracil a purine or pyrimidine?
Pyrimidine
36
Which pyrimidine carbon bonds with pentose's C1?
C1
37
Which purine carbon bonds with pentose's C1?
C9
38
What is the bond between the pentose and phosphate group called?
Phosphodiester bond
39
What does the sugar-phosphate backbone provide?
Support
40
What gives DNA it's negative charge?
Phosphate group
41
What makes up a nucleoside?
Pentose sugar & base
42
Describe the DNA shape Watson & Crick built based on Franklin's research?
Right-handed, clockwise helix
43
What did Franklin find with her x-ray diffraction?
The double helical DNA structure
44
Adenine fits with...
Thymine
45
Cytosine fits with...
Guanine
46
What is the length of one helical turn?
34 Angstrom, or 3.4 nm
47
How many base pairs (bp) per turn?
10 to 10.5
48
Which two types of groove along a helix help to maintain its structure and integrity?
Major & minor
49
Generally describe a major groove.
Wide & deep
50
Generally describe a minor groove.
Shallow & broad
51
What are Chargaff's rules?
1) G is proportionate to C, and A to T
2) G = C, and A = T
3) # of purines & pyrimidines exist 1:1
52
Why does the G-C duplex have a stronger base pair bond?
It has 3 hydrogen bonds as opposed to the 2 that the A-T duplex has
53
What form is the typical double helix in?
B
54
Major groove (B form) length is...
22 Angstrom
55
Minor groove (B form) length is...
12 Angstrom
56
How does A-form DNA differ from B-form?
A-form is shorter, thicker, dehydrated B-form
57
Under what conditions will you find Z-form DNA?
High salt concentration
58
What are 3 factors contributing to the DNA forms?
Ionic environment, hydration environment, & protein bind to helical conformation
59
Which process of the central dogma is reversible?
Transcription
60
How does replication differ from translation and transcription?
Replication deals with the inheritance of gene info while translation and transcription deal with expressing that info
61
Why do RNA viruses mutate so often?
RNA is unstable because of the OH group on the ribose sugar
62
What is the result of RNA virus mutation?
Large-scale variation
63
How do retroviruses work?
They use reverse transcription to make a DNA intermediate and incorporate that DNA into the host genome
64
Why does genome size vary between organisms?
Different organisms require different amounts of protein to be produced
65
Do eukaryotes or prokaryotes have the larger genome?
Eukaryotes
66
What is DNA supercoiling?
Over- or underwinding of DNA and is an expression of the strain on that strand
67
Why is supercoiling important?
To be able to compact DNA for packaging within cells
68
What are the 2 states of DNA in terms of coiling?
Relaxed & supercoiled
69
DNA that has a normal number of bp per helical turn is said to be in its...
Relaxed state
70
What are the 2 types of supercoiling?
Positive and negative
71
Describe positive supercoiling.
Twists in the same direction; overwinding
72
Describe negative supercoiling.
Twisting in opposite direction; underwinding
73
What is the linking number (L)?
Number of times a strand wraps around another
74
What two components make up the linking number?
Twist (T) and writhe (W)
75
Define twist (T).
Number of helical turns
76
Define writhe (W).
Number of times double helix crosses itself (i.e. the supercoils)
77
What is the general formula for supercoiling?
L = T + W
78
What is the supercoiling formula for relaxed DNA?
L = T
79
What is melting temperature (T)?
The midpoint of the temperature range where DNA strands separate
80
What does melting temp depend on?
G-C content
81
What is the relationship between G-C content and melting temp?
^G-C content = ^energy to break bonds = ^T
82
What is hybridization?
Renaturation of complementary nucleic acid sequences
83
Which sequences can hybridize into a duplex?
Complementary sequences
84
What are the 4 RNA bases?
Adenine, cytosine, guanine, and uracil
85
What are the 3 types of RNA?
1) Messenger RNA (mRNA)
2) Ribosomal RNA (rRNA)
3) Transfer RNA (tRNA)
86
What is the key to DNA's longevity?
The absence of the OH makes it more stable
87
What is the purpose of mRNA’s presence in gene expression?
It turns genes ON and OFF depending on if mRNA is present or not
88
How does the OH group in RNA help when a gene is defective?
The OH helps decompose the RNA, and mRNA can turn off those defective genes once decomposed
89
What is the endgame of DNA's longevity?
To carry all genetic information needed to build up an organism
90
Which is more resistant to photochemical mutation? Thymine or cytosine?
Thymine
91
How does thymine help the genetic message?
Thymine makes it more stable
92
Cytosine frequently deaminates to...
Uracil
93
Why is the deamination of cytosine so harmful to DNA (HINT: repair enzymes)?
The repair enzymes can't tell the difference between C & U, particularly if U is already present in the DNA, and U is very prone to photochemical mutations
94
How does thymine remedy cytosine deamination (HINT: thymine's methyl group)?
T's hydrophobic methyl ensures proper base pairings while C sorts itself out and replaces the defective one
95
What are two advantages to uracil's resistance to oxidation in the cytoplasm?
Reduced energy expense & surviving outside the nucleus in RNA
96
What is RNA's general function?
To carry genetic info from DNA into the cytoplasm
97
What is the predominant form of RNA?
mRNA
98
What is the purpose of RNA being the intermediate of the central dogma?
DNA is vital and never leaves the nucleus, so a liaison is needed to carry genetic info
99
What are 2 possible damages DNA could sustain if RNA didn't exist?
1) Frequent unwinding & unwrapping of chromosomes
2) The collision of replication & proteinsynthesis
100
How many possible codons are there to account for the 20 amino acids?
64
101
This is described as the blueprint of DNA and RNA...
The genetic code
102
Define codon
Nucleotide triplet that codes for an amino acid
103
What is the unambiguous rule of codons (HINT: the codon's faithfulness & fidelity)?
One codon codes for one amino acid
104
Amino acids can be considered hoes because...
They are not bound by any one codon
105
How many codons actually code for amino acids?
61
106
What are the 3 types of codons?
Sense, start, and stop
107
What is the function of a sense codon?
To code for amino acids
108
What is the function of the start codon?
To initiate an amino acid sequence
109
What is the start codon and its associated amino acid?
AUG - methionine
110
What is the function of a stop codon?
To end proteinsynthesis
111
Name the 3 stop (nonsense) codons.
UAA
UAG
UGA
112
The genetic code is non-overlapping. What does this mean?
One base cannot participate in the formation of more than one codon
113
Why is reading a codon left to right different from reading it right to left?
The direction will specify different amino acids
114
What are the 3 types of mutation?
1) Substitution
2) Insertion
3) Deletion
115
What is a nonsense mutation?
A single substitution leading to the end of proteinsynthesis
116
What is a substitution (point/missense) mutation?
A single base is substituted for another
117
What is an insertion mutation?
Base is added to sequence
118
What is a deletion mutation?
Base is deleted from sequence
119
Insertion and deletion mutations can lead to a frameshift. What happens with a frameshift mutation?
Bases deleted or inserted cause a shift in the codon set
120
Which type of mutation has the least effect?
Substitution
121
Which mutation has the greatest effect?
Frameshift
122
What are the 3 possible reading frames for nonoverlapping triplets?
1st, 2nd, and 3rd position
123
What is the purpose of an open reading frame?
To be the sequence translated into the polypeptide.
124
How many open reading frames are in any stretch of DNA?
Usually no more than 1
125
Why are alternate reading frames not often considered?
They're frequent to stop codons
126
What is the antisense/template strand?
The DNA strand complementary to the mRNA sequence
127
What is the coding/sense strand?
The top DNA strand that runs from 5' to 3' and is nearly identical to the mRNA sequence (has thymine instead of uracil)
128
Define gene expression.
Process by which genetic info is used to make RNA/polypeptides
129
What are the 3 main components of an amino acid?
Amino group, carboxyl group, and an R-group
130
The amino group is the { } terminal of an amino acid.
End
131
The carboxyl group is the { } terminal of an amino acid.
C
132
What are the 4 distinct R-groups for the amino acids as depicted in the lecture?
1) Nonpolar hydrophobic
2) Polar uncharged
3) Polar acidic
4) Polar basic
133
The peptide bond is the result of...
The condensation/dehydration reaction occurring between amino acids
134
How many amino acid residues are there in a protein?
More than 60
135
What is the shape of primary protein structure?
Linear peptide chain
136
What does primary protein structure dictate protein function?
Indirectly through additional structure levels
137
What 2 conformations can secondary protein structures be presented as?
Alpha helices & beta sheets
138
What is secondary protein structure responsible for?
Generating overall conformation and fold of a protein
139
What type of bond forms under secondary structure?
H-bonds
140
What is tertiary protein structure?
The folding of secondary components into 3D configuration
141
What interactions in tertiary structure are believed to contribute to protein stability?
The hydrophobic interactions from nonpolar side chains
142
What is quaternary structure?
The folding of 2 or more tertiary structures into multi-subunit proteins
