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Biology in Society > Exam 4 > Flashcards

Exam 4 Flashcards

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1
Q

DNA was first (1869) isolated by Swiss chemist

A

Friedrich Meischer; called it “nuclein”.

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2
Q

(1929) Phoebus Levene discovered

A

deoxyribose as sugar component of DNA.
Discovered four nitrogenous bases of DNA: thymine, adenine, guanine, and cytosine.
Tetranucleotide hypothesis: DNA consisted of short chains of 4 repeating nucleotide units.

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3
Q

(1928-1943) Several investigators reported experimental results suggesting that DNA carried

A

heritable information

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4
Q

Nucleic acids are polymers of

A

nucleotides

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5
Q

nucleotides are consisted of

A

pentose sugar
- ribose in RNA
- deoxyribose in DNA

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6
Q

nitrogenous base consists of

A

purines and pyrimidines.
Purines: G, A
Pyrimidines: C, T (DNA), U (RNA)

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7
Q

Phosphate group consists of

A

Nucleoside: nitrogenous base + sugar.
Nucleotide: nucleoside + ≥ 1 phosphate.

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8
Q

Chargaff and Base Composition of DNA

A

analyzed base composition of DNA from several different species
base comparison varies between species
- suggests molecular diversity
regularity in the ratio of nucleotide bases

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9
Q

Chargaff’s Rules

A

Rule 1: Base composition of DNA varies btw species.
Rule 2: %A ≈ %T; %G ≈ %C.
- Use to calculate unknown %s.
Exception: фX174 = bacteriophage
- Has single stranded, circular genome.

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10
Q

Rosalind Franklin (7/25/1920 – 4/16/1958)

A

British biophysicist working in X-ray crystallography.
- ↑ understanding molecular structure of DNA, RNA, viruses.
Data was critical to Watson-Crick DNA model.
- Shown to Watson w/o her knowledge.
- Prepared papers recognizing two forms A and B-DNA

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11
Q

Franklin’s X-ray Crystallography Data

A

X-rays are deflected as pass through DNA fibers.
Watson and Crick assembled models conforming to Franklin’s data and Chargaff’s rules.

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12
Q

Watson-Crick Model of Double Helix

A

Duplex DNA: structure consists of two strands.
Two strands are anti-parallel:

Followed Franklin’s conclusion: sugar-phosphate backbone was outside.
- Places hydrophobic bases interior.
Helix makes a full turn every 3.4 nm and bases are stacked 0.34 nm apart.

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13
Q

Nucleic Acids are Directional

A

Phosphodiester bonds result in a polymer w/ distinct ends.
5’ end: ends in terminal phosphate.
3’ end: ends in pentose sugar with free 3’ hydroxyl group.

Covalently linked sugars and phosphates make up phosphodiester backbone.

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14
Q

________ - ________ only pairing that fits.

A

Purine-pyrimidine
Strands stabilized by hydrogen bonds.
Explains Chargaff’s Rules
Dictates combos btw strands
No sequence restrictions along strand

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15
Q

Watson-Crick base pairing is key to information sharing in

A

DNA replication
Transcription (DNA > RNA)
Translation (mRNA > polypeptide [protein])

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16
Q

Leading strand

A

synthesized continuously in direction of replication fork.

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17
Q

Lagging strand

A

synthesized discontinuously in direction away from replication fork

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18
Q

Helicase

A

uses ATP hydrolysis to unwind DNA duplex

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19
Q

Primase

A

Synthesizes a short RNA primer.

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20
Q

DNA polymerase

A

DNA-dependent synthesis of comple-mentary DNA molecule.

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21
Q

DNA ligase

A

joins adjacent replicated strands.

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22
Q

Enzymes that catalyze synthesis of new DNA by adding _________ to a preexisting chain.

A

nucleotides
Require primer and a template strand.

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23
Q

E. coli

A

several DNA polymerases; two most important for DNA replication
DNA Pol I: removes RNA primer and replaces w/ DNA.
- DNA Pol III: adds DNA nucleotide to RNA primer and continues to add Nts complementary to template strand.

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24
Q

Rate of elongation

A

≈ 500 Nt/sec in bacteria and ≈ 50 Nt/sec in human cells.

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25
Q

DNA polymerase

A

catalyzes addition of a nucleotide to the 3’ end of a growing chain

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26
Q

Each nucleotide added is in the form of dNTP

A

dNTP

  • each monomer is added, pyrophosphate is lost.
  • Hydrolysis of pyrophosphate is a coupled exergonic rxn.
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27
Q

Structural differences RNA vs. DNA

A

Sugar = ribose (2’ OH)
Uracil (U) instead of thymine (T).
Usually single stranded

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28
Q

Messenger RNA

A

mRNA: carries information from DNA to ribosome

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29
Q

Transfer RNA

A

tRNA: delivers specific amino acids to ribosome

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30
Q

Ribosomal RNA

A

rRNA: structural and catalytic part of ribosome.

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31
Q

Regulatory RNA

A

regulate gene expression; include microRNA (miRNA), long, non-coding RNA (lncRNA), small interfering RNA (siRNA).

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32
Q

intramolecular base pairings of purines and pyrimidines
A=U
G=C
creates intramolecular regions with different structures;

A

stem: complementary base pairing by antiparallel turns of RNA strand.
loop: unpaired region

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33
Q

(Francois Jacob and Jacques Monod, 1961) hypothesized that single-stranded RNA

A

messenger RNA carries info from DNA to ribosomes.

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34
Q

Gene Expression in Bacteria

A

Most genes are continuous.
Some genes are organized into operons.
- Produce a polycistronic mRNA.
Lack of compartment-alization allows coupling of transcription and translation

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35
Q

Template strand

A

used to direct transcription; complementary and antiparallel to RNA.
- Also called antisense strand.

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36
Q

Non-template strand

A

NOT usually transcribed; same sequence and polarity as RNA
- contains U instead of T.
- also called sense = coding strand.

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37
Q

Promoter

A

DNA sequence immediately upstream (5’) of transcription start site (tss);
- Not transcribed; controls binding of RNA polymerase

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38
Q

RNA coding region:

A

portion of gene transcribed into mRNA

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39
Q

Termination region

A

sequences located 3’ to coding region; signals end of transcription

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40
Q

A single promoter controls the expression of 3 genes

A

lacZ, lacY, and lacA
Products of lacZ and lacY genes involved in lactose metabolism

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41
Q

3 clustered genes are coordinately expressed in single mRNA

A

polycistronic mRNA

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42
Q

uncoupled

A

Nuclear envelope separates trans-cription and translation
- transcription = nuclear.
- mRNA is transported to cytoplasm for translation.

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43
Q

RNA splicing

A

introns are removed from pre-mRNA

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44
Q

5’ cap

A

addition of a modified guanine to 5’ end of mRNA.
- added after ≈ 20-40 Nts are transcribed.

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45
Q

poly-A tail

A

addition of 50-250 adenine residues of 3’ end of pre-mRNA.
Functions:
- Prevent degradation
- Help mRNA transport
- Help position mRNA on ribosome

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46
Q

Primary transcript is processed to mature mRNA.

A

introns: regions of gene that are transcribed, but not included in mature RNA.

exons: regions of transcribed RNA retained in mature RNA.

Exons included translated and untranslated regions.

47
Q

RNA Splicing

A

Pre-mRNA strand includes exons and introns.
RNA splicing: removal of introns and joining of exons to produce mature mRNA

48
Q

Most contain RNA coding regions and noncoding regions

A
  • Exons: RNA coding regions.
  • Introns: non-RNA coding regions.

EX: Ovalbumin gene ≈ 7,700 bp
8 exons, 7 introns;
Mature mRNA 1,872 bases

49
Q

Transfer RNA = tRNA

A

delivers specific amino acids to ribosome.
- Specific interactions w/ codon of mRNA.

50
Q

Ribosomes

A

complex of proteins and rRNA that serve as platforms for translation.
- Orient mRNA.
- Position tRNAs
- Catalyze addition of amino acid to growing polypeptide chain.

51
Q

Character

A

: a heritable feature that varies among individual.
- EX: flower color.

52
Q

Trait

A

each variant for a character;
- EX: purple vs white flowers

53
Q

Gregor Mendel (1822-1884)

A

Austrian monk who worked out principles of transmission genetics (simple inheritance).
Proposed the first theory about the units of inheritance (genes).
- Law of segregation
- Law of independent assortment

54
Q

Hypothesis of Blended Inheritance

A

hereditary determinants carried by gametes blend as gametes fuse in fertilization
- Blended determinants would produce intermediate traits.
- Parental trait should not reappear if blended

55
Q

Hypothesis of Particulate Inheritance

A

determinants of inheritance are physically distinct.
- Remain intact when gametes fuse

56
Q

True breeding

A

gives rise to plants w/same traits over successive generations

57
Q

Cross-pollination

A

directed mating technique to ensure parentage of each generation of peas.
- reciprocal cross: switch parents contributing trait.

58
Q

The Parental generation is the

A

P generation

59
Q

the first filial generation is the

A

F1 Generation

60
Q

Alternative versions of genes account for variations in inherited characters are called;

A

alleles
an organism inherits two alleles, one from each parent

61
Q

If two alleles at a locus differ, then the ___________ _______ determines the organism’s appearance.

A

dominant allele

62
Q

Law of segregation

A

the two alleles for a heritable character segregate during gamete formation and end up in different gametes.

63
Q

Monohybrid cross

A

cross between individuals who are heterozygous for a character.

64
Q

P generation

A

true-breeding = identical alleles.
Gametes produced by one parent will contain same allele.

65
Q

F1 generation

A

union of parental gametes produces F1 hybrids (Pp)
When hybrids produce gametes, the two alleles segregate.

66
Q

F2 generation

A

Random combination of gametes in F1 x F1 cross result in 3:1 ratio observed by Mendel.

67
Q

Genotype (two types)

A

combination of alleles ≥ 1 gene of an organism.
homozygous: pair of identical alleles
heterozygous: 2 different alleles

68
Q

Phenotype (two types of traits)

A

one or more of an organism’s observable traits.
Dominant trait: expressed in F1 organism
Recessive trait: masked in F1 but reappears F2 generation.

69
Q

complete dominance

A

when true-breeding parents carry different traits then,
F1 genotypic proportions: all Rr
F1 phenotypic proportions: all express dominant phenotype.
- F2 genotypic proportions: ¼ RR, 2/4 R/r, ¼ rr.
- F2 phenotypic proportions: ¾ dominant, ¼ recessive.

70
Q

transmission of genetic traits is determined by the _______ on homologous chromosomes

A

alleles

71
Q

Alleles of a gene reside at the same position =

A

locus on homologous chromosomes

72
Q

Dependent assortment

A

: two characters assort as a package during gamete formation.
Parental combinations of alleles stay together.

73
Q

Independent assortment

A

two characters assort independently during gamete formation.
- Nonparental combinations of alleles can occur.

74
Q

Dihybrid cross

A

obtain characteristic 9/16, 3/16/, 3/16, 1/16 phenotypic proportions

75
Q

Multiplication rule

A

probability of ≥ 2 independent events occurring together is product of their individual probabilities.
- P(2H,2 tosses) = (1/2)(1/2) = 1/4
(Practice Slide 27 G&H)

76
Q

Addition rule

A

probability of any one of ≥ 2 mutually exclusive events is sum of their individual probabilities.
- P(F2 = heterozygous) = ¼ +1/4) = ½
- Two ways to achieve outcome.
(Practice Slide 27 G&H)

77
Q

lack of compartment allows

A

coupling of transcription and translation

78
Q

F1 phenotype is __________ phenotype of parents.

A

intermediate

79
Q

Heterozygote

A

phenotypes of both alleles are measurable

80
Q

ABO blood typing

A

3 alleles
Exhibit both complete dominance and codominance.
IA vs. IB = codominant
IA, IB vs. i = complete dominance
Use to determine transfusion compatibility.

81
Q

Autosomal

A

located on chromosomes 1-22.

82
Q

Sex chromosome

A

: located on X or Y.

83
Q

In pictorial representation of family history a horizontal line represents:

A

mating

84
Q

In pictorial representation of family history a vertical line represents:

A

connects parents to children

85
Q

In pictorial representation of family history a shading line represents:

A

indicates whether a person is affected with the trait

86
Q

penetrance

A

proportion of individuals w/ a genotype that express corresponding phenotype;
- trait due to acquisition of new mutation.

87
Q

Incidence of some autosomal dominant disorders is high:
Familial hypercholesterolemia
Myotonic dystrophy
Huntington’s Disease

A

: ≈ 1/500 in families of European or Japanese descent.
≈ 1/550 in regions of northeastern Quebec vs. 1/8000 worldwide
: ≈ 5.7/1x105 if European, N. American, or Australian descent; ≈ 4/1 x 106 if Asian descent.

88
Q

Carrier

A

individual w/ heterozygous genotype, who is unaffected, but can pass on disease causing allele.

89
Q

Co-sanguinity

A

: mating btw closely related people.
- Increases probability mating between two heterozygotes.
- ≈ 1/4 offspring will be affected

90
Q

Genotypes for XX
Genotypes for XY

A

inherit two alleles; homozygous dominant, heterozygous, homozygous recessive.

only one allele for each gene = hemizygous
Not the same as gender: sex characteristics that are socially constructed.

91
Q

Congenital Generalized Hypertrichosis (CGH)

A

X-linked dominant disorder.
Increased number of hair follicles and body hair.
- ♂: full body expression;
- ♀: asymmetrical; may be present in patches.

92
Q

Regarding a mutation in a gene on the X chromosome causes the phenotype to be expressed in MALES:

A

hemizygous for the mutation b/c only contain one X chromosome

93
Q

Regarding a mutation in a gene on the X chromosome causes the phenotype to be expressed in FEMALES:

A

homozygous for the mutation (copy on each of their 2 X chromosomes).

94
Q

DNA > RNA (mRNA) >

A

protein

95
Q

a site

A

aminoacyl-
holds an tRNA carrying the next amino acid to be added s

96
Q

p site

A

peptidyl-
hold tRNA with the growing polypeptide attached

97
Q

e site

A

site from which discharged tRNA will exit

98
Q

triplet code

A

smallest units possible to code for 20 biological amino acids
(4)(4)(4) = 64 possible combinations

99
Q

information flow from DNA to protein is written in a non-overlapping genetic code
DNA:
mRNA:
Protein:

A

DNA: instructions for protein written as series non-overlapping nucleotides

mRNA: series of non-overlapping 3 nucleotide “words” = codons

Protein: each codon interacts with tRNA to specify amino acids

100
Q

lack of ambiguity

A

no codon specifies > 1 amino acid

101
Q

redundancy

A

some codons are synonyms; specify the same amino acid

102
Q

reading frame

A

translational machinery reads as series of non=overlapping 3 letter words = codon

103
Q

nearly universal

A

conserved from bacteria to plants and humans
- allows genes to be transplanted from one species to another
»>gene transcribed and translated in cells of second species

104
Q

implication

A

near universality indicates “language” present early in life
- shared by common ancestor

105
Q

melanocortin

A

hormone influencing deposit of dark pigment in fur
mice with dark fur GCG > CGC > Arg
mice with light fur ACG > UGC > Cys

106
Q

nucleic acid is

A

DNA or RNA

107
Q

covered in a protein coat

A

capsid

108
Q

covered in a coat of membrane

A

envelope

109
Q

lytic cycle

A

after making many copies of phage, cell breaks open to release particles

  • phage injects DNA, which circularizes
  • phage DNA and proteins are synthesized
  • phage particles assemble
  • cell lyses to release phages
110
Q

isogenic cycle

A

viral DNA inserts into bacterial chromosome and DNA replication occurs without death of bacterium

111
Q

papaya ringspot potyvirus

A

spread of aphids wiped out native papaya in certain parts of Hawaii

reintroduction of genetically engineered PRSV-resistant papaya plants allowed reintroduction

112
Q

3 types of COVID tests approved by FDA

A

rapid antigen tests: nasal swab, immunoassay, antibodies are the detection method

molecular tests:

antibody (serology) test: blood sample to detect circulating antibodies, detect with color change

113
Q
A

Biology in Society (4 decks)

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