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Biochemistry (aka hell) > Test 4. Chapter 17 > Flashcards

Test 4. Chapter 17 Flashcards

1
Q

Miescher was the first person to

A

see DNA

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2
Q

Mendel was the first ___________-

A

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.

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3
Q

Levene was first to discover?

A

order of the three major components of a single nucleotide (phosphate-sugar-base)

carbohydrate component of RNA (ribose) and DNA (deoxyribose)

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4
Q

what is chargarff’s rule?

A

nucleotide compostion of DNA varies among species

in DNA, purines=pyrimidines

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5
Q

what are the purines?

A

adenine guanine

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6
Q

what are the pyrimidines?

A

cytosine uracil thymine

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7
Q

describe the hershey and chase experiment

A

Bacteriophages are viruses that infect bacteria; they consist of a protein coat surrounding a nucleic acid.

  1. Radioactively label components
    Label DNA with 32P
    Label protein with 35S

Infect unlabeled bacteria
Separate bacteria from virus

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8
Q

each DNA nucleotide monomer is composed of __________,_________,___________-

A

nitrogenous base, deoxyribose sugar, phosphate

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9
Q

nucleotides are linked by 3’ 5’ _______ bond

A

phosphodiester bonds

these bonds join the 3’ hydroxyl of one nucleotide to hte 5’ phosphate of another

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10
Q

dna molecules consist of two chains of ____________ directionality intertwined to form a right-handed double helix

A

opposite directionality

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11
Q

the sugar-phosphate back bones are ___________ the helix, whereas the bases are ________ the helix

A

outside

inside

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12
Q

The bases are ___________ to the axis of the helix with adjacent bases separated by 3.4 A

A

perpendicular

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13
Q

the dna helix is approximately ________ wide

A

20 A wide

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14
Q

guanine and cytosine have how many hydrogen bonds?

A

3

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15
Q

adenine and thymine have how many hydrogen bonds

A

2

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16
Q

DNA is a relatively stable molecule with several ____________ interactions adding to its stability

A

noncovalent

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17
Q

“DNA”

hydrophobic interaction

A

internal base clustering

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18
Q

“DNA”

hydrogen bonds

A

formation of preferred bonds; three between CG base pairs and two between AT base pairs

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19
Q

“DNA”

base stacking

A

bases are nearly planar and stacked, allowing for weak van der Waals forces between rings

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20
Q

“DNA”

hydration

A

water interactions with the structure of DNA to stabilize structure

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21
Q

“DNA”

electrostatic interactions

A

destabilization by negatively charged phosphates of sugar phosphate backbone are minimized by the shielding of effect of water on Mg+2

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22
Q

semiconservative replication

A

Hypothesis proposed by Watson and Crick

Two strands of DNA separate

Each strand acts as template for synthesis of new strand

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23
Q

conservative

A

entire DNA molecule acts a stemplate for synthesis of entirely new one

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24
Q

dispersive

A

the original DNA double helix breaks apart into fragments, and each fragment then serves as a template for a new DNA fragment

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25
Q

semiconservative

A

two original strands seperate and each strand then serves as a template for a new DNA strand

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26
Q

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 ___________-

A

denaturation or melting

27
Q

the temperature at which half of the DNA molecules are denatured is called the _____________-

A

melting temperature

28
Q

upon cooling, the two strands can bind to one another to reform the double helix, a process called __________-

A

reannealing

29
Q

what forms can DNA double helix adopt?

A

B form, A form, Z form

30
Q

Watson and Crick discovery is referred to as ________ for DNA

A

B formed DNA (sodium salt)

31
Q

another form is the _________ which forms when RNA/DNA duplexes form

A

A DNA form

32
Q

__________ (zigzag conformation) is left handed DNA that can form as a result of torsion during transcription

A

Z DNA

33
Q

DNA can form other structures, including cruciforms, which are cross like structures, probably a result of palindromes (___________)

A

inverted repeats

34
Q

packaging large DNA molecule to fit inside a cell or nucleus requires a process termed __________–

A

supercoiling

35
Q

The major and minor grooves are lined by sequence specific _____________ groups

A

hydrogen bonding groups

36
Q

DNA super cooling faciliates several biological processes including :

A

packaging of DNA, replication, and transcription

Linear and circular DNA can be in a relaxed or supercoiled shape

37
Q

when DNA is underwound, it twist to the right to relieved strain, causing __________-

A

negative supercoiling

38
Q

supercoiling that forms during strand separation can be relieved by a class of enzymes called ________-

A

topoisomerases

they make reversible cuts that allow the supercoiled segments to unwind

39
Q

nucleosomes are complexes of _______ and ________–

A

DNA and histones

40
Q

histone ______ binds to the nucleosome where the DNA enters and acts as a clamp that prevents unraveling

A

H1

41
Q

approximately _________ bp are in contact with the histone octamer (1.8 helical turns)

A

145 np

42
Q

connections between nucleosomes requires approximately _________ bp of linker DNA (may vary between 20 and 70 depending on the speices and tissue)

A

60 bp

43
Q

each of the highly conserved histone core proteins contains a common structure feature called _______ fold

A

histone fold

44
Q

the N- terminal tails of histones protrude from the nucleosomes and can be covalently modfied (___________ and ___________)

A

methylation and acetylation

45
Q

in anticipaiton of cell division chromatin must be compacted into ________—

A

chromosomes

46
Q

nucleosomes are coiled into _______nm fiber which is further coiled to form _________ filament

A

30nm fiber

200 nm filaments

200 nm fibers have numerous supercoiled loops attached to a central nuclear scaffold

47
Q

during interphase, chromatin can be in one of two forms?

A

heterochromatin (more condensed)

euchromatin
less condense

48
Q

investigation of E. Coli revealed the following prokaryotic features?

A
  1. Genome size—usually considerably less DNA and fewer genes (E. coli 4.6 megabases) than eukaryotic genomes
  2. Coding capacity—compact and continuous genes
  3. Gene expression—genes organized into operons
49
Q

prokaryotes often contain ________ which are usually small and circular DNA with additional genes

A

plasmids

50
Q

What are unique eukaryotic genome features?

A
  1. Genome size—eukaryotic genome size does not necessarily indicate complexity
  2. Coding capacity—enormous protein coding capacity; 80% of human DNA sequences have biological functions
  3. Coding continuity—genes are interrupted by noncoding introns, which can be removed by splicing from the primary RNA transcript
51
Q

about _______ of the human genome is intergenic or __________-

A

noncoding sequences

52
Q

what are some differences between DNA and RNA primary structure?

A
  1. Ribose vs deoxyribose
  2. Uracil vs thymine
  3. RNA exists as a single strand that can form complex 3D structures by base pairing with itself
  4. Some RNA molecules have catalytic properties, or ribozymes (e.g., self-cleavages or cleave other RNA)
53
Q

T/F in RNA non Watson Crick base pairs occur frequently?

A

True making 3D structure harder to predict

54
Q

In RNA more elaborate structures may form, often stabilized by ______ ions

A

Mg+2

55
Q

What do the following types of RNA do?

A

tRNA: brings aa to ribosome

rRNA: translates mRNA

mRNA: encodes aa seq

56
Q

name types of ncRNA (noncoding)

A

miRNA: regulate gene expression

siRNA: RNA degradation (siRNA)

snoRNA: chemical modification

snRNA: mRNA processing

57
Q

__________ transport amino acids to ribosomes for assembly (15% of cellular RNA)

A

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

58
Q

amino acids are attached via specific ___________ to the end opposite of the three nucleotide anticodon

A

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

59
Q

___________ is the most abundant RNA in the living cells with a complex secondary structure

A

rRNA

Components of ribosomes (eukaryotes and prokaryotes)
Scaffolding &
Enzymatic roles

60
Q

compare eukaryotic rRNA with prokaryotic

A

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

61
Q

what is a ribosome made out of?

A

RNA and protien

62
Q

_________ mediate modifications of other RNA nucleotides

A

Sno RNAS

63
Q

Sno RNAs direct __________ and _________ enzymes to the appropriate rRNA nucleotide

A

methyltransferase

pseudouridine synthase

Biochemistry (aka hell) (14 decks)

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