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MCBM Exam 4 Kat > Intro to DNA/RNA I > Flashcards

Intro to DNA/RNA I Flashcards

1
Q

Who originally found DNA and what did he call it?

A

Friedrich Miescher in 1871. He called them nucleins

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2
Q

What is the Griffith Experiment (1928)?

A

The first demonstration of transformation of a specific genetic trait from one organism to another.

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3
Q

What did Avery, MacCarty & McLeod do in 1944?

A

They fractionated cell-free extraction of virulent pneumococcus and identified that DNA, not protein, caused transformation. First evidence that DNA carries genetic information.

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4
Q

What did Hershey and Chase do in 1951?

A

Sometimes called the “Waring Blender” experiment. They watched a T2 bacteriophage infect the bacteria Escherichia coli. DNA “has some function” as genetic material.

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5
Q

What kind of polarity does DNA have?

A

5’-3’

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6
Q

How are deoxyribose or ribose linked?

A

Via phosphate groups The 3’-OH of one group is linked to the 5’-OH of the next by a phosphodiester bridge. This is the backbone of DNA

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7
Q

Do bases project away from the backbone or toward the backbone?

A

Away from the backbone.

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8
Q

Chargraff’s Rule

A

%G=%C, %A=%T i.e %purines=%pyrimidines ALWAYSSS!!!!

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9
Q

What did Franklin and Wilkins do in 1953?

A

Showed that DNA gave a characteristic X-ray diffraction pattern.

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10
Q

What was the pattern that was found of DNA?

A

Helical Comprised of two strands Has 2 periodicities along long axis (0.34nm and 3.4nm)

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11
Q

What did Watson and Crick do in 1953?

A

Developed a 3D model of DNA that was not fully accepted until 1960.

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12
Q

Are strands of DNA parallel or antiparallel?

A

Antiparallel that are said to be complementary to each other.

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13
Q

What are some other conformations the DNA molecule can adopt?

A

B form (right handed helix - main) Z form (left hand form) Cruciform (more exotic)

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14
Q

What can DNA triple helices possibly be used for?

A

A novel class of drugs designed to modify gene expression like oncogenes in cancer.

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15
Q

What does DNA’s flexibility allow?

A

To be folded when being packed into the nucleus To wrap around proteins like histones

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16
Q

What type of coiled state is DNA in while in a cell?

A

A negative supercoil (underwound)

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17
Q

What two enzymes can modify supercoiling?

A

Topoisomerase I DNA Gyrase Helicases

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18
Q

What does Topoisomerase do?

A

Relaxes supercoiled DNA which is energetically favorable

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19
Q

What does DNA Gyrase do?

A

Converts relaxed DNA into negatively supercoiled DNA which requires ATP

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20
Q

What four antibiotics inhibits Bacterial DNA gyros?

A

Novobiocin Nalidixic acid Ciproflaxacin

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21
Q

What do helicases do?

A

Unwinds the two DNA strands which requires ATP to break hydrogen bonds

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22
Q

What happens when DNA is heated then cooled?

A

When heated it goes through denaturation which separates the strand then when it cools down the strands go through annealing thus reforming bonds between complementary strands

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23
Q

How many hydrogen bonds do GC and AT pairs contain?

A

GC = 3 bonds AT = 2 bonds The more GC content the higher the melting temperature of DNA

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24
Q

What is hypochromism?

A

When DNA strands are allowed to anneal, base stacking reduces UV absorbance

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25
Q

What is hyperchromism?

A

If helix is denatures, base stacking is destroyed resulting in UV absorbance going up

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26
Q

Define a gene.

A

Portion of a chromosome that determines phenotype Changes in gene alter phenotype

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27
Q

Who found the one gene-one enzyme hypothesis?

A

Garrod in 1909 when working on human alkaptonuria Genes work by controlling synthesis of specific enzymes

28
Q

What did Sumner do in 1926?

A

Showed that enzymes are proteins

29
Q

What did Beadle and Tatum do in 1941?

A

Working on mutants in mold Neurospora they found that each mutant lost one enzyme.

30
Q
A
31
Q

What is the physical template stand of a gene called?

A

The antisense strand

32
Q

What is the non-template strand of a gene called?

A

Sense or coding strand/sequence

33
Q

Does mRNA have the same sequence as the sense strand or the antisense strand?

A

The sense strand with the exception of using U instead of T

34
Q

Define Genome.

A

The total amount of DNA within a cell

35
Q

What are some examples of extrachromosomal DNA?

A

Bacterial plasmids

Eukaryotic mitochondrial DNA

36
Q

Does genome size correlate with species complexity?

A

Nope it does not

37
Q

Describe bacterial chromosomes

A

Always double stranded (ds) DNA

Single, circular chromosome

38
Q

Describe Extrachromosomal DNA (plasmids)

A

Non-essential

Always ds DNA, circular arrangement

Often carries genes for antibiotic resistance (R factors)

39
Q

What are Eukaryotic genomes comprised of?

A

1) Chromosomal DNA - always linear ds DNA
2) Mitochondrial DNA - always circular ds DNA

40
Q

Are the 22 pairs of autosomes numbered from largest to smallest or smallest to largest?

A

Largest to smallest

41
Q

What is a Karyotype?

A

Cytogenic techniques use stains to identify banding patterns. Chromosomes are arrested in metaphase when they are duplicated and maximally condensed.

42
Q

Classes of Short Interpersed Elements (SINES)

A

Satellite DNA - alpha satellites, mini satellies, Heterochromatin

43
Q

What is Chromatin?

A

DNA + proteins

44
Q

Why are proteins important in chromatin composition?

A

Critical for DNA compaction

45
Q

How many types of histones (proteins) are there and are they basic or acidic?

A

5 types: H1, H2A, H2B, H3, and H4

Very Basic (lots of lys and arg)

46
Q

What happens if the protein scaffold of chromatin is digested away?

A

DNA unwinds

47
Q

What is the primary structure of DNA compaction?

A

Nucleosomes

48
Q

How many bp’s of DNA wrap around a histone octomer?

A

140bp

49
Q

What is a nucleosome?

A

DNA + a histone core

50
Q

What are nucleosomes connected by?

A

20-60 bp “linker” associated with histone H1

51
Q

What do nucleosomes look like?

A

Beads on a string

52
Q

Compaction overview

A

Chromatids> Coil > Rosette > Loop > Solenoid (30nm fiber) > Nucleosome > Double helix

Start at double helix

53
Q

What is the primary structure of compaction?

A

Nucleosome

54
Q

What is the secondary structure of compaction?

A

Solenoids

55
Q

What is the tertiary structure of compaction?

A

Loop - primary form of chromatin found in interphase nucleus

56
Q

What are the 3 specialized regions of chromosomes?

A

Origins of replication (ori)

Telomeres

Centromeres

57
Q

What is the origin of replication?

A

Specific DNA sequence recognized by proteisn required for replication

58
Q

What are telomeres?

A

Regions at the end of chromosome with many repetitive sequences that are no replicated during S-phase

59
Q

How are the repetitive elements added to the end of replicated chromosomes?

A

By an enzyme called telomerase

60
Q

What are the functions of Telomeres?

A

Seal chromosome ends to prevent fusion

Attach chromosome to nuclear envelope

Facilitate replication

61
Q

What are centromeres?

A

Signle region of each chromosome that serves as an attachment point for proteins which link the chromosome to the mitotic spine.

62
Q

What is the specific attachment region of the centromere called?

A

Kinetochore

63
Q

How are centromeres classified?

A

By location

Metacentric: center

Submetacentric: slightly off center

Acrocentric: near one end

64
Q

What are short arms of chromosomes called?

A

p

65
Q

What are long arms of chromosomes called?

A

q

66
Q

Which 5 chromosomes are condensed to form the nucleolus?

A

13, 14, 15, 21, 22

MCBM Exam 4 Kat (10 decks)

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