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BMS 610 Exam 2 > Chapter 24: Genes and Chromosomes > Flashcards

Chapter 24: Genes and Chromosomes Flashcards

1
Q

What form are chromosomes in our body packed in?

A

Tertiary packing, aid in storage

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2
Q

Phenotype

A

Visible proerpty

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3
Q

Mutations

A

Alteration in DNA sequence

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4
Q

One Gene One Enzyme Hypothesis

A

gene is a segment that encodes for one enzyme later replaced by one gene one polypeptide

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5
Q

Regulatory sequences

A

non coding sequences of DNA that control gene expression, transcription, or replication

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6
Q

Functions of regulatory sequences

A

Denote the begning or end of genes
inflnce gene transciption
initiation site for replication

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7
Q

Explain the collinearity of DNA, mRNA, and protein

A

DNA determines the resulting protein

Specific DNA Sequence -> specific mRNA is created -> specific amino acid sequence -> specific protein created

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8
Q

The fact that a DNA sequence directly maps to the sequence of amino acids in a protein is called

A

Collinear

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9
Q

What is a codon?

A

three nucleotides that code for in amino acid in a polypep chain

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10
Q

Different type of chromosomes have different

A

number of genes

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11
Q

Compare human gene vs E. coli gene number

A

Human: 3.2 billion bp 20.00-30,00 genes
E. coli: 4,300 genes

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12
Q

Humans have how many genes across 24 different chromsomes

A

20,000 - 30,000 genes

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13
Q

Compare the size of the cell vs size of the chromosomal DNA

A

Chromosomal DNA is much longer that whatever cell or virus contains it

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14
Q

Virus

A

infectious paraste that require host cell to propagate

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15
Q

Almost all plant and some bacterial/animal viruses have

A

RNA genomes [tend to be particularly small]

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16
Q

Replicative forms

A

When a virus infects a host they have specific intermediate DNA structures during replication

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17
Q

Examples of replicative forms

A
  1. Many linear DNA become circular
  2. All single stranded DNAs become double stranded
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18
Q

Bacterial Plasmids

A

Small circular DNA molecules in bacteria

Replicate independently and carry important genes [antibiotic resistance]

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19
Q

One example of plasmids

A

Plasmids carrying the gene for enzyme b-lactamase cinfer resistance to b-lacatam antibiotics such as pencillin amplicillin, and

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20
Q

Where is genetic material of eukaryotic cell distributed

A

Into chromosomes

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21
Q

What does the diploid (2n) number depend on

A

The species

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22
Q

What is the duplex DNA?

A

Basic B form DNA / very large

carries a characteristic set of genes

each chromosome has a single

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23
Q

How many chromosomes do human somatic cells have?

A

46 Chromosomes

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24
Q

Human cells are __

A

diploid

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25
Q

Human cell are diploid, so it has how many m of DNA?

A

2m

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26
Q

Mitochondrial DNA [mtDNA] codes for

A

Encodes for mitochondrial tRNAs and rRNAs and a few mitochondrial proteins

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27
Q

Mitochondrial DNA [mtDNA]

A

Smaller than DNA found in the nucleus

Less than 20,000 base pairs and circular

Each mitochondrion has 2-10 copies of this DNA

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28
Q

When does the mtDNA copies increase

A

During embryo development as cells differentiate

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29
Q

Plant mtDNA is

A

Much larger

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30
Q

Chloroplast DNA [cpDNA]

A

Smaller than nuclear DNA

Exist in multiple copies per organelle

Has their own unique set of genes for specific organelle functions

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31
Q

Introns

A

non translated regions in genes that do not code for the amino acid sequence

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32
Q

Exons

A

coding DNA segments
only 1.5% of human DNA

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33
Q

How do introns disrupt collinearity?

A

The non coding sequences in DNA do not directly correspond to the protein amino acid sequence

34
Q

In hgher eukaryotes genes have

A

more introns than exons

35
Q

Highly repetitive sequences or simple sequence repeats

A

short repetitive DNA sequences that are often associated with chromosomes structures like centromeres and telomeres

36
Q

Repetitive sequences make up

A

about 3% of the human genome

37
Q

Satellite DNA

A

migrates satelite bands in a cesium chloride densiy gradient

38
Q

Centromeres

A

DNA sequences that act as attachment points for proteins during cell dvision

39
Q

Why are centromeres important?

A

Essential for chromosome segregation

40
Q

Telomeres

A

repeaitve sequences at the end of chromsomes that portect them from degradation

41
Q

When does telomere shortening occur

A

during each round of DNA replication

linked to aging

42
Q

What are the twon main ways of DNA compaction?

A

neutralze the - charge of phopshoryl groups in dna backbone with cations and polyamines

sueprcoilign

43
Q

What is a supercoil

A

Additional twisting of DNA beyond its regular helical structure

coiling of a coil

44
Q

unwound DNA

A

Fewer turns than normla, leads to supercoiling that helps DNA packaging and cess during transcription/replication

45
Q

Why form is most cellular DNA in?

A

supercoiled, intrinic property of DNA 3rd structure

46
Q

Relaxed DNA

A

no net bend of the dna axis on itself

47
Q

Closed Circular DNAs

A

small curcular DNAs that have no breaks in eiher strand

48
Q

When does DNA become thermodynamically strained?

A

Turns are removed

49
Q

How is DNA strain accomdated?

A

By forming a supercoil or seperating the two dna strands over a short diatnce

50
Q

How does dna maintain an underwound state

A

a closed circle
bound and stabilized protein

51
Q

Linking Number

A

number of time the twisting strand penetrates a surface

52
Q

Topomerases

A

Enzymes that can change the LK of DNA

53
Q

What exactly do topoisomerases do

A

change the linking number and play a role in replication and DNA packaging

54
Q

Formula of Lk0

A

of bp / # of bp per turn

55
Q

What happens to the Lk if there is a break in the topological bond?

A

The bond is lost and Lk is undefined

56
Q

Formula for change in linking #

A

∆Lk = Lk - Lk0

57
Q

Explain the rules of Linking Numbers

A

Circular DNA = Whoel # integer
Right handed helix [b-form] = postivie
Left handed helix [Z-form] = negative

58
Q

What determines whether a linking number is positive or negative?

A

The twisting direction

59
Q

What is specific linking difference or super helical density?

A

Measure how much DNA is underwound or overwound compare to relaxed DNA

60
Q

If the super helical density has a negative ∆Lk what does this tell us?

A

Underwinding is occuring
so we will have (-) or lwft handed supercoils

61
Q

If the super helical density has a positive ∆Lk what does this tell us?

A

Overwinding has occured and we will have (+) or right handed supercoils

62
Q

Whats the usual superhelical density of cellular DNA

A

5% TO 7%

63
Q

Underwinding results in

A

negative coils

64
Q

overwinding results in

A

Positive supercoils

65
Q

The cruciform structureHow does underwinding support both the cruciform and Z-DNA formation

A

It allows the DNA to twist ans seperate in ways that support these structures

66
Q

Goal of Topoisomerase

A

relive strain in the DNA not to create more

thye make DNA more relaxed

67
Q

Topoisomerases 1

A

Break one strain

reduce strain by changing the linking number in increments of 1

68
Q

Topoisomerase 2

A

Break both strains

Reduce strain by changing the linking number in increments of 2

69
Q

In a gel electrophoresis, supercoiled DNA moves

A

Faster beaucse it’s more compact

70
Q

In a gel electrophoersis, relaxed DNA moves

A

slower because its less compact

71
Q

How many topoisomerase does E.coli have?

A

4 Types

72
Q

Type 1 topoisomerases [1 and 3] in Prokaryotes

A

Removes (-) coils
increases the linking number

73
Q

Type 2 topoisomerase [2 and 4] in Prokaryotes

A

adds (-) coils
two strands

74
Q

Another name for topoisomerase 4

A

DNA gyrase

75
Q

In eukaryotes how many topoisomerases are there?

A

only two types

76
Q

Type 1 topoisomerase [1 and 3] in Eukaryotes

A

Relax supercoiling

77
Q

Type 2 topoisomerases [IIa and IIb] in Eukaryotes

A

cant introduce negative supercoils
can relax both postive and negative supercoils

can untangle

78
Q

Main difference between Prokaryotic topoisomerase and Eukaryote topoisomerase

A

Prokaryotic can create negative supercoiling eukaryotic can not

79
Q

Why is the DNA gyrase in prokaryotes important?

A

helps maintain proper DNA structure and supports replication and transcription

80
Q

What do prokaryotes and eukaryotes share in terms of topoisomerases?

A

Their Type 1 [1 and 3] topoisomerase both relax DNA by removing supercoils

81
Q

In prokaryotes what type of topoisomerase is DNA gyrase?

A

Type 4

82
Q
A

BMS 610 Exam 2 (5 decks)

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