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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
Human cell are diploid, so it has how many m of DNA?
2m
26
Mitochondrial DNA [mtDNA] codes for
Encodes for mitochondrial tRNAs and rRNAs and a few mitochondrial proteins
27
Mitochondrial DNA [mtDNA]
Smaller than DNA found in the nucleus Less than 20,000 base pairs and circular Each mitochondrion has 2-10 copies of this DNA
28
When does the mtDNA copies increase
During embryo development as cells differentiate
29
Plant mtDNA is
Much larger
30
Chloroplast DNA [cpDNA]
Smaller than nuclear DNA Exist in multiple copies per organelle Has their own unique set of genes for specific organelle functions
31
Introns
non translated regions in genes that do not code for the amino acid sequence
32
Exons
coding DNA segments only 1.5% of human DNA
33
How do introns disrupt collinearity?
The non coding sequences in DNA do not directly correspond to the protein amino acid sequence
34
In hgher eukaryotes genes have
more introns than exons
35
Highly repetitive sequences or simple sequence repeats
short repetitive DNA sequences that are often associated with chromosomes structures like centromeres and telomeres
36
Repetitive sequences make up
about 3% of the human genome
37
Satellite DNA
migrates satelite bands in a cesium chloride densiy gradient
38
Centromeres
DNA sequences that act as attachment points for proteins during cell dvision
39
Why are centromeres important?
Essential for chromosome segregation
40
Telomeres
repeaitve sequences at the end of chromsomes that portect them from degradation
41
When does telomere shortening occur
during each round of DNA replication linked to aging
42
What are the twon main ways of DNA compaction?
neutralze the - charge of phopshoryl groups in dna backbone with cations and polyamines sueprcoilign
43
What is a supercoil
Additional twisting of DNA beyond its regular helical structure coiling of a coil
44
unwound DNA
Fewer turns than normla, leads to supercoiling that helps DNA packaging and cess during transcription/replication
45
Why form is most cellular DNA in?
supercoiled, intrinic property of DNA 3rd structure
46
Relaxed DNA
no net bend of the dna axis on itself
47
Closed Circular DNAs
small curcular DNAs that have no breaks in eiher strand
48
When does DNA become thermodynamically strained?
Turns are removed
49
How is DNA strain accomdated?
By forming a supercoil or seperating the two dna strands over a short diatnce
50
How does dna maintain an underwound state
a closed circle bound and stabilized protein
51
Linking Number
number of time the twisting strand penetrates a surface
52
Topomerases
Enzymes that can change the LK of DNA
53
What exactly do topoisomerases do
change the linking number and play a role in replication and DNA packaging
54
Formula of Lk0
of bp / # of bp per turn
55
What happens to the Lk if there is a break in the topological bond?
The bond is lost and Lk is undefined
56
Formula for change in linking #
∆Lk = Lk - Lk0
57
Explain the rules of Linking Numbers
Circular DNA = Whoel # integer Right handed helix [b-form] = postivie Left handed helix [Z-form] = negative
58
What determines whether a linking number is positive or negative?
The twisting direction
59
What is specific linking difference or super helical density?
Measure how much DNA is underwound or overwound compare to relaxed DNA
60
If the super helical density has a negative ∆Lk what does this tell us?
Underwinding is occuring so we will have (-) or lwft handed supercoils
61
If the super helical density has a positive ∆Lk what does this tell us?
Overwinding has occured and we will have (+) or right handed supercoils
62
Whats the usual superhelical density of cellular DNA
5% TO 7%
63
Underwinding results in
negative coils
64
overwinding results in
Positive supercoils
65
The cruciform structureHow does underwinding support both the cruciform and Z-DNA formation
It allows the DNA to twist ans seperate in ways that support these structures
66
Goal of Topoisomerase
relive strain in the DNA not to create more thye make DNA more relaxed
67
Topoisomerases 1
Break one strain reduce strain by changing the linking number in increments of 1
68
Topoisomerase 2
Break both strains Reduce strain by changing the linking number in increments of 2
69
In a gel electrophoresis, supercoiled DNA moves
Faster beaucse it's more compact
70
In a gel electrophoersis, relaxed DNA moves
slower because its less compact
71
How many topoisomerase does E.coli have?
4 Types
72
Type 1 topoisomerases [1 and 3] in Prokaryotes
Removes (-) coils increases the linking number
73
Type 2 topoisomerase [2 and 4] in Prokaryotes
adds (-) coils two strands
74
Another name for topoisomerase 4
DNA gyrase
75
In eukaryotes how many topoisomerases are there?
only two types
76
Type 1 topoisomerase [1 and 3] in Eukaryotes
Relax supercoiling
77
Type 2 topoisomerases [IIa and IIb] in Eukaryotes
cant introduce negative supercoils can relax both postive and negative supercoils can untangle
78
Main difference between Prokaryotic topoisomerase and Eukaryote topoisomerase
Prokaryotic can create negative supercoiling eukaryotic can not
79
Why is the DNA gyrase in prokaryotes important?
helps maintain proper DNA structure and supports replication and transcription
80
What do prokaryotes and eukaryotes share in terms of topoisomerases?
Their Type 1 [1 and 3] topoisomerase both relax DNA by removing supercoils
81
In prokaryotes what type of topoisomerase is DNA gyrase?
Type 4
82

BMS 610 Exam 2 (5 decks)

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