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Pathology > Cell as A Unit of Health & Disease > Flashcards

Cell as A Unit of Health & Disease Flashcards

1
Q

What is referred to as the gene complement of an organism

A

Genome

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2
Q

This sequence of letters
comprises the blueprint of the human body,
called

A

Human Genome

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3
Q

is the assignment of
genes to specific chromosomes (each of those
chromosomes have genes

A

GENOMIC MAPPING

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4
Q

The human genome contains roughly______________________

DNA base pairs

A

3.2 billion

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5
Q

Within the genome, there are about ___________________comprising only about 1.5% of the genome.

A

20,000 protein-encoding genes

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6
Q

Protein-encoding genes are the hollow

blocks of the human body.

A

Proteins like collagen, elastin, enzymes, etc

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7
Q

Worms are composed of fewer than 1,000 cells with genomes of only

A

about 0.1 billion DNA base

pairs - are also assembled using about 20,000 genes to produce proteins

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8
Q

What then is the difference between worms and

humans?

A 
The answer is not completely known but
the weight of current evidence suggests
that much of the difference lies in the
98.5% of the human genome that does
not encode protein
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9
Q

How much of the genome is used for the formation of proteins

A

Only 1.5%

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10
Q

Which parts of the genome provide architectural planning?

A

non-Coding Region

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11
Q

promoters and enhancers

A

NON- PROTEIN CODING SEQUENCES

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12
Q

Non-coding regulatory RNAs

A

○ Micro-RNAs

○ Long non-coding RNAs

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13
Q

Mobile genetic elements (ex. transposons)

A

jumping genomes- during evolution

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14
Q

Telomeres (chromosomal ends)

A 
with every successive division of
a telomere only it's chromosomal
the end will be duplicated until it
becomes short to senescent
then undergo apoptosis.
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15
Q

Centromeres (chromosome “tethers”)

A 
holds the chromosome together.
A major component of
centromeres is so-called
satellite DNA, consisting of
large arrays—up to megabases
in length—of repeating
sequences. It is also important
in maintaining the dense, tightly
packed organization of
heterochromatin.
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16
Q

how much of the DNA is shared between 2 individuals

A

99.5%

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17
Q

The two most common forms of DNA variation are:

A

● Single nucleotide polymorphism (SNPs)

● Copy number variations (CNVs)

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18
Q

SNPs

A

● Variants at single nucleotide (nitrogen base +
sugar + phosphate) positions
○ A nucleotide is just a combination of 3
letters (CGA or TAT for example).
● If you change just one letter, for example instead
of CGA it becomes CGG, then there’s already a
DNA variation.
● Biallelic (only two choices exist)
○ Either a C or a G, an A or a T

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19
Q

They occur across the genome - with exons,

introns, intergenic regions, and coding regions

A

○ EXONS - coding region

○ INTRONS - non-coding region

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20
Q

SNPs occur in coding regions

A

1%

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21
Q

COPY NUMBER VARIATIONS (CNVs)

A

● Longer than SNPs. Instead of just one, series of letters were altered.
● can be biallelic and simply duplicated or, alternatively, deleted in some individuals
● Consists of different numbers of large
contiguous stretches of DNA from 1,000 base pairs to millions of base pairs.

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22
Q

epigenetics—

A

heritable changes in gene

an expression that is not caused by variations in DNA sequence

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23
Q

HISTONE ORGANIZATION

A

ll cells in the body contain same genetic material,
terminally differentiated cells have distinct structures and
functions. Different cell types are distinguished by
lineage-specific programs of gene expression. Such cell
type-specific differences in DNA transcription and
translation depend on epigenetic factors

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24
Q

What consists of Nucleosomes?

A 
○ Nucleosomes consist of DNA segments
147 base pairs long that are wrapped
around a central core structure of highly
conserved low molecular weight
proteins called HISTONES.
25
Q

DNA-Histone complex
resembles a series of beads joined by
short DNA linkers and is called

A

CHROMATIN

26
Q

what are the 2 types of chromatic and histones

A

Fine granular and Coarse

27
Q

HETEROCHROMATIN

A 
■ cytochemically dense and
transcriptionally inactive (they
are not transcribed)
■ Coarsely granular structures of
the nucleus
28
Q

EUCHROMATIN

A

■ cytochemically dispersed and
transcriptionally active
■ Finely granular structures of the
nucleus

29
Q

how is a bone cell different from the neuron or any other cell

A

Remember that the nucleus of the brain cell will
have the same chromosome material as the nucleus of a bone cell or of a liver cell. But in a bone cell, the structures are not active so they are probably in heterochromatin.

30
Q

Histone methylation

A 
○ Both lysines and arginines can be
methylated by specific writer enzymes;
methylation of histone lysine residues
can lead to transcriptional activation or
repression, depending on which histone
the residue is marked.
31
Q

Histone acetylation

A 
○ Lysine residues are acetylated by
histone acetyltransferases (HATs),
whose modifications tend to open the
chromatin and increase transcription. In
turn, these changes can be reversed by
histone deacetylases (HDACs),
leading to chromatin condensation.
32
Q

Histone phosphorylation

A 
○ Serine residues can be modified by
phosphorylation; depending on the
specific residue, the DNA maybe
opened for transcription or condensed
and inactive.
33
Q

DNA methylation

A 
○ High levels of DNA methylation in gene
regulatory elements typically result in
transcriptional silencing. Like histone
modifications, DNA methylation is tightly
regulated by methyltransferases,
demethylating enzymes, and
methylated-DNA-binding proteins.
34
Q

Chromatin organizing factors

A 
○ Much less is known about these
proteins, which are believed to bind to
noncoding regions and control
long-range looping of DNA, thus
regulating the spatial relationships
between enhancers and promoters that
control gene expression.
35
Q

NON-CODING RNAs

A

Genes can also be regulated by noncoding RNAs. These genomic sequences are transcribed but not translated

36
Q

how does transcribing different from the transcription?

A

Transcription and translation are
different. You may have a gene for the
production of collagen but it is not
translated. Meaning to say, collagen is not formed. Yes you have the gene for
that but it is not translated into protein

37
Q

Micro-RNA (miRNA)

A

● Short RNAs (22 nucleotides on average)
● Do not encode proteins
● Functions primarily to modulate the translation of
target mRNA into their corresponding proteins

38
Q

Posttranscriptional silencing of gene expression

A

miRNA is a fundamental and well-conserved
mechanism of gene regulation present in all
eukaryotes (plants and animals)

39
Q

what happens if the oncogene is not silenced?

A

forms neoplasia

40
Q

how many miRNA does the human genome code for?

A

6000, 30%.

41
Q

This generates mature single-stranded miRNAs of 21 to 30 nucleotides that associate with a multiprotein aggregate called

A

RNA-induced silencing complex (RISC).

42
Q

Small interfering RNAs (siRNAs)

A

are short RNA sequences that can be introduced
experimentally into cells where they serve as substrates for Dicer and interact with RISC, thereby reproducing endogenous miRNAs function

43
Q

LONG NON-CODING RNA (lncRNA)

A 
● The number of lncRNAs may exceed coding
mRNAs by 10- to 20- fold
● Modulate gene expression in many ways:
○ Gene activation
○ Gene suppression
○ Promote chromatin modification
○ Assembly of protein complexes
44
Q

what are the steps of cellular housekeeping

A 
○ Protection from the environment
○ Nutrient acquisition
○ Communication
○ Movement
○ Renewal of senescent molecules
○ Molecular catabolism
○ Energy generation
45
Q

PROTEASOMES

A 
“Disposal” complexes that degrade
denatured or otherwise “tagged”
cytosolic proteins.
○ In antigen-presenting cells, the resulting
short peptides are presented in the
context of Class I or Class II major
histocompatibility complex to help drive
the adaptive immune respons
46
Q

what is the composition of the cytoskeleton?

A

Microfilaments and microtubules

47
Q

what is the importance of cytoskeleton?

A

to maintain polarity

48
Q

ACTIN MICROFILAMENTS

A 
○ 5 to 9nm diameter
○ formed from the globular protein actin
(G-actin)
○ most abundant
○ G-actin monomers noncovalently
polymerize into long filaments
(F-actin) that intertwine to form
double-stranded helices with a defined
polarity.
○ New subunits are typically added at the
“positive” end of the strand and
removed from the “negative” end—a
process referred to as actin
treadmilling
49
Q

INTERMEDIATE FILAMENTS

A 
○ 10nm diameter
○ predominantly form ropelike polymers
and do not usually actively reorganize
like actin and microtubules
○ provide tensile strength so that cells
can bear mechanical stress, e.g., in
epithelia
○ They form the major structural proteins
of skin and hair.
50
Q

what filaments are the origin for poorly differentiated tumors

A

intermediate filaments

51
Q

what are the filaments in mesenchymal cells?

A

Vimentin

52
Q

muscle cells forms
the scaffold on which actin
and myosin contract.

A

Desmin

53
Q

ritical for
neuronal axon structure and
confer both strength and
rigidity

A

Neurofilaments

54
Q

is expressed in glial cells.

A

Glial fibrillary acidic protein

55
Q

MICROTUBULES

A

○ 25nm thick
○ composed of noncovalently polymerized
α- and β-tubulin dimers organized into
hollow tubes

56
Q

how is microtuble organizing center denoted?

A

”-“

57
Q

This end elongates or recedes
in response to various stimuli by
the addition or subtraction of
tubulin dimers.

A

”+”

58
Q

Kinesins - anterograde

A

(− to +)

59
Q

Dyneins - retrograde

A

(+ to −)

Pathology (13 decks)

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