Cell as A Unit of Health & Disease

Question 1

What is referred to as the gene complement of an organism

Answer 1

Genome

Question 2

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

Answer 2

Human Genome

Question 3

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

Answer 3

GENOMIC MAPPING

Question 4

The human genome contains roughly______________________

DNA base pairs

Answer 4

3.2 billion

Question 5

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

Answer 5

20,000 protein-encoding genes

Question 6

Protein-encoding genes are the hollow

blocks of the human body.

Answer 6

Proteins like collagen, elastin, enzymes, etc

Question 7

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

Answer 7

about 0.1 billion DNA base

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

Question 8

What then is the difference between worms and

humans?

Answer 8

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

Question 9

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

Answer 9

Only 1.5%

Question 10

Which parts of the genome provide architectural planning?

Answer 10

non-Coding Region

Question 11

promoters and enhancers

Answer 11

NON- PROTEIN CODING SEQUENCES

Question 12

Non-coding regulatory RNAs

Answer 12

○ Micro-RNAs

○ Long non-coding RNAs

Question 13

Mobile genetic elements (ex. transposons)

Answer 13

jumping genomes- during evolution

Question 14

Telomeres (chromosomal ends)

Answer 14

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.

Question 15

Centromeres (chromosome “tethers”)

Answer 15

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.

Question 16

how much of the DNA is shared between 2 individuals

Answer 16

99.5%

Question 17

The two most common forms of DNA variation are:

Answer 17

● Single nucleotide polymorphism (SNPs)

● Copy number variations (CNVs)

Question 18

SNPs

Answer 18

● 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

Question 19

They occur across the genome - with exons,

introns, intergenic regions, and coding regions

Answer 19

○ EXONS - coding region

○ INTRONS - non-coding region

Question 20

SNPs occur in coding regions

Answer 20

1%

Question 21

COPY NUMBER VARIATIONS (CNVs)

Answer 21

● 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.

Question 22

epigenetics—

Answer 22

heritable changes in gene

an expression that is not caused by variations in DNA sequence

Question 23

HISTONE ORGANIZATION

Answer 23

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

Question 24

What consists of Nucleosomes?

Answer 24

○ 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.

Question 25

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

Answer 25

CHROMATIN

Question 26

what are the 2 types of chromatic and histones

Answer 26

Fine granular and Coarse

Question 27

HETEROCHROMATIN

Answer 27

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

Question 28

EUCHROMATIN

Answer 28

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

Question 29

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

Answer 29

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.

Question 30

Histone methylation

Answer 30

``` ○ 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. ```

Question 31

Histone acetylation

Answer 31

``` ○ 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. ```

Question 32

Histone phosphorylation

Answer 32

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

Question 33

DNA methylation

Answer 33

``` ○ 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. ```

Question 34

Chromatin organizing factors

Answer 34

``` ○ 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. ```

Question 35

NON-CODING RNAs

Answer 35

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

Question 36

how does transcribing different from the transcription?

Answer 36

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

Question 37

Micro-RNA (miRNA)

Answer 37

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

Question 38

Posttranscriptional silencing of gene expression

Answer 38

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

Question 39

what happens if the oncogene is not silenced?

Answer 39

forms neoplasia

Question 40

how many miRNA does the human genome code for?

Answer 40

6000, 30%.

Question 41

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

Answer 41

RNA-induced silencing complex (RISC).

Question 42

Small interfering RNAs (siRNAs)

Answer 42

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

Question 43

LONG NON-CODING RNA (lncRNA)

Answer 43

``` ● 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 ```

Question 44

what are the steps of cellular housekeeping

Answer 44

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

Question 45

PROTEASOMES

Answer 45

``` “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 ```

Question 46

what is the composition of the cytoskeleton?

Answer 46

Microfilaments and microtubules

Question 47

what is the importance of cytoskeleton?

Answer 47

to maintain polarity

Question 48

ACTIN MICROFILAMENTS

Answer 48

``` ○ 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 ```

Question 49

INTERMEDIATE FILAMENTS

Answer 49

``` ○ 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. ```

Question 50

what filaments are the origin for poorly differentiated tumors

Answer 50

intermediate filaments

Question 51

what are the filaments in mesenchymal cells?

Answer 51

Vimentin

Question 52

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

Answer 52

Desmin

Question 53

ritical for neuronal axon structure and confer both strength and rigidity

Answer 53

Neurofilaments

Question 54

is expressed in glial cells.

Answer 54

Glial fibrillary acidic protein

Question 55

MICROTUBULES

Answer 55

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

Question 56

how is microtuble organizing center denoted?

Answer 56

"-"

Question 57

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

Answer 57

"+"

Question 58

Kinesins - anterograde

Answer 58

(− to +)

Question 59

Dyneins - retrograde

Answer 59

(+ to −)