Gene Expression

Question 1

T or F. All the cells in the human body contain the exact same genome and it is only what genes are expressed that differs

Answer 1

True

Question 2

Each cell is programmed in a way to express only a specific subset of these genes at specific times, and in response to specific stimuli

Answer 2

Gene expression

Question 3

The process by which stem cells differentiate into different tissues and specialized cell types in the body during development

Answer 3

Cell differentiation

Question 4

T or F. Stem cells are cells during embryonic stage of development

Answer 4

False. Adults also have stem cells known as somatic stem cells

Question 5

Somatic stem cells include

Answer 5

Hematopoietic stem cells - generate blood cells of the body
Intestinal stem cells
Mesenchymal stem cells- produce fat, bone, and liver cells

Question 6

Stem cell potency

Answer 6

Refers to their limits on cell differentiation

Question 7

Totipotent cell

Answer 7

Can differentiate into any type of cell

In humans, this only applies to early embryos, up to morula or 16-cell stage

Question 8

Pluripotent

Answer 8

• Can differentiate into any cells of the ectoderm, mesoderm, or endoderm
• Cannot differentiate into cells of the placenta

Question 9

Multipotent

Answer 9

Can differentiate into a limited subset of cell types within a germ layer
(Ex. Adult stem cells)

Question 10

Totipotent and pluripotent cells- target of biomedical research

Answer 10

Can be used to generate tissue and organ grafts for transplant from a patient’s own stem cells which can be used to replace failing organ or repair degenerative tissue like damaged heart muscle

Question 11

Dilemma of stem cells from embryo

Answer 11

Totipotent cells can only be found from the embryos, therefore much research now is focused on making adult stem cell Totipotent or pluripotent

Question 12

Programmed cell death

Answer 12

Apoptosis

Question 13

Apoptosis in embryonic development

Answer 13

It helps define the boundaries of organs and tissues
(Ex. Developing embryos- webbed fingers and toes - coordinated apoptosis cause the disappearance of these webbed structures during embryogenesis)

Question 14

Apoptosis as checkpoint

Answer 14

The body would rather sacrifice a cell than let it persist with serious organelle dysfunction or DNA mutations that could lead to cancer

Question 15

T or F. Cell differentiation is irreversible

Answer 15

Cell differentiation usually does not reverse in normal human physiology. However, cancer cells can become less differentiated, and pluripotency can be artificially induced

Question 16

As cell potency move from Totipotency to multipotency these qualities increase

Answer 16

1. Expression of lineage-specific genes: as pluripotent cells develop into multipotent cell, they express a greater percentage of lineage-specific genes due to specialization
2. Methylation of genes required for differentiation into other lineages: DNA methylation “turns off” genes. It is expected that a differentiated cell would methylate genes required for differentiation into other lineages

Question 17

Genetic system used by prokaryotes to regulate the expression of specific genes

Answer 17

Operon

Question 18

Operon can be either ___________ or ___________ controlled genes

Answer 18

Positive or negative

Question 19

Genes expressed when activator present

Answer 19

Positively controlled gene

Question 20

Genes expressed unless repressor present

Answer 20

Negatively controlled gene

Question 21

Binds and stimulate transcription in prokaryotes

Answer 21

Activator

Question 22

Repressor binds to what in the Operon. What does it mean for transcription and when repressor is bound?

Answer 22

It binds to the operator in the Operon. Transcription cannot occur when repressor is bound to the operator.

Question 23

Two examples of operons that are under negative control which means that repressor can inhibit transcription

Answer 23

Lac operon and trp operon

Question 24

Negative inducible operon definition and example

Answer 24

No transcription is the default position. But gene expression can be induced by a specific signal or change in the environment that removes the repressor, allowing transcription to occur

Ex. lac operon

Question 25

Negative repressible operon definition and example

Answer 25

The default is the “on” position (transcription occurs), but gene expression can be repressed by binding of the repressor in certain conditions. Ex. trp operon

Question 26

Lac operon

Answer 26

Contains genes for enzymes that metabolize lactose. Only activated when glucose levels are low.

Question 27

3 structural genes of lac operon

Answer 27

Lac Z, lac Y,and lac A Also includes promoter where RNA polymerase binds to initiate transcription Also includes operator and CAP binding sequence

Question 28

Inactive LAC repressor

Answer 28

Usually bound to the operator of lac operon, preventing the transcription of RNA polymerase bound to the CAP binding site of the promoter

Question 29

When lactose is present, its isomer ____________ binds the repressor and prevents it from interacting with the operator

Answer 29

Allolactose

Question 30

cAMP when glucose levels are low

Answer 30

cAMP binds to the CAP-binding site to really ramp up transcription in times of need - this is an example of positive control (which is when an activator stimulates transcription)

Question 31

T or F. Lac operon is under both negative inducible control and positive control

Answer 31

True

Question 32

Contains genes for the synthesis of the amino acid, tryptophan.

Answer 32

Trp operon- an abundant amount of tryptophan represses expression of these genes (negative feedback on its own synthesis)

Question 33

A short sequence upstream of its target gene that serves as the initial binding site for RNA polymerase to initiate transcription

Answer 33

Promoter- in eukaryotes most contain the TATA box which is about 30bp upstream of the coding sequence The GC and CAAT boxes, up to 10 to 150 bp upstream of the TATA box

Question 34

Proteins that bind to specific DNA sequences to regulate gene expression, recruiting other regulatory proteins that might affect gene transcription or that make chemical modifications to the DNA

Answer 34

Transcription factors

Question 35

Play a critical role in determining the activity and the identity of a given cell

Answer 35

Transcription factors

Question 36

Sequences that promote enhanced expression of genes in response to appropriate stimuli. May be located upstream or downstream of their target genes and even thousands of bp away from the coding sequence

Answer 36

Enhancers

Question 37

Enhancers bind transcription factors known as _____________ and these help twist the DNA into a hairpin loop back onto itself to bring the enhancer region closer to the gene sequence in order to facilitate the initiation of transcription

Answer 37

Activators

Question 38

Example of activator binding to enhancer

Answer 38

Estrogen binding its nuclear estrogen receptor, which then binds enhancers, known as estrogen response elements, to enhance transcription of specific genes

Question 39

Sequences that when bound by repressor, repress the expression of specific genes

Answer 39

Silencers

Question 40

In the nucleus, DNA is wound around ________ and then condensed further into densely-packed _____________ or relatively looser ___________

Answer 40

Histones; heterochromatin; euchromatin

Question 41

Certain enzymes can modify histones by adding or removing

Answer 41

Acetyl groups- referred to as acetylation or deacetylation | *affect how tightly DNA is packaged

Question 42

What enzymes add acetyl groups to histones and what is the effect of this?

Answer 42

Histone acetyltransferases | They reduce histone-DNA interactions which makes DNA more accessible for transcription

Question 43

What enzymes remove acetyl groups and what is the effect of this

Answer 43

Histone deacetylases | Promote Histone-DNA interactions, making it less accessible for transcription

Question 44

The addition of methyl groups directly to cytosine or adenine nucleotides in DNA

Answer 44

Methylation

Question 45

Methylation effect

Answer 45

Generally deactivates or silences gene sequences, preventing their expression *plays an important role in epigenetics

Question 46

Refers to heritable changes that affect gene expression without directly changing the genetic sequence itself

Answer 46

Epigenetics * some epigenetic changes can be transmitted through multiple generations * can affect metabolism, aging, cancer, and other disease processes

Question 47

Certain types of non coding RNA can literally interfere with gene expression by degrading mRNA prior to translation. Pretty much intercepting the pass between DNA and protein

Answer 47

RNA interference

Question 48

Two non coding RNAs that could interfere

Answer 48

Small interfering RNA (siRNA)and microRNA- similar function but differs a bit in structure

Question 49

Differing structures of siRNA and microRNA

Answer 49

microRNA- single stranded | siRNA- double stranded

Question 50

How siRNA and microRNA interfere with mRNA

Answer 50

RNA-induced silencing complex -> cleavage of target mRNA -> death of target mRNA