Regulation of Gene Expression

Question 1

Gene Expression

Answer 1

lets cells be different

• mainly controlled through transcriptional regulation
• additional controls: postranscriptional, translational, and posttranslational

Question 2

Operon

Answer 2

A cluster of prokaryotic genes and DNA regulatory sequences

Question 3

Transcriptional unit

Answer 3

cluster of genes

Question 4

Operator

Answer 4

regulatory DNA sequences in operon

-regulatory proteins bind the operator

Question 5

Repressor proteins

Answer 5

prevent operon genes from being expressed

Question 6

Activator proteins

Answer 6

turn on expression of genes from operon

Question 7

Lac Operon

Answer 7

lactose metabolism in E.Coli requires three genes: lacZ, lacY, and lacA (lac operon contains all three)
lac operon sequence is between promoter and lacZ

Question 8

What happens when lactose is absent?

Answer 8

stops lac operon expression
encoded by lacI, synthesized in active form
binds operator
prevents transcription

Question 9

What happens when lactose is present?

Answer 9

Allolactose- made from lactose. it is the inducer of lac operon by binding to lac repressor
therefore inducible operon because inducer increases expression

Question 10

Catabolite Activator Protein

Answer 10

• activator that stimulates gene expression
• CAP activated by cAMP
• cAMP only abundant when glucose levels are low

Question 11

trp Operon

Answer 11

default state is expression since trp repressor is inactive
trp operon is repressible operon
lac and trp operons both exhibit negative gene regulation

Question 12

Gene regulation in eukaryotes

Answer 12

more complex, no operon, genes are scattered, chromatin has histones, different types of cells, nuclear envelope

Question 13

Transcriptional Regulation

Answer 13

1. initiation of transcription
2. methylation of DNA
3. chromatin structure

Question 14

Three DNA binding activators motifs

Answer 14

1. helix turn helix
2. zinc finger
3. leucine zipper

Question 15

Coactivators

Answer 15

bridge enhancer and promoter which increases transcription to maximal rate

Question 16

Respressors

Answer 16

oppose the effect of activators and decrease transcription

Question 17

Combinatorial gene regulation

Answer 17

high gene regulation with low numbers of activators

Question 18

Hormones

Answer 18

signal molecules activate all cells with specific hormone receptors
-all genes regulated by a specific hormone contain a steroid hormone response element

Question 19

DNA methylation

Answer 19

adds methyl group to cytosine

-gene silencing occurs when DNA methylation is located in promoters

Question 20

Genomic imprinting

Answer 20

permanent silencing of a maternal/paternal allele

• inherited methylated allele is silenced
• methylation maintained as DNA is replicated

Question 21

Nucleosomes

Answer 21

Eukaryotic DNA + histones= nucleosomes

Question 22

Chromatin remodeling

Answer 22

1. activators recruit remodeling complexes that displace nucleosomes
2. activators recruit histone acetyltransferase enzyme that acetylates and loosens histone association with DNA
   - makes gene promoters more accessible

Question 23

Posttranscriptional regulation

Answer 23

controls the availability of mRNA to ribosomes

Question 24

Micro-RNA

Answer 24

regulates gene expression through RNA interference

miRNA binds to any complementary mRNA sequence and silences it

Question 25

Small interfering RNA

Answer 25

from RNA encoded outside the cell's genome | -often used by viruses

Question 26

Translational regulation

Answer 26

controls rate at which mRNAs are used in protein synthesis | increasing length of poly(A) tail increases translation of mRNA

Question 27

Posttranslational regulation

Answer 27

controls functional proteins: - chemical modification alters activity of protein - processes inactive precursers to active proteins - rate of degradation, ubiquitin

Question 28

Epigenetic gene regulation

Answer 28

persists through cell or organismal generation | -does not result from changes in DNA nucleotide sequence

Question 29

Two epigenetic mechanisms

Answer 29

1. Feedback loops: self-sustaining regulatory loop | 2. Chromatic packaging- regulation of packaging of DNA and its associated proteins

Question 30

Tumor

Answer 30

a mass of cells due to dedifferentiation

Question 31

Oncology

Answer 31

branch of medicine for the study, treatment and prevention of cancer

Question 32

Carcinoma

Answer 32

tumor in cells of epithelial origin eg breast

Question 33

Sarcoma

Answer 33

tumor in cells of connective tissue

Question 34

Leukemia

Answer 34

tumor in cells of the blood

Question 35

Lymphoma

Answer 35

cells of the immune system

Question 36

Tumor grade (1-3)

Answer 36

resemblance of tumor to normal tissue

Question 37

Tumor stage (1-4)

Answer 37

degree of tumor invasion

Question 38

Prognosis

Answer 38

probability of survival five years after diagnosis

Question 39

Pronto-oncogenes

Answer 39

encode proteins that stimulate cell division

Question 40

Oncogenes

Answer 40

are altered pronto-oncogenes that cause a cell to be cancerous

Question 41

Tumor suppressor genes

Answer 41

genes encode proteins that inhibit cell division | -in cancer, tumor suppressor genes can be mutated

Question 42

BRCA1 and BRCA2

Answer 42

- both tumor suppressor genes - both involved in DNA damage repair - mutated genes are risk factors for breast cancer - 60% breast cancers have BRCA1 or 2 mutation - up to 85% risk

Question 43

Tumor angiogenesis

Answer 43

tumor cells signal the formation of new blood vessels

Question 44

Intravasation

Answer 44

cancer cells enter blood vessels

Question 45

Extravasation

Answer 45

cancer cells exit the blood vessels

Question 46

Surgery

Answer 46

removal of tumor and lymph nodes

Question 47

Chemotherapy

Answer 47

chemical that are selective and non-selective to cancer cells

Question 48

Radiotherapy

Answer 48

radiation treatment of cancer

Question 49

Targeted therapy

Answer 49

specific to cancer cells

Question 50

Herceptin

Answer 50

targeted therapy against Her2 | - specifically binds Her2 receptor and stops cell division