Gene Expression

Question 1

Genes

Answer 1

sequences of DNA that code for diffrent RNA’s

Question 2

mRNA

Answer 2

codes for proteins various functional RNA’s

Question 3

During embryonic development

Answer 3

• many diffrent cell types are developed
• they all have the same genetic material

Question 4

cloning experiments

Answer 4

proof that adult cells contain entire set of genes needed to form the whole organism

Question 5

control of Gene Expression

Answer 5

The amount of DNA is not correlated with the complexity of an organism

Question 6

Mammalian genome

Answer 6

several billion nucleotides

• Enough to code 3 million proteins
• Yet only 60,000 proteins likely
• Therefore, only 1-2% of the DNA codes for essential products ( proeins and functional RNA’s)

Question 7

Functions of the “extra” DNA?

Answer 7

• introns
• regulatory sequences
• accumulated genetic noise

Question 8

in our bodies, hundreds of different cell types carry out a variety of specialized functions-

Answer 8

results of different genes being switched on in these cells

Question 9

Cells use only some of the genes they have in the ______?

Answer 9

genome

Question 10

Differences between cell types depend on the precise control of gene expression-

Answer 10

cells make and accumulate different sets of RNA and proteins.

Question 11

Differences in gene expression between different cell types are illustrated by the protein______?

Answer 11

composition

Question 12

Some proteins common to almost all cells of a organism

Answer 12

housekeeping proteins

Question 13

housekeeping proteins

Answer 13

• structural proteins of chromosomes
• DNA and RNA polymerase
• DNA repair enzymes
• ribosomal proteins
• enzymes of glycolysis
• cytoskeletal proteins

Question 14

Specialized proteins-

Answer 14

responsible for the distinctive properties of different cell types.

Question 15

it is estimated that a typical differentiated human cell may express-

Answer 15

10,000-20,000 genes ( out of 30,000) at any time based on the number of diffrent mRNA sequences present)

Question 16

From DNA to proteins

Answer 16

• multistep process
• all steps can be possibly controlled and regulated:
• Transcription
• RNA processing
• RNA transport
• Translation
• Protein activity

Question 17

Transcription Control

Answer 17

• Most important from of gene regulation
• turns genes “on” and “off”
• regulates reate of transcription -expression
• mediated by DNA- binding gene regulatory proteins

Question 18

In addition to the promoter genes have regulatory DNA sequences:

Answer 18

• used to switch genes “ on” and “off”
• 10 to 10,000 base pairs in length
• can respond to a variety of signal
• serve as binding sites for regulatory proteins

* gene activator proteins

*gene repressor proteins

_ may be lacated a great distance from the gene regulated In fact the combination of DNA sequences and its associated proteins acts as the transcription control switch

Question 19

Hundreds of regulatory DNA sequences identified in cells-

Answer 19

each recognized by one or more gene regulatory proteins

Question 20

Surfaces of gene regulatory proteins fot tightly to double helix of the regulatory ________ _______?

Answer 20

DNA sequences

Question 21

Most often gene regulatory proteins insert into the major groove of the DNA helix and make multiple hydrogen and ionic bonds, and hydrophobic interactions with the edges of base ppairs exposed in the grooves of double helix without disrupting bonds between bases.

Question 22

DNA- protein interactions

Answer 22

one of the strongest and most specific interactions known in biology.

Question 23

Gene regulatory proteins contain very stable folding patterns (‘motifs”) that fit into the groove of DNA helix.

Common structural “ motifs”

Answer 23

• Homeodomain motif
• zinc finger motif
• Leucine zipper motif

Question 24

in all motifs-___?

Answer 24

one or more alpha-helices from the protein bind to bases in the major groove of the DNA double helix.

Question 25

Repressors and Activators of Transcription:

Answer 25

two ways to turn genes off

Question 26

Negative regulation

Answer 26

_ binding of a repressor protein turns the gene off

• repressors- molecules that bind to a specific region of DNA to prevent transcription of an adjacent gene

Question 27

Positive regulation

Answer 27

• Binding of an activator protein turns the gene on
• Activators - molecules that bind to the promoter and enhance