Chapter 18

Question 1

Operons

Answer 1

Cluster of functionally related genes that can be under coordinated control by a single on-off switch
Found in prokaryotes
Consists of 3 parts
Operator- Controls access of RNA polymerase to the genes. Found within the promoter site or betwen the promoter and the protein coding genes of the operon
Promoter-Where RNA polymerase attaches
Genes of the operon- The entire strech of DNA required for all the enzymes produced on the operon

Question 2

Repressor

Answer 2

Operon can be switched off by a protein
Repressor prevents gene transcription by binding to the operator and blocking RNA polymerase
Can be in active or inactive form depending on the prescence of other molecules

Question 3

Regulatory Gene

Answer 3

Produces repressor proteins that may bind to the operator site

Question 4

Corepressor

Answer 4

Molecules that cooperates with a prepressor protein to switch an operon off

Question 5

Inducible Operon

Answer 5

Normally off but it can be activated
Normally catabolic, breaking down food molecules for energy
Represor protein usually active, and to turn this on the inducer binds to an inactivates the repressor protein, which takes it off the gene
Ex. lac

Question 6

Inducer

Answer 6

Specific small molecule that binds to a repressor and allows it to come off of the inducible operon

Question 7

Repressible Operon

Answer 7

Normally on but can be inhibited, Normally is anabolic, building of an essential organic molecule
Ex. Trp

Question 8

Differential Gene Expression

Answer 8

The expression of different genes within the same genome

Question 9

DNA Methylation

Answer 9

The addition to methyl groups to DNA , which tightly packs the DNA which causes reduced transcription

Question 10

Histone Acetylation

Answer 10

Acetyl groups are added to the lysine tails of the histone tails, which loosens chromatin, which promotes the initiation of transcription

Question 11

Epigenetic Inheritance

Answer 11

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence, The DNA is not changed, but its expression is changed

Question 12

Enhancer Regions

Answer 12

DNA sequences far from the Gene that are bound to activators

Question 13

Activators

Answer 13

Proteins that are bound to the enhancer region that bind to the transcription factors to help them form an active transcription initiation complex

Question 14

Coordinately controlled genes

Answer 14

These are similar genes that can be expressed together. These genes can be located all over the chromosome, but because they have the same control elements, they are all transcribed at the same time

Question 15

miRNA

Answer 15

Too small single stranded RNA molecules that can bind to mRNA. This degrades mRNA or block its translation

Question 16

Three transformations of the Zygote

Answer 16

Cell Division- Mitotic divisions that increase the number of cells
Cell Differentiation- Process by which cells become specialized in structure and function
Morphogenesis- Physical process that gives organisms its shape

Question 17

Controlling Differentiation and Morphogenesis

Answer 17

Cytoplasmic Determinants- Maternal substances in the egg that influence the course of early development, distributed evenly early in the cell and lead to different effects
Cell-Cell signals- -molecules such as growth factors produced by one cell

Question 18

Induction

Answer 18

A process in which signal molecules cause transcriptional changes in other cells

Question 19

Determination

Answer 19

Series of events that lead to observable differentiation of a cell. Caused by cell signals, and is irreversible

Question 20

Pattern Formation

Answer 20

The development of spatial organization of tissues and organs, and it begins with the establishment of major axes

Question 21

Morphogens

Answer 21

Substances that help to establish the axes

Question 22

Oncogenes

Answer 22

Cancer causing genes

Question 23

Proto-oncogenes

Answer 23

The corresponding normal cellular genes that are changed to oncogenes

Question 24

Tumor Supressor Genes

Answer 24

Genes that help prevent uncontrolled cell growth

Mutation in this gene can also cause cancer

Question 25

p53 gene

Answer 25

1. p53 gene activates the p21 gene whose products halt the cell cycle
2. p53 protein activates a group of miRNAs which inhibits the cell cycle
3. p53 protein turns on genes directly involved in DNA repair
4. Apoptosis when DNA is too greatly damaged