Biology 13: Regulation Of Genes

Front 1

Jacob and Monod

Back 1

Proposed operon model to explain regulation of gene expression in prokaryotes.

Front 2

Operon

Back 2

Group of structural and regulatory genes that unction as s single unit.

Front 3

Operon Components

Back 3

Regulatory gene that codes for a repressor protein.

Promoter.

Operator.

Structural Genes.

Front 4

trp operon, trp present

Back 4

Tryptophan combines with repressor as a co-repressor. This makes it functional. This blocks synthesis of enzymes in the pathway for tryptophan synthesis.

Front 5

trp operon, trp absent

Back 5

Repressor unable to attach to the operator, RNA polymerase binds to the promotor. Enzymes for synthesis of tryptophan produced.

Front 6

lac operon, lactose absent

Back 6

repressor attaches to operaor, expression is normally off.

Front 7

lac operon, lactose present

Back 7

lactose combines with repressor and renders it unable to bind to the operator - lactose is then an inducer. RNA polymerase binds to promotor. Three enzymes needed for lactose catabolism are produces.

Front 8

lac maximally activated by

Back 8

absence of glucose

Front 9

lac, glucose absent

Back 9

Cyclic AMP accumulates, binds to CAP, binds to site near lac operator, RNA then binds better, structural gene expressed more efficiently.

Front 10

lac, glucose present

Back 10

little cAMP, CAP inactive, lac operon not expressed maximally.

Front 11

Five steps of control

Back 11

(nuclear level)

Chromatin structure

Transcription control

Posttranscription control

(cytoplasm level)

translational control

posttranslational control

Front 12

Chromatin Structure control

Front 13

Chromatin

Back 13

DNA plus histones

Front 14

Nucleosomes

Back 14

Portion of DNA wrapped around a group of histone proteins.

Front 15

Histones have two types of tails

Back 15

Euchromatin (acetylated)

Heterochromatin (methylated)

Front 16

Barr Body

Back 16

Females have two X chromosomes, only one is active. Patches of different active cells.

Front 17

Epigenetic Inheritiance

Back 17

Histone modification where variation in patterns of inheritance is not sue to change in DNA sequence.

Front 18

Genomic Imprinting

Back 18

Parental allele methylated during gamete formation, cannot be expressed.

Front 19

Transcription Control

Back 19

Involves participation of transcriptional factors, activators and repressors.

Front 20

Transcription Factors

Back 20

bind to the promotor adjacent to the gene. This attracts and binds RNA polymerase but transcription does not start.

Front 21

Transcription Activators

Back 21

bind to regions of DNA called enhancers

Front 22

Mediator proteins

Back 22

Act as a bridge between transcriptions factors and activators at the promotor. Now RNA polymerase begins.

Front 23

Transposons

Back 23

Can move within and between chromosomes

Front 24

Posttranscriptional Control

Back 24

Includes mRNA processing and the speed with whch mRNA leaves the nucleus. Introns excised, exons spliced together.

Front 25

sRNA

Back 25

Regulates gene expression:

Has effect on compaction of DNA

Can dampen translation of DNA

Can target specific mRNAs and prevent their expression

Front 26

Translational control

Back 26

Affects the protein product.

Front 27

Translational control regulates:

Back 27

Activation on inactive protein

Degradatio rate as proteosomes allowing proteins to enter to be broken down.

Front 28

Gene Mutation

Back 28

A permanent change in the sequence of bases on the DNA strand.

Front 29

Effects of gene mutations

Back 29

No effect on protein activity

Complete inactivation

Front 30

Mutation is sex cells

Back 30

Germ-line

Front 31

Mutation in somatic cells

Back 31

Somatic mutation

Front 32

Types of genetic mutations

Back 32

Spontaneous

Induced

Point

Frameshift

Front 33

Spontanous mutation

Back 33

Chemical change in DNA leads to mispairing during replication. Movement of transposons. DNA polymerase proofreads and corrects

Front 34

Induced Mutations

Back 34

Caused by mutagens like radiation and organic chemicals. many are carcinogens. Eg UV and tabacco

Front 35

Point Mutations

Back 35

Involve a change in a single DNA nucleotide. Change one codon to another. Three effects on protein: nonfunctional, reduced function, unaffected.

Front 36

Frameshift Mutations

Back 36

One or two nucleotides either inserted or deleted.

Front 37

Cancer and accumulating mutations:

Back 37

Tumour suppressor genes and proto-oncogenes. Stimulate cell cycle uncontrollably and lead to tumours.