This document discusses gene expression and regulation. It begins by defining gene expression as the process by which information from a gene is used to create a functional gene product like a protein. This occurs through two main steps - transcription of DNA into mRNA in the nucleus, and translation of mRNA into proteins in the cytoplasm. Regulation of gene expression controls which genes are expressed, such as through the lac operon which expresses lactose metabolism genes only in the presence of lactose. The lac operon provides an example of positive and negative gene regulation through a repressor protein that binds to the operon's DNA to block or allow transcription.

1. By:- AKANKSHA SINGH
M.PHARM Ist YEAR

2.  Introduction of gene expression
 Transcription
 Translation
 Regulation of gene expression
 Lac operon theory

3.  Gene expression is the process by which the information encoded in a gene
is used to direct the assembly of a protein molecule.
 It is explored through a study of protein structure and function,
Transcription and Translation.
 It is the process by which information from a gene is used in the synthesis
of a functional gene product.

4. When genes are expressed, the genetic information (base sequence) on DNA is first copied to a molecule of mRNA
(transcription). The mRNA molecules then leave the cell nucleus and enter the cytoplasm, where they participate in
protein synthesis by specifying the particular amino acids that make up individual proteins (translation).

5.  Genetic information , chemically determined by Dna structure is
transferred to daughter cells by DNA replication and expressed by
Transcription followed by Translation.
 This series of events is called “ Central Dogma” is found in all cells and
proceeds in similar ways except in retroviruses which posses an enzyme
reverse transcriptase which converts RNA into complementry DNA.
The extended central dogma of molecular
biology includes all the cellular processes
involved in the flow of genetic information

6.  Gene Expression contains main 2 steps;
 Transcription and
 Translation.
 Together , they are known as gene expression, During the process of
transcription, the information stored in a gene’s DNA is passed to a
similar molecule called RNA in the cell nucleus.

7.  Transcription takes place in the nucleus. It uses DNA as a template to make
an RNA (mRNA) molecule. During transcription, a strand of mRNA is
made that is complementary to a strand of DNA.
 Transcription takes place in three steps: initiation, elongation, and
termination.
 Step 1: Initiation
 Initiation is the beginning of transcription. It occurs when the enzyme
RNA polymerase binds to a region of a gene called the promoter. This
signals the DNA to unwind so the enzyme can ‘‘read’’ the bases in one of
the DNA strands. The enzyme is now ready to make a strand of mRNA
with a complementary sequence of bases.

9.  Step 2: Elongation
 Elongation is the addition of nucleotides to the mRNA strand. RNA
polymerase reads the unwound DNA strand and builds the mRNA
molecule, using complementary base pairs. There is a brief time during this
process when the newly formed RNA is bound to the unwound DNA.
During this process, an adenine (A) in the DNA binds to an uracil (U) in
the RNA.
 Step 3: Termination
 Termination is the ending of transcription, and occurs when RNA
polymerase crosses a stop (termination) sequence in the gene. The mRNA
strand is complete, and it detaches from DNA.

10.  It is a process by which proteins are synthesized. Translation is a complex
cellular process where mRNA molecules, ribosome, tRNA molecules,
amino acids, energy sources ATP and GTP and a no. of factors act
together in a highly coordinated way.
 Translation is the process in which ribosome in the cytoplasm or
endoplasmic reticulum synthesize proteins after the process of transcription
of DNA to RNA in the cell’s nucleus.

11.  Initiation: Ribosomal subunits bind to mRNA.
 Elongation: The ribosome moves along the mRNA molecule
linking amino acids and forming a polypeptide chain.
 Termination: The ribosome reaches a stop codon, which terminates
protein synthesis and releases the ribosome.

13.  Stimulates the expression of certain gene and inhibit that of others is
called regulation of gene expression.
 The first discovered example of a gene regulation system was the lac
operon , discovered by Jacques Monod , in which protein involved in
lactose metabolism are expressed by E.coli only in the presence of lactose
and absence of glucose.

14.  Transcription Level (Formation of primary transcription).
 Processing of level (Regulation of splicing).
 Transport of mRNA from nucleus to the cytoplasm.
 Translation level.

15. Diagram showing at which stages in the DNA-mRNA-protein pathway
expression can be controlled

16.  POSITIVE REGULATION: When the expression of genetic
information is quantitatively increased by the presence of specific
regulatory element is known as positive regulation.
 it is known as activator or positive regulator.
 NEGATIVE REGULATION: When the expression of genetic
information is diminised by the presence of specific regulatory element is
known as negative regulation.
 its known as repressor.
 EXAMPLE OF GENE REGULTION:
 The lac operon is an intresting example of how gene expression can be
regulated.

17.  it helps in Lactose metabolism.
 Lac – lactose , glucose + galactose
 Operon – group of gene.
 Its expressed only when lactose is present & glucose is absent.
 The lac operon is an operon, or group of genes with a single promoter
(transcribed as a single mRNA). The genes in the operon encode proteins
that allow the bacteria to use lactose as an energy source.

18.  The lac operon contains three genes: lacZ, lacY, and lacA. These
genes are transcribed as a single mRNA, under control of one
promoter.
 In addition to the three genes, the lac operon also contains a number
of regulatory DNA sequences. These are regions of DNA to which
particular regulatory proteins can bind, controlling transcription of
the operon.

19. P = promoter
I = repressor initiation gene
O= operator (where repressor attached)
Z = 8- galactose (separate lactose)
Y = permease (import lactose)
a = Transacylase (function unknown)

20.  The promoter is the binding site for RNA polymerase, the enzyme that
performs transcription.
 The operator is a negative regulatory site bound by the lac repressor
protein. The operator overlaps with the promoter, and when
the lac repressor is bound, RNA polymerase cannot bind to the promoter
and start transcription.
The lac repressor
 The lac repressor is a protein that represses (inhibits) transcription of
the lac operon. It does this by binding to the operator, which partially
overlaps with the promoter. When bound, the lac repressor gets in RNA
polymerase's way and keeps it from transcribing the operon.

21.  When lactose is not available, the lac repressor binds tightly to the
operator, preventing transcription by RNA polymerase. However, when
lactose is present, the lac repressor loses its ability to bind DNA. It floats
off the operator, clearing the way for RNA polymerase to transcribe the
operon.

22.  This change in the lac repressor is caused by the small
molecule allolactose, an isomer (rearranged version) of lactose. When
lactose is available, some molecules will be converted to allolactose inside
the cell.
 Allolactose is an example of an inducer, a small molecule that triggers
expression of a gene or operon. The lac operon is considered an inducible
operon because it is usually turned off (repressed), but can be turned on in
the presence of the inducer allolactose.

24.  https://courses.lumenlearning.com/suny-wmopen-
biology1/chapter/regulation-of-gene-expression/
 https://en.wikipedia.org/wiki/Regulation_of_gene_expression
 https://www.ncbi.nlm.nih.gov/books/NBK459456/
 https://bioprinciples.biosci.gatech.edu/module-4-genes-and-genomes/4-7-
gene-regulation/

25. THANK YOU!