These are simplified slides from the first lecture in a three-lecture series by Dr. Sidra Arshad, diving into the significance of genetic control which stands as one of the most intricate, yet complex, physiological control mechanisms intimately interlinked with homeostasis and cellular functioning. Learning objectives: 1. Describe the structure of DNA 2. Recognise the different types of RNA 3. Briefly describe the steps of transcription to elucidate the functions of different types of RNA Study Resources: 1. Chapter 3, Guyton and Hall Textbook of Medical Physiology, 14th edition 2. Chapter 1, Ganong’s Review of Medical Physiology, 26th edition 3. RNA Structure, https://www.ncbi.nlm.nih.gov/books/NBK558999/

1. Cell Physiology
The Genetic
Control of Cellular
Functions I
Dr. Sidra Arshad
Assistant Professor
MBBS, FCPS (Physiology)

2. Learning Objectives:
• Describe the structure of DNA
• Recognise the different types of RNA
• Briefly describe the steps of transcription to elucidate the functions of
different types of RNA

4. The Building Blocks of DNA

5. The Building Block of DNA

7. • A gene is that part of DNA which encodes for a particular sequence
of amino acids for a specific polypeptide
• That polypeptide can then become a part of many proteins

8. The Genetic Code
• Consists of successive triplets of bases
• Each three successive bases is a code
word
• Each code word is responsible for
placement of a particular amino acid
in a newly formed molecule of protein

9. • code triplets in the DNA  formation of complementary code triplets
in the mRNA
• which are then known as codons
• codons will control the sequence of amino acids in a protein

10. Building blocks of RNA are nucleotides
as well, like the DNA, except:
Ribose sugar instead of deoxyribose
Uracil instead of thymine

11. Types of RNA
Precursor messenger RNA (pre-
mRNA)
immature, single strand of RNA that is processed in the
nucleus to form mature messenger RNA (mRNA)
Small nuclear RNA (snRNA)
directs the splicing of pre-mRNA to form mRNA
Messenger RNA (mRNA)
carries the genetic code to the cytoplasm for
controlling the type of protein formed
Transfer RNA (tRNA)
transports activated amino acids to the ribosomes to
be used in assembling the
protein molecule
Ribosomal RNA
along with about 75 different proteins, forms
ribosomes
MicroRNAs (miRNAs)
regulate gene transcription and translation

12. Transcription
• transfer of cell nucleus DNA code to cytoplasm RNA code
Why is transcription required? Why cannot DNA be directly translated
to proteins?
The entire machinery for protein synthesis is present in the cytoplasm

13. Steps of mRNA Synthesis
RNA polymerase activates the
nucleotides (phosphates added)
RNA polymerase becomes
attached to the promoter
Unwinding of DNA helix
Addition of a new activated RNA
nucleotide to the end of the
newly forming RNA chain

14. Post-transcriptional Modification
1. Capping
• At 5’ end
• Addition of 7-methylguanosine triphosphate
2. Adding a tail
• At 3’ end
• Addition of a long chain of adenine
nucleotides (poly-A tail)
3. Splicing
• Removal of introns
• By spliceosomes or self-splicing

16. Precursor messenger RNA (pre-mRNA)
• a large, immature, single strand of RNA
• processed in the nucleus to form mature
messenger RNA (mRNA)
• includes two different types of segments:
• Introns - removed by a process called splicing
• Exons - retained in the final mRNA

17. Ribosomal RNA (rRNA)
• constitutes about 60% of the ribosome
• genes located in five pairs of chromosomes collect in the nucleolus where they
combine with other proteins
• Subunits move out of the nuclear pores
• Assembled in the cytoplasm  mature ribosomes are formed

18. MicroRNAs
• often called noncoding RNA
• several types
• regulate gene expression by mRNA degradation or
translational repression
• one similar type is small interfering RNA (siRNA) which
blocks translation

19. Study Resources
1. Chapter 3, Guyton and Hall Textbook of Medical Physiology, 14th
edition
2. Chapter 1, Ganong’s Review of Medical Physiology, 26th edition
3. RNA Structure, https://www.ncbi.nlm.nih.gov/books/NBK558999/
2/1/2024 Dr. Sidra Arshad, Asst. Prof., Physiology CIMS