Genetics and Evolution

Molecular Basis of Inheritance

Production of mature mRNA
Importance of RNA processing
Pre-mRNA splicing
Addition of a 5’ cap
Addition of a poly-A tail

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Production of mature mRNA

Synthesis of primary transcript
RNA processing steps
Removal of introns
Addition of a cap and tail
Formation of mature mRNA

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Importance of RNA processing

Ensures stability of mRNA
Facilitates transport from nucleus to cytoplasm
Allows for translation of mRNA into protein
Controls gene expression
Influences alternative splicing

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Pre-mRNA splicing

Removal of introns
Conserved splice donor and acceptor sites
Formation of spliceosome complex
Recognition of intron/exon boundaries
Cleavage and ligation reactions

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Addition of a 5’ cap

Facilitates mRNA stability
Protects mRNA from degradation
Aids in translation initiation
Modification at the 5’ end of pre-mRNA
Consists of a methylated guanine nucleotide

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Addition of a poly-A tail

Enhances mRNA stability
Protects mRNA from degradation
Facilitates nuclear export of mRNA
Increases translational efficiency
Consists of a string of adenine nucleotides

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Synthesis of primary transcript

Initiation of transcription at the promoter site
RNA polymerase binding to DNA template strand
Elongation of RNA molecule
Termination of transcription at the terminator site
Formation of pre-mRNA molecule

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Removal of introns

Recognition of intron/exon boundaries
Splicing out of introns by spliceosome
Formation of mature mRNA molecule
Retention of exons for protein coding
Alternative splicing possibilities

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Formation of spliceosome complex

Consists of snRNPs (small nuclear ribonucleoproteins)
Recognition of intron/exon boundaries
Assembly of spliceosome at the splice sites
Catalyzes the splicing reaction
Allows for removal of introns and ligation of exons

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Recognition of intron/exon boundaries

Conserved nucleotide sequences at splice sites
5’ splice site (splice donor site)
3’ splice site (splice acceptor site)
Intronic branch point sequence
Consensus sequences that guide splicing process

Slide 11

Addition of a 5’ cap

Facilitates mRNA stability
Protects mRNA from degradation
Aids in translation initiation
Modification at the 5’ end of pre-mRNA
Consists of a methylated guanine nucleotide (7-methylguanosine)

Slide 12

Addition of a poly-A tail

Enhances mRNA stability
Protects mRNA from degradation
Facilitates nuclear export of mRNA
Increases translational efficiency
Consists of a string of adenine nucleotides (generally 100-200 nucleotides long)

Slide 13

Synthesis of primary transcript

Initiation of transcription at the promoter site
RNA polymerase binding to DNA template strand
Elongation of RNA molecule by adding nucleotides
Termination of transcription at the terminator site
Formation of pre-mRNA molecule after completion of transcription

Slide 14

Removal of introns

Recognition of intron/exon boundaries by spliceosome
Splicing out of introns by spliceosome
Formation of mature mRNA molecule consisting of exons
Retention of exons for protein coding
Possibility of alternative splicing leading to different mRNA isoforms

Slide 15

Formation of spliceosome complex

Consists of snRNPs (small nuclear ribonucleoproteins)
snRNPs recognize conserved sequences at splice sites
Assembly of spliceosome at the splice sites
Catalyzes the splicing reaction
Allows for removal of introns and ligation of exons

Slide 16

Recognition of intron/exon boundaries

Conserved nucleotide sequences at splice sites
5’ splice site (splice donor site) - GU
3’ splice site (splice acceptor site) - AG
Intronic branch point sequence - A near the 3’ end of intron
Consensus sequences guide the splicing process and provide specificity

Slide 17

Importance of RNA processing

Ensures stability of mRNA
Facilitates transport from nucleus to cytoplasm
Allows for translation of mRNA into protein
Controls gene expression by regulating splicing patterns
Influences alternative splicing leading to multiple protein isoforms

Slide 18

Pre-mRNA splicing

Pre-mRNA undergoes alternative splicing to generate different splice variants
Spliced genes can code for different protein products
Example: Fibronectin gene, which can generate over 20 different mRNA variants
Alternative splicing contributes to proteome diversity

Slide 19

Production of mature mRNA

The primary transcript undergoes various processing steps before becoming mature mRNA
This includes splicing, capping, and polyadenylation
The mature mRNA is exported from the nucleus to the cytoplasm
It can then be translated into a protein by the ribosomes
Mature mRNA is more stable and functional compared to the primary transcript

Slide 20

Regulation of RNA processing

RNA processing can be regulated at various levels
Transcription factors and chromatin modifications can influence splicing patterns
RNA-binding proteins can enhance or inhibit splicing efficiency
Alternative splicing can be regulated by signaling pathways and cellular conditions
Dysregulation of RNA processing can lead to genetic disorders and diseases

Slide 21

Regulation of gene expression

Transcriptional regulation
- Promoters and enhancers
- Transcription factors
- Chromatin remodeling
Post-transcriptional regulation
- mRNA stability
- Translation initiation
- RNA interference (miRNA, siRNA)
Epigenetic regulation
- DNA methylation
- Histone modification
- Non-coding RNAs

Slide 22

Transcriptional regulation

Promoters and enhancers control transcription initiation
Transcription factors bind to specific DNA sequences
Activators enhance transcription, repressors inhibit it
Chromatin remodeling influences DNA accessibility
Coactivators and corepressors modulate transcriptional activity

Slide 23

Post-transcriptional regulation

mRNA stability determines its abundance
Regulatory proteins and RNA-binding proteins control stability
AU-rich elements (AREs) promote mRNA degradation
Translation initiation is regulated by various factors
RNA interference (RNAi) involves small non-coding RNAs (miRNA, siRNA)

Slide 24

Epigenetic regulation

DNA methylation adds methyl groups to cytosine residues
Methylated DNA reduces gene expression
Histone modification alters chromatin structure
Acetylation, methylation, phosphorylation, etc.
Non-coding RNAs regulate gene expression at the transcriptional level

Slide 25

Examples of gene regulation

Lac operon in bacteria
Promoter sequence and the role of lactose and glucose
Transcriptional activator (CAP) and repressor (LacI)
Regulation of p53 tumor suppressor gene
Feedback loops and cell cycle regulation
X-chromosome inactivation in females

Slide 26

Gene expression and development

Differential gene expression leads to cell specialization
Homeobox genes and body plan development
Hox genes and segmental patterning in animals
Induction and cell signaling during embryogenesis
Environmental factors and gene expression

Slide 27

Molecular basis of genetic diseases

Mutations can disrupt gene function
Single gene disorders and inherited traits
Cystic fibrosis, sickle cell anemia, Huntington’s disease, etc.
Polygenic disorders and complex traits
Diabetes, Alzheimer’s disease, heart disease, etc.
Genetic testing and counseling

Slide 28

Gene therapy and genetic engineering

Gene therapy for genetic disorders
Introduction of functional genes into affected cells
Viral vectors and non-viral delivery systems
Ethical considerations and safety concerns
Genetic engineering and biotechnology applications
GMOs, gene editing (CRISPR), cloning, etc.

Slide 29

Population genetics and evolution

Genetic variation and allele frequencies
Hardy-Weinberg equilibrium and genetic drift
Natural selection and adaptation
Genetic flow and migration
Speciation and reproductive isolation

Slide 30

Human evolution

Shared ancestry with other primates
Fossil record and hominid species
Homo habilis, Homo erectus, Homo neanderthalensis, etc.
Out-of-Africa hypothesis and modern human origins
Major milestones in human evolution

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