Slide 1

Genetics and Evolution - Molecular Basis of Inheritance

• Introduction to the molecular basis of inheritance
• Understanding the role of genes and DNA
• Importance of genetic information for evolution

Slide 2

DNA Structure

• Double-helix structure
• Complementary base pairing (adenine-thymine, guanine-cytosine)
• Sugar-phosphate backbone

Slide 3

Central Dogma of Molecular Biology

• DNA replication
• Transcription (DNA to mRNA)
• Translation (mRNA to protein)

Slide 4

Gene Expression

• Importance of gene expression
• Regulation of gene expression
• Role of transcription factors

Slide 5

Genetic Code

• Codons and triplets
• Role of amino acids in protein synthesis
• Start and stop codons

Slide 6

Initiation Codon

• The initiation codon is AUG
• Encodes for the amino acid methionine
• Signals the start of protein synthesis

Slide 7

Importance of Initiation Codon

• Initiates the assembly of ribosomes on mRNA
• Determines the reading frame for protein synthesis
• Essential for the proper functioning of genes

Slide 8

Examples of Initiation Codons

• AUG is the most common initiation codon
• Other initiation codons include GUG and UUG
• Different organisms may have variations in initiation codons

Slide 9

Mutations and Initiation Codons

• Mutations in initiation codons can lead to genetic disorders
• Non-functional initiation codons can disrupt protein synthesis
• Frameshift mutations can also affect the initiation codon

Slide 10

Summary

• The initiation codon is an essential component of the genetic code
• It signals the start of protein synthesis
• Mutations in initiation codons can have detrimental effects on gene expression and protein synthesis

11. Which Codon is Called Initiation Codon?

• The initiation codon is the codon that signals the start of protein synthesis.
• In the standard genetic code, the initiation codon is AUG.
• AUG codes for the amino acid methionine, which is often the first amino acid in a protein sequence.

12. Importance of the Initiation Codon

• The initiation codon plays a crucial role in protein synthesis.
• It determines the reading frame for translation.
• It helps assemble ribosomes on the mRNA molecule.

13. Initiation Codon Variations

• While AUG is the most common initiation codon, there are some exceptions.
• In specific organisms, initiation codons like GUG and UUG can also be used.
• However, AUG is by far the most prevalent and widely recognized initiation codon.

14. Examples of Initiation Codons

• In humans, the vast majority of protein-coding genes start with the AUG initiation codon.
• However, there are exceptions where alternative initiation codons may be used.
• For example, the gene for the growth hormone receptor starts with the initiation codon CUG.

15. Mutations in Initiation Codons

• Mutations in the initiation codon can have severe consequences.
• A mutation that changes the initiation codon can prevent the proper initiation of translation.
• This can lead to the production of non-functional or incomplete proteins.

16. Non-Functional Initiation Codons

• Non-functional initiation codons can arise due to point mutations or indels (insertion or deletion of bases).
• They can prevent ribosome binding or disrupt the reading frame, resulting in non-functional protein production.
• Non-functional initiation codons can lead to genetic disorders or impaired cellular processes.

17. Frameshift Mutations and Initiation Codons

• Frameshift mutations can also affect the initiation codon.
• Addition or deletion of nucleotides can shift the reading frame, altering the entire sequence downstream of the mutation.
• This can cause a different codon to be interpreted as the initiation codon, leading to abnormal protein synthesis.

18. The Role of Initiation Codon in Translation

• The initiation codon plays a dual role in translation - it defines the start site for protein synthesis and establishes the reading frame.
• Initiation factors aid in the recognition and binding of the initiation codon by the ribosome.
• Once the initiation codon is identified, the ribosome assembles and begins the process of protein synthesis.

19. Initiation Codons in Different Organisms

• Different organisms may have variations in initiation codons.
• For example, in bacteria, the initiation codon can be either AUG or GUG.
• Mitochondria in some organisms also use alternative start codons like AUA or AUU.

20. Summary

• The initiation codon, typically AUG, is the codon that signals the start of protein synthesis.
• It determines the reading frame for translation and is crucial for proper initiation of translation.
• Mutations in the initiation codon can lead to genetic disorders or impaired protein synthesis.

Slide 21

Genetic Code Variations

• Some organisms have variations in the genetic code
• Example: Mitochondria in certain species use alternative initiation codons like AUA or AUU
• These variations can have implications for protein synthesis and gene expression

Slide 22

Silent Mutations

• Silent mutations do not result in a change in the amino acid sequence
• They occur when a different codon still codes for the same amino acid
• Example: GCU, GCC, GCA, and GCG all code for the amino acid alanine

Slide 23

Nonsense Mutations

• Nonsense mutations introduce a premature stop codon
• This leads to the production of a truncated and non-functional protein
• Example: UAA, UAG, and UGA are stop codons

Slide 24

Frameshift Mutations

• Frameshift mutations occur due to insertions or deletions of nucleotides that are not in multiples of three
• This shifts the reading frame and alters the entire sequence downstream of the mutation
• Example: Insertion of an extra base - AGGCGA –> AGGACGA

Slide 25

Missense Mutations

• Missense mutations result in the substitution of one amino acid for another in the protein sequence
• This can impact protein structure and function
• Example: GAG (glutamic acid) to GTG (valine) in the beta-globin gene causes sickle cell anemia

Slide 26

Mutagens and Mutations

• Mutagens are agents that can induce mutations
• Examples: Radiation, chemicals, and certain viruses
• Mutations can have harmful, neutral, or occasionally beneficial effects on an organism

Slide 27

Gene Mutations and Inheritance

• Gene mutations can be inherited from parents
• If a mutation occurs in germ cells (sperm or egg), it can be passed on to offspring
• Example: Mutations in the BRCA1 gene can increase the risk of breast and ovarian cancer

Slide 28

Genetic Disorders

• Genetic disorders are caused by mutations in specific genes
• Examples: Cystic fibrosis, Down syndrome, Huntington’s disease
• These disorders can result from different types of mutations and have varying inheritance patterns

Slide 29

Genetic Testing

• Genetic testing helps identify mutations and genetic disorders
• Examples: Carrier screening, prenatal testing, diagnostic testing
• Testing allows for early detection, treatment, and informed reproductive decisions

Slide 30

Gene Therapy

• Gene therapy aims to correct or replace faulty genes to treat genetic disorders
• Different approaches include gene addition, gene editing, and gene silencing
• This field holds promise for potential medical advancements and therapies