Genetics And Evolution- Molecular Basis Of Inheritance - Which Is The First Nucleotide Bieng Added During Transcription

Slide 1: Introduction to Molecular Basis of Inheritance

DNA and RNA are the molecules that play a crucial role in inheritance.
This branch of genetics focuses on understanding the processes involved in inheritance at the molecular level.
The key processes that we will discuss include transcription, translation, mutations, and gene regulation.

Slide 2: Transcription

Transcription is the process in which RNA molecules are synthesized using a DNA template.
It takes place in the nucleus of eukaryotic cells and involves three main steps: initiation, elongation, and termination.
The enzyme RNA polymerase catalyzes the synthesis of RNA during transcription.

Slide 3: Initiation of Transcription

The process of transcription begins when RNA polymerase binds to a specific region on the DNA called the promoter.
The promoter contains a sequence of nucleotides that signals the start of a gene.
After binding to the promoter, RNA polymerase begins to unwind the DNA strand for further transcription.

Slide 4: Elongation of Transcription

Once the DNA strand is unwound, RNA polymerase starts adding complementary RNA nucleotides to the growing RNA strand.
The RNA nucleotides are added in a specific order dictated by the DNA template.
DNA serves as a template for the synthesis of RNA, with adenine (A) pairing with uracil (U) and cytosine (C) pairing with guanine (G).

Slide 5: Termination of Transcription

The termination of transcription occurs when RNA polymerase reaches a specific DNA sequence called the terminator.
The terminator signals the end of the gene and causes RNA polymerase to detach from the DNA template.
Finally, the newly transcribed RNA molecule is released, and the DNA double helix reforms.

Slide 6: Structure and Types of RNA

RNA molecules are single-stranded and have a structure similar to DNA.
The three main types of RNA are messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).
mRNA carries the genetic information from DNA to the ribosomes, tRNA helps in protein synthesis, and rRNA forms the core components of ribosomes.

Slide 7: Translation

Translation is the process in which the genetic information carried by mRNA is used to synthesize proteins.
It occurs in the cytoplasm and involves three main steps: initiation, elongation, and termination.
Numerous enzymes and specialized molecules are involved in the translation process.

Slide 8: Initiation of Translation

The process of translation begins when the small ribosomal subunit binds to the mRNA molecule.
The ribosome then scans the mRNA until it encounters the start codon, usually AUG.
The start codon signals the recruitment of the large ribosomal subunit and the initiation of protein synthesis.

Slide 9: Elongation of Translation

Once initiation is complete, the ribosome starts the elongation phase of translation.
tRNA molecules carrying specific amino acids bind to the corresponding codons on mRNA.
The ribosome facilitates the formation of peptide bonds between amino acids, resulting in the growing polypeptide chain.

Slide 10: Termination of Translation

The termination of translation occurs when the ribosome reaches a stop codon.
Stop codons do not code for any amino acid but signal the end of protein synthesis.
Upon reaching a stop codon, the newly synthesized protein is released, and the ribosome dissociates from the mRNA.

Slide 11: Mutations

Mutations are permanent changes in the DNA sequence and can occur naturally or be induced by external factors.
There are two main types of mutations: point mutations, which involve changes in a single nucleotide, and chromosomal mutations, which involve changes in the structure of chromosomes.
Point mutations can be further classified as substitutions, insertions, or deletions.

Slide 12: Substitutions

Substitutions occur when one nucleotide is replaced by another in the DNA sequence.
Substitutions can be silent, missense, or nonsense mutations, depending on the effect on the resulting protein.
Silent mutations do not change the amino acid sequence, missense mutations result in the substitution of one amino acid for another, and nonsense mutations result in the premature termination of protein synthesis.

Slide 13: Insertions and Deletions

Insertions and deletions involve the addition or removal of nucleotides from the DNA sequence.
These mutations can have significant effects on the resulting protein, as they shift the reading frame during translation.
Frameshift mutations can lead to the production of non-functional or truncated proteins.

Slide 14: Gene Regulation

Gene regulation refers to the processes by which genes are turned on or off in response to various stimuli.
It plays a crucial role in determining cell fate, development, and response to environmental cues.
Gene regulation occurs at both the transcriptional and post-transcriptional levels.

Slide 15: Transcriptional Regulation

Transcriptional regulation involves the control of gene expression at the level of transcription.
It is mediated by a variety of proteins and regulatory elements, such as transcription factors and enhancers.
Transcription factors bind to specific DNA sequences and either promote or inhibit the initiation of transcription.

Slide 16: Post-transcriptional Regulation

Post-transcriptional regulation involves the control of gene expression after the mRNA molecule has been synthesized.
It includes processes such as alternative splicing, RNA editing, and mRNA degradation.
Alternative splicing allows a single gene to generate multiple mRNA isoforms with different functional properties.

Slide 17: Regulation of Protein Synthesis

The process of translation can also be regulated to control gene expression.
Regulatory proteins can bind to mRNA molecules and either enhance or inhibit translation.
Small molecules, such as microRNAs, can also bind to mRNA and lead to its degradation or inhibition of translation.

Slide 18: Epigenetics

Epigenetics refers to heritable changes in gene expression that do not involve changes in the DNA sequence.
It involves modifications to the DNA or histone proteins that can influence gene expression.
DNA methylation and histone modification are two examples of epigenetic marks that can regulate gene expression.

Slide 19: DNA Methylation

DNA methylation is the addition of a methyl group to the DNA molecule, usually at cytosine residues.
Methylation can silence gene expression by preventing the binding of transcription factors to the DNA.
DNA methylation patterns can be inherited and play a role in developmental processes and disease.

Slide 20: Histone Modification

Histone modification involves the addition or removal of chemical groups to the histone proteins around which DNA is wrapped.
These modifications can alter the structure of chromatin and influence gene expression.
Examples of histone modifications include acetylation, methylation, phosphorylation, and ubiquitination.

Slide 21: Genetic Code

The genetic code is the set of rules that determines how DNA and RNA sequences are translated into proteins.
It is based on codons, which are three-letter sequences of nucleotides that specify each amino acid.
There are 64 possible codons, including start and stop codons.

Slide 22: Start and Stop Codons

The start codon, AUG, signals the beginning of protein synthesis and codes for the amino acid methionine.
There are three stop codons: UAA, UAG, and UGA. These codons do not code for any amino acid but instead signal the termination of protein synthesis.

Slide 23: Gene Expression Regulation

Gene expression can be regulated at multiple points to control the production of specific proteins.
Regulatory elements, such as enhancers and silencers, can modulate the activity of promoters and enhancers.
Transcription factors bind to specific DNA sequences and either activate or repress gene transcription.

Slide 24: Gene Amplification

Gene amplification is a process that leads to an increase in the number of copies of a particular gene.
It can occur through mechanisms such as gene duplication or DNA replication errors.
Gene amplification can result in the overexpression of particular genes, leading to various genetic disorders.

Slide 25: RNA Interference (RNAi)

RNA interference is a mechanism by which gene expression is inhibited by small RNA molecules.
Small interfering RNAs (siRNAs) or microRNAs (miRNAs) can bind to complementary mRNA sequences and prevent their translation or induce mRNA degradation.
RNAi plays a vital role in regulating gene expression and maintaining cellular homeostasis.

Slide 26: Transposons

Transposons are DNA sequences that can move or “jump” within the genome.
They can have both beneficial and harmful effects on the organism.
Transposons can disrupt gene function, cause genetic diseases, or contribute to genome evolution.

Slide 27: DNA Repair Mechanisms

DNA repair mechanisms are cellular processes that correct DNA damage and maintain the integrity of the genome.
There are several types of DNA repair mechanisms, including base excision repair, nucleotide excision repair, and mismatch repair.
Mutations in DNA repair genes can lead to genetic disorders and an increased risk of cancer.

Slide 28: DNA Recombination

DNA recombination is a process that exchanges genetic material between two DNA molecules.
It can occur through homologous recombination, site-specific recombination, or transposition.
DNA recombination plays a vital role in evolution, genetic diversity, and repairing DNA damage.

Slide 29: Telomeres and Telomerase

Telomeres are repetitive DNA sequences located at the ends of chromosomes.
They protect the chromosome ends from degradation and fusion with other chromosomes.
Telomerase is an enzyme that maintains telomeres’ length by adding repetitive DNA sequences, preventing the loss of genetic information during replication.

Slide 30: Applications of Molecular Genetics

The molecular basis of inheritance has numerous applications in various fields.
Genetic engineering allows the manipulation of DNA to produce desirable traits in organisms or create genetically modified organisms (GMOs).
Molecular diagnostics use genetic information to diagnose diseases and predict the risk of developing certain conditions.