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Gene Structure

What is a gene?

A gene is a segment of DNA (deoxyribonucleic acid), which carries the genetic information for a specific trait or function. This information is encoded in a biochemical language – the DNA molecule, which is made up of four different types of nucleotides: adenine (A), cytosine (C), guanine (G), and thymine (T).

How is information in a gene used within the cell?

Information within a gene is used by the cell machinery to create proteins. This is a two-step process: transcription, where a segment of DNA is copied into RNA (ribonucleic acid), and translation, where the RNA is used as a blueprint to create proteins.


What is the structure of a gene?

A gene is made up of several components including promoter regions, exons, introns, and terminator sequences. Promoter region is where the transcription process begins. Exons are sequences that are translated into proteins while introns are not. Terminator sequences signal the end of the gene.

What's the difference between an exon and an intron?

The key difference between an exon and an intron lies in the role they play in gene expression. Exons are the coding sequences that are expressed in the process of protein synthesis, while introns, or intervening sequences, are not used in protein synthesis.


What is DNA transcription?

Transcription is the process where the DNA sequence of a gene is copied into mRNA (messenger RNA). The mRNA then exits the nucleus, enters the cell's cytoplasm, and is used as a template for protein synthesis.

What are the main steps in transcription?

The main steps in transcription include initiation, elongation, and termination. Initiation is when enzymes unwind the DNA helix. During elongation, an RNA polymerase moves along the DNA template strand, synthesizing mRNA. Termination occurs when the RNA polymerase hits a stop sequence.


What is DNA translation?

DNA translation is the process by which the information in mRNA is used to create proteins. The mRNA's sequence is 'read' by cellular machinery called ribosomes, and then amino acids are connected together to form the protein described by the mRNA.

How do ribosomes read mRNA sequences?

Ribosomes read mRNA sequences in units of three nucleotides, known as codons. Each codon corresponds to a specific amino acid or signals to start or stop protein synthesis.


What is gene expression and regulation?

Gene expression refers to the process by which the information stored in genes is converted into proteins. Gene regulation refers to mechanisms that can increase or decrease the expression of specific genes. This can involve a range of processes like DNA methylation, histone modification, and the action of transcription factors.

Why is gene regulation important?

Gene regulation is crucial because it allows an organism to adapt to changing environments, carry out specialized functions, and can help prevent abnormalities that could lead to diseases.


What is a mutation?

A mutation is a change in a DNA sequence in a gene or chromosome. This change can create a new trait or characteristic, or lead to a disease or disorder. Mutations can occur spontaneously or can be induced by environmental factors like chemicals or radiation.

What are the three types of mutations?

The three main types of mutations are base substitution, deletion, and insertion. Base substitution is when one base replaces another. Deletion is when one or more bases are removed. Insertion is when one or more bases are added to the DNA sequence.


What is genetic recombination?

Genetic recombination is a process that introduces genetic diversity by shuffling genes between two chromosomes. This process happens during meiosis, a type of cell division involved in producing sperm and egg cells.

Why is genetic recombination important?

Genetic recombination is crucial because it introduces diversity, which is key to the survival and adaptability of species. It also ensures that offspring are genetically different from their parents.


What is a genome?

A genome is the complete set of DNA in an organism, including all of its genes. It contains all of the information needed to build the organism and allow it to grow and develop.

How does a genome differ across species?

The size, number, and content of genes within a genome varies widely across different species. Some organisms have larger genomes with more genes, and others have smaller genomes with fewer genes. The content of genes can also be very different, reflecting the vast range of biological diversity.


What is a genotypic ratio?

A genotypic ratio is a comparison of the frequencies of different genes or traits in the offspring resulting from a particular genetic cross. It represents the genetic diversity that results from the combination of alleles.

How does a genotypic ratio differ from a phenotypic ratio?

While a genotypic ratio refers to the frequency of genetic combinations, a phenotypic ratio refers to the frequency of visible traits or characteristics in the offspring.


What is a genetic disorder?

A genetic disorder is a disease caused by an abnormality in an individual's DNA. These abnormalities can be small, like a single-base mutation, or large, like a chromosome abnormality. These disorders can be inherited or can be the result of a new mutation.

Can you give an example of a genetic disorder?

An example of a genetic disorder is Down syndrome, which is caused by an extra copy of chromosome 21. This results in physical and mental developmental delays and disabilities.