What is Alternative splicing

After splicing in the pre-mRNA, the exons can recombine from the DNA sequence to produce different mRNAs from the same gene. This process is called alternative splicing. In this process, different types of proteins are produced from the same gene. 1,00,000 types of proteins are produced from 20,000 genes in the human body due to alternative splicing.

Transcription : Definition, components and steps of Transcription

The process by which mRNA is produced from DNA is called transcription. Reverse transcription occurs in HIV. The length of DNA that an RNA transcribes is called a transcription unit. Transcription unit consists of promoter, start point and termination point. Transcription is a very fast process. It takes one second to transcribe an mRNA of 1000 nucleotides from a gene in E. coli bacteria. In actual cells, an mRNA is transcribed from a gene and a protein is translated from it. This is called monocistronic transcript. Multiple proteins are translated to transcribe a recipe in progenitor cells. This is called a polycistronic transcript.

Essential components of transcription
1. Requires mRNA template.
2. Requires RNA polymerase enzyme.
3. Requires free ribonucleotide triphosphate (ATP, GTP, TTP, UTP).
4. Chemical energy that breaks down triphosphate to produce ATP.
5. Some associate proteins are required.

Process of Transcription
Transcription is a complex process. The steps in this process are – transcription initiation, mRNA amplification, mRNA termination and mRNA termination.
1. Initiation
(i) Transcription takes place inside the cell nucleus. DNA is inside the nucleus. DNA molecules contain genes. Every gene has a promoter. The promoter sequence is 5-TATAWAWA-3. In real cells it is called TATA box or Goldberg-Hogness box. In progenitor cells, the TATA box is replaced by TATAAT and is called the Pribnow box.
(ii) Transcription factors, promoters and RNA polymerase enzymes associate to form transcription complexes.
(iii) RNA polymerase enzyme opens up patches (at least 20 pairs) of DNA molecules and breaks hydrogen bonds. As a result, two single formulas are created. One is the template formula and the other is the coding formula.
(iv) Template formula acts as a template for making mRNA. It has two dots. start site and terminal site. Transcription starts from the start point.
2. mRNA Elongation
(i) RNA polymerase enzyme adds new nucleotides to the template. Nucleotides tend to join 3-5 carbons.
(ii) Uracil (U) is added to complement adenine (A) and cytosine (C) to complement guanine (G) according to base pairing principle. That is, if the ATTCGA sequence is present in the DNA source, the UAAGCU sequence is formed in the mRNA source. The portion of DNA molecule from which mRNA is produced is called transcription unit.
(iii) The mRNA chain continues to grow until the termination point of the template strand is reached. At the same time, the transcribed segment becomes double helix.
3. mRNA Termination: The mRNA sequence grows and touches the terminator point of the DNA. Touching the termination point releases the RNA polymerase enzyme. As a result, mRNA production stops. The mRNA thus produced is called pre-mRNA.
4. mRNA termination
(i) Capping: 7 guanosine nucleotides are added to the 5 end of pre-mRNA to form a guanine cap. This is called capping. It is also called 5 caps. It ensures ribosome attachment during translation.
(ii) Tailing: 50-150 adenines are added to the 3 end of pre-mRNA to form a poly A tail. This process is called tailing. It protects mRNA from the damaging effects of hydrolytic enzymes and accelerates transport.
(iii) Splicing: Pre-mRNA consists of two parts. Exon or coding part and Intron or non-coding part. Translation never occurs from an intron. Therefore, introns are excised from pre-mRNA during splicing process in the presence of spliceosome. The resulting final mRNA is obtained. The final mRNA is suitable for the cytoplasmic environment. therefore passes through the pores of the nucleus into the cytoplasm.

Steps of Transcription , Process of Transcription

Transcription is a complex process. The steps in this process are – transcription initiation, mRNA amplification, mRNA termination and mRNA termination.
1. Initiation
(i) Transcription takes place inside the cell nucleus. DNA is inside the nucleus. DNA molecules contain genes. Every gene has a promoter. The promoter sequence is 5-TATAWAWA-3. In real cells it is called TATA box or Goldberg-Hogness box. In progenitor cells, the TATA box is replaced by TATAAT and is called the Pribnow box.
(ii) Transcription factors, promoters and RNA polymerase enzymes associate to form transcription complexes.
(iii) RNA polymerase enzyme opens up patches (at least 20 pairs) of DNA molecules and breaks hydrogen bonds. As a result, two single formulas are created. One is the template formula and the other is the coding formula.
(iv) Template formula acts as a template for making mRNA. It has two dots. start site and terminal site. Transcription starts from the start point.
2. mRNA Elongation
(i) RNA polymerase enzyme adds new nucleotides to the template. Nucleotides tend to join 3-5 carbons.
(ii) Uracil (U) is added to complement adenine (A) and cytosine (C) to complement guanine (G) according to base pairing principle. That is, if the ATTCGA sequence is present in the DNA source, the UAAGCU sequence is formed in the mRNA source. The portion of DNA molecule from which mRNA is produced is called transcription unit.
(iii) The mRNA chain continues to grow until the termination point of the template strand is reached. At the same time, the transcribed segment becomes double helix.
3. mRNA Termination
The mRNA sequence grows and touches the terminator point of the DNA. Touching the termination point releases the RNA polymerase enzyme. As a result, mRNA production stops. The mRNA thus produced is called pre-mRNA.
4. mRNA termination
(i) Capping: 7 guanosine nucleotides are added to the 5 end of pre-mRNA to form a guanine cap. This is called capping. It is also called 5 caps. It ensures ribosome attachment during translation.
(ii) Tailing: 50-150 adenines are added to the 3 end of pre-mRNA to form a poly A tail. This process is called tailing. It protects mRNA from the damaging effects of hydrolytic enzymes and accelerates transport.
(iii) Splicing: Pre-mRNA consists of two parts. Exon or coding part and Intron or non-coding part. Translation never occurs from an intron. Therefore, introns are excised from pre-mRNA during splicing process in the presence of spliceosome. The resulting final mRNA is obtained. The final mRNA is suitable for the cytoplasmic environment. therefore passes through the pores of the nucleus into the cytoplasm.

Definition of Transcription

The process by which mRNA is produced from DNA is called transcription. Reverse transcription occurs in HIV. The length of DNA that an RNA transcribes is called a transcription unit. Transcription unit consists of promoter, start point and termination point. Transcription is a very fast process. It takes one second to transcribe an mRNA of 1000 nucleotides from a gene in E. coli bacteria. In actual cells, an mRNA is transcribed from a gene and a protein is translated from it. This is called monocistronic transcript. Multiple proteins are translated to transcribe a recipe in progenitor cells. This is called a polycistronic transcript.

Echinodermata : characteristics, classification and eaxample of Echinodermata

The word Echinodermata is formed from the Latin words Echinus meaning prickly, derma meaning skin and ata meaning bearing. Animals whose body is symmetrical, five-segmented, ciliated, headless, circulatory system and echinodermata are called Echinodermata. They are called conifers. Animals like sea star, sea cucumber, sea lilies, sea urchin, sand dollar etc. belong to this phase. The number of species is about 7,550. Jacob Klein (1734) named Echinodermata.
Characteristics of Echinodermata
1. Their bodies are unsegmented, cylindrical or spherical or star-shaped or flower-shaped.
2. Their body is bilaterally symmetrical or pentalaterally symmetrical or orally symmetrical or divided into five equal parts.
3. Body skin prickly. The exoskeleton is composed of numerous ossicles composed of spines and pedicellaries and the endoskeleton composed of calcium carbonate. It is covered by ciliated membranes.
4. The body is organized into distinct verbal and non-verbal levels. Five ambulacral grooves are present on the oral floor.
5. They have a water circulatory system, which carries out respiration and locomotion.
6. There are ring vessels, radial canals, medriporites, stone canals and lateral canals for water transport.
7. Their moving parts are podia. It is responsible for respiration and food absorption.
8. The Himalayan and Perihimalayantra work on circulation.
9. The body does not have a brain, respiratory system, excretory system and circulatory system.
10. All animals are marine.
11. The life cycle consists of bipinaria, auricularia, ophiopluteus, echinopluteus larvae.

[Key words to remember features: unsegmented, bony, oral floor, bimucous, canaliculi, himal and perihimalatantra]

Classification of Echinidermata
The order Echinidermata is divided into five classes.
1. Asteroids: Their bodies are star-shaped with five arms. Tube fit exists. Spines and pedicilli are present on the body. For example – sea star (Asterias vulgaris).
2. Ophuroidea: Their bodies are pentamerous discs. Tube fit and spine present on the body. Their arms are long. For example – Cucumaria (Cucumaria planci).
3. Echinoidea: Their bodies are hemispherical. Tube fit exists. The body has no arms. Spine present. For example, sea urchin (Echinus esculentus).
4. Holothuroids: Their bodies are long cylindrical in shape. The body has no arms, spines and pedicellariae. But tube fit exists. For example, sea cucumber (Holothuria impatiens).
5. Crinoid: Their bodies are star-shaped. The body does not have tube feet, spines, pedicillaries etc.
Some animals of Echinodermata
Sea cucumber – Holothuria impatiens
Pink feather star – Antedon bifida
Brittle Star – Ophiothrix fragilis
Sea stars- Asterias vulgaris, Astropecten euryacanthus
Snake star- Ophiura ciliaris
Sea urchin- Echinus esculentus
Cucumaria- Cucumaria planci
Sea daisy- Xylopax medusiformes
Gorgonocephalus – Gorgonocephalus arcticus
Bristle star- Ophiocoma scolopendrina
Sea pentagon- Oreaster reticulatus
Aka sea star – Anthenea pentagonula

Water vascular system
A water circulation system is a water-filled cavity. Animals of the order Echinodermata have various shaped tubes filled with water inside the body called water circulatory system. A water circulation system is created by changing parts of the silo. It transports various types of objects through it.
Ambulacral groove
A shallow groove along the digital midline of each arm is called an ambulacral groove in the phylum Echinodermata. These grooves arise from each side of the five corners of their mouth. For example, sea star (Asterias vulgaris).
Tube feet
Tube fit is the moving part. The body of animals of the order Echinodermata is equipped with two rows of tubes called tube feet. Tube feet are narrow, hollow, muscular and elastic. Tube fits occur along the length of the ambulacral groove. For example, sea star (Asterias vulgaris).
Star fish
The star-shaped animals of the order Echinodermata are called starfish. They look like stars as they have five arms. Such as Asterias vulgaris, Astropecten euryacanthus, Ophiura ciliaris.