28. Structure and replication of DNA, Nucleolus Flashcards
Nucleolus
What is the nucleolus main job? How many nucleolus can you find in one nucleus? How are the cells of nucleolus? How do they increase? Does it have a membrane? How is the shape of nucleolus?
Fibrillar Center
What kind of filaments does fibrillar Center have? What kind of transcription does it do?
Fibrillar part
What does it consist of? What does it have that is newly synthesised?
Granular part
What is it composed of?
Nuclear matrix
What is it also known as? What kind of structure is the nuclear matrix? What is it a molecular machinery for?
Composition
What is it composed of?
The main job of the nucleolus is to synthesise rRNA and assemble ribosomes. The number of nucleolus varies in a cell but it can be from 1 up to 10 max. The number is increased by metabolically active and rapidly growing and dividing cells like in embryonic and cancerous cells. It does not have its own membrane that separates it from the nuclear matrix. The shape can be spherical, compact, reticular or annular.
Fibrillar center
It has fine filaments. It does transcription of rRNA and small nucleollar rRNA.
Fibrillar part
It consists of nucleoleonlema. It has newly synthesised rRNA.
Granular part
It is composed of rRNA and ribonucleoprotein granules.
Nuclear matrix
It is also known as the nucleoskeleton . It is a highly dynamic amorphous structure. It is a molecular machinery for RNA, DNA and protein synthesis.
Composition
It is composed of protein,RNA, nuclear lamina with its lamins, actin, Emerin, different enzymes, metabolites and ions.
DNA
What is DNA?
Chemical composition
What is it’s strands composed of? What are the strands composed of?
Structure
Does it have anti parallel strands? What does it look like? What are the sides of the ladder composed of? What kind of bonds are the rungs of the ladder? What does adenine only bond to? What does guanine only bond to? How is it arranged?
DNA is the nucleic acid that contains the genetic information which are stored in genes.
Chemical composition
The strands are nucleotides strands composed of long chain polymers. Each of those composed of phosphate, deoxyribose, nitrogenous bases, purine, adenine, cytosine, guanine and thymine.
Structure
It has two anti parallel strands. It looks kind of like a twisted ladder. The sides of the ladder a composed of nucleotides. The rungs of the ladder are bonds between the bases. Adenine only forms bonds with thymine. Guanine only forms bonds with cytosine. It’s arranged in the form of a double helix structure.
What is a DNA replication? Why is it important? Why is DNA replication described as semi conservative?
Mutations in DNA
What are causes of mutations?
DNA replication is an process occurring in an living organism to copy their own DNA. The overall DNA replication is important for both cell growth and reproduction in organisms. It is also vital for the cell repair process.
Mutation in DNA
Sometimes there can be mutations in the DNA caused by various different reasons. The causes can be: Radiation, viruses, transpoisons and mutagenic chemicals, errors that occurred during meiosis or DNA replication.
DNA replication
What does each DNA strand have? What direction are the strands run and what does it determine?
What happens in the first step? What enzyme is unzipping the DNA? What is the formation of it when it’s been unzipped by the enzyme? What do the separated strands provide for template?
What happens in the second step? What enzyme is making the new DNA strands? What does the enzyme make? What is it called? Which enzyme comes then and what does it do? In what direction can it ad bases? From what end? What strand is made continuously?
What is the opposite strand called? Why can’t it also ad new bases continuously? What does the DNA polymerase do here unlike the other strand? What is this called? What are each fragments started with? What does the DNA polymerase do then? Where is the next primer then added? What’s made again? Does it repeat again?
What happens once the new DNA has been made? Which enzyme is it? Which enzyme fills in the gaps? What’s the finishing step? What enzyme is sealing it? What does it form?
Each DNA strand has a 5 prime end and a 3 prime end. The two strands run in opposite directions which determines how each strand of DNA is replicated.
First the two strands are separated from each other. It is done by an enzyme called helicase. When the unzipping is done it will have an formation of an replication fork. The separated strands each provide a template for creating a new strand of DNA.
Then new DNA strands are made. It is made by an enzyme called primase. The primase makes small pieces of RNA on the strand which are called primer. Then the enzyme DNA polymerase binds to the primer and makes new strands of DNA. It can only add DNA bases in one direction from 5 prime end to the 3 prime end. The leading strand is made continuously with the DNA polymerase adding bases one by one in the 5 prime end to the 3 prime end direction.
The opposite strand is called the lagging strand. The lagging strand can’t ad bases continuously because it runs in the opposite direction. Unlike the leading strand here the DNA polymerase can only make strands in a series of small chunks called Okazaki fragments. Each of the fragments are started with an RNA primer. Then the DNA polymerase ads a short row of DNA bases in the 5 prime end to the 3 prime end direction. The next primer is then added further down the lagging strand. Another Okazaki fragment is then made and the process repeats it self.
Once the new DNA has been made the enzyme exonuclease removes all the RNA primers from both strands of DNA. Then another DNA polymerase fills in the gaps that are left behind with DNA. The final step is to seal the fragments in both strands. It is done by the enzyme DNA Ligase which seals up the fragments of DNA in both strands to form a continuous double strand.
Genome
What is an genome? How is the genome of Homo sapiens stored?
Genes
What are genes the basic units of? Does DNA contain codon or non-coding sequences of DNA? What is a coding sequence? What is a non-coding sequence?
Genetic code
What is genetic code?
A genome is the inherited information of an organism. The genome of Homo sapiens are stored on 23 chromosome pairs.
Genes
Genes are the basic unit of heredity in a living organism. DNA contain both coding and non-coding sequences of DNA. Coding sequences determines what the gene does. Non-coding sequences determines when the gene is active.
Genetic code
Genetic code is the information used for translation into a functional protein.
