Molecular Biology Flashcards
What is molecular biology?
A branch of biology that seeks to understand the molecular basis of biological activity in and between cells.It studies the composition,structure, and interactions of cellular molecules.
What is a chromosome?
-Bar like bodies of tightly coiled chromatin.
-Thread like structures located inside the nucleus of animal or plant cells.
-Each is made up of protein,and a single molecule of DNA
-Passed on from parents to offspring,DNA contains specific instructions that make each type of creation unique.
Describe the structure of chromosomes
-In eukaryotes there are multiple,large and linear.
-Present in the nucleus of the cell.
-Each typically has one centromere and one/two arms that project from the centromere.
List and describe the three parts of a chromosome.
1.Pellicle:
Outer envelope around the substance of chromosome. It is very thin,formed by a chromatic substances.
2.Matrix
The ground substance of chromosome which contains chromonemata,also formed by non-genic materials.
3.Chromonemata
-Two identical,spirally coiled threads embedded in the matrix of each chromosome.They are tightly coiled together appearing as a single thread.Each contains 8 microfibrils formed by a DNA.
List the types of Chromosomes
*Autosomes and sex chromosomes
Autosomes-22 pairs,carry the rest of genetic information.
Gonosomes-2 pairs(XX/XY),linked to the sex of the person
*Basis of number of centromeres
-Monocentric,Dicentric,Polycentric,Acentric,Diffused/non-located.
*Basis of location of location of centromere.
-Telocentric,Acrocentric,sub-metacentric,metacentric.
What are the functions of chromosomes?
-Number of chromosomes is constant for a particular species,therefore these are great in the determination of phylogeny and taxonomy of the species.
-Genetic code storage:Chromosomes contains genetic material required by organism to develop and grow.DNA is made up of chain of units called genes.
-Sex determination.
-Control of cell division.
-Formation of proteins and storage.
Explain the packaging of DNA double helix to condensed chromosomes.
-The double helix of DNA is negatively charged due to phosphate in the backbone.
-The cell makes proteins called histones which bind to DNA and help in DNA packaging.
-Histones are positively charged.
-The double stranded DNA loops around 8 histones twice forming a nucleosome.
-A nucleosome is a building block of chromatin packaging.
-DNA is further packaged by forming coils of nucleosomes called chromatin fibers.
-The fibers are condensed into chromosomes during mitosis.
-The packaging of chromatin into chromosomes occurs only during few stages of mitosis.
-Most of the time DNA is loosely packaged.
List the steps involved in DNA replication and synthesis.
1.DNA helices unwind from nucleosome.
2.Helicase enzyme untwists the double helix and gradually separates the DNA molecules into its two complementary nucleotide chains exposing nitrogen bases.
3.Each freed nucleotide strand serves as a template for building a new complementary nucleotide strand from free DNA precursors in the nucleoplasm.Adenine bonds to Thymine,Guanine bonds to Cytosine(Hydrogen bonds).DNA polymerase catalyses the nucleotide bonding.
4.DNA is spliced together by DNA ligase forming two DNA molecules identical to the original DNA helix.
5.As soon as replication ends,histones associate with the DNA,completing formation of the two strands,chromatin strands condense to form chromatids which are united by a centromere.
Why is DNA replication important?
For cell growth,repair,reproduction
