definitions and imp points Flashcards
nucleosome
it is a core of eight histone molecules with double DNA strands around fit
nucleotide
it is the unit of DNA comprising of i) sugar ii) nitrogenous base and phosphate
gene
sequence of nucleotides on a chromosome that encodes a specific protein to express a particular physical feature of the body
chromosome
it is a condensed form which is visible during the start of cell devision which consists of two sister chromatids joined at some point along the length an d the point of attachment is called centromere
components of chromatin / chromosome
histone and DNA
nitrogenous bases in RNA
adenine, guanine, cytosine, uracil
nitrogenous bases in DNA
adenine, guanine, cytosine, thymine
components of nucleotide
nitrogenous base, phosphate, pentose sugar
the element (type of bond) joining nitrogenous bases
hydrogenous bonds
between adenine and thymine the bond there are __ Hydrogen bonds
double hydrogen bond
Between Guanine and Cytosine there are __ Hydrogen bonds
triple hydrogen bond
shape of DNA
stranded helix
need for new cells
replacement repair reproduction and growth
deifne cell cycle
is series of evens that take place in a cell leading to the duplication of its DNA and the subsequent division of the cell tom produce the 2 daughter cells
Mitosis:
Produces two genetically identical daughter cells.
sed for growth and repair in somatic cells
Meiosis:
Produces four genetically unique daughter cells.
Reduces chromosome number by half, crucial for sexual reproduction.
Interphase:
Key Event: Preparation phase. DNA replication occurs.
Sub-phases:G1: Cell growth.S: DNA synthesis.G2: Preparation for mitosis.
Prophase:
Chromosomes condense.
Nuclear membrane starts disintegrating.
Spindle fibers form.
Metaphase:
Chromosomes align at the metaphase plate.
Anaphase:
Sister chromatids are pulled apart to opposite poles.
Telophase:
Chromosomes decondense.
Nuclear envelope reforms.
Cytokinesis:
Cytoplasm divides, resulting in two daughter cells.
Longest Phase:
Interphase (in both mitosis and meiosis):
Reason: It is the preparation phase where the cell grows, replicates DNA, and prepares for division. It can take up to 90% of the total cell cycle time.
Key Processes:G1: Cell growth and preparation.S: DNA replication.G2: Final preparation for division.
Shortest Phase:
Anaphase (in mitosis and meiosis):
Reason: It involves a quick separation of chromatids (in mitosis) or homologous chromosomes (in meiosis) to opposite poles.
Key Process: The spindle fibers rapidly pull the chromatids or chromosomes apart, ensuring equal distribution.
