Wanderer Archive
DNA! The stuff that makes up us~
DNA (deoxyribonucleic acid)1
Chromosomes and their genes are made of tightly coiled DNA that carry genetic information in the cell
They carry instructions for making all the structures and materials the body needs to function
Building blocks of DNA are nucleotides; they are a phosphate group, deoxyribose sugar and 1 of 4 nitrogenous bases
4 bases are Adenine, Thymine, Cytosine and Guanine (A always bonds with T, and C always bonds with G and vise versa)
Analogy!
DNA is like a ladder, the sides are made of the phosphate and sugar, while the ‘rungs’ of the ladder are the nitrogenous bases
DNA is held together by pairs of chemicals called ‘bases’ The 4 bases are used to hold together the ‘rungs’ of the DNA ladder Order of bases is the DNA sequence
There are two types of bases: Adenine and Guanine are purine bases and Cytosine and Guanine are pyramidine bases Purines only pair with pyramidines It takes 3 hydrogen bonds for Guanine to bond with Cytosine, 2 hydrogen bonds for Adenine to bond with Thymine
1/2 of the structures goes one way, and the other half goes the other way We state the direction with ‘, ‘ = prime One strand goes from 5’ to 3’, and the other goes from 3’ to 5’ 2
Chromosomes are thread like structures that occur in the nuclei of all body cells except red blood cells They are made from chromatin -> made of 2 chromatids held by a centromere
In eukaryotic cells, DNA is packaged as chromosomes in the nucleus Associated with proteins called histones; they form chromatin
DNA strands are long uncoiled string-like substances; they wrap around histones (a type of protein) to form chromatin (?? too much new terminology that I didn’t write notes on sorry TwT)
In prokaryotic cells (the simple cells; usually unicellular), DNA is loose in cytoplasm; there is no histones or chromosomes
Chromatin is a double stranded helical structure of DNA DNA wrapped around histone - packed to form chromatids
Anything starts with ‘chrom’ is one of these chromosomes thingy…
I gave up trying to learn which one is which
Somatic cells (all body cells except sex cells) of the body contain chromosomes in matching pairs. These pairs are called homologous chromosomes. These cells are referred to as diploids (2n)
There are 23 pairs of chromosomes (46 chromosomes in totals; 23*2 is 46)
A karyotype is a photograph of the chromosomes in a cell that is used to check for abnomalities
They can check for diseases using this
e.g. if 3 copies of chromosomes 21 instead of a pair, this results in down syndrome
A chromosome consists of 100’s or 1000’s of genes Genes contain the blueprints for all our hereditary information
e.g. eye colour, hair colour, height, ear lobes etc.
A complete set of genes is called a genome and contains the information needed to build the entire (human) body One gene can code for one or more traits, somtimes, usually more than one gene code for one trait