4.1.2 Eukaryotic DNA Flashcards
Chromosomes are made of
one very long, condensed DNA molecule associated with proteins (in eukaryotic cells)
The main proteins present are
the large positively charged globular proteins called histones
The main proteins present are the large positively charged globular proteins called histones, their role is to
organise and condense the DNA tightly so that it fits into the nucleus
The other proteins are enzymes used in
copying and repairing the DNA
The tightly coiled combination of DNA and proteins is called
chromatin – this is what chromatids, and therefore chromosomes, are made of
DNA is coiled around histone proteins to make chromatin
During interphase (S phase) the DNA
replicates to create two identical strands of DNA called chromatids
During interphase (S phase) the DNA replicates to create two identical strands of DNA called chromatids, joined together by a narrow region called
the centromere
The two chromatids that make up the double structure of a chromosome are known as
sister chromatids
It is important that the sister chromatids are
identical (contain the same genes)
It is important that the sister chromatids are identical (contain the same genes) because
this is key to cell division, as one chromatid goes into one daughter cell and one goes into the other daughter cell during mitosis, ensuring the daughter cells are genetically identical
Each chromatid is made up of one
very long, condensed DNA molecule, which is made up of a series of genes
The ends of the chromatids in chromosomes are ‘sealed’ with protective structures called
telomeres
Simplified diagram of the structure of a chromosome
Diagram illustrating the structure of a chromosome before and after the S phase
