DNA structure - lesson two Flashcards
how does DNA fit
DNA can be a very long molecule and as such must be stored effectively
what DNA wrapped around
special proteins called histones
what is a nucleosome?
A nucleosome is a combination of DNA and protein
what do lots of nucleosomes joined together form
chromatin
what is chromatin
Chromatin is a long thin thread-like structure, made up of DNA and histones. Stretches of chromatin can code for genes
what is a chromosome
A chromosome is a single chain of DNA that has been coiled up into a thread-like structure. Each chromosome contains a large amount of genetic material in a compact form.
what is a gene
A gene is a small section of DNA that codes for a specific protein.
what are alleles
Alleles are slightly different from genes. Alleles refer to different versions of genes. They exist in the same positions along the chromosome but code for different proteins.
what are the two types of DNA
- exons
- introns
what were introns called
“junk DNA”
what are introns
non coding DNA
what is the function of introns
Introns play important roles in the regulation of gene expressions and evolutionary variation
what form does DNA exist in prokaryotes
DNA exists as a circular loop floating in the cytoplasm
what can prokaryote’s DNA be referred to as
bacterial chromosome as it is not considered a true chromosome due to its different structure
do prokaryotes have histones
No they do not. They have similar and smaller proteins to organise DNA.
