3.3 How development is controlled Flashcards
Beta-galactosidase
An enzyme that converts the disaccharide lactose into glucose and galactose. This reaction is an example of hydrolysis. Lactose is split into glucose and galactose by adding a molecule of water.
Epigenome
DNA modifications that do not change the DNA sequence can affect gene activity. Chemical compounds that are added to single genes can regulate their activity; these modifications are known as epigenetic changes. The epigenome comprises all of the chemical compounds that have been added to the entirety of one’s DNA (genome) as a way to regulate the activity (expression) of all the genes within the genome. The chemical compounds of the epigenome are not part of the DNA sequence, but are on or attached to DNA Epigenomic modifications remain as cells divide and in some cases can be inherited through the generations. Environmental influences, such as a person’s diet and exposure to pollutants, can also impact the epigenome.
Histone
Chromosomes contain proteins as well
as DNA. The most abundant of these proteins
are the histones. Histones help to package DNA,
which is wound tightly round them. Prokaryotic
cells such as bacteria do not contain histones.
Cell
The basic unit from which living organisms
are built. A cell consists of a mass of cytoplasm
surrounded by a cell surface membrane. Plants
and animals are made up from many different
types of cells, each of which is specialised for a
particular function.
Tissue
A group of cells which have a similar
structure, and together carry out a particular
function. Epithelial tissue, for example, forms
the outer surface of many animals. It also lines
the cavities of organs such as the gut and lungs.
Plants are also made up of different types of
tissues including vascular tissue. Vascular
tissues transport substances through the plant.
Organ
A structure which is made up of different
tissues and has a specific function. The lung is
an example of an organ. It is lined with epithelial tissue and its airways contain cartilage
which is an example of a connective tissue.
Lungs have a good blood supply; blood is
another tissue.
