Epigenetics An organism’s internal or external?environment?can?influence gene expression?patterns The levels of?regulatory proteins?or?transcription factors?can be affected in response to?environme...
Cell Differentiation Stem cells?become?specialised?through?differential gene expression This means that only certain genes in the DNA of the stem cell are?activated?and get?expressed Every nucleus ...
Stem Cells in Medicine As stem cells have the ability to?differentiate?into other?specialised cell types, they are very?valuable?in?medical research and treatments?as they have the potential to?rep...
Stem Cells A?stem cell?is a cell that can divide (by mitosis) an unlimited number of times Each new cell (produced when a stem cell divides) has the potential to remain a stem cell or to develop in...
Meiosis: Source of Genetic Variation Meiosis gives rise to cells that are?genetically different?from each other and is the type of cell division used to produce?gametes?(sex cells) During meiosis, ...
Locations of Genes on a Chromosome Every?chromosome?consists of a long DNA molecule that contains several hundred or even thousands of?different genes?coding for different proteins A length of DNA ...
Fertilisation in Mammals During sexual intercourse, semen is ejaculated high up into the?vagina?of the female,?near the cervix The sperm cells then follow a?chemical trail released by the egg cell?...
Mammalian Gametes Gametes Gametes are the?sex cells?of an organism For example, the?sperm?and?egg?(ovum) cells in humans Gametes fuse during fertilisation to form a?zygote Fertilisation is the?fusi...
Pracitical: Identifying Mitosis in Plant Cells Growth in plants occurs in specific regions called?meristems The root tip meristem can be used to study?mitosis The root tip meristem can be found?jus...
