Cell division and growth Flashcards
why are new cells needed?
they are needed for growth and repair of damaged cells
what must new cells have?
they must have the same genes as the original
what is a chromosome?
a long thread like structure in the nucleus made of DNA, they carry the genes
humans have 23 pairs
what is DNA?
it is a chemical that carries the genetic codes and makes up chromosomes
what is a gene?
parts of your DNA hat tells the cell how to make a type of protein
what is an allele?
different version of the same gene
how many chromosomes do the body cell contain?
46 chromosomes 23 pairs ( one from each parent )
how many chromosomes do gametes contain?
23
How do cell become specialised?
sperm and egg meet fertilisation zygote forms cell division CELL BECOMES SPECIALISED
what needs to happen for an organism to grow?
cells need to multiply
describe the process of mitosis
- thin strands of DNA in the nucleus of the parent cell thicken to form chromosomes
- the chromosomes make copies of themselves
- the nuclear membrane starts to break down
- the copied chromosomes line up in the centre of the cell
- half of the chromosomes are pulled to opposite sides of the cell.
- the cell membrane starts to pinch at the centre
- new nuclear membrane form around the chromosomes
- two identical daughter cells are formed.
what is mitosis?
its when identical copies of the original cells are made
it is for the growth and repair of cells and tissues.
describe the process of meiosis
- the cell duplicates its DNA
- identical chromosomes line up in the cells centre
- chromosomes separate
4 splits into two producing two cells with different chromosomes - the chromosomes separates for a second time
you are left with four egg cells each one contains
23 pair of chromosomes
what is meiosis?
the production of cells which have half the normal number of chromosomes
- these are called gametes ( sex cells )
explain the process of fertilisation
- during sexual reproduction the sex cells ( gametes) combine to form a new individual
- gametes only have 23 chromosomes therefore when they combine you get 46 chromosomes.
- the new individual will have a mixture of the set of features from both parents (Variation)
what are stem cells?
stem cells are cells that can turn into any different type of cells,if given the right instructions.
where can they be found?
- early human embryos
- umbilical cord
- adult bone marrow
what can they be used for?
in medicine to…
- treat blood diseases (sickle cell anaemia)
- replace faulty cells in sick people ( insulin producing cells, nerve cells)
Points against stem cell research
- embryos are potential human life
- curing patients that are already exist is more important
- scientists should concentrate on finding and developing other sources of stem cells
- embryos cannot give permission
- patients may develop cancer when being treated using stem cells
what are stem cells in plants called?
meristem cells
what is a dominant allele?
when you only need one allele to show the dominant characteristic (represented by CAPITAL LETTER)
what is a recessive allele?
when you need two alleles for the characteristic to be recessive(represented by a lower case letter)
define hetrozygous
if the two alleles for a particular gene are different then it is referred to as hetrozygous
define homozygous
if the two alleles for a particular gene are the same then it is referred to as homozygous
what is the shape of DNA?
a double helix structure
