chromosomes and mitosis Flashcards
(18 cards)
what are stem cells
undifferentiated cells that haven’t lost the ability to differentiate and can divide by mitosis to differentiate into different cell types
where are embryonic stem cells and adult stem cells found
in early human embryos or bone marrow
what can embryonic stem cells differentiate to and why are they important
any kind of cell so they’re important for growth and development
why aren’t adult stem cells as versatile as embryonic ones and what are they used for in animals
as they can only produce certain cell types, in animals they are used to replace damaged cells
why do doctors use adult stem cells
to cure disease
benefits of using a persons own stem cells to cure a disease
no need to find a donor which could be time consuming
no need for tissue typing (compatible)
no rejection as transplanted cells aren’t foreign
ethical reason against stem cell research
could be a potential human life
positive arguments for stem cell research (2)
some think it’s more important to cure existing suffering patients than the rights of embryos
embryos used in research are usually unwanted ones from fertility clinics and would be destroyed if not used
steps in mitosis (5)
1) The cell has two copies of its DNA all spread out in long strings
2) Before the cell divides the DNA forms X shaped chromosomes with each arm an exact copy of the other
3) They then lineup at the centre of the cell where cell fibres pull them apart
4) The two arms of each chromosome go to the opposite poles
membranes form around each sets of the chromosomes which become the nuclei
5) Then the cytoplasm divides forming 2 daughter cells
how many pairs of chromosomes does a human cell have
23
what are gametes and how many copies of each chromosome does it have and how do you get a full set
sex cells
one copy
when male and female gamete fuse together during fertilisation
process of meiosis (4)
1) before the cell starts to divide it duplicates its genetic information forming two exact copies of armed chromosomes which arranged themselves two pairs
2) In the first division, the chromosome pairs lineup in the sense of the cell and get pulled apart each cell only has one copy of each chromosome
3) In the second division, the chromosomes lineup again at the centre and the arms get pulled apart
4) You get four daughter cells called gametes each with half the number of chromosomes of the parent cell
why are the gametes after meiosis genetically different
as the chromosomes get shuffled up during meiosis and each gamete only gets half of them at random
what is meiosis
The type of cell division which only occurs for formation of sex comments like egg and sperm for sexual reproduction
How do multicellular organisms use mitosis?
to grow, replace cells that have been worn out and repair damaged tissue
what is cancer
uncontrolled mitosis
what does meiosis produce
producing cells which have half the number of chromosomes
what is mitosis?
The type of cell division which organisms use for growth repair of damage cells and replacements of old cells
