5 Simple inheritance in animals and plants Flashcards
Why do organisms need new cells?
to grow
to replace cells which are worn out and to repair damaged tissue
What is a gene?
a small packet of information that controls a characteristic or part of a characteristic of your body
it is a section of DNA
What is an allele?
different forms of the same gene
What is a chromosome?
genes grouped together
How many chromosomes are in the nucleus of a human body cell?
46
23 pairs
How does the human body gain 46 chromosomes?
One of each pair is inherited from your father and one from your mother
your sex cells - gametes only have one pair of each pair of chromosomes
What is mitosis?
the cell division in normal body cells which produces two identical cells
What happens in asexual reproduction?
cells of the offspring are produced in mitosis from the cells of their parent
contain exactly the same alleles as their parent with no genetic variation
Why is mitosis important?
must replace cells which are constantly being lost
e.g. skin - must make new cells to replace those lost from the surface
300 million body cells die each minute
What is the name given to cells which are unspecialised?
stem cells
Where can we find stem cells in humans?
human embryos have only unspecialised cells which specialise over time
can also be found in adult bone marrow but not as effective
What is the name given to cells which have now got a particular job e.g. liver, skin or muscle cells?
they have differentiated
What does it mean when a cell has differentiated?
when they divide in mitosis they can only form more of the same type of cell
restricted
Are plants cells differentiated?
no
they continue to grow for their entire life and don’t differentiate permanently
How easy is it to clone plants and animals?
plants = easy because they can become unspecialised and undergo mitosis many times to form a clone animals = difficult because cells are permanently differentiated - must use embryo
What is meiosis?
cell division takes place only in reproductive organs of animals and plants
in humans this is the ovaries and the testes
meiosis results in sex cells, called gametes, with only half the number of chromosomes (ova and sperm)
How does meiosis work?
the genetic material is copied
cell divides twice to form four gametes, each with a single set of chromosomes
What happens during fertilisation?
each gamete has a single set of chromosomes
they fuse together, sharing DNA to create a single cell with a full set of chromosomes
once complete, the unique ovum (genetically varied) begins to divide by mitosis to form a new individual etc.
What are the differences between sexual and asexual reproduction?
sexual = gametes produced by meiosis in sex organs of parents, introduces variety as each gamete is different, one set of chromosomes from each parent fuses together
asexual = produced as a result of mitosis from parent cells, contain exactly the same chromosomes and genes as the parent, no genetic variation
What is a zygote?
a single new cell formed from an egg and sperm cell fusing