Biology - cell division and sex determination Flashcards
mitosis function
growth, repair, replacement of damaged cells
asexual reproduction
where does mitosis occur
damaged cells
organisms that reproduce asexually
mitosis stages
interphase: chromosome number doubles
dna from nucleus split in a singular division
daughter cells produced by mitosis
2 identical daughter cells which are clones of parent cell
diploid daughter cells
identical to parent cell
`meiosis function
create genetically diverse offspring
where does meiosis occur
in human reproductive organs (ovaries and testes)
produces genetic variation
meiosis stages
fertilisation: male and female gametes fuse to form a zygote with diploid number
2 rounds of cell division to reduce to haploid number
daughter cells produced by meiosis
4 genetically diverse daughter cells
gametes
haploid
asexual reproduction
- requires one parent, no fusion of gametes
- offspring will be genetically identical to parent
- e.g. strawberry runners
- e.g. bacterial cells undergo binary fission however due to mutations when dna is copied the bacteria produced are not always genetically identical
sexual reproduction
- two parents, fusion of gametes
- offspring are genetically different to parents due to receiving only half from each
- offspring are genetically different from each other due to random fusion of gametes
- creates genetic variation - important for survival through natural selection
sex determination - X and Y
23rd pair of chromosomes are X and Y
women have XX, male have XY
sperm decides sex of zygote
how does sex determination happen
in a male, a single gene on the Y chromosome is transcribed and translated into a protein, which results in the development of testes. testes then go on to produce male sex hormones, which cause male characteristics.
female lacks gene so develops ovaries, female reproductive hormones and female characteristics
what is the probability of male/female
50/50
x x
x xx xx
y xy xy
