1.2 cell division and 6.1 reproduction Flashcards
1st stage of cell division
replication of dna to form two copies of each chromosome and synthesis of new sub-cellular structures
- protein synthesis
-making organelles
-dna replication
2nd stage cell division
nucleus divides
stage 3 cell division
cytoplasm, me,brane divides (cell divides in two)
cytokinesis
cytoplasm and cell membrane divides
what happens during mitosis
1 set of chromosomes pulled to each side of the cell
results in 2 daughter cells which are genticslly identical to each other and parent
define chromosome
long structure made of dna
contains many genes
mitosis provides new cells for two processes name these processes
growth of orfanism
repair of tissue
gametes
sex cells
half the oriniginal num ber lf chromosomes
haploid
plant gametes
eggs and pollen
why do gametes contain one set of chromosomes
at fertilisatjon the haploid nuclei combine to form a diploid zygote
what happens during meiosis
2x dna replication (2 divisions)
4 4 daughter cells genetically unique haploid
asexuel reproduction
mitosis
bacteria—>asexual reproduction = binary fission
no fusion of gametes
one parent only
rapidly procue many offspring
all offspring are genetically identical
ad and dis of asexual reproduction
rapidly colonise an area if well-adapted
all offspring are clones so all vulnerable if environment becomes unfavourable(climate change/new pathogen
sexual reproduction 2 processes
meiosis—chromosomes assort randomly into gametes
fertilisation—it is random which sperm feetilises which egg
advantage of sexual reproduction
survival advantage when there is an environment change
genes
