function of mitosis
- growth of multicellular organsims
- repair of worn out tissues , replace worn out cells
- asexual reporduction
what does homolgous chromosome mean
a pair of chromosomes with the same shape, length and order of gene loci.
one chromosome in the pair frm mother and other from father
need for reduction division in meiosis process prior to fertilisation in sexual repro
- gametes with half the numberof chromosomes as parents cells are produced
- during fertilisation, nuclei of female gamete fuses with nuclei of male gamete to form a zygote with dilpoid number of chromosomes
- this restores th diploid number of chromosomes to ensurethe number of chromosomes in cells do not double over the generations
haploid meaning
haploid cell: 1 set of chromosome
haploid number: 23 chromosomes in cell
diploid meaning
diploid cell: 2 sets of chromosomes, 1 frm each parent
diploid number: 46 chromosomes in cell
how meiosis leads to variation
- Prophase I - crossing over of non sister chromatids of HC to form chiasma -> new combinations of alleles in the chromosome of gametes
- metaphase I - independent assortment of HC -> diff combinations of chromosomes in gametes at the end of meiosis
how meiosis leads to variation
- Prophase I pf meiosis- crossing over of non sister chromatids of HC to form chiasma -> new combinations of alleles in the chromosome of gametes
- metaphase I of meiosis - independent assortment of HC -> diff combinations of chromosomes in gametes at the end of meiosisr
role of meiosis
- produces haploid gametes so that diploid gametes can be restored during fertiliasation - reduction explanation
- promoting genetic variation to ensure survival of oragsnism when there are changes to envt - explanantion
fertilisation’s role in promiting genetic variation
- fertilisation is random
-variations in gametes - variation in offspring
the need for the production of genetically identical cells
maintai genetic stability:
- 2 udaghter nuclei contain same number of chromosomes and are genetically identical as parent nucleus
- interphase in mitosis - replication of chromosomes
- metaphase in mitosis - random assortemnt of sister chromatids at equator of spindle
- anaphase in mitosis - separation of sister chromatids
mitosis def
a form of nuclear division that produces 2 denetically identical daughter nuclei containing the same nuber of chromosome as parent cell
why dna replication in mitosis b=must be precsiely controleld
- enusres all daughter cells have smame genetic info as parent -> genetically identical
- error in replication -> diff DNA strand formed -> mutation -> oassed onto daughter cell -> harmful changes to gene -> produce abnormal proteins
- gee mutation -> uncomtrolled cell division -> cancer -> fatal
interphase of mitosis
- replication of DNA
what structures in a cell replicates during interphase
chromosome, mutochondria, chloroplasts
