y11 test2 Flashcards
how many chromosomes are in a human parent cell
46
what does diploid mean
there are two copies of each chromosome, one from the biological mother and one from the biological father which both code for the same protein
what happens in interphase
each chromosome duplicates
what happens in prophase
the nuclear membrane disappears
the DNA condenses
spindle fibres form from the centriole
what happens in metaphase
chromosomes line up at the equator
spindle fibres attach to the chromosomes at the centromere
what happens in anaphase
sister chromatids are pulled to opposite poles by the spindle fibresah
what happens in telophase
nuclear membrane reforms around each set of chromosomes
DNA de-condenses
what happens in cytokinesis?
NOT PART OF MITOSIS
cytoplasm and cell membrane divide to create 2 new daughter diploid cells, identical to the parent cells and each other
what is the purpose of meiosis I
halves the chromosome number
what is the purpose of meiosis II
halves the amount of genetic material
what happens in prophase I
nuclear membrane disappears
spindle fibres form
recombination occurs, creating variation
what happens in metaphase I
homologous chromosome pairs line up along the equator
spindle fibres attach to the chromosomes at the centromere
what happens in anaphase I
homologous chromosome pairs are pulled to opposite poles
what happens in telophase I
nuclear membrane reforms
what happens in cytokinesis I
cytoplasm and cell membrane divide to create 2 haploid daughter cells
what does homologous mean?
codes for the same thing (like eye colour)
what happens in prophase II
nuclear membrane disappears
spindle fibres form
what happens in metaphase II
chromosomes line up at the equator
spindle fibres attach to chromosomes at the centromere
what happens in anaphase II
chromatids are pulled to opposite poles by the spindle fibres
what happens in telophase II
nuclear membrane reforms
what happens in cytokinesis II
4 granddaughter cells are formed, all different to each other and to the parent cell
what is recombination
the exchange of DNA between sister chromatids
what does haploid mean
genetically different to each other and the parent cell
what is random fertilisation
any egg can be released and any sperm can reach the egg- creates variation
what are the animal sex cells
eggs and sperm
what are the plant sex cells
eggs and pollen
what are the features of sexual reproduction
involves meiosis to form gametes, then division by mitosis after fertilisation
needs 2 parents
gametes have a half set of genetic material and fuse at fertilisation
variation
what are the features of sexual reproduction
only involves mitosis
only needs one parent
no fusing of sex cells
offspring are genetically identical to parent (clones)
what are the advantages of sexual reproduction
variation (survival advantage)
plants can colonise new areas by seed dispersal
what are the disadvantages of sexual reprodution
time consuming
energy efficient
what are the advantages of asexual reproduction
only one parent needed
time and energy efficient
no wasted gametes
many identical offspring can be produced in favourable conditions
what are the disadvantages of asexual reproduction
if all offspring are identical, they could be at risk from disease/extinction
no variation
Describe reproduction in a malarial parasite (plasmodium)
reproduces sexually in the host mosquito
reproduces asexually in the human host
Describe reproduction in fungi
fungi are made of masses of threads called hyphae
produce spores asexually in ideal conditions
when conditions aren’t ideal, hyphae from different fungi join to create a diploid hypha which undergoes meiosis to produce spores
Describe reproduction in a strawberry plant
Sexually, gametes combine in pollination to form diploid seeds that germinate to create a new plant
Asexually, it can produce runners which create genetically identical plants (even if flowers are destroyed, frozen, eater or aren’t pollinated
Where in the body does mitosis occur?
body cells
Where in the body does meiosis occur?
ovaries and testes
What is the purpose of mitosis?
growth and repair
What is the purpose of meiosis?
To produce gametes
What happens to the DNA in mitosis and meiosis before division?
It duplicates (interphase)
How many divisions are in mitosis?
1
How many divisions are in meiosis?
2
How many chromosomes are in each cell after mitosis?
46
How many chromosomes are in each cell after meiosis?
23
