cell cycle

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Stages of mitosis

interphase- chromosomes replicate, growth of organelles, checking of mutations

prophase - chromosomes condense and shorten. become visable as two sister chromatids

metaphase- replicated chromosomes line up in the equator of the cell

anophase- each chromosome is pulled apart and moves to opposite poles of the cell

telophase- two nuclei are formed

nuclear envelope forms around nucleus

mitosis is the growth and repair/replacement of cells. it occurs in the embryo and divides until the 8th cell stage. it happens in asexual production, one limitation of this is that it mean cells produced are genetically identical to the parent cell and therefore it decreases the amount of variation in the population.

Sexual reproduction

occurs when the nuclei of two gametes come together during fertilisation to form a zygote. gametes have half the number of chromosomes compared to a normal body cell, 23 chromosomes from each homologous pair.

Gametes are produced by meiosis

homologous pairs come together

homologous pair separate in division 1

sister chromatids separate in division 2

four gametes produced with haploid (half) chromosome number

mitosis in animal and plant cells

animal cell plant cell

doesnt have cell plates has cell plate

cytokinthesis occurs on outer edges cytokinthesis occurs in the middle

all of its cells divide by mitosis expect gametes only meristem cells divide by mitosis

has centrioles doesnt have centrioles

the formation of nuclear envelope occurs in telophase. nuclear envelope doesnt usually form

Yeast budding

DNA replication

swelling on surface emerges

bud becomes larger as DNA replicates

the nucleus moves into swelling

nuclear membrane breaks down and spindle forms

mitosis occurs and pulls half the number of chromosomes into the original and into the swelling

two seperate nuclei form and cytokinthesis occurs separating the swelling from the original bud and the swelling pinches off.

this bud might not look the same as the other bud due to an uneven distribution of cytoplasm. but they will be genetically identical.

reproductive potential of a yeast cell is based on how the scars are formed. if they are produced together (touching) there will be more room for other scars to from nut if there are spaces between the scars, new scars might not have enough room to form and therefore the potential will decrease.

diploid cells- 2 copies of each chromosome, 2 homologous chromosomes

haploid cells- one of each chromosome. maintain chromosome number for each generation.

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