life science grade7
chpt 4 reproduction
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a type of reproduction in which the genetic materials from two different cells combine, producing an offspring.
where do sex cells form?
the female sex cell
forms in the ovary
the male sex cell
forms in the testis
process in which an egg cell and sperm cell join together.
produces a new cell (zygote)
the new celll that forms from fertilization
following fertilization, what processes does the zygote go through?
mitosis and cell division
organisms that reproduce sexually form what two kinds of cells?
body cells (similar chromosomes occur in pairs)
`cells that have pairs of chromosomes
pairs of chomosomes that have genes for the same traits arranged in the same order.
why aren't chromosomes identical?
because one chromosome is inherited from each parent
different organisms have different numbers of chromosomes. Why is having the correct number of chromosomes important?
if a zygote has too many or too few chromosomes it will not develop properly
cells that have only one chromosome from each pair
how do diploid cells differ from haploid cells?
In a "diploid" cell, there are two copies of each chromosome In a "haploid" cell, there's only one copy of each chromosome.
Most of your body's cells are diploid. Only the gametes, the sperm (in men) and the eggs (in women) are haploid
Diploid cells reproduce by mitosis
Haploid cells are a result of the process of meiosis
What process do organisms use to produce sex cells?
one diploid cell divides and makes four haploid sex cells
meiosis occurs only during the formation of sex cells
what happens to a reproductive cell before beginning meiosis I?
- cell grows and duplicates chromosomes
what are the phases of meiosis I?
duplicated chromosomes condense
homologous chromosomes form pairs
membrane around nucleus breaks apart
homologous chromosome pairs line up in middle of cell
spindle fiber attaches to each chromosome
chromosome pairs separate and are pulled toward opposite ends of cell
(sister chromatids stay together)
nuclear membrane forms around each group of duplicated chromosomes
cytoplasm divides through cytokinesis, making two daughter cells
sister chromatids remain together
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