Page 82 - Science Course 2 (Book 1)

Mo3-L3a: What is Sexual Reproduction?

The male sex cell, a Different organisms have different numbers of
sperm, forms in the chromosomes.
testis.
Homologous Homologous
chromosomes chromosomes
Nucleus

Cytoplasm Centromere
Replication

During a process called fertilization, an egg cell and
a sperm cell join together to create a zygote.

Sister Chromatids

CHROMOSOMES OF SELECTED ORGANISMS
Number of
Fertilization Zygote Organism Number of Homologous
Chromosomes
Pairs
Fruit fly 8 4
Diploid Cells
Rice 24 12
Organisms that Diploid(2n)
reproduce sexually Yeast 32 16
form body cells 2 copies of each chromosome Cat 38 19
and sex cells.
Human 46 23
In body cells of Dog 78 39
most organisms,
similar chromosomes Fern 1,260 630
occur in pairs.
Three pairs of homologous
Diploid cells are cells chromosomes of maternal Haploid Cells
that have pairs of and partenal origin. Haploid(n)
chromosomes. Haploid cells are cells 1 copy of each chromosome
that have only one
Eye color chromosome
from each pair of
chromosomes

Enzyme Three non-homologous
chromosomes.

Cytochrome C

Pairs of chromosomes that have genes for the
same traits arranged in the same order are
called homologous chromosomes.

Because one chromosome is inherited from
each parent, the chromosomes are not identical.
A duplicated chromosome A duplicate chromosomes
(came from mother) (came from father)

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