Chapter 10- Sexual Reproduction and Genetics
Section 1- Meiosis
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Human body contains _______ chromosomes
o Each parent contributes _________chromosomes
o _____________________ chromosomes- a pair, one from each parent
 carry genes that control the same inherited trait
Male sperm and female egg are called gametes
o contain 23 chromosomes
o haploid (one set of chromosomes from a single parent)- designated as n chromosomes (1 set)
Once male sperm and female egg fuse they form a diploid cell- 2 sets of chromosomes (2n), one from each
parent
o All cells in the human body are diploid EXCEPT the gametes- sperm and egg
Meiosis produces gametes
o Meiosis is for sexual reproduction (offspring production)
o Mitosis is for cellular reproduction (growth and repairing old tissues)
Stages of Meiosis
o diploid cell with a homologous set of chromosomes go through 2 consecutive cell divisions called
meiosis I and meiosis II to become haploid gametes
o Meiosis I Interphase I
 Prophase I- ______________________ produces exchange of genetic information
 Metaphase I
 Anaphase I
 Telophase I – at this point the cells are still diploid
o Meiosis II Prophase II
 Metaphase II
 Anaphase II
 Telophase II
 Cytokinesis- 4 haploid cells form
The Importance of Meiosis
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results in genetic ________________
depending on how the chromosomes line up, four gametes with four different combinations of chromosomes
can result (We will see the possible combinations when we do punnet square crosses later)
_____________________________- results in genetic variation because segments of the chromosomes may be
switched between 2 homologous chromosomes.
Sexual vs. Asexual Reproduction
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Asexual Reproduction- new individual is genetically _____________________ to its parent
Sexual Reproduction- genes from both parents, therefore beneficial genes multiply ____________ over time,
survival of the fittest.
Comparing Mitosis and Meiosis:
In Mitosis: the parent cell (diploid- 2n) forms 2 daughter cells (each diploid- 2n)
In Meiosis: the parent cell (diploid-2n) forms four daughter cells (each haploid-1n)
Mendelian Genetics
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____________________________________________-during Meiosis, the gametes have multiple chromosomal
possibilities depending on how they line up. There is a random distribution of alleles during meiosis.
______________- an alternative form of a gene passed on from parent to offspring (you get one allele for each
gene from each parent, so a single gene is represented by a pair of alleles)
o Ex: B=allele for brown hair b= allele for blonde hair
o Capital letters mean the allele is __________________, lower case letters mean the allele is
___________________.
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______________________- both alleles are the same (BB)= B from dad and B from mom
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_______________________- both alleles are different (Bb)= B from dad and b from mom