31721589
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Mind Map by Natalia Lehnhoff Faillace, updated more than 1 year ago
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Created by Natalia Lehnhoff Faillace
over 3 years ago
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9.10 HOW DO MEIOSIS AND SEXUAL
REPRODUCTION PRODUCE GENETIC VARIABILITY?
- The individual members of most species are genetically different from one
another. The offspring of a single pair of parents are usually genetically different
from one another and parents.
- Mutations occur randomly.
- Mutations occur randomly.
- Shuffling of homologues creates
novel combinations of chromosomes
- One mechanism is the random distribution of maternal and
paternal homologues to the daughter nuclei during meiosis I
- During metaphase I the paired of homologues line up at the
center of the cell. But which homologs face
which pole is random.
- During metaphase I the paired of homologues line up at the
center of the cell. But which homologs face
which pole is random.
- In people, meiosis randomly shuffles 23 pairs of homologues
chromosome, and theoretically produce more than 8 million
(2^23) different combinations of maternal and paternal
chromosomes in gametes.
- At metaphase I, the chromosomes can align in four
possible configurations.
- Anaphase I can produce eight possible sets of
chromosomes. (2^3 = 8).
- Anaphase I can produce eight possible sets of
chromosomes. (2^3 = 8).
- One mechanism is the random distribution of maternal and
paternal homologues to the daughter nuclei during meiosis I
- Crossing over creates chromosomes with a novel combination of genes
- Crossing over produces chromosomes with
combinations of alleles that differ from those of
either parent.
- Some of these new combinations may have never existed before because
homologues chromosomes cross over in new and different places at each
meiotic division.
- Some of these new combinations may have never existed before because
homologues chromosomes cross over in new and different places at each
meiotic division.
- 1 in 8 million gametes could have the
same combination of maternal and
paternal chromosomes.
- Crossing over ensures that none of those
chromosomes will be purely maternal or purely
paternal.
- Every sperm and every egg is genetically unique.
- Every sperm and every egg is genetically unique.
- Crossing over ensures that none of those
chromosomes will be purely maternal or purely
paternal.
- Crossing over produces chromosomes with
combinations of alleles that differ from those of
either parent.
- The fusion of gametes adds furthers genetic variability to the offspring
- At fertilization, two gametes, each containing a
unique combination of alleles, fuse to form a diploid
offspring.
- Theoretically, every human can produce about 8 million different gametes
based on the random separation of homologues.
- Fusion of just two people could produce 8 million x 8 million, or
64 trillion, genetically different children.
- Fusion of just two people could produce 8 million x 8 million, or
64 trillion, genetically different children.
- The chances that your parents could
produce another child who is genetically
identical the same as you are about
1/8,000,000 x 1/8,000,000 or 1 in 64 trillion.
- At fertilization, two gametes, each containing a
unique combination of alleles, fuse to form a diploid
offspring.
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