meiosis and human reproduction spermatogenesisoogenesis
TRANSCRIPT
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Meiosis and Human Reproduction SPERMATOGENESIS OOGENESIS
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Learning Targets“I Can . . .”
-State the number of chromosomes in a typical human being.
-Name the two sex chromosomes in a human female.
-Name the two sex chromosomes in a human male.
-Define “nondisjunction.”
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Chromosomes
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Review
1. Human cells are diploid, meaning there are 23 pairs of chromosomes for a total of 46.
2. Human sex cells are haploid. Each sex cell (gamete) has 23 chromosomes and only one copy of every gene.
Sperm (23) + Egg (23)
=A new human (46) !
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Review3. Genes are located on chromosomes. The location where they are found on that chromosome is called a locus (pl. loci)
*Chromosome theory of heredity: Genes are located on the chromosomes and each gene occupies a specific place on a chromosome. A gene may exist in several forms called alleles, and each chromosome contains one allele for each gene.
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Review
4. Genes are swapped between homologous chromosomes during prophase I of meiosis when chromosomes are paired as tetrads. This process is called crossing over
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Sex Determination
1. Autosomes (22 pairs): chromosomes that are the same in males and females
2. Sex chromosomes (23rd pair): final “pair” of chromosomes that are different in males and females
a. Females are XX
b. Males are XY
3. Genes that are found on sex chromosomes are sex-linked.
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Chromosome mutations: change in the number or structure of chromosomes
1. Inversion: a section of a chromosome is reversed in order
2. Translocation: non-homologous chromosomes swap regions
3. Deletion: part of a chromosome is removed4. Duplication: region of a chromosome is doubled5. Nondisjunction: chromosome pairs do not separate
during meiosis
*Many genetic disorders result from chromosome nondisjunction during meiosis (diagram, page 401)
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Chromosome mutations: change in the number or structure of chromosomes
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Chromosome mutations can be observed using a karyotype
1. Karyotype: the arrangement of homologous pairs of chromosomes
2. Common chromosomal defectsa. Down Syndrome (Trisomy 21)b. Edwards Syndrome (Trisomy 18)c. Patau Syndrome (Trisomy 13)d. Turner Syndrome (X)
e. ______________ Syndrome (XXY)
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Karyotype for a person with Down Syndrome
Extra chromosome at the 21st position
Characteristics facial features such as widely-spaced eyes, flat noses, and large tongues
Mild to severe mental retardation
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Down Syndrome
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Edwards Syndrome
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Edwards Syndrome
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Patau Syndrome
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Patau Syndrome
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Sex Chromosome Disorders
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Turner Syndrome
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Klinefelter Syndrome
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References• http://staff.jccc.net/PDECELL/celldivision/chromosome1.gif• http://www.dhss.mo.gov/Genetics/TalkCornerArchives/07_Prenatal
DiagnosticImage5.gif• https://images2.clinicaltools.com/images/gene/karyotypes/trisomy13
.jpg• http://images2.clinicaltools.com/images/gene/trisomyxxy.jpg• http://images2.clinicaltools.com/images/gene/karyotypes/turnersynd
romexnoy.jpg• http://www.bbc.co.uk/scotland/education/bitesize/higher/img/biology/
genetics_adaptation/mutations/07chromosome_mutation.gif
• http://www.biologycorner.com/bio1/meiosis.html
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References• http://www.ispub.com/xml/journals/ijtwm/vol4n2/edwards-fig1.
jpg• http://www.wehs.warren.k12.ky.us/WEHS/Departments/
Science%20Department/AP%20Web%20Sites/kruti/edwards.jpg
• http://www.specialchild.com/archives/poster-child075.jpg• http://www.wehs.warren.k12.ky.us/WEHS/Departments/
Science%20Department/AP%20Web%20Sites/kruti/patau.jpg• http://medicalimages.allrefer.com/large/syndactyly.jpg• http://www.somi.org/newspubs/profiles/photos/jenna_cole.jpg
• www6.district125.k12.il.us • https://www.youtube.com/watch?v=6EG6u-
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