Leq how do the events of meiosis account for mendel s laws
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LEQ: How do the events of meiosis account for Mendel ’ s laws?. 9.18. Chromosome Theory of Inheritance. Genes occupy a specific location on a chromosome Chromosomes undergo segregation and independent assortment.

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Chromosome theory of inheritance
Chromosome Theory of Inheritance

Genes occupy a specific location on a chromosome

Chromosomes undergo segregation and independent assortment


* Segregation occurs when homologous chromosomes are separated during anaphase I.* Independent Assortment occurs when homologous chromosomes line up together during metaphase I.


Leq how are linked genes inherited

LEQ: How are linked genes inherited? separated during anaphase I.

9.19 and 9.20


Linked genes
Linked Genes separated during anaphase I.

  • Genes found on the same chromosome

  • Linked genes do NOT independently assort

  • Look and behave like a monohybrid Punnett square


Thomas hunt morgan
Thomas Hunt Morgan separated during anaphase I.

  • American embryologist – early 1900’s, studied fruit flies, identified the process of “crossing over” by studying linked genes

  • Why is Drosophila melanogaster a good organism to study?

    • Few chromosomes

    • Small

    • Easy to care for

    • Lots of offspring

    • Quick generation time


How do you get genetic diversity with linked genes
How do you get genetic diversity with linked genes? separated during anaphase I.

Crossing over occurs. Chromatids with new gene combinations are referred to as recombinant chromatids.


Recombination frequency
Recombination Frequency separated during anaphase I.

The percentage of recombinants from a cross. In this example Morgan observed 17% recombination frequency.


Leq how is gender determined

LEQ: How is gender determined? separated during anaphase I.

9.22


Sex determination systems
Sex Determination Systems separated during anaphase I.

  • X-Y: humans & fruit flies; XX = female; XY = male; sperm determines sex

  • X-O: insects (grasshoppers & roaches) O = absence of a sex chromosome; XX = female; X- = male; sperm determines sex by having an X or having no sex chromosome

  • Z-W: fish, butterflies, & birds; ZZ = male; ZW = female; egg determines sex

  • Number: ants & bees; females are diploid – fertilized eggs; males are haploid – unfertilized eggs


Leq how are some traits linked to our gender

LEQ: How are some traits linked to our gender? separated during anaphase I.

9.23


Sex linked genes
Sex Linked Genes separated during anaphase I.

  • Genes that are located on sex chromosomes

  • Thomas Hunt Morgan identified sex linked traits by studying eye color in fruit flies

  • He noticed that white eye color is more common in males than females


Fruit fly eye color
Fruit Fly Eye Color separated during anaphase I.


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