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What is the difference between Isogamous and Heterogamous organisms?
Isogamous organisms have gametes of equal size, structure, & motility. While Heterogamous have differences.
Describe the gametes of Oogamous organisms.
Larger non-motile egg; smaller motile sperm.
What are the five subdivisions of Prophase 1 of meiosis?
What takes place in Leptotene?
- Sister chromatids condense & become visible.
- Often take on a horse shoe shape; ends associated with proteins on the nuclear lamina.
What takes place in Zygotene?
- Synapsis (homologous sisters join along their lengths)
- Bivalents are formed and are joined at synaptonemal complex to form Tetrads.
What happens in Pachytene?
- Crossing over occurs; forming recombinant DNA.
- Enzymes that are involved : Endonucleases (cut), DNA Ligases (glue ends), DNA polymerases (repair)
- Chiasma is the site or crossing over.
What happens in Diplotene?
- Synaptonemal complex dissolves.
- Bivalents come appart.
- In females meiosis is arrest at this stage when female embryos are 5 months and will not resume until puberty.
What happens in diakinesis?
- Nuclear membrane disappears completely.
- Nucleolus disappears.
Describe the various system of sex determination.
- XY system : Mammals. Male is heterogametic and female is homogametic.
- XO system : Insects. Male has one chromosome and gemale is homogametic.
- ZW system : birds and fish. Male is homo gametic and females are heterogametic.
What is a test cross?
Crossing an unknown genetotype with a homosygous recessive organism to conclude the genotype of the unknown parental organism.
What is a reciprocal cross?
A cross to determine if a gene is located on the X chromosome.
Males transmit thier X chromosome to _____ offspring.
Females transmit X chromosome to ______ offspring.
Male and female.
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