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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.
Describe the various system of sex determination.
: Mammals. Male is heterogametic and female is homogametic.
: Insects. Male has one chromosome and gemale is homogametic.
: 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.
Dr Troy Bray
Lecture test number one.