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Chapter 4

CAS BI 206 Chapter Notes - Chapter 4: Spermatogenesis, Spermatogonium, Ovulation


Department
Biology
Course Code
CAS BI 206
Professor
Chip Celenza
Chapter
4

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Chapter 4: Chromosome Theory of Inheritance
Chromosome theory of inheritance chromosomes are carriers of genes
Mitosis cell division resulting in 2 identical daughter cells w full genetic information
Meiosis cell division resulting in 2 gametes haploid cells with half genetic information
During metaphase chromosome structure can be observed
Chromosomes consist of 2 identical sister chromatids attached at a centromere
Metacentric connected near middle; acrocentric connected near one end
Homologous chromosomes chromosomes that match in size/shape/banding
Autosomes chromosomes belonging to matching pair
Sex chromosomes chromosomes that determine sex of offspring
In humans F=X M=Y; all humans (should) have at least one X from mother, second
chromosome from father determines sex
Sex chromosomes/determining mechanisms vary greatly between species
Heterogametic sex having 2 different sex chromosomes
Criss cross inheritance male inherit from maternal; female inherit from paternal
Hemizygous individuals have half the number of alleles (ie male has one female has 2)
Nondisjunction failure of separation of chromosomes during meiosis
Sex-limited traits traits affecting sex-linked traits
Sex-influence traits traits showing up in both sexes with different effects
Mitosis
Interphase consists of 3 parts: G1 S G2
G1 lasts from birth of new cell to beginning of chromosome replication; period of
growth
S cell duplicates genetic material; chromosomes double sister chromatids join at
centromere
G2 cell growth after chromosome duplication; synthesis of proteins required for
replication
Centrosome microtubule organizing center; duplicate in S/G2
Prophase duplicated chromosomes begin to condense
Prometaphase
Breakdown of nuclear envelope microtubules enter nucleus
Chromosomes attach to microtubules through kinetochore (part of centromere)
Mitotic spindle formed from 3 microtubules
Kinetochore microtubules extend from centrosome to kinetochore
Polar microtubules come from opposite centrosomes and meet in middle of cell
Astral microtubules extend toward cell periphery
At end 2 microtubules attached to kinetochore chromosomes align w each side facing
one centrosome
Metaphase chromatids align along cell equator (metaphase plate)
Anaphase simultaneous severing of centromeric connection of sister chromatids
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