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2970 Test 1
Genetics
24
Biology
Undergraduate 2
09/27/2010

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Term
homologous chromosomes
Definition
members of a chromosome pair that contain the same genes and that pair during meiosis, creating sister chromatids held together at the centromere
Term
centromere
Definition
can be metacentric (centromere at center), submetacentric (one end shorter), acrocentric (one end a lot shorter), and telocentric (centromere at end). Important for cell division
Term
S phase
Definition
DNA replicated
Term
prophase
Definition
chromosomes (2 sister chromatids) condense, nucleolus shrinks, and the spindles assemble outside the nucleus
Term
prometaphase
Definition
nuclear envelope breaks down, spindle enters nuclear area, kinetochores bind to each centromere (where spindle fibers attach)
Term
metaphase
Definition
kinetochore microtubules orient chromosomes on the metaphase plate
Term
anaphase
Definition
joined sister chromatids separate=>2 daughter chromosomes. Daughter chromosomes pulled to opposite poles by microtubules
Term
telophase
Definition
chromosomes begin to uncoil, nuclear envelope forms, spindles disappear, nucleolus reforms
Term
prophase I
Definition
composed of leptonema, zygonema, pachynema, and diplonema
Term
leptonema
Definition
extended chromosomes begin to condense. Cell now committed to meiosis
Term
zygonema
Definition
homologous pairs of chromosomes find each other and align along their lengths=>synapsis-formation along the length of a zipperlike structure (synaptonema complex) that aligns the two homologs base pair for base pair
Term
pachynema
Definition
synapsed sets of homologous chromosomes are now called a bivalent/tetrad. Step at which crossing over occurs
Term
diplonema
Definition
synaptonema complex disassembles, homologous chromosomes begin to move apart, now attached at only chiasmata
Term
diakinesis
Definition
chromosomes condense even more
Term
prometaphase I
Definition
nucleoli disappear, nuclear envelope breaks down, spindle enters nuclear area. Kinetochores attach to both sister kinetochores
Term
metaphase I
Definition
kinetochores align tetrads on the metaphase plate
Term
anaphase I
Definition
chromosomes in each tetrad separate, forming 2 dyads. Homologous chromosomes have segregated from each other, but sister chromatids remain attached
Term
telophase I
Definition
dyads complete migration to opposite poles, spindle disassembles
Term
Meiosis II
Definition
just like mitosis. Daughter chromosomes pulled to opposite poles. Separated chromatids are now considered chromosomes in their own right
Term
Turner syndrome
Definition
XO individuals. Female, providing evidence for Y chromosome mechanism of sex determination (as opposed to # of x chromosomes)
Term
Klinefelters
Definition
XXY, providing evidence for Y chromosome mechanism of sex determination
Term
Dosage compensation and Lyon hypothesis
Definition
Humans regulate the effects of the X chromosome (since males have 1 copy and females have 2) by inactivating one x chromosome in females. This process, called lyonization, produces an inactive x chromosome called a barr body. Which is is inactivated is randomly decided in every cell
Term
Mendel's first law
Definition
copies of a gene separate when creating gametes
Term
Mendel's second law
Definition
different genes separate independently of one
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