Chapter 4 Flashcards

1
Q

Sex

A

refers to sexual genotype; male or female; XX or XY (not including rare exceptions)

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2
Q

Sex Determination

A

the mechanism by which sex is established; the sex of an individual organism refers to it’s phenotype;

sometimes an individual can have genes that are associated with one sex but a morphology corresponding to the opposite sex

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3
Q

Sex Chromosome

A

a pair of chromosomes in many organisms that differ between males and females

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4
Q

Autosome

A

nonsex chromosomes, which are the same for males and females

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5
Q

Heterogametic Sex

A

males, because males produce 2 different types of gametes with respect to the sex chromosomes

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6
Q

Homogametic Sex

A

females, because females produce gametes that are all the same with respect to the sex chromosomes

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7
Q

Pseudoautosomal Region

A

a small region that allows the X and Y chromosomes to pair and segregate into different cells, in which they have the same genes; it’s essential for the X-Y pairing in meiosis for the male;

in humans, there are pseudoautosomal regions at both tips of the X and Y chromosomes (on the telomeres)

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8
Q

Sex-Determining Region Y (SRY) Gene

A

the male-determining gene in humans; it encodes a transcription factor (a protein) that binds to the DNA and stimulates other genes that promote the differentiation of the testes

it is not the entire Y chromosome that determines the sex of an organism, it is only this gene

males with XX chromosomes have this gene, females with XY chromosomes do not

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9
Q

Sex-Linked Characteristics

A

characteristics determined by genes located on the sex chromosomes

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10
Q

X-Linked Characteristics

A

genes on the X chromosome; most sex-linked characteristics found are X-linked

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11
Q

Y-Linked Characteristics

A

genes on the Y chromosome; Y chromosome typically contains little genetic information

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12
Q

Hemizygosity

A

Possession of a single allele at a locus

males of organisms with XX-XY sex determination are hemizygous for X-linked loci because their cells only possess a single X chromosome

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13
Q

Nondisjunction

A

failure of homologous chromosomes or sister chromatids to separate in anaphase in either mitosis or meiosis

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14
Q

Dosage Compensation

A

equilizes the amount of protein produced by X-linked genes in the 2 sexes

it is necessary for species with XX-XY sex determination because females produce 2x as much gene product as males

gene product (proteins) play a crucial role in development

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15
Q

Barr Body

A

darkly staining body in the nuclei; found in cells of female placental mammals; it is an inactivated X chromosome

females are hemizygous at the cellular level for X-linked genes; cells in these females are not identical with respect to the expression of genes on the X chromosome; females are mosaics for the expression of X-linked genes

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