Term
| chromosome theory of inheritance |
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Definition
1. mendelian genes have specific loci on chromosomes
2. chromosomes undergo segregation and independent assortment. |
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Term
| why fruit flies for Morgan's studies? |
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Definition
1. the breed at a high rate
2. a generation can be bred every two weeks
3. they only have four pairs of chromosomes |
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Term
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Definition
a gene located on either sex chromosome and follow a specific pattern of inheritance:
1. a female needs two copies of a recessive allele
2. a male only needs one copy a the recessive allele |
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Term
| why are sex linked recessive disorders more common in males? |
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Definition
| because males only need one copy of a recessive sex linked gene to express it |
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Term
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Definition
colorblindness
duchenne muscular dystrophy
hemophilia |
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Term
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Definition
in mammalian females, one of the two x chromosomes in each cell is randomly inactivated during embryonic development. if she is heterozygous for a gene on the x chromosome, she will become a mosaic for that character
ex- calico cats |
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Term
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Definition
| genes on the same chromosome that tend to be inherited together |
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Term
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Definition
| the production of offspring with combinations of traits differing from either parent |
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Term
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Definition
| offspring with nonparental phenotypes |
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Term
| a ___% frequency of recombination is observed for any two genes on different chromosomes |
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Definition
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Term
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Definition
| occurs while replicated homologous chromosomes are paired during prophase I, the physical connection between genes on the same chromosome is broken and a set of proteins orchestrates an exchange of corresponding segments of one maternal and one paternal chromatid. portions of two nonsister chromatids trade places each time a crossover occurs |
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Term
| basis for Sturtevant's genetic map |
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Definition
| the farther apart two genes are, the higher probability that a crossover will occur between them and therefore the higher the recombination frequency |
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Term
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Definition
| a genetic map of a chromosome based on recombination frequencies. consistis of map units based on a 1% recombination frequency. does not give precise locations of genes |
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Term
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Definition
| if genes are on the same chromosome, they will be physically linked but genetically unlinked. 50% and over behaves like the genes are found on different chromosomes |
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Term
| large scale chromosome alterations |
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Definition
| alterations of this scale often lead to spontaneous abortions or a variety of developmental disorders. not very viable |
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Term
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Definition
| pairs of homologous chromosomes do not separate normally during meiosis or mitosis. |
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Term
| possible results of nondisjunction in sex chromosomes |
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Definition
YO- not viable
XO- Turner syndrome, mostly infertile
XXY- Klinefelter syndrome, reduce fertility
XXX- triple X syndrome, fertile
XYY- fertile |
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Term
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Definition
| results from the fertilization of gametes in which nondisjunction occurred. results in an abnormal number of a particular chromosome |
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Term
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Definition
| has only one copy of a particular chromosome (2n-1) |
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Term
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Definition
| has three copies of a particular chromosome (2n+1) |
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Term
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Definition
a condition in which an organism has more than two complete sets of chromosomes. more common in plants than animals, polyploids are more normal in appearance than aneuploids
triploidy- 3n
tetraploidy- 4n |
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Term
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Definition
| the arise either during somatic doubling during mitosis or nonreduction in meiosis (nondisjunction in meiosis 1) |
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Term
| alterations of chromosome structure |
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Definition
1. deletion- removes a segment
2. duplication- repeats a segment
3. inversion- reverses a segment
4. translocation- moves a segment from one chromosome to another |
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Term
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Definition
| an aneuploid condition that results from three copies of chromosome 21 |
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Term
| what are some inheritance patterns that are exceptions to standard chromosome theory? |
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Definition
| genes located in the nucleus and genes located outside the nucleus |
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Term
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Definition
| variation in a phenotype dependent on whether an allele is inherited from the male or female. similar to sex-linked, but occurs mostly on autosomes. occurs during gamete formation and results in the silencing or a particular allele or certain genes. most imprinted genes are critical for embryonic development |
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Term
| what other organelles contain DNA |
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Definition
| mitochondria, chloroplasts, and other plant plastids carry small circular DNA |
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Term
| how are extranuclear genes inherited? |
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Definition
| extranuclear genes are inherited maternally because the zygote's cytoplasm comes from the egg |
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