Sex and mitochondrial inheritance.txt
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What is the Lyon Hypothesis?
At least one X chromosome is inactivated to allow "dosage compensation"
What are the four characteristics of the Lyon Hypothesis?
- 1) X inactivation is Random2) X inactivation is Early
- 3) X inactivation is Permanent4) X inactivation is Incomplete
What is the specific inactive area on an X chromosome called?
How do you calculate Barr bodies?
Number of X chromosomes - 1
What % of genes on the X chromosome escape inactivation?
What two genes are still expressed in inactivated X chromosomes?
- XIST gene (XIC center)
- Pseudoautosomal regions
What effect does a pseudoautosomal gene have on a male and femal?
- Male = inherited part of maternal X chromosome
- Femal = inherited part of Paternal X chromosome through synapsis
- **not sex linked
What sex is more likely to express an X-linked recessive disease?
Males, because they are hemizygous (XY)
What are the 3 guidelines for determining X-linked recessive genes?
- Males affected more than females
- No Father-son transmission
- skip generations due to female carriers
What are the 3 guidelines for determining X-linked dominant genes?
- 1) males transmit to daughters only
- 2) Females more highly affected (2x's), but expression less severe than male heterozygotes
- 3) vertical transmission
- 4) no father-to-son transmission
What is a sex-influenced trait?
Autosomal trait expressed more frequently in different sex
What are three examples of a sex-influenced trait?
- 1) male baldness
- 2) Gout
- 3) Hereditary hemochromatosis
What is a sex-limited trait?
only one sex affected
How many genes are in mitochondrial DNA?
What are the three features of mitochondria?
- 1) Replicative segregation, random
- 2) Homoplasmy/Heteroplasmy
- 3) Strictly maternal inheritance (egg has more mt)
What is Heteroplasmy/Homoplasmy?
- Heteroplasmy: When one infected mtDNA and one normal mtDNA passed on
- Homoplasmy: When either two infected or two normal mtDNA are passed on
What are three characteristics of mt inheritance?
- 1) only females transmit
- 2) non-mendelian inheritance
What two areas are most affected by mt diseases and why?
- Muscular system and CNS
- **happens because Mt are present in sites of high ATP/ETC
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