13.2 Genetics and Inheritance Flashcards
What is the name of the genes on the proximal and distal ends of the sex chromosomes that are inherited in the same manner as autosomal genes? How?
- Pseudo Autosomal Regions
- Same between males and females
What is an inactivated X chromosome called during X inactivation?
Barr Body
When does X inactivation occur in a human?
Early in embryonic life
Is X chromosome inactivation random or pre-determined?
Random; about 50:50 split between cells
Is X inactivation maintained throughout cell division?
Yes
X inactivation mech
- One of two X chromosomes express Xist on X inactivation centre
- When expressed, Xist forms Xist RNA that coats entire Xi chromosome (heterochromatization)
- Maintained throughout division
What are the consequences of X inactivation
Females contain a mixture of cells that contain active paternal and maternal X chromosomes, leading to different expression of cells throughout the entire organism
Is mitochondrial inheritance maternal or paternal?
Maternal
Is mitochondrial DNA linear or circular?
Circular (endosymbiotic theory)
Is mitochondrial DNA packaged into chromatin by histones?
No
Why is mitochondrial DNA maternally inherited?
The only DNA passed on from sperm is that from the nucleus of the sperm, the mitochondria of sperm remain outside the fertilized egg., Therefore, mtDNA cannot be paternally inherited.
How can mtDNA mutations be passed from an unaffected mother to an affected child?
High prominence of mutated mitochondria in oocyte that is fertilized before birth. This is why heteroplasmy can be dangerous/
Why do some diseases affecting mitochondrial function not show mitochondrial inheritance?
Because they may be caused by mutation of genes in the nuclear genome that lead to mitochondrial dysfunction instead of within mtDNA genome.
