Errors In Meiosis + X-Inactivation Flashcards
Is an abnormal number of a particular chromosome
Aneuploidy
*aneu = abnormal
Failure of chromosomes to separate properly during meiosis
Non-disjunction
Klinefelter Syndrome commonly occurs in?
Males (because of XXY chromosome)
XXY chromosomes; described by symptoms such as breast development/wide hips/small testicular size
Klinefelter syndrome
Turner syndrome mostly occurs in? Why?
Females because it lacks another X chromosome
Characterises the absence of a chromosome (so only one X chromosome present)
Turner syndrome
What are Down Syndrome, Klinefelter and Turner Syndrome?
Aneuploidies *an abnormal number of chromosomes in their sex chromosome
Chromosome of four resulting gametes during non disjunction at anaphase 1
(N+1)(N+1)(N-1)(N-1)
*remember normal number of chromosomes = 2
Chromosome of four resulting gametes during non disjunction in anaphase 2:
(N+1)(N-1)(N)(N)
This is the possession of multiple sets of chromosomes
Polyploidy
How is polyploidy corrected?
Through self-fertilisation. That’s why most polyploidy occurs in plants
The offspring produced after self-fertilisation.
Autopolyploid / zygote
Why are the resulting gametes of polyploidy infertile?
Because there’s not enough chromosomes to line up and divide properly. Meiosis won’t work, thus genes cannot be passed on.
This removes a chromosomal segment.
Deletion
Reverses a segment within a chromosome
Inversion
Repeats a segment
Duplication
Moves a segment from one chromosome to a non-homologous (not the same) chromosome
Translocation
This is the deletion of the tip of short arm of chromosome 5
Lejeune syndrome
When the chromosomal segments of chromosome 9 are swapped with chromosome 22
Philadelphia Translocation
When the genes in a cell are active all the time. The cell cycle is going at a constant rate.
Overexpression
While it can produce standard gametes, there is also a chance that this can produce gametes with genes coding for Down Syndrome/lethal genes.
Familial Down Syndrome
Familial Down syndrome is also known as what?
Robertsonian Translocation (between chromosome 14 & 21)
has 47 chromosomes, trisomy 21
Standard Down Syndrome
What is mosaic patterning?
The random inactivation of X chromosomes
- which means that in some parts of an organisms body, the X gene will be activated (because it is easily accessible by the machinery that will use it); whereas in some parts, the X gene will be inactivated because they are tucked away where they aren’t as accessible
- it creates a mosaic pattern
- each X chromosome codes for a phenotype
