GENOMICS Numerical Chromosomal Abnormalities Flashcards
What happens in G1 of cell cycle?
Cellular contents, excluding the chromosomes are duplicated
What happens in S phase of cell cycle?
Each of the 46 chromosomes is duplicated by the cell
What happens in G2 phase of the cell cycle?
The cell ‘double checks’ the duplicated chromosomes for error, making any needed repairs
What is a genetic locus?
A genetic locus is the location of a particular gene on a chromosome
What does an individual have at each genetic locus?
At each genetic locus, an individual has 2 alleles, one on each homologous chromosome
What happens during interphase in mitosis?
Chromosomes duplicate and the copies remain attached to each other
What happens in prophase in mitosis?
In the nucleus, chromosomes condense and become visible.
In the cytoplasm, the spindles form
What happens in prometaphase in mitosis?
The nuclear membrane breaks apart, and the spindle starts to interact with the chromosomes
What happens in metaphase in mitosis?
The copied chromosomes align in the middle of the spindle
What happens in anaphase in mitosis?
Chromosomes separate into 2 genetically identical groups and move to opposite ends of the spindle
What happens in telophase in mitosis?
Nuclear membrane form around each of the 2 sets of chromosomes, and the chromsomes begin to spread out, and the spindle begins to break down
What happens in cytokinesis in mitosis?
The cell splits into 2 daughter cells each with the same number of chromosomes as the parent. This forms a diploid.
What are the steps involved in meiosis?
- DNA replication
- Pairing of duplicated homologues and recombination
- Homologue pairs line up on the spindle
- Separation of homologues at anaphase 1
- Completion of cell division 1
- Separation of sister chromatids at anaphase 2
- Cell division 2 occurs which leaves us with haploid gametes
What happens in bivalents and recombination?
-Homologous chromosomes align
-Form a bivalent structure
-Exchange genetic material(Recombine)
What is crossing over of chromosomes?
Reciprocal breaking and rejoining of the homologous chromosomes in meiosis
What does crossing over of chromosomes result in?
Results in exchange of chromosomal segments and new allele combinations
What are the 2 phases of meiosis?
meiosis I and meiosis II
What occurs in meiosis 1?
- Chromosomes Align as 23 bivalents
- Allows for chiasma formation (i.e. recombination)
- Pulls apart homologues from one another
- Daughter cells have 23 chromosomes (each with 2 chromatids)
What occurs in meiosis 2?
- Align as independent chromosomes
- Sister chromatids pulled apart
- Daughter cells have 23 chromosomes (each of 1 chromatid)
What does meiosis introduce?
introduce natural variation via independent assortment of chromosomes and recombination
How can numerical chromosomal changed be detected?
Can detect through traditional karyotyping, FISH, QF-PCR, NGS
What is polyploid?
multiple of the haploid number (e.g. 4n=92)
What is aneuploid?
chromosome number which is not an exact multiple of haploid number - due to extra or missing chromosome(s) (e.g. 2n+1=47) (trisomy, monosomy)
What is the primary mechanism by which aneuploidy arises?
Non-disjunction
What does trisomy 13 cause?
Patau’s sydrome
What does trisomy 18 cause?
Edwards syndrome
What does trisomy 21 cause?
Downs syndrome
What aneuploidies is turners syndrome?
(45,X)
What aneuploidies is triple X syndrome?
(47,XXX)
What aneuploidies is Klinefelter’s?
(47,XXY)
What is mosaicism?
The presence of two or more genetically different cell lines derived from a
single zygote
What is an example of chromosomal mosaicism?
Two types of cells in the body
-One with normal cell with 46 chromosomes
-One with cells missing a chromosome
What is the severity like for mosaic phenotype?
Mosaic phenotype thought to be less severe
Why is mosaicism difficult to assess?
- What are the proportions of different cell types?
- Which tissue/organs are affected?
What does full monosomy arise by?
Full monosomy arises by non disjunction
