Meiosis Flashcards
How many version of each chromosome do diploid organisms have?
2
What 2 locations does meiosis occur?
- ovary
- testes
What 2 processes occur during meiosis 1?
Crossing-over & segregation (genetic diversity is generated by recombination between homologous chromosomes)
What is the main difference between meiosis 2 and mitosis?
the cells on meiosis 2 are haploid, whereas the cells in mitosis are diploid
What must occur for homologous recombination to take place?
everything must be very close together
What proteins (complexes) facilitate pairing of homologous pairs?
synaptonemal complex proteins
What are the 2 purpose of meiotic prophase?
- aligns the chromosomes up ready for anaphase
- allows for genetic recombination between paternal & maternal DNA on the same chromosome
How close are chromosomes homologs bought together?
40nm
What is the purpose of the axial core?
Proteins that bind the chromatin via cohesion
What is the fundamental difference between mitosis & meiosis?
Mitosis - sister chromatids separate
Meiosis - homologs separated
What is the role of the synaptonemal complex?
- aligns the two chromosomes
- helps in homologous recombination
What allows for crossing over?
physical linkage between homologs
How many crossings are there per bilavent?
at least 1, no more than 4 (ensures at least 1 crossover forms)
What is the result of crossover interference?
once one crossover forms, it inhibits others close by.
What are 2 categories of chromosomes abnormalities?
- abnormalities in chromosome number.
- chromosome structural rearrangements
What is aneuploidy?
when there is is a non-typical number of chromosomes in a cell
What is the name given when there is a whole extra set of chromosome?
polyploidy
What are the 2 types of aneuploidy?
- Monosomy - 1 copy of a chromosome
- Trisomy - 3 copies of chromosome
What is aneuploidy caused by?
non-disjunction
Can polyploidy be embryonically lethal?
Yes
What is the result of aneuploidy in sex chromosomes?
Additional sex chromosomes - minor problems relatively normal lifespan
Lacking sex chromosomes - turner’s syndrome (lacking X), rest normal but infertile
What are the consequences of autosomal trisomy 22?
- congenital heart disease
- malformed ears
- underdeveloped mid face
What are the consequences of autosomal trisomy 18?
Edwards syndrome:
- severe intellectual disability
- low birth weight
- small jaw/mouth
What is an example of a disease resulting from monosomy?
Turner’s syndrome
What % of trimester abnormalities are caused by structural arrangements?
4.7%
What does pairing of homologues before segregation allow for?
crossing over
