Chromosomal inheritance Flashcards
What is the difference of meiosis between the two sexes?
In males (spermatogenesis): - symmetrical In females: - asymmetric - meiosis 1: oocyte (large cell) + polar body (discarded) - meiosis 2: mature egg + polar body
What are the key points of meiosis (2)?
- Synaptonemal complex: join homologous chromosomes together
- Chiasma: point of chromosomal crossover
What are the key points of the chromosomal theory of inheritance (2)?
- Genes have specific loci
- Chromosomes undergo segregation on independent assortment
What is lyonisation?
The inactivation of one of the x chromosomes via a tightly packed structure (heterochromatin)
What are linked genes?
if both genes can be crossed over together (usually close together)
What did Alfred Sturtevant do?
- Used linked genes/ recombinants to create a genetic map
- recombination frequencies reflect distance between gene
If genes are close together they have a higher chance of recombinant events. True or False?
False.
What are map units?
Distance between genes (1 map unit = 1% RCB frequency)
What is nondisjunction?
error in the distribution of chromosomes in meiosis:
- homologous chrom move apart in M1
- sister chromatids fail to separate in M2
What is aneuploidy?
aberrant gamete: abnormal number of chromosomes
What is Trisomy?
triplicate chromosome
What is monosomic?
missing chromosome
What is polyploidy?
More than 2 chromosome sets
- Triploidy (3n)
- Tetraploidy (4n)
Why does polyploidy occur?
- Non disjunction of all chromosomes
- Failure of zygote to divide
What are the 4 alterations to the chromosome structure?
- Deletion
- Duplication
- Inversion (reattached in reverse orientation)
- Translocation (fragment attached to non homologous)
