inheritance and genetic diseases Flashcards
How is genetic variation generated?
- mutation
- diploid cells (random fertilisation)
- homologous recombination between chromosomes during meiosis
Describe homologous recombination
- occurs during long prophase of meiosis 1
- 2-3 crossover events per chromosome per meiosis
- highly similar DNA sequence binds to complementary sequence on homologous chromosome
How does genetic variation happen during gamete formation?
- independent assortment of chromosomes
- homologous recombination
What is non-disjunction?
When a pair of homologous chromosomes fail to seperate during meiosis
What are the 3 types of survivable trisomy?
- 21 (down’s syndrome)
- 13 (patau’s syndrome)
- 18 (edwards syndrome)
What are autosomal chromosomes?
not sex chromosomes
How are genetic diseases passed down through the generatons?
- autosomal dominant
- autosomal recessive
- x-linked
Define genotype?
set of genes carried by an individual
Define phenotype?
observable characteristic of an organism
Define allele?
an alternative form/different version of a gene
What percentage of miscarriages are due to chromosomal abnormalities?
around 50%
What is Turner’s syndrome?
monosomy of C chromosome
What are some other sex chromosome disorders (XXY, XXX, XYY)?
- XXY: Klinefelter
syndrome (male,
reduced fertility, lower IQ)
May go undiagnosed - XXX: undiagnosed
- XYY: undiagnosed
What is CFTR and where is the gene for it located?
- Cystic Fibrosis Transmembrane Conductance Regulator
- chromosome 7
What is an example of an autosomal ‘incomplete’ recessive disease?
sickle cell disease