Flashcards in Lecture 7 Deck (23):
What are mendelian traits?
Discrete phenotypic character differences generally determined by a single gene difference
What are complex traits?
Phenotypes which vary over a continuous range and are usually mutigenic. They normally show normal distribution.
What are the three causes of continuous variation of a character?
What is the basis of the additive model of polygenic inheritance?
Two unlinked genes contribute to give a variety of possible phenotypes
What is a karyotype?
The complete set of chromosomes in a cell
What are autosomes?
Chromosomes which are not involved in sex determination
How did scientists come to a conclusion that the human karyotype contained 22 autosomes and 1 sex chromosome?
In 1952 a technician used distilled water instead of saline water for washing the cells. This hypotonic treatment allowed seperatuon before squashing
What is colchicine used for?
It arrests the chromosomes at mitotic metaphase
What is the Denver system?
A method of organising the genome into 7 groups, organised by size and relative centromere position
What is G banding?
A karyogram of human male using Giemsa staining: about 400 bands per haploid set
What is Q banding?
Uses quinacrine mustard creates bands on the chromosomes which allow them to be mapped into regions which allows the chromosomes to be accurately identified
What is FISH?
Flourescent in-situ hybridization otherwise known as chromosome painting. It enables each chromosome to be uniquely visualised
What are Idiograms?
Divided into bands and sub-bands, comes from both G and Q banding
What are pseudoautosomal regions?
Genes located within PAR1 & 2 are inherited just like any autosomal genes. They escape X inactivation and are therefore candidates for having gene dosage effects in sex chromosomes aneuploidy conditions.
What is SRY?
The sex-determining gene on the Y chromosomeshich encodes the testis determining factor
Give 3 examples of sex linked traits in humans
Duchenne Muscular Dystrophy
Red-green colour blindness
How can we track parental inheritance on the maternal side?
By looking at mitochondrial DNA as this is cytoplasmic
What are Barr bodies?
Condensed X-chromosome which is genetically silent, inactivation occurs early in embryonic development
What is aneuploidy?
Loss or gain of one chromosome
What isa polyploidy?
More than 2 complete sets of chromosomes
What is allopolyploidy?
Two or more sets of genetically distinct chromosomes
What is down syndrome?
Trisomy on chromosome 21