Inheritance Patterns Flashcards
What is a Chromosome abnormality?
Alteration to the structure of a chromosome
What does Clinical Cytogenetics show?
Structural variation in Chromosomes
Term for missing small piece of a chromsome?
Microdeletion (Too to be detected e.g. by a microscope)
What does winding/unwinding of DNA do to a gene?
Turns the genes on and off
Name the sequence of DNA to Chromosomes (3)
1) DNA wraps around histones
2) Packaged into nucleosomes
3) Condenses down into the chromosomes
3 Mendelian Principles of Genetics?
1) Segregation
2) Dominance
3) Independent Assortment (One genes inheritance tends not to affect inheritance of another)
Symbols of a Pedigree? (6)
1) Square: Male, Circle Female
2) Coloured in: Affected
3) Double Line: Consanguinity
4) Triangle: In Utero
5) Line between 2 siblings: Identical, triangular w/o if unidentical
6) Diagonal Line: Deceased
Definition of an Autosome?
Any chromosome other than sex chromosome
What is Allelic heterogeneity?
Different mutations in same gene result in same clinical condition
How many individuals will be affected by Autosomal Recessive disorder?
Only one in a single generation e.g. Two unaffected parents have an affected offspring
Proportion of being a carrier in Autosomal Recessive?
2/3 carriers (2 carry, 1 affected, 1 unaffected)
Cystic Fibrosis e.g. 1/25 caused by CFTR
Risk of a child being affected if both parents carriers?
1/4
Consanguinity definition?
Reproductive union between 2 relatives (1/8 shared in cousins)
Autozygosity definition?
Homozygosity by descent (e.g. Inheritance of same altered allele through 2 branches of same family –> Consanguinity over many generations)
Chance of Autosomal Dominant condition being passed on?
1/2
What is penetrance?
Percentage of individuals with specific genotype showing expected phenotype (Older you get more likely to show an illness)
Recurrence risk definition?
Chance transmission of mutation
Expressivity definition?
Range of phenotypes expressed by a specific genotype
What is meant by anticipation?
Genetic Disorder affects successive generations earlier/more severely
What is triplet repeat?
Repeat of sequence of DNA, which in high numbers can cause an illness/disease e.g. Myotonic Distrophy
Difference between Somatic and Gonadal Mosaicism?
Somatic: Genetic fault in only some body tissues
Gonadal: Genetic fault in Gonadal tissue
Chance of being affected by X Linked?
Males 1/2 affected
Females 1/2 both for carrier and unaffected
(XLD more common in W,
XLR more common in M)
What is Lyonization?
Only one of two X chromosomes active in each female
What is meant by Epigenetics?
Change in DNA which can be inherited (W/O changing sequence) e.g. Increased Methylation
What is Imprinting?
Epigenetic phenomenon that causes genes to be expressed in parent-of-origin manner e.g. gene inactive on Paternal allele
What is Heteroplasmy?
Multiple copies of mtDNA in each cell
Homoplasmy: Copies of mtDNA all identical in Euk cell
