What is the normal male genotype?
XY.
What is the normal female genotype?
XX.
What is sickle cell disorder caused by?
Abnormal haemoglobin gene.
What is cystic fibrosis caused by?
Single gene.
How many people are affected by CF?
1/25 carrier
1/2500 affected
What chance does each child have of inheriting trait in autosomal dominant inheritance?
50%
Does autosomal dominant inheritance skip generations?
No.
What are examples of autosomal dominant inheritance?
Achondroplasia
Huntington’s Disease
What is achondroplasia?
Autosomal dominant- dwarfism.
What is Huntington’s disease?
Autosomal dominant- neurodegenerative.
What is Duchennes Muscular Dystrophy caused by?
X-linked.
Who is affected in X-linked inheritance?
Males.
Can X-linked inheritance skip generations?
Yes.
Who can transmit in X-linked inheritance?
Unaffected women and affected men.
Is male-male transmission present in X-linked inheritance?
No.
What are the 3 types of chromosome abnormality?
Numerical
Structural
Mutational
What are numerical abnormalities based on?
Trisomy
Monosomy
What is non-dysjunction?
The failure of homologous chromosomes to separate properly during cell division.
What are autosomal aneuploidy syndromes?
The presence of an abnormal number of chromosomes in a non-sex chromosome.
What are 3 examples of autosomal aneuploidy syndromes?
Down syndrome
Patau syndrome
Edwards syndrome
What is a Trisomy 21 aneuploidy syndrome?
Downs syndrome.
What characterises Down syndrome?
Facial dysmorphologies, low IQ, lower life expectancy.
What is a Trisomy 13 aneuploidy syndrome?
Patau syndrome.
What characterises Patau syndrome?
Mental retardation / facial dysmorphia.
What is a Trisomy 18 aneuploidy syndrome?
Edwards syndrome.
What characterises Edwards syndrome?
Severe developmental problems.
What are sex chromosome aneuploidy syndromes?
Syndromes of abnormal chromosome number in sex chromosomes.
Give 2 examples of sex chromosome aneuploidy syndromes.
Turner
Klinefelter
What happens in Turner syndrome?
X chromosome loss- wide nipples, short stature, infertile, neck webbing.
What happens in Klinefelter syndrome?
Extra XXY chromosome- tall stature, long limbs, male but infertile, small testes, mild learning difficulties.
What can mutational abnormalities be?
Balanced or unbalanced.
What are the 4 types of mutational abnormality?
Silent
Missense
Nonsense
Frameshift
What is a silent mutation?
Synonymous with normal function.
What is a missense mutation?
Doesn’t fit.
What is a nonsense mutation?
Stop codon- prevents development.
What is a frameshift mutation?
Deletion / insertion.
What are the differences between the general genome and the mitochondrial genome?
General has more genes, less coding though.
Nuclear deals with mendelian inheritance; mitochondrial deals with maternal inheritance.
What shape is mitochondrial DNA?
Loop.
How many copies of genes are in nuclear genome?
2
How many copies are in mitochondrial genome?
Thousands- polyploidy present.
What is homoplasmy / heteroplasmy?
The fact that mitochondrial DNA can be from same or different populations.
Why is the mitochondrial genome a mutation hotspot?
Lack efficient DNA repair system
Lack protective proteins.
What are examples of mitochondrial disease?
LHON
MELAS
What is genomic imprinting?
When genes are expressed from only one chromosome.
What happens with 2 maternal genomes?
Normal embryo
Abnormal membrane / placenta
What happens with 2 paternal genomes?
Abnormal embryo
Normal membrane / placenta
What are some human models of genetic imprinting?
Angelmans syndrome
Prader-Willi
Is Prader-Willi or Angelmans maternal?
Prader-Willi.
What does Angelmans syndrome lack?
Lacks maternal chromosome.
What does Prader-Willi syndrome lack?
Lacks paternal chromosome.
What does methylation do?
Marks the chromosome- stops transcription.
How are famine and schizophrenia linked?
Famine exposure provides increased link to schizophrenia.
What is the polygenic risk score?
Risk factor scale for polygenic risk.
