Lecture 4: What I need to know Flashcards
How does aneuploidy arise?
- occurs in older women
- nondisjuntion at anaphase 1-three copies (XXY (kleinfelter) or XXX)
- nondisjunction at anaphase 2-three copies (XXY or XXX) or 1 (XO)
- coding of gene disrupted then the chromosome don’t seperate
Pedigree interpretation
- demonstrates inheritance
- first thing that occurs in genetic testing
- picks up patterns of inheritance consanguinity-recessive traits come out of nowhere
- double line means mating between couples with a common ancestor
Describe the inheritance of a mutation in a single gene but with reduced penetrance
- rare human disorders
- has the same genotype but not expressing it
- ex. 6 or 7 fingers
- father or mother may not express it but in order for there child to have an extra digit one of the parents had the mutation but was not expressing it
Describe the inheritance of a mutation in a single gene but with reduced penetrance example
Huntington disease
- triple repeat mutation in the coding region of the huntington protein gene HTT on chromosome 4
- if expansion between 36-39 repeats:may or may not get HD
Describe the inheritance of a gene with an expanded repeat, anticipation
-go through family pedigree, disease gets worse Huntington disease -triple repeat mutation in the coding region of the huntington protein gene HTT on chromosome 4 -27-35 unstable repeat may expand in parent leading to HD in offspring, especially in a male during spermatogenesis -produce toxic protein that cause defect -can expand Fragile X -3 base repeating -hunting in the coding -large testis -stop expression of MMR gene -degeneration of the brain -loose control of movement
Describe the inheritance of a mutation in a single gene with variable expression
- same genotype but expressing it differently
- can have more serious phenotype than others
- ex. NF1
Describe the inheritance of a mutation in one gene with a lethal genotype
- ex. achondroplasia, autosomal dominant dwarfism
- gene is FGFR3
- mutation interrupt chondrocyte
- production results in shortening of long bones
- interrupts the development of the limbs
- heterozygous dominant
- 1 in 4 pregnancies will terminate
Describe the inheritance of a single gene with multiple mutations
example: Cystic fibrosis (CF) -over 2000 mutations -127 of them result in defective protein -deletion of phenylalanine-common -ethic origin determines likelihood of mutation that will lead to CF
Describe the inheritance of many different genes (heterogeneity)
- 120 independent genes influence deafness
- same phenotype, but different genes (x-linked or autosomal)
- different genes contributing to breast cancer
Describe the inheritance of many genes and the environment
ex. neural tube defects, schizophrenia
- multifactorial-strong genetic component but also influence by the environment
- threshold
- accumulate some of each
- different for men and women
- show phenotype or not
- ex.spino bifida
- what causes it to increase in the environment
- take folic acid in the beginning of pregnancy to reduce risk
- things you can and can’t control
- can’t control age, sex, genes from mom and dad
- can control environmental influence (like smoking for heart attack)
- only if we knew the environmental factors for cancer like breast caner
Describe the inheritance of a gene influenced by the sex of the transmitting parent-genomic imprinting
-gene only express from either paternal or maternal
- ex. chromosome 15
- paternal
- obesity syndrome
- reduce testis
- Prader Willi syndrome
- maternal
- angelmann region
-some genes only inherited from copy of mom or from dad
Describe the inheritance of a gene influenced by a mitochondrial gene
- all mom
- have own genome in mitochondria
- male mitochondria disintegrates
- own genome and sequence
- 6,000 bases
- genes associated with energy and metabolism
- 100 mutations can result in phenotypic outcome
- nucleus is 1/56 to grandmother
- son will not pass mitochondria to offspring
