Non-Mendelian Genetics- Lecture 8/26/21

Question 1

Trinucleotide repeat disorders

Answer 1

Trinucleotide repeats are present throughout the genome, usually stable but sometimes this copy number is increased and transmitted

Question 2

Anticipation

Answer 2

An increase in severity or earlier onset of a phenotype in successive generations, the greater the number of repeats the earlier onset the symptoms

Question 3

Myotonic Dystrophy

Answer 3

Affects skeletal and smooth muscle as well as eye heart and endocrine system
-Severity of the disease is dependent on number of repeats, mild is 50 ~150
Classic ~100 to 1000
Congenital >1000

Question 4

Fragile X syndrome

Answer 4

Most common inherited cause if intellectual disability, caused by CGG repeat expansion in the FMR1 gene on X chromosome
Over 200 repeats, gene is methylated and turned off, increase in repeats do NOT lead to increase of severity

Question 5

Mosaicism

Answer 5

The presence of multiple cell lines in the same individual

Question 6

Somatic mosaicism

Answer 6

Mutation occurs in the somatic cells, cannot be transmitted to offspring

Question 7

Gonadal mosaicism

Answer 7

Does not present in the patient, but can be passed on to a couple offspring (de novo)

Question 8

Mosaic Down syndrome

Answer 8

May be less severely affected than full trisomy 21, because some cells have the regular 46 chromosomes

Question 9

Pallister-Killian syndrome

Answer 9

Mosaic tetrasomy 12p, full tetrasomy not compatible with life

Question 10

Achondroplasia

Answer 10

Type of dwarfism that is often a de novo mutation (gonadal mosaicism), short limbs and big head

Question 11

Imprinting

Answer 11

The different epigenetic modification of the maternal and paternal genetic contributions to the zygote, some genes are preferentially expressed from the maternal or paternal alleles

Question 12

Imprinting reset

Answer 12

Maternal and paternal genes are differentially methylated, reset during gametogenesis depending on sex

Question 13

Uniparental dismount

Answer 13

When you get two copies of a gene from one parent, does not always result in a known phenotype, may play a role in unexplained pregnancy loss and IUGR (intra uterine growth restriction)

Question 14

Prader-Willi syndrome

Answer 14

Lack of expression from genes in the critical region that are normally the paternal allele, could be caused by deletion or maternal UPD

Question 15

Angel man syndrome

Answer 15

Same chromosomal deletion as prader-Willi, but on the chromosome that came from mother