Genetics and Genomics

Question 1

Down Syndrome
(Name physical characteristics, chromosomal abberation (gene or chromosomal disorder? why?), pathophysiology, associated systemic disorders.
Could a Punnett square be used to predict occurrence? Why or why not?

Answer 1

Physical Characteristics:
-low nasal bridge, poor muscle tone, epicanthal folds, low set ears, protruding tongue

Chromosomal Abberation/Pathophysiology:
-Trisomy (autosomal aneuploidy) of chromosome 21, caused by nondisjuction or translocation. Chromosomal disorder (aneuploidy), not genetic/heritable

Associated Disorders
-Heart disease, Alzheimers, higher risk for Leukemia & respiratory disease (weakened immune system)

Punnett’s square could not be used–it’s not genetic/heritable

Question 2

Chromosomal aberrations; autosomal vs sex chromosome aneuploidy, polyploidy

Answer 2

-Aneuploidy: an ‘error’ in a chromosomal pair (ex: monosomy, trisomy). Can be autosomal (affecting non-sex chromosome) or sexed (affecting XX/XY chromosomes–more common)

Question 3

Turner’s syndrome
(Name physical characteristics, chromosomal abnormality (gene or chromosomal disorder? why?), pathophysiology.

Who tends to be the primary donor of the X chromosome here? How many chromosomes will those w/ Turner’s have?

Answer 3

Physical characteristics:
-short stature, webbing of neck, underdeveloped breasts/ovaries

Chromosomal abnormality/pathophys
-Monosomy of X sex chromosome (sex chromosome aneuploidy)

-XX mother is primary donor (75% of the time)–an XX is more likely to donate an X than an XY person is obvs
-missing one chromosome, so 46-1 = 45.

Question 4

Klinefelter’s syndrome
(Name physical characteristics, chromosomal abnormality (gene or chromosomal disorder? why?), pathophysiology.

Who tends to be the primary donor of the X chromosome here? How many chromosomes will those w/ Turner’s have?

Answer 4

Physical characteristics:
-small tests, gynecomastia, long limbs, sparse body hair, moderate mental impairment, high voice

Chromosomal abnormality/pathophysiology:
-Aneuploidy of X chromosome with Y–XXY, XXXY (sex chromosome aneuploidy)

Question 5

What maternal factor is associated with increased chances of having a child w/ Down Syndrome

Answer 5

Advanced maternal age (>35)

Question 6

Define, give examples of single gene disorders

Answer 6

Single gene disorders = disorders caused by a single a gene (as opposed to polygenic/multifactorial)
-can be autosomal recessive/dominant, or x-linked recessive/dominant (4 classifications)
-“mendelian”–i.e., these are the ones you could draw Punnett’s squares for.

Examples:
-nuerofibromatosis, Huntington Disease (autosomal dominant)
-cystic fibrosis, sickle cell, Tay Sach’s, PKU (autosomal recessive)
-Duchenne muscular dystrophy, colorblindness, hemophilia (x-linked recessive)

Question 7

X-linked inheritance

Answer 7

Diseases/conditions linked to the X chromosome–expressed in XY more than XX b/c of domination of second X chromosome.

Question 8

Replication of autosomal cells vs gametes (which process? meiosis vs mitosis)

Answer 8

Autosomal/somatic = mitosis
-chromosomes duplicate
-results in two cells w/ 46 chromosomes each (diploid cells)

Gametes (sex cells) = meiosis
-chromosomes ‘cross over’
-results in four cells w/ 23 chromosomes each (haploid cells)

Question 9

What is a pedigree chart

Answer 9

A ‘family tree’ that traces the inheritance of a genetic disorder

Question 10

Define multifactorial inheritance

Answer 10

When environmental factors influence the expression of a trait. Ex: height, IQ

Question 11

Fragile X (Name physical characteristics, chromosomal abberation (gene or chromosomal disorder? why?), pathophysiology, associated systemic disorders.
Could a Punnett square be used to predict occurrence? Why or why not?

Answer 11

PC: intellectual disability
CA: fragile site on the arm of an X chromosome. Sex-linked recessive. Single gene disorder.

Question 12

Define epigenetics vs genetics

Answer 12

Genetics: the study of inheritance, genes, the human genome
Epigenetics: how environmental factors affect the expression of genes

Question 13

DNA Methylation…why are we concerned?

Answer 13

-it’s really important for development–when it’s messed w/ its badddd
-it IS the process that renders genes active or silent
-tends to be influenced by environmental factors (diet, hormones, stress, drugs, exposure to
environmental chemicals)
-closely related to tumor-suppressor genes (result of DNA hypermethylation?)

Question 14

Risk factors for common genetic disease

Answer 14

IN UTERO (effects on fetus): Malnutrition (diabetes/obesity), ethanol exposure (FAS) , environmental exposure to drugs
-Vitamin B12 & folate help w/ DNA methylation and reduce risk of genetic disease (?)

Question 15

Define genetic/genomic imprinting and give examples

Answer 15

Genetic imprinting = inactivation/silencing of genes on just one copy of a chromosome.

Examples: Prader-Willi syndrome, Angelman syndrome (both result of deletion on long arm of chromosome 15) –aneuploidy?

Question 16

Prader-Willi syndrome

Answer 16

-Deletion on long arm of chromosome 15 inherited from father
-short stature, hypotonia, small hands/feet, obesity, mentally challenged

Question 17

Angelman syndrome

Answer 17

-Deletion on long arm of chromosome 15 inherited from mother
-seizure, ataxic gait, severely mental challenged