Genetics

Question 1

What is the difference between mitosis and meiosis?

Answer 1

Mitosis- more copies with the same # of chromosome (growth)

Meiosis- reproduction

Question 2

What are genes? Genome? How many genes in humans? What is an allele?

Answer 2

Genes- encode basic info to make proteins
Genome- full set of genes in each cell of an organism
25,000
Allele- alternate forms of the same gene

Question 3

What is the difference in the DNA responsible for?

Answer 3

Biological diversity- disease, disease susceptibility, different response to drugs

Question 4

What is a SNP?

Answer 4

Single nucleotide polymorphism…different single base pair.

Question 5

What is the difference between hereditary disorders and congenital?

Answer 5

Hereditary- transmitted through the germline

Congenital- present at birth

Question 6

What are the 3 types of classifications of human genetic disorders?

Answer 6

1. Mendelian- mutations in single genes, highly penetrant
2. Complex multigenic disorders- involves multiple genes, complex, common, genetic heterogeneity (mutations in several locations have impact on same trait/disorder))
3. Chromosomal disorders- changes in autosome or sex chromosome number or structure, highly penetrant, not common

Question 7

How are mendelian disorders transmitted?

Answer 7

Autosomal dominant (heterozygous possible, variations in penetrance and expressivity)
Autosomal recessive (homozygous, complete penetrance)
X-linked: all sex-linked are X linked

Question 8

What is the difference between expressivity and penetrance?

Answer 8

Expressivity- depending on the severity of the disorder, different phenotypes can develop
Penetrant- if you have the genetic mutation, how likely you are to express the trait.

Question 9

What types of mutation are there?

Answer 9

Permanent changes in DNA via meiosis or mitosis

Deleterious

Question 10

What is a point mutation? What are the subtypes?

Answer 10

happens at a specific base pair
silent- doesn't change phenotype
missense- gives a different AA
nonsense- stop codon
*if it is in a non-coding region, can still alter transcription (promoter, enhancer) or RNA splicing

Question 11

What is a frameshift mutation?

Answer 11

Extra AA is put in or taken out, which throws off all subsequent triplets
Tay-Sachs- hexaminodase gene mutation
CF- CFTR gene mutation

Question 12

What is a trinucleotide repeat mutation?

Answer 12

characterized by repeat of 3 base pair sequence
Fragile X-repeat of CGG in gene FMR1
HD- repeat in CAG in huntington
*greater number of repeats=earlier onset, generally

Question 13

What method is used to look at specific DNA sequences?

Answer 13

Sequencing: denaturation, annealing, extension

Also FISH for fluorescently labeling sequences

Question 14

What are the three categories of proteins affected by mutations?

Answer 14

1. Structural proteins- widespread secondary effects: hereditary spherocytosis, osteogenis imperfecta
2. Enzymes-reduced activity or amount of enzyme
3. Receptor and Transport system- CF, familial hypercholesterolemia

Question 15

What syndrome involves elastic fibers?

Answer 15

• Marfan- mutation in gene encoding protein Fibrillin 1

- leads to fewer microfibrils and weak elastic fibers. -Autosomal dominant.

Question 16

Where is cartilage found?

Answer 16

skin, ligaments, joints, tendons, cornea, bone, organ and blood vessel walls, the gut, IV disc

Question 17

What is Ehlers Danlos Syndrome?

Answer 17

• Heterogeneous mutations disrupt the structure, production, and processing of collagen
• dominant negative (incorrectly made collagen dominates the correctly made)
• Contortion artists

Question 18

What are the causes of lysosomal storage diseases? What are the types?

Answer 18

enzymes not being properly stored or made
I cell
Tay Sachs
Gaucher disease
Nieman Pick Disease

Question 19

What causes Tay Sachs?

Answer 19

• lysosomal storage disease
• Tay Sachs- gangliosides accumulate in the brain
• mutations in hexosaminidase A, include bp insertions, deletions,point mutations, and more complex patterns
• autosomal recessive

Question 20

What causes Gaucher Disease?

Answer 20

-lysosomal storage disease
-mutation in GBA=accumulation in phagocytes
type 1 (some enzyme activity)
type 2 (no enzyme=early death)
type 3 (in between 1 and 2)

Question 21

What is Nieman Pick Disease?

Answer 21

-lysosomal storage disease
accumulation of sphingomyelin (lipid)- lack of acid sphyingomyelinase- leads to FOAM cells
type A (no enzyme activity) type B (10% enzyme activity) type C (defect in lipid transport-more common)
-Autosomal recessive

Question 22

What is Pompe Disease?

Answer 22

• lysosomal storage disease
• accumulation of glycogen due to acid-alpha-glucosidasae enzyme deficiency
• Autosomal recessive

Question 23

What is Familial hypercholesterolemia?

Answer 23

• defect in gene endcoding LDL receptor so LDL cannot be transported into cells
• autosomal dominant

Question 24

What is the underlying defect in CF?

Answer 24

CFTR gene mutation so Cl- cannot be transported and Na transportation is also affected
-Autosomal recessive

Question 25

What is I cell?

Answer 25

• Autosomal Recessive
• Lysosomal Storage Disease
• Mutation in phosphotransferase, which marks proteins with mannose so they can be transferred into the lysosome

Question 26

What is dwarfism?

Answer 26

• mutation in fibroblast growth factor receptor
• Achondroplasia (homozygous is lethal) and Thanatophoric Displasia (heterozygous is lethal)
• Autosomal dominant

Question 27

What is Sickle Cell disease?

Answer 27

• mutation in hemoglobin= sickle shaped cells

- heterozygous carrier has advantage in fighting malaria

Question 28

What is heomphilia?

Answer 28

• mutation in clotting/coagulation.
• sex-linked
• Recessive

Question 29

When is a karyotype and when can it be used?

Answer 29

• total # of chromosomes to diagnose abnormalities
• especially recommended for advanced maternal age, repeated miscarriages, familial risk
• used to diagnose numerical and structural disorders

Question 30

What are the types of aneuploidy?

Answer 30

Down syndrome (trisomy 21)
Edwards syndrome (trisomy 18)
Patau syndrome (trisomy 13)

Question 31

What is mosaicism?

Answer 31

mitotic error, especially in sex chromosomes= some normal cells and some abnormal cells

Question 32

What are the types of structural abnormalities?

Answer 32

deletions, duplications, inversion, translocations, and robertsonian translocations

Question 33

Why don’t females experience any symptoms from having 2 Xs?

Answer 33

Lynoization- inactivation of one of the Xs (at least part of it). Happens early and randomly in development- irreversible except for the germline.

Question 34

What is Klinefelter syndrome?What is turner syndrome? What is trisomy X?

Answer 34

Extra X in males (90% non-dysjunction, 10% mosaicism).
Only one X in males.
Female with 3 Xs don’t see any physical changes but increased risk of learning disability

Question 35

What is genomic imprinting? What are the syndromes associated with it?

Answer 35

selective inactivation of either maternal or paternal allele.
Paternal silencing= Prader-Willi
Maternal silencing=Angelman Syndrome

Question 36

What is epigenetics?

Answer 36

Modifications leading to gene silencing.

• Methylation of cytosine in CpG rich regino upstream of imprinted genes lead to chromosome condensation.
• De-acetylation of histones so nucleosomes condense into tightly bound structures.