module 2 gentic diseases

Question 1

1. define chromatin
2. define chromatid
3. Chromosome:
4. Gene:
5. locus
6. Allele
7. genotype vs. phenotype:
8. dominant vs recessive
9. carrier:
10. what is p? q?
11. what is the centromere?

Answer 1

1. dna wrapped around histones
2. condensed dna wrapped around histones. One half of the x
3. the whole x (2 sister chromatids
4. unit of genetic heredity
5. position on gene
6. variant form of a gene
7. genotype is genetic info vs phenotype is how it appears in person
8. dominant needs just one to express vs recessive which needs 2 to express
9. carrier has one defective gene but isn’t affected
10. P is short arms on top of chromosome. Q is the long arms on bottom
11. center of chromosome

Question 2

1. What is aneuploidy?
2. what is trisomy? Monosomy? Are they lethal?
3. How does anueploidy happen?
4. What is the best known disease of aneuploidy?
5. What is the main risk in this disease? Why?
6. What are the characteristics of down syndrome?
7. What is trisomy 13? Trisomy 18? Are these fatal?

Answer 2

1. a somatic cell that doesn’t have a multiple of 23
2. a cell containing 3 copies. Monosomy only has 1 copy. Monosomy is not compatible with life, trisomy can live depending which chromosome
3. nondijunction: when sister chromatids fail to separate correctly in anaphase
4. Down Syndrome (trisomy 21)
5. maternal age >35 due to old eggs.
6. epicanthal folds, congenital heart disease, leukemia, low nasal bridge
7. Patau syndrome (usually fatal , but maybe 1-2 days of life). Edwards syndrome (usually fatal , but maybe 1-2 weeks of life)

Question 3

1. What is sex chromosome aneuploidy?
2. If a person has only the x, what syndrome happens, and what are the deformations that occur?
3. What syndrome occurs with extra x?
4. Do sex chromosome aneuploidies cause mental retardation?

Answer 3

1. missing/extra x or y
2. Turner syndrome: sterility from underdeveloped ovaries, shot stature, webbing of neck, underdeveloped breasts w wide nipps, edema of hands and feet, aorta problems
3. Kleinfelter Syndrome: male phenotype w/some female features (due to estrogen). Tall, no facial hair, narrow shoulders, testicular atrophy, gynecomastia, wide hips
4. no

Question 4

1. What is Cri du Chat syndrome?
2. What are its defects?
3. How else can chromosomes be damaged (aside from breakage)?
4. What is a clastogen?
5. Can chromosomal breakage be fixed?

Answer 4

1. a syndrome caused by chromosome breakage deletion of short arm of chromosome 5
2. low birth weight, severe mental retardation, microencephaly
3. duplication of gene sequence, reversal of gene order, translocation of info from other chromosomes
4. a source that causes chromosomal breakage such as radiation, chemicals, etc
5. Can often be fixed, but alters chromosome.

Question 5

1. What is a single gene disorder, and how are these classified?
2. What is expressivity?
3. If one parent has an autosomal dominant disorder, and the other parent is normal, what is the risk percentage for each offspring?
4. What is penetrance?
5. What is incomplete penetrance?
6. Can a a person with a dominant gene disorder be a carrier?
7. • 9. Name 3 autosomal dominant single-gene disorders and some buzz words for each:
8. Do autosomal dominant disorders skip generations? What do they attack within the affected person?

Answer 5

1. a disorder stemming from a single gene. Classified by dominant, recessive or x-linked recessive.
2. the degree to which a gene is expressed indicating the SEVERITY of disease.
3. 50%
4. the likelihood that a disease will occur when a particular genotype is present.
5. Individual has gene for a disease but does not express the disease (doesn’t pass to offspring)
6. No, they would actually be affected. Carriers only happen with recessive gene disorders.
7. Huntington: CNS degeneration, depletes GABA chromosome 4
8. Marfans: connective tissue
9. Neurofibromatosis: Von Reckinghousen. Cafe au lait, neurofiromas (nasty looking) chromosome 17
10. no, structural

Question 6

1. T or F, in autosomal recessive gene disorders, (most of the time) both parents of affected individuals are carriers? What would the risk percentage for affected offspring?
2. • 6. Name 4 autosomal recessive disorders and some buzz words for each:
3. What is consanguinity?
4. What do autosomal recessive disorders attack?

Answer 6

1. True. Owen. 25%
2. Cystic Fibrosis: CTFR gene, lungs, pancreas, digestion, mucous, chloride channels
3. Sickle Cell: Africa, evolution to protect from malaria, abnormal hemoglobin, rbc deformity by dehydration
4. Phenylketonuria- brain damage from inability to break down phenylalanine
5. Tay-Sach’s: Jews. lack hexosaminidase, fats attack CNS causing neurological problems and death. Chromosome 15
6. Thalassemia: defect in hemoglobin chains. Inadequate hemoglobin.
7. Mating of relatives. Dramatically increases the risk of recessive disorders.
8. enzymes

Question 7

1. Most X-linked disorders are ………….. .
2. Why are females carriers of X-linked disorders, while males are affected?
3. Can males pass x-linked disorders to their sons?
4. Can affected males pass x-linked disorders to their daughters?
5. Sons of female carriers have a …….% risk of being affected no matter what the father. If mother is affected?
6. Normal mothers + affected fathers = ………
7. Affected father + Carrier mother = ……….

Answer 7

1. recessive
2. Female has 2 X’s. the defective x gets overidden creating a carrier. However, if the boy receives the defective X, he will be affected since he only has the one x.
3. No because males pass Y’s to sons
4. Yes because the x that they pass is defective.
5. 50%, 100% of sons would be affected if mom is affected.
6. 100% normal sons and carrier daughters.
7. 50% carrier girl, 50% affected girl

Question 8

1. Name the classic X-linked recessive disease that causes excess bleeding:
2. This disease manifests in ………. and is carried by ……….
3. Hemophilia A:
4. Hemophilia B:
5. Hemophilia C:

Answer 8

1. Hemophilia
2. males, females
3. factor VIII deficiency. von Willebrand disease
4. factor IX deficiency
5. factor XI deficiency