CH. 6 Genetic and Developmental Disorders

Question 1

1. Review of Genetic Processes

Answer 1

DNA, GENES, CHROMOSOMES, CHROMOSOMAL REPLICATION

Question 2

Deoxyribonucleic Acid (DNA)

Answer 2

• a type of nucleic acid containing the sugar DEOXYRIBOSE.
• Most DNA is found in the cell nucleus, but can also be found in the MITOCHONDRIA and CYTOPLASM.
• stores GENETIC INFO, consisting of 4 nitrogenous bases: Class Purine (Adenine and Guanine) and Class Pyrimidine (Cytosine and Thymine) in DOUBLE STRANDED form.

Question 3

Genes

Answer 3

• smallest FUNCTIONAL hereditary units located on a specific site of the CHROMOSONE.
• they contain the GENETIC CODE to make a specific protein.
• they appear in PAIRS somatically and SINGLE in gamete form.
• NUCLEOTIDE TRIPLETS is a codon, needed to code for protein synthesis. Which creates AMINO ACIDS (building block of PROTEIN)
• 20 diff types of A.A. combine to create the basis of human proteins, produced by RIBONUCLEIC ACID after reading the aforementioned genetic code.

Question 4

Chromosomes

Answer 4

• composed of DOUBLE-STRANDED DNA containing threadlike sections of genes COMMONLY found in the cell nucleus.
• held together by CENTROMERE. CHROMATIDS are the 4 arms sticking out of chromosomes. The tips very tips of the arms are made up of the DNA segments called TELOMERES.

-Each human somatic body cell has 23 pairs of chromosomes or 46 in TOTAL DIPLOID. 2 are sex chrom. 44 AUTOSOMES (not sex).

-gamates (ovum and sperm) only have 23 chromosomes in each cell HAPLOID.

Question 5

2. Inheritance of Genetic Disorders

Answer 5

1. Transmission and Expression of Genetic Traits
2. Inheritance of Single Gene Disorders
3. Inheritance of Chromosomal Alterations

Question 6

1.

Answer 6

Traits transmitted by gamates. Each parent contributes one set of chromosomes, ensuring that each offspring has two genes/alleles at each LOCUS or location of chromosome.

The combination of ova and sperm determines genetic makeup of person or GENOTYPE. PHENOTYPE are observable traits - BLOOD TYPE, EYE COLOR, ETC.

POLYGENIC traits result from the interaction of SEVERAL genes & influenced by ENVIRONMENTAL FACTORS.

Question 7

1. Continued

Answer 7

• Errors in DNA duplication are genetic MUTATIONS that become permanent structural alterations in DNA.
• They can be repaired to prevent SERIOUS harm, but if this fails, the damaged genetic material is passed on.
• SOMATIC MUTATION (not heritable) can result in POLYMORPHISM (gene occurring in more than one form) has NO IMPACT on health, cannot be passed down.

Question 8

2.

Answer 8

Traits passed by single gene transmission is single gene traits. When people have IDENTICAL ALLELES on each chromosomes, they are homozygous for that gene. If they have TWO DIFFERENT ALLELES on each chromosome, they are heterozygous (only one copy) for that gene. DOMINANT forms of gene are more LIKELY to be expressed in person. Recessive genes are less influencial.

Question 9

2. continued

Answer 9

FEMALES = XX
MALES = XY

Traits passed on by sex chromosomes are SEX-LINKED. MOST LIKELY recessive and linked to X chromosome.

In males, the genes are inherited on the single copy of the X chromosome. Males are usually affected by this recessive disorder because they only have ONE X CHROMOSONE.

Question 10

2 CONTINE

Answer 10

Single gene disorders occur at a specific, single site on a strand of DNA because of:
-Deletion
-Duplication
-Inversion
-Insertion
-Translocation

In offspring that get a damaged allele, the dominant nature of the gene can lead to disease, even if offspring is heterozygous for the allele.

ex. HD, Marfan, osteogenesis imperfecta

Question 11

look at Table 6.3 for Patterns of Inheritence

Answer 11

PAGE 146
for autosomal dominant disorders, autosomal recessive disorders, sex-linked disorders, mitochondrial disorders

Question 12

2. autosumal recessive disorders

Answer 12

Offspring must be homozygous for the mutated gene to EXPRESS DISEASE.

Meaning both parents must be a carrier of one damaged allele to be passed on to the child. Can be expressed in genotype but not phenotype.

Question 13

2. Sex linked Disorders

Answer 13

Many linked to X and recessive. Again, since males have 1 X, more likely to be expressed for them. When dad hax defective X gene, all daughters will be affected, sons unaffected. When mom is a CARRIER, girls have 50% chance of being carrier, sons have 50% of being affected.

Question 14

2. Mitochondrial Diseases

Answer 14

results from MITO. inability to COMPLETLY burn nutrients and oxygen to GENERAT adequate cellular energy.
SOME DNA FOUND IN MITO. ASSOCIATED W/ OVERALL FUNCTION AND RELATED TO ENERGY PRODUCTION. SPERM doesn’t carry any mito. so CANNOT PASS DOWN DISEASES to offspring.

Question 15

Inheritance of Polygenic Disorders

Answer 15

Involves multiple alleles at diff LOCI affecting phenotype. The expression of these genes is dependent on environmental interaction.
Factors that can increase the expression of disease:
is ALCOHOL
TOBACCO
DRUGS
HORMONES
NUTRITION
ALTITUDE

Question 16

Inheritance of Chromosomal Alterations

Answer 16

A karyotype is a picture of the # and visual appearance of chromosomes which are matched by centrosome location and banding pattern. A striped appearance is from the dye-stained regions rich in A-T base pairs.

Monosomy occurs when nondisjunction results in cells w/ 1 copy of a chromosome instead of two. NOT COMPATIBLE W/LIFE.

CAN BE compatible with sex chrom., but w/ signif. physical and mental defects

ex. Turner Syndrome

Question 17

inheritance of chromosomal inheritance continued

Answer 17

Trisomy is the presence of 3 COPIES of chrom. in cell. The VIABILITY of a person DEPENDS on what chrom. was affected. If it is a larger chrom, incompatible w/ life since it has MORE GENETIC MATERIAL in jeopardy.

Alteration in Structure
Translocation - large segments of DNA break off and reattach to another, OFTEN, during Meosis. If balanced or equal exchange, nothing occurs because everything there is retained. If defective, can cause offspring to have missing or excessive genes in offspring.

Question 18

Environmental Factors

Answer 18

May contribute to disease in adulthood can be linked to events that occur during fetal development. Most diseases have been linked to a fetal environment that IMPAIRS growth of fetus. if the intrauterine growth is restricted and may be experience: hypertension, diabetes, and breast cancer.

Question 19

5. Clinical Models

Answer 19

1) Autosomal Dominant Genetic Disorder: Huntington’s Disease

2) Autosomal Recessive Disorder: Sickle Cell Disease

3) Mitochondrial Disease: Mitochondrial Encephalomyopathy lactic acidosis and stroke like episodes (MELAS)

4) Alteration in Autosome Chromosome Number: Down Syndrome

5) Alteration in Sex Chromosome Number: Turner and Klinefelter Syndrome

6) Sex-Linked Genetic Disorder: Fragile X Syndrome (FXS)

7) Developmental Maladaptation: Neural Tube Defect

Question 20

Huntington’s Disease

Answer 20

A neurologic disorder - degeneration of the basal ganglia and cortical regions of the brain

Manifests by mid-40s and include impaired movements, emotion, cognition.

NO CURE.

Question 21

HD’S
Patho, Clinical M., Diagnostic, Treatment

Answer 21

p: autosomal dominant disorder caused by defect in the Huntingtin (HTT) gene on chromosome 4. More of the gene is PRESENT THAN NEEDED!

LEADS TO destroying of nerve cells = BRAIN ATROPHY.

C.M.:
- INVOLUNTARY movements, cognitive impairment, emotional disturbance like PERSONALITY CHANGES, loss of memory, antisocial and impulsive behavior. Early stage motor issues include restlessness, fidgitlike activity, abnormal eye movements, dsykinesia, chorea - both involuntary movement.

D:based on family and personal medical history physical exam. Genetic testing, Blood samples, CT, MRI, PET to find annomalies like shrinkage of BASAL GANGLIA.

T: NO CURE. OT, PT, speech therapies, nutrition management

Question 22

2) SCD Pathos, Clinical M, Diagnostic, Treatment
Normal Hb level Male - 14-16
Nomral Hb level Female - 12-16
under 7, aneamic and need blood transfusions

Answer 22

A group of inherited RBC disorders AFFECTING hemoglobin. Hemoglobin S = diff. moving through blood, vessels because of new shape.
People with this are protected from malaria: sub-saharan, S.A., Carib, C.A., Saudi, India, Meditrttsnean countries like Turkey, Greece, Italy.

P-RBC lifespan goes from 120 to 16 days, pushing body to create more RBCs. Anemia, degreased oxygenation. Necrosis and organ failure if left untreated. CM: vasooclusion and hemolysis releasing contents into circulation. Jaundice results from release of bilirubin as a result of RBC damage. Tissue ischemia/ no oxygen. Pain in chest, extremities, abdomen. Priapism (erection).

D: Hb electrophoresis (Draw blood/wash blood)
DNA analysis.
Prenatal diagnosis from chroniac villus or amniotic fluid. CBC, liver and kidney test

T: Immunization againsts illness like pneumococcal, pneumonia, influenza, meningococcal memnigitis Pain management. HbF promoting lifespan of cells lowers HbS.

Question 23

MELAS P, CM, D, T

Answer 23

YOUNG people w/strokes.

p: maternally inherited by mitochondrial DNA mtDNA.

cm: develops when mtDNA reaches 56-95% 10 years of age for onset to begin
Over abundance of electricity in BRAIN.
Stroke-like episodes in individuals younger than 40
encephalopathy, including seizures abd dementia
lactoc acidosis

some may have these s/s- hearing, blindless, headaches, vomiting, hemiparesis, hemiplagia, cariomyopathy, diabetes, myopathy,

d:family history and cerebrospinal fluid levels of pyrucic and lactic acid (heart uses) serum creatine kinasae (produced when heart injured), skeletal muscle biopsy, blood sample. Imaging like CT and MRI to detect stuff. EEG, ecg

t;kepera, DILANTIN,ATAVIN, PHENOBARTIVAL TETRATOL VALPOIC ACIS
anticonvulsant treats seizures