Development & genetic diseases

Question 1

genome mutation

Answer 1

loss or gain of entire chromosome

rare but lethal

Question 2

chromosomal mutation

Answer 2

alteration in one or more chromosomes, can be identified by karyotyping

Question 3

gene mutation -partial or complete

Answer 3

partial- mutation of one of the nucleotide bases. Complete- deletion of gene from chromosome

Question 4

Overall effects seen from single gene mutation

Answer 4

can alter structure/function of nonenzymatic protein.
can alter plasma membrane, affecting transport
can result in enzyme defect
can cause unusual reaction to medication

Question 5

Classes of DNA mutation

Answer 5

-Point mutation
>>silent mutation
>>missense mutation
>>nonsense mutation
-frameshift mutation
-trinucleotide repeat disorders

Question 6

Point mutation

Answer 6

change in a single nucleotide in a gene. Can be 3 different types of point mutations– silent, missense, and nonsense.

Question 7

Silent mutation

Answer 7

where mutation codes for same amino acid. This means there is not phenotypic effect/CS&S.

Question 8

Missense mutation

Answer 8

where mutation codes for different amino acid. more likely to cause phenotypic effect/CS&S.
EX: sickle cell anemia

Question 9

sickle cell anemia

Answer 9

where adenine is replaces thymine, which causes valine to be expressed in transcription. This causes beta globin chain deformation, which causes shape deformation. Shape deformation leads to loss of lumen when sickle cells buildup and cause an occlusion in BV

Question 10

Nonsense mutation

Answer 10

mutation codes for premature termination of protein synthesis. Will have phenotypic effect/ CS&S. EX. beta-thalassemia.

Question 11

Beta thalassemia

Answer 11

No synthesis of hemoglobin a. RBCs are smaller in size, decreased ability to carry oxygen–> anemia

Question 12

Frameshift mutation

Answer 12

insertion/deletion of nucleotides. This shifts reading frame for DNA, which can cause coding for different proteins. Ex. Tay-Sachs disease

Question 13

Tay-Sachs

Answer 13

frameshift mutation on chromosome 15.
Autosomal recessive inheritance.
more prevalent in European descent.
Body lacks hexosaminidase A which breaks down gangliosides —lipids in neurons

Question 14

Tay-Sachs CS&S

Answer 14

progressive neurologic degeneration:
Cherry red spot in eye!, deafness, dementia, decreased motor tone, paralysis, seizures/epilepsy
Appears at 3-6 months of age, child dies around 4-5. Palliative treatment only

Question 15

Trinucleotide repeat disorders

Answer 15

errors in DNA replication due to amplification three nucleotides. increases 10 fold each generation, CS&S may not show in first or second, and become more severe with every generation–> associated with ANTICIPATION
Ex. Huntingtons disease and Fragile X

Question 16

Fragile X

Answer 16

Sex linked (X) disorder, trinucleotide repeat disorder. CS&S= anxiety, hyperactive, ADD, 1/3rd autistic/-like. sometimes seizures. 
Long narrow face, large ears, prominent jaw& forehead, flexible fingers, macroorchidism after puberty. Normally FMR1 helps with synapse formation and shuttles mRNA and is CGG repeated 10-40 times. when mutated, CGG repeats 200+ times and S&S seen

Question 17

Down syndrome

Answer 17

Autosome disorder, extra copy of chromosome 21. most common chromosomal disorder. Chances of getting DS increases with age of mother, 1:25 births if over age of 45. CS&S- flat face, epicanthic folds, macroglossia, simian crease, cardiac malformation, ^susceptibilty to infection, ^ risk of leukemias, alzheimer type dementia developed young. Amniocentesis detects with ^ beta hCG, and low alpha fetoprotein

Question 18

Cause of Down Syndrome

Answer 18

95% due to maternal meiotic nondisjunction.
4%Robertsonian translocation, fusion of chromosome arms
1% due to mosaicism

Question 19

Patau syndrome/ trisomy 13

Answer 19

results from nondisjunction during maternal meiosis. CS&S: congenital heart defects, eye defects, cleft lip/palate, holoprosencephaly, mental retardation, deafness. most die withing 2.5 days after birth

Question 20

Cytogenic disorders of sex chromosomes

Answer 20

Turner syndrome, Klinefelters syndrome

Question 21

Turner’s syndrome

Answer 21

sex chromosome disorder in females involving 2nd X chromosome- can either be altered/missing- also called monosomy X. the cause of TS is spontaneous nondisjunction in 60% and mosaicism in 40%.
correlated with missing one SHOX gene -since one on each chromosome, which is protein that helps development of skeletal system –> short, malformed limbs

Question 22

Turner’s syndrome CS&S

Answer 22

short stature/ limbs, loss of OVARIAN FUNCTION, webbed neck, low hairline, wide set nipples, shield like chest, short fingers, moles.
lymphedema of hands and feet in infancy, 1/3rd born w/ heart defects, NORMAL intelligence

Question 23

Klinefelter’s syndrome

Answer 23

sex chromosome disorder in males w/ extra X chromosome added. Hypogonadism in males.
Caused by nondisjunction. Decreased levels of testosterone because inhibin causes a sequence of events that eventually turns it into estradiol, which gives feminine appearance. Small testis, gynecomastia, dec. facial/body hair, infertile, tall stature, learning disabilities-speech/language. ^ chance of breast cancer/lupus.

Question 24

Genetic disorders: Mendelian pattern of inheritance

Answer 24

Autosomal dominant, autosomal recessive, and sex linked

Question 25

Autosomal dominant

Answer 25

heterozygous for one mutant allele.
Males/females equally affected.
Half of offspring are affected.
Mutations are in structural proteins, receptors, and transport proteins. EX. Marfan syndrome, retinoblastoma, familial hypercholesterolemia

Question 26

Marfan syndrome

Answer 26

Autosomal dominant disorder.
Musculoskeletal disease that affects connective tissue, specifically in lungs, heart, eyes, skeleton, and large blood vessels. Caused by mutation in Fibrillin-1 gene. Affected fibrillin protein cannot bind to proteins to form microfibrils. Without microfibrils which contain transforming growth factor beta, wound repair does not happen. Difficult to screen for d/t many possible mutations. Located on chromosome 15.

Question 27

Marfan syndrome CS&S

Answer 27

tall, slender, arachnodactyly, long arm span, flexible joints, long narrow face, crowded teeth, Pectus excavatum/carinatum, vision problems, heart abnormalities.

Question 28

Familial hypercholesterolemia

Answer 28

Autosomal dominant disorder.
metabolic disorder in 1:500 Americans. Mutation in gene encoding receptor for LDLs. Inability to remove LDLs leads to deposition in various tissues, such as blood vessels–> atherosclerosis, and xanthomas –> in connective tissue of joints. Progression slowed by low fat diet

Question 29

Retinblastoma

Answer 29

Autosomal dominant disorder, eye cancer affecting one eye in children. Leukocoria- cat eye/light reflects off eye, crossed eye/redness/pain/irritation. Removal of tumor when early cures. Occurs in 250-350/year, 4% of all childhood cancers. Caused by mutation/deletion of tumor suppressor gene RB1. Found on chromosome 13. 40% of cases are germinal

Question 30

Autosomal recessive disorders

Answer 30

Homozygous for mutant allele. Males/females equally affected. Skips generation. Causes dysfunction of enzyme.

Question 31

PKU

Answer 31

Phenylketonuria. Autosomal recessive disorder. mutation in phenylanine hydroxylase (PAH) which breaks down phenylanine, a substance found in high protein foods that is toxic to your brain. CSS severe mental retardation, mousy odor, seizures. Treatment= low phenylanine (protein) diet

Question 32

Sex linked disorders

Answer 32

gene effect usually only evident in males. Transmitted from asymptomatic mother. Sisters of affected may be carriers, brothers of aff. do not carry trait.. Affected males do not transmit to sons but all daughters are asymptomatic carriers.