Genes and Genetic Diseases

Question 1

What is a gene?

Answer 1

the basic unit of heredity

Question 2

Define locus

Answer 2

a specific location of a chromosome where a particular gene is located

Question 3

What is an allele?

Answer 3

different versions of the same gene

Question 4

What is a chromosome?

Answer 4

wound up nucleosomes

Question 5

What are autosomes?

Answer 5

all chromosomes other than X and Y, the first 22 of 23

Question 6

What is a sex chromosome?

Answer 6

the last pair of chromosomes that codes for sex, X and Y

Question 7

What does diploid mean?

Answer 7

2 copies of each chromosome, 46 chromosomes and 23 pairs

Question 8

What does haploid mean?

Answer 8

1 chromosome present from each pair, 23 chromosomes

Question 9

What is aneuploid?

Answer 9

an abnormal amount of chromosomes

Question 10

What is trisomy?

Answer 10

three copies of a given chromosome

Question 11

What is chromosomal nondisjunction?

Answer 11

failure of homologous chromosomes or sister chromatids to separate normally during meiosis/mitosis

Question 12

What is a silent mutation?

Answer 12

one base pair changes, but no amino acids change

Question 13

What is a missense mutation?

Answer 13

one base pair changes, and one amino acid changes

Question 14

What is a nonsense mutation?

Answer 14

mRNA stop codons produced too early, too late, or not at all resulting in premature termination or elongation

Question 15

What is a frameshift mutation?

Answer 15

DNA altered so that one or more base pairs are added or deleted leading to a complete change in “reading frame”; super dangerous

Question 16

What is consanguinity?

Answer 16

incest or imbreeding

Question 17

How does consanguinity contribute to genetic disorders developing?

Answer 17

disorders and diseases are repeated in families as those affected are mating with other also affected which increases the risk and chance of development

Question 18

Who do autosomal dominant disorders effect?

Answer 18

both males and females, male to female transmission is possible

Question 19

Who do autosomal recessive disorders effect?

Answer 19

both males and females, male to female transmission is possible

Question 20

Who do X-linked recessive disorders effect?

Answer 20

males are affected more and females are often carriers, male to female transmission is possible

Question 21

Is generational skipping often present in autosomal dominant disorders?

Answer 21

no

Question 22

Is generational skipping often present in autosomal recessive disorders?

Answer 22

often present

Question 23

Is generational skipping often present in X-linked recessive disorders?

Answer 23

yes

Question 24

What is penetrance?

Answer 24

percent of individuals with a specific genotype that also express the expected phenotype; complete = 100% of individuals express, incomplete = 90% of individuals express

Question 25

What is expressivity?

Answer 25

how the disease shows up, varies in severity and variability

Question 26

What is multifactorial inheritance?

Answer 26

genetic disorders that result from multiple genetic and environmental factors

Question 27

What are some common autosomal dominant disorders?

Answer 27

achondroplasia, huntington's disease, type 1 neurofibromatosis (von recklinghausen disease), and type 1 osteogenesis imperfecta

Question 28

What is achondraplasia?

Answer 28

it's a common form of dwarfism; 7/8 times it's due to spontaneous mutation in the parent (often father)

Question 29

What rule of autosomal domaint disorders does achondroplasia break?

Answer 29

every affected child has a parent that is affected; this isn't true due to spontaneous mutation that does not affect the parent in most cases

Question 30

What is huntington's disease?

Answer 30

an alteration in huntington protein function that alters nerve function; leads to progressive dementia and uncontrolled motor movements (chorea); has age-dependant penetrance as it shows up around 40 years of age; fatal after about 15 years

Question 31

What is type 1 neurofibromatosis (NF1)?

Answer 31

a gene mutation that causes neurofibromin (a protein that suppresses tumors) production to be altered

Question 32

What are the symptoms of NF1?

Answer 32

cafe-au-lait spots, lisch nodules on iris, axillary/groin freckling, neurofibromas, optic gliomas, bone deformities, and learning disabilities

Question 33

What is type 1 osteogenesis imperfecta?

Answer 33

"brittle bone disease"; the bones of the body are weakened resulting in frequent fracturing and breaks; fully penetrant

Question 34

What are some common autosomal recessive disorders?

Answer 34

cystic fibrosis and sickle cell disease

Question 35

What is cystic fibrosis?

Answer 35

altered Cl- transport proteins in epithelial cells cause issues such as chronic lung problems, pancreatic insufficiency, digestive problems, and sterility in males (1 in 2,500 caucasians affected)

Question 36

What is sickle cell disease?

Answer 36

RBCs take on sickle shapes which alters blood flow as they clump together causing ischemia (1 in 60 African-Americans affected)

Question 37

What are some common sex-linked disorders?

Answer 37

hemophilia A and neural tube defects

Question 38

What is hemophilia A?

Answer 38

a deficiency in factor VIII (clotting factor) causing blood to take longer to clot; sons are more likely affected and daughters more likely to be carriers

Question 39

What are some common neural tube defects?

Answer 39

spina bifida, anencephaly, and encephalocele

Question 40

What is spina bifida?

Answer 40

the vertebral column doesn't fully close in utero

Question 41

What is anencephaly?

Answer 41

major portion of brain doesn't develop

Question 42

What is encephalocele?

Answer 42

a portion of the skull doesn't develop

Question 43

What are some common disorders from chromosomal alterations?

Answer 43

trisomy 21, trisomy 18, trisomy 13, turner syndrome, klinefelter syndrome, cri-du-chat, and fragile x syndrome

Question 44

What is trisomy 21?

Answer 44

down syndrome; characterized by intellectual disability, low nasal bridge, low birth weight, short stature, poor muscle tone, increased risk for congenital heart disease/leukemia/alzerheimer's

Question 45

What is trisomy 18?

Answer 45

intellectual disability, low birth weight, heart defects, extra digits, and clenched fists w/overlapping fingers

Question 46

What is trisomy 13?

Answer 46

intellectual disability, brain and spine defects, extra digits, cleft palate, and abnormal genitals

Question 47

What is turner syndrome?

Answer 47

female with only one x chromosomes; sterility, short stature, spare body hair, underdeveloped breast, and widely spaced nipples

Question 48

What is klinefelter syndrome?

Answer 48

individuals with XXY chromosomes; intellectual disability, male appearance, sterility, gynecomastia (development of breast tissue), long limbs and high-pitched voice

Question 49

What is cri-du-chat?

Answer 49

intellectual disability, high pitched cry, low birth weight, small jaw, heart defects, wide-set eyes

Question 50

What is fragile X syndrome?

Answer 50

intellectual disability, anxiety, delayed speech, seizures, narrow face, large ears, enlarged testes