consequences of genomic alteration

Question 1

what are the four main categories of genetically determined diseases

Answer 1

single gene disorders
chromosomal disorders
multifactorial genetic disorders
somatic cell disorders

Question 2

mutation

Answer 2

any permanent heritable change in the sequence of genomic DNA - any alteration in DNA from its natural state

Question 3

polymorphism

Answer 3

a natural variant in the population, two or more alternative genotypes that exist in a population at a frequency greater than that which can be maintained by recurrent mutation alone (doesn’t need to be selected just natural variance)

Question 4

5 types of mutations

Answer 4

silent - change in a single base but no change in amino acid

missense - change in a single base causing a change in amino acid

nonsense - change in a single base causing a change in amino acid to stop codon

frameshift - insertion or deletion of bases

splice donor / acceptor - alteration of
Sequences for accurate splicing of introns

Question 5

germline VS somatic mutations

Answer 5

germline mutations occur in the gametes and allow for mutations to be passed on
somatic mutations occur in non-gamete-forming cells and therefore limited to the person it affects

Question 6

null allele

Answer 6

no gene made or no function from mutation

Question 7

dominant negative

Answer 7

heterozygous loss of function mutation, where one inherited mutation is enough to stop function of the protein

Question 8

autosomal inheritance

Answer 8

23 pairs of chromosomes
genes occupy specific positions on chromosomes
alleles are alternative forms of a gene

Question 9

homozygous

Answer 9

if maternal and paternal alleles are identical

Question 10

heterozygous

Answer 10

if maternal and paternal alleles differ

Question 11

autosomal dominant inheritance

Answer 11

• affected person usually has one affected parent
• affects either sex
• transmitted by either sex
• 50% chance of offspring being affected

Question 12

autosomal recessive inheritance

Answer 12

• affected person usually born to an unaffected parent
• affects either sex
• increased incidence when parents are related
• 25% chance of another child being affected when one is

Question 13

sex-linked inheritance

Answer 13

• female has two X chromosomes
• male has one X and one Y
• lyonization: random inactivation of part of one X chromosome in female somatic cells

Question 14

X-linked recessive inheritance

Answer 14

• affects mainly males
• affected males usually born to unaffected parents
• no male to male transmission
• all daughters of affected males are carriers

Question 15

X-linked dominant inheritance

Answer 15

• affects either sex, more females though
• Because of lyonization females are more mildly and variably affected than males
• child of affected females has 50% chance of being affected
• for affected males, all daughters will be affected but none of his sons

Question 16

Y-linked inheritance

Answer 16

• only affects males
• affected males always have an affected father
• all sons of an affected father are affected

Question 17

complications to basic Mendelian pedigree patterns

Answer 17

• common recessive conditions can give a pseudo-dominant pattern
• variable penetrance
• variable expression (signs and symptoms)
• new mutation

Question 18

allelic heterogeneity

Answer 18

when a disease can be caused by different mutations in the same gene locus

Question 19

locus heterogeneity

Answer 19

mutation at different loci (positions)

- can lead to the same clinical syndrome