genetics

Question 1

allelic heterogeneity

Answer 1

similar phenotype caused by different mutation in the same gene
(common in diseases that result from loss of function because many mutations within the gene could cause this)
*ex. beta thalessemia

Question 2

locus heterogeneity

Answer 2

the same phenotype can be caused by mutations in different genes
(ex. mutations in genes encoding different subunites of a multisubunit protein or proteins that interact together)

Question 3

example of non-mandelian inheritance

Answer 3

mitochondrial genes- affected mother passes to all children

Question 4

how to determine x linked dominant

Answer 4

all affected males have an affected mother
if affected father: all daughters are effects and no sons are affected

• never transmitted father to son
• all daughters of affected father are affected

Question 5

how to determine autosomal dominant

Answer 5

if all affected individuals have an affected parent
and if one of the following is false:
-all affected males have affected mother
-if father is affected, all daughters are affected
-if father is affected, no sons are affected

• doesnt skip generations
• affected parents can have unaffected children

Question 6

how to determine x linked recessive

Answer 6

not all affected individuals have an affected parent
mostly males are affected and not father to son transmission

• more males affected than females
• mother passes to son
• father passes to daughter

Question 7

how to determine autosomal recessive

Answer 7

not all affected individuals have an affected parent
50:50 distribution between males and females

• skips generations
• unaffected parents can have affected children

Question 8

ABO locus

Answer 8

chromosome 9 (encodes glycosyltransferase)

Question 9

A allele expression in ABO

Answer 9

glycosyltransferase adds N-acetylgalatosamine to H antigen

Question 10

B allele expression in ABO

Answer 10

glycosyltransferase that adds D-galactose to the H antigen

Question 11

O allele expression in ABO

Answer 11

inactivate glycosyltransferase adds no sugars to the H antigen due to single bp deletion in the gene that produces a frameshift and results in an inactive enzyme

Question 12

codominant

Answer 12

products of both alleles are expressed

ex. AB blood type

Question 13

compound heterozygote

Answer 13

have 2 alleles

ex. AB blood type having both A allele and B allele

Question 14

when analyzing the children of two heterozygous parents for a autosomal recessive trait, what are the odds a child is affected? a carrier? homozygous normal? odds that an unaffected sibligh is a carrier?

Answer 14

affected: 1/4
carrier: 1/2
homozygous unaffected: 1/4
unaffected carrier: 2/3

Question 15

transition vs transversion

Answer 15

transition: purine sub for purine or pyrimidine for pyrimidine, more common than transversion
transversion: sub puine for pyrimidine

Question 16

types of point mutations

Answer 16

silent: nucleotide change codes for same amino acid
missense: change in amino acid
nonesense: change to a stop codon which terminates protein synthesis

Question 17

frame shift

Answer 17

addition or deletion of 1-2 nucleotides or more results in misreading subsequent codons and usually results in a truncated protein

Question 18

linkage

Answer 18

when two loci are located close enough that their recombination frequency is less than 50%

Question 19

recombination frequency

Answer 19

probablility of recombination between two loci, if greater than 50% then not linked and behave as if on separate chromosomes