extension to mandelian inheritance

Question 1

complete dominance

Answer 1

one allele completely masks the other gene 3:1 ratio

Question 2

incomplete dominance

Answer 2

one allele does not completely mask the other, 2 of the same allele is needed. the heterozygous is a blend of the two.

Question 3

co-dominance

Answer 3

both alleles are present in phenotype - neither is dominant ratio = 1:2:1

Question 4

ABO (co-dominance)

Answer 4

A and B are dominant, O is recessive. glycosyl-transferase enzyme adds a sugar group. it can create the A or B antigen. if both transferases are active both antigens are present

Question 5

overdominance

Answer 5

the heterozygote is better for survival/reproduction than either homozygote

Question 6

sickle cell anemia

Answer 6

homozygous dominant - unaffected but non resistant
heterozygous - unaffected and resistant
homozygous recessive - affected but resistant

Question 7

mosaicism

Answer 7

present in individual or tissue of at least two cell lines that differ but come from a single zygote

Question 8

somatic mosaicism

Answer 8

present in some tissues but not in the gametes

Question 9

germ-line mosaicism

Answer 9

mutation is only in germ line cells

Question 10

lethal alleles

Answer 10

homozygous genotype is lethal changing 1:2:1 to 2:1 ratoi

Question 11

penetrance

Answer 11

some have the same genotype but not express the phenotype. when penetrance is <100% it is incomplete penetrance

Question 12

variable expressivity

Answer 12

penetrance is all or nothing

expressivity is the severity of expression of phenotype

Question 13

pleiotropy

Answer 13

one variant has multiple effects

Question 14

genetic heterogeneity

Answer 14

single phenotype caused by variants at different alleles or different loci

Question 15

allelic heterogeneity

Answer 15

different variants within a give locus can be seen with a genetic condition

Question 16

locus heterogeneity

Answer 16

same phenotype from variants at many different loci

Question 17

complementation test

Answer 17

test whether mutant alleles are in the same gene (non-complement) or in different genes (complement)

Question 18

different gene

Answer 18

homozygous for mutations that show same phenotype but are in different genes, the progeny are wild-type. they complement one another

Question 19

same gene

Answer 19

homozygous for mutations that show same phenotype but are in same gene, the progeny are mutant. they fail to complement one another

Question 20

anticipation

Answer 20

trait becomes more strongly expressed or expressed earlier passed from one generation to generation
common caused by dynamic mutations, expansion of trinucleotide repeats in tandem

Question 21

complementary gene action

Answer 21

both genes are required for the correct phenotype ratio = 9:7

Question 22

epistasis

Answer 22

phenotype produced by variant of one gene that blocks or masks the phenotype of another

Question 23

recessive epistasis

Answer 23

ratio 9:3:4. only able to block phenotype if homozygous recessive

Question 24

bombay phenotype (recessive epistasis)

Answer 24

O blood type parent and A blood type parent making a AB offspring. due to presence/absence of substance H. it allows antigens to bind to it. if not there prevents binding.

Question 25

dominant epistasis

Answer 25

ratio 12:3:1. if dominant allele B is present. B phenotype is present. if b is recessive and A is dominant, A phenotype is present. if both recessive other phenotype is present

Question 26

duplicate genes

Answer 26

either dominant gene is required. 15:1

Question 27

effect of environment on phenotype

Answer 27

1. temperature
   e. g. coat colour change in the arctic fox (cold = white, warm = brown
2. chemicals
   e. g. phenylketonuria (PKU) in humans loss of enzyme to metabolise amino acid Phe. low Phe diet = good. alter environment to remove Phe

Question 28

genomic imprinting

Answer 28

allele is transcriptionally inactive depending on parent whom you received the allele from. methylation or chromatin modifications (epigenetic changes)

Question 29

sex-linked traits

Answer 29

inherited characteristics conditioned by sex of individual

e.g. baldness is autosomal dominant in males and recessive in females

Question 30

sex-limited traits

Answer 30

characteristic only appears in one sex

e.g. ovary development

Question 31

cytoplasmic inheritance

Answer 31

inheritance of parental characters through non-chromosomal DNA
mitochondrial DNA is cytoplasmically inherited since the information is not segregated at mitosis

Question 32

homoplasmy

Answer 32

every mitochondrial genome carries the causative mutation

Question 33

heteroplasmy

Answer 33

contain a mixed population of normal and mutant genomes in each cell