Genetics Terminology

Question 1

Gene Locus

Answer 1

specific location or position of a gene, DNA sequence, on a chromosome

Question 2

Codominance

Answer 2

Both Alleles contribute to phenotype of heterozygote

Ex: Blood Types, Alpha 1 antitrypsin deficiency

Question 3

Variable Expressivity

Answer 3

Same genotype but phenotype varies between individuals

Ex: 2 patients with Neurofibromatosis and one has a more SEVERE disease

Question 4

Incomplete Penetrance

Answer 4

Same Genotype in two individuals but one shows the mutant phenotype where the other does not
EX: BRCA1 mutations do not always lead to breast/ovarian cancer

Question 5

Pleiotropy

Answer 5

One gene contributes to multiple phenotypes

Ex: PKU (untreated) causes light skin, intellectual disability, musty body odor

Question 6

Anticipation

Answer 6

Increased severity or earlier onset of disease in succeeding generations
Ex: Huntington’s Disease–>more CAG repeats in offspring

Question 7

Loss of Heterozygosity

Answer 7

Patient Inherits or develops a mutation in a tumor supressor gene, the complementary allele must be deleted/mutated for cancer to happen! NOT TRUE OF ONCOGENES
Ex: Retinoblastoma gene and two-hit hypothesis

Question 8

Dominant Negative Mutation

Answer 8

Heterozygote produces a functional and non functional protein that will prevent the functional protein from doing its job EXERTING A DOMINANT EFFECT!
Ex: Nonfunctioning transcription factor binds DNA and prevents the good copy from doing its job!

Question 9

Linkage disequilibrium

Answer 9

Tendency for certain alleles at 2 linked loci to occur together more or less often than expected due to chance alone. MEASURED IN POPULATIONS NOT FAMILIES AND VARIES BETWEEN POPULATIONS

Question 10

Mosaicism

Answer 10

Presence of genetically distinct cell lines in the same individual
Ex: Katia’s eyes!

Question 11

Somatic Mosaicism:

Answer 11

mutation arises form mitotic error after fertilization and propagates into tissues/organs

Question 12

Gonadal mosaicism

Answer 12

Mutation only in egg or sperm cells

Question 13

McCune Albright syndrome

Answer 13

Mutation in g protein signaling
Unilateral cafe au last spots, polyostotic fibrous dysplasia, precocious puberty, multiple endocrine abnormalities
LETHAL IF mutation occurs BEFORE fertilization
Survivable IF have mosaicism!

Question 14

Locus Heterogeneity

Answer 14

Mutations at different loci produce a similar phenotype

Ex: Albinism

Question 15

Allelic Heterogeneity

Answer 15

Different mutations in the SAME locus produce the same phenotype
Ex: Beta thalassemia

Question 16

Heteroplasty

Answer 16

Presence of both normal and mutated mitochondrial DNA results in variable expression in mitochondrially inherited disease

Question 17

Uniparental Disomy

Answer 17

Kido gets 2 copies of a chromosome from 1 parent and no copies from the other parent. Two Types Heterodisomy and Isodisomy
THESE KIDS ARE EUPLOID
Consider if kid is suffering from autosomal recessive and only one parent is a carrier!

Question 18

Heterodisomy

Answer 18

Heterozygous: meiosis I error

Question 19

Isodisomy

Answer 19

Homozygous: meiosis II error OR post zygotic chromosomal duplication of one of the pair of chromosomes and loss of the other of the original pair

Question 20

Hardy Weinberg Equilibrium Assumptions (4)

Answer 20

1) No mutaation occurring at the locus
2) Natural selection is not occurring
3) Completely Random mating
4) No net migration

Question 21

p+q=1

what do p and q stand for?

Answer 21

they are the frequencies of the separate alleles

this equation describes genotype!

Question 22

p^2+2pq+q^2=1

what do each of the factors stand for?

Answer 22

P^2= frequency of homozygotes for the allele p
2pq= frequency of heterozygosity (carrier frequency if we are talking bout an autosomal recessive disease yo)
q^2= frequency of homozygotes for the allele q
this equation describes phenotype!

Question 23

What is the frequency of and X linked recessive disease in males and females equal to?

Answer 23

Males = q
females = q^2

Question 24

Imprinting

Answer 24

At some loci one allele is active and the other is inactive (probs due to methylation). And if the other gene that is active decides to go on vacation (deleted or mutated ) you will get disease

Question 25

Autosomal Dominant

Answer 25

often pleiotropic and often due to defects in structural genes; also variable expressivity is common
Many generations and both male and female affected

Question 26

Autosomal Recessive

Answer 26

Commonly more severe than dominant disorders; patients often present in childhood
increased risk in consanguineous families

Question 27

X-linked recessive

Answer 27

Sons of heterozygous mothers have 50/50 shot of being affected. NOT MALE TO MALE TRANSMISSION
Skips generations
More severe in males and females normally have to be homozygous to be affected

Question 28

X linked dominant

Answer 28

Transmitted through both parents! Mothers transmit to 50% of sons and daughters and fathers transmit to ALL daughters but no sons

Question 29

Mitochondrial Inheritance

Answer 29

Transmitted through the mother. All offspring of affected females may show signs of disease.