Mendelian Inheritance

Question 0

gamete?

how many chromosomes?

Answer 0

sex cells (ova and sperm cells). 
one copy of each chromosome, 1-22 plus x or y. (23)

Question 1

somatic cell?

how many chromosomes?

Answer 1

any cell which is not a gamete.

2 copies of chromosomes 1-22, plus xx or xy. (46)

Question 2

autosome?

Answer 2

any chromosome not considered a sex chromosome (1-22)

Question 3

Allosome

Answer 3

Sex chromosome

Question 4

Gonosome

Answer 4

Sex chromosome

Question 5

Haploid

ex?

Answer 5

Having one copy of each chromosome.

gamete.

Question 6

Diploid

ex?

Answer 6

Having two copies of each chromosome.

somatic cell, secondary spermatocyte/oocyte.

Question 7

gene

Answer 7

a sequence of DNA that encodes a specific protein or RNA

Question 8

Allele

Answer 8

one of several alternative forms of a gene sequence at a locus

Question 9

An autosomal gene has how many alleles?

Answer 9

2; maternal and paternal

Question 10

Polymorphism

Answer 10

When a locus has multiple alleles present in a population (with at least 1% incidence)

Question 11

Locus

Answer 11

A specific location on a chromosome

Question 12

Wild-type

Answer 12

The allele that is present in the majority of the population. (Not deleterious)

Question 13

Mutant

Answer 13

The allele that differs from wild-type due to mutation

Question 14

Genotype

Answer 14

Set of alleles an individual possesses.

Question 15

Phenotype

Answer 15

expression of the alleles (clinical manifestations)

Question 16

Homozygous

Answer 16

two alleles at a particular locus are identical

Question 17

Heterozygous

Answer 17

two alleles at a particular locus are different

Question 18

Hemizygous

Answer 18

refers to X-linked genes in males, who only have one x-chromosome

Question 19

pleiotropism

Answer 19

a single mutant gene may result in many phenotypic variants

Question 20

recurrance risk

Answer 20

probability that an offspring will express a genetic disease

Question 21

pedigree analysis

Answer 21

information obtained from a family tree tracing a certain trait

Question 22

Dominant allele

Answer 22

Allele that is always expressed, even if another allele is present

Question 23

Incompletely dominant

ex?

Answer 23

expression of two different alleles results in intermediate phenotype
(red flower plus white flower equals pink flower)

Question 24

Codominant

ex?

Answer 24

each allele results in observable phenotype

blood type: AA, BB, AB all different phenotypes

Question 25

Recessive

Answer 25

requires presence of 2 identical alleles to express phenotype

Question 26

Loss-of-function

Answer 26

reduced production of a gene product or inactive protein

Question 27

Gain of function

Answer 27

gene product gains new function (most often toxic properties)

Question 28

Autosomal dominant

Answer 28

most often affects enzymes, receptors, feedback inhibitors and structural proteins

Question 29

typical mating pattern of autosomal recessive

Answer 29

heterozygous affected with homozygous nml

skipped generations are unlikely

Question 30

Dominant negative

Answer 30

mutant allele negatively affects nml allele

Question 31

Haploinsufficiency

Answer 31

Nml physiology requires more than half of the fully functional gene product

Question 32

Penetrance

Answer 32

frequency in which the allele expresses itself phenotypically

Question 33

Incomplete penetrance

Answer 33

the allele is NOT expressed phenotypically

Question 34

Autosomal recessive (mating patterns)

Answer 34

parents not usually affected, can skip a generation

Question 35

Autosomal recessive (penetrance, mutation source)

Answer 35

Usually completely penetrant, not usually a new mutation, onset usually early in life

Question 36

X-linked dominant

Answer 36

cannot be passed father to son; heterozygotic females affected

Question 37

Dosage compensation

Answer 37

x-linked recc hetero females usually don’t express full phenotypic change (affected and nml alleles randomly shut off in somatic cells, leading to variable expression)

Question 38

In X-linked recessive, males….

Answer 38

Will all be affected

Question 39

Cosanguinuity

Answer 39

Mating between related individuals; more likely to result in recessive disorderes being expressed

Question 40

Y-linked disorders

Answer 40

Generally affect fertility, so not considered a means of inheritance

Question 41

X-inactivation

Answer 41

inactivates 1 copy of X-chromosome in all somatic cells in females

Question 42

when/how does x-inactivation occur?

Answer 42

During blostocyst formation, gene regions are methylated and condensed into heterochromatin. (Random: 50/50 maternal/paternal)

Question 43

Barr Body

Answer 43

highly condensed chromosome visible in nuclei of cells in interphase

Question 44

Genetic Mosaicism

Answer 44

condition in which cells with different genotypes or chromosome constitutions are present in the same individual (stems from inactivations). Once fixed, all decendents will have same deletion

Question 45

Incomplete x-inactivation

Answer 45

some regions not inactivated; manifesting heterozygotes; some females will express x-linked recessive mutation due to x-inactivation

Question 46

locus heterogeneity

Answer 46

single disorder caused by mutations at different chromosome loci

Question 47

consequences of enzyme defects

Answer 47

accumulation of substrate, decreased end product, failure to inactivate a damaging substrate

Question 48

Expressivity

Answer 48

severity of expression of the phenotype among individuals with genotype

Question 49

variable expression

Answer 49

variability in degree of phenotypc expression

Question 50

allelic heterogeneity

Answer 50

different mutations can be responsible for more or less severe expression (usually not within a family)

Question 51

pleiotropy

Answer 51

a single disease-causing mutation affects multiple organ systems

Question 52

proband

Answer 52

first studied in a pedigree