1
Traits produced by a gene can be either dominant or recessive. A trait is dominant when the trait appears when only one copy of the gene is present. A trait is recessive when the trait only appears when two copies of the gene for that trait are present. What is the term used for people who have only one copy of an abnormal gene for a recessive trait?
Carriers
Human chromosomes contain a long strand of DNA and many genes. With the exception of sperm and egg cells, how many pairs of chromosomes are contained in each human cell?
23
For many genes, there are single prevailing allele, present in the majority of individuals, that geneticists call the...
wild type or common allele
The_________ of a person is the set of alleles that make up his or her genetic constitution, either collectively at all loci or, more typically, at a single locus.
genotype
The___________ is the observable expression of a genotype as a morphological, clinical, cellular or biochemical trait.
phenotype
To inherit a recessive disorder, a person usually must receive two abnormal genes, one from each parent. If both parents have one abnormal and one normal gene, neither parent has the disorder. However, each parent has a 50% chance of passing the abnormal gene to their children. What percentage is the likelihood each child has of inheriting two normal genes?
25%
A segment of DNA occupying a particular position or location on a chromosome is a...
locus
a given set of alleles at a locus or cluster of loci on a chromosome is referred to as a
haplotype
When a person has a pair of identical alleles at a locus encoded in nuclear DNA, he or she is said to be_______
homozygous
The term___________ is used in medical genetics in two senses: sometimes to indicate a new genetic change that has not been previously known in a family and sometimes merely to indicate a disease-causing mutant allele
mutation
The person who brings the family to attention by consulting a geneticist is referred to as the
consultand
When a person has a pair of different alleles at a locus encoded in nuclear DNA he or she is said to be__________
heterozygous
The member through whom a family with a genetic disorder is first brought to the attention of the geneticist is the____________
proband
Couples who have one or more ancestors in common are ___________
consaguineous
Geneticists coined the term ___________ as a measure of the impact of a condition on reproduction.
fitness
A phenotype expressed in both homozygotes and heterozygotes for a mutant allele is inherited as_____________
dominant
___________ is the probability that a gene will have any phenotypic expression at all.
Penetrance
A _______________ is one that is determined primarily by the alleles at a single locus.
single-gene disorder
Variant alleles arose by mutation at some time in the recent or remote past. If there are at least two relatively common alleles at the locus in the population, the locus is said to exhibit .....
polymorphism
____________ is the severity of expression of the phenotype among individuals with the same disease-causing genotype
Expressivity
________________ may be the result of different mutations at the same locus, mutations at different loci or both.
Genetic Heterogeneity
The chance that both parents are carriers of a mutant allele at the same locus is increased substantially if the parents are related and could each have inherited the mutant allele from a single common ancestor, a situation called________________
consanguinity
_______________ describes the situation in which individuals from a small population tend to choose their mates from within the same population for cultural, geographical or religious reasons.
Inbreeding
The term ___________ ____________ is used to describe a genotype in which two different mutant alleles of the same gene are present, rather than one normal and one mutant.
compound heterozygote
_______________ is a well-known, incompletely dominant skeletal disorder of short limbed dwarfism and large head.
Achondroplasia