Chapter 12 VocabINHERITANCE PATTERNSAND HUMAN GENETICS

Holt Modern Biology Textbook

Sex Chromosome

a chromosome that determines the sex of an individual

(We can see that this karyotypecodes for a male)

Autosome

Any chromosome that is not a sex chromosome

Sex-linked Trait

a trait that is determined by a gene found on one of the sex chromosomes, such as the X chromosome or the Y chromosome in humans

Linked Gene

One of a pair of genes that tend to be inherited together

Chromosome Map

A diagram of gene positions on a chromosome

Map Unit

in chromosome mapping, an increment of 1 percent in the frequency of crossing-over

Germ-cell Mutation

mutation that occurs in an organism's gametes

Somatic-cell Mutation

A mutation that occurs in a body cell

Lethal Mutation

a gene or chromosomal mutation that influences the development of an organism in such a way that the organism cannot survive

Deletion

Loss of a part of DNA from a chromosome

Inversion

a kind of mutation in which the order of the genes in a section of a chromosome is reversed

Translocation

an exchange of chromosome parts

Nondisjunction

meiosis in which there is a failure of paired homologous chromosomes to separate

Point Mutation

gene mutation involving changes in one or a few nucleotides

Substitution

A mutation in which a nucleotide or a codon in DNA is replaced with a different nucleotide

Frameshift Mutation

mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide

Insertion Mutation

a mutation in which one or more nucleotides are added to a gene

Pedigree

A diagram that shows the occurrence of a genetic trait in several generations of a family

Carrier

an inactive substance that is a vehicle for a radioactive tracer of the same substance and that assists in its recovery after some chemical reaction

Genetic Disorder

an abnormal condition that a person inherits through genes or chromosomes

Polygenic

of or relating to an inheritable character that is controlled by several genes at once

Complex Character

characters that are influenced strongly both by the environment and by genes

Multiple Allele

genes with three or more alleles

Codominance

situation in which both alleles of a gene contribute to the phenotype of the organism

Incomplete Dominance

one allele is not completely dominant over the other allele

Sex-influenced Trait

an autosomal trait that is influenced by the presence of male or female sex hormones

Huntington’s Disease

A human genetic disease caused by a dominant allele; characterized by uncontrollable body movements and degeneration of the nervous system; usually fatal 10 to 20 years after the onset of symptoms.

Amniocentesis

Technique that allows a physician to remove from the amnion, the sac that surrounds the fetus, between the 14th and 16th week of pregnancy

Chorionic Villi Sampling

Sampling of cells derived from the zygote that grow between the mother's uterus and placenta between the 8th and 10th week of pregnancy

Genetic Counseling

Guidance for prospective parents on the likelihood of genetic disorders in their future children

Gene Therapy

The insertion of working copies of a gene into the cells of a person with a genetic disorder in an attempt to correct the disorder

Crossing-Over

the exchange of genetic material between homologous chromosomes during meiosis

can result in genetic recombination