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32 terms

Modern Biology Chapter 12

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sex chromosome
one of the pair of chromosomes that determine the sex of an individual
autosome
any chromosome that is not a sex chromosome, not directly involved in determining the sex of an individual
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, a trait that is coded for by an allele on a sex chromosome
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, do not affect the organism itself but can be passed on
somatic-cell mutation
a mutation that occurs in a body cell and can affect the organism, cannot be inherited
lethal mutation
a gene or chromosomal mutation that influences the development of an organism in such a way that the organism cannot survive, causes death, often before birth
deletion
the loss of a piece of of chromosome due to breakage
inversion
a chromosomal segment breaks off, flips around backward, and reattaches
translocation
a piece of one chromosome breaks off and reattaches to a nonhomologlous chromosome
nondisjunction
the failure of homologous chromosomes to separate during meiosis. One gamete receives an extra copy and another gamete receives no copies
point mutation
a change that occurs within a single gene or other segment of DNA on a chromosome
substitution
a mutation in which one nucleotide is replaced by another nucleotide
frameshift mutation
a mutation, such as the insertion or deletion of a nucleotide in a coding sequence, that results in the misreading of the code during translation because of a change in the reading frame
insertion mutation
a mutation in which one or more nucleotides are added to a gene, which can also result in a frameshift mutation
pedigree
a diagram that shows how a trait is inherited over several generations
carrier
they have one copy of the recessive allele but do not have the disease
genetic disorder
diseases or disabling conditions that have a genetic basis
polygenic
describes a characteristic that is influenced by many genes
complex character
a character such as skin color that is influenced strongly by both genes and the environment
multiple alleles
more than two alleles (versions of the gene) for a genetic trait
codominance
a condition in which both alleles for a gene are fully expressed in the phenotype of a heterozygote
incomplete dominance
a condition in which a trait in an individual is intermediate between the phenotype of the individual's two parents because the dominant allele is unable to express itself fully
sex-influenced genes
an autosomal trait that is influenced by the presence of male or female sex hormones
Huntington's disease
an autosomal dominant condition characterized by forgetfulness and irritability
amniocentesis
a procedure used in fetal diagnosis in which amniotic fluid is removed from the uterus of the pregnant woman
chorionic villi sampling
a procedure in which the chorionic villi to are analyzed to diagnose fetal genotypes
genetic counseling
the process of testing and informing potential parents about their genetic makeup and the likelihood that they will have offspring with genetic defects or hereditary diseases
gene therapy
a technique that places a gene into a cell to correct a hereditary disease or to improve the genome
deletion mutation
one ore more nucleotides in a gene are lost