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45 Cards in this Set

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  • Back
many genes working together
polygenes
allele that is expressed when present in either the heterozygous or homozygous condition
dominant
lost one copy of an autosome
monosomics
the genetic constitution underlying a single trait or set of traits
genotype
when expressed causes death of an organism; some recessive, some dominant
lethal alleles
the realized expression of the genotype, the physical appearance or functional expression of a trait
phenotype
any eukaryotic chromosone that is not a sex chromosome; present in the same number and kind in both males and females
autosomes
mating between a phenotypically dominant individual of unknown genotype and a homozygous "tester"; is done to test whether is homo. or hetero.
testcross
consists of two similar chromosomes in females and two dissimilar chromosomes in males
sex chromosomes
the union of egg and sperm produced by a single hermaphroditic organism
self-fertilization
when a couple is expecting a child and pedigree analysis indicates that both of them have a significant probability of being heterozygous carriers of a recessive alleles responsibile for a genetic disorder
high risk pregnancy
diagram that show the possibilities after fertilization
Punnett square
a deeply, staining structure, seen in the interphase nucleus of a cell of an individual with more than one X chromosome
Barr body
process by which alternative forms of traits are expressed in offspring rather than blending each trait of the parents in the offspring
segregation
gained an extra autosome
trisomics
one of two or more alternative states of a gene
alleles
a congenital symdrome caused by the presence of an extra copy of chromosome 21
Down's syndrome
having two identical alleles of the same gene
homozygous
the physician removes cells from the chorion and is done in the eighth week of pregnancy
chorionic villi sampling
the position on a chromosome where a gene is located
locus
failure of chromosomes to separate properly at meiosis I
primary nondisjunction
allele that is only expressed when present in the homozygous condition, while being hidden in the heterozygous by dominant
recessive
a emembranous part of the placenta that nourishes the fetus
chorion
alternative alleles of a character segregate from each other in heterozygous individuals and remain distinct
Mendel' First Law of Heredity or the Law of Segregation
recognize very specific DNA sequences
restriction enzymes
basic unit of heredity
genes
a hereditary condition caused by a dominant allele that leads to the progressive deterioration of brain cells
Huntington's disease
having two different alleles of the same gene
heterozygous
states that genes located on different chromosomes assort independently
Mendel's second law of heredity or law of independent assortment
genes are close enough together on a chromosome that they do not assort independently are said to be
linked
when a detrimental allele occurs at a significant frequency in a population, the harful effect it produces is
a gene disorder
most common genetic disorder among whites; fatal disease in which the body cells secrete a thick mucus that clogs the airways of the lungs
cystic fibrosis
caused by a single-nucleotide change in the gene for hemoglobin, producing a protein with a nonpolar amino acid on its surface that tends to make the molecules clump together
sickle cell anemia
genetic changes of character involve the physical exchange of chromosome arms
crossing over
individuals heterozygous for both genes
dihybrid
measures distance between genes in terms of the frequency of recombination
genetic map
many genes that act sequntially or jointly
polygenes
a cross involving three linked genes is called a
three-point cross
interaction between 2 nonallelic genes in which one of them modifies the phenotypic expression of the other
epistasis
a "map unit" defined as the distance within which a crossover event is expected to occur in an average of 1% of gamates
centimorgan
hereditary disorder in which the nervous system deteriorates
Tay-Sachs disease
trait determined by a gene on the X chromosome
sex-linked
a hereditary disorder in which the blood is slow to clot or does not clot at all
hemophilia
a mutated gene; an organism carrying a gene that has undergone a mutation
mutant
the most common allele of a gene is often denoted with the symbol "+" and is designated as
wild type