Chapter 29 1110/1120 Flashcards
is the study of heredity—that is, the characteristics children inherit from their parents.
Genetics
the study of how genetic traits are passed from parent to offspring. Mendelian genetics allows us to make predictions about the patterns of how traits are passed from one generation to the next.
Mendelian genetics
e genetic approach to the diagnosis and management of disease, has indeed come a long way since its early beginnings.
genomic medicine
or sex cells, each gamete receives one of these factors. Then two gametes combine to produce the next generation, so that each member of the next generation of pea plants has two heritable factors for each characteristic.
gametes
is the genes an organism has for a given trait. The actual genetic constitution of an individual is its
genotype
is the expression of the genes as a trait.
phenotype
Mendel stated that genes occur in dominant and recessive forms. Alternate forms of genes
alleles
for a trait if the two alleles for the trait are identical.
homozygous
for a trait if the two alleles for the trait are different.
heterozygous
results in a lack of normal coloring of the skin, hair, and eyes. Several human genes produce the enzymes that are necessary for the synthesis of melanin, the pigment responsible for skin, hair, and eye color
albinism
has extra fingers or toes. One allele for polydactyly is dominant over the recessive, normal allele that results in the normal number of fingers or toes.
polydactyly
are all the cells of the body except the gametes. Examples of somatic cells are epithelial cells, muscle cells, neurons, fibroblasts, lymphocytes, and macrophages
Somatic cells
The somatic cells have a normal number of chromosomes
diploid
The normal number of chromosomes in a gamete
haploid
Humans have 22 pairs of this. which are all the chromosomes except the sex chromosomes, and 1 pair of sex chromosomes, which determines the sex of the individual. Sex chromosomes are denoted as X or Y chromosomes.
autosomal chromosomes
is a display of the chromosomes of a somatic cell during metaphase of mitosis. It is produced by photographing the cell’s stained chromosomes through a microscope and arranging the photographed chromosomes in pairs
karyotype
An individual has only two alleles for a given gene, one on each homologous chromosome. At the population level, however, many forms of an allele may exist.
multiple alleles
is an autosomal recessive trait with multiple alleles. A gene on chromosome 12 encodes for an enzyme that converts the amino acid phenylalanine to the amino acid tyrosine
phenylketonuria
his type of inheritance pattern in which the dominant allele is fully expressed over the recessive allele
complete dominance
two alleles at the same locus are expressed, so that separate, distinguishable phenotypes occur at the same time.
codominance
the dominant allele does not completely mask the effects of the recessive allele in the heterozygote. The heterozygote produces less of the protein product than the homozygous dominant and has phenotypic characteristics intermediate between the homozygous dominant and the homozygous recessive.
incomplete dominance
is a disorder of a gene on chromosome 11. It affects the synthesis of β-globulin polypeptide chains, which are part of the hemoglobin in red blood cells.
beta thalassemia
two abnormal alleles are present, and much lower-than-normal amounts of β-globulin polypeptide chains are synthesized.
major thalassemia
which is a deficiency of hemoglobin in the blood. Symptoms include pallor, weakness, fatigue, and spleen enlargement. Blood transfusions are necessary to maintain hemoglobin levels. In the heterozygous condition
anemia
one normal allele and one abnormal allele are present. The production of hemoglobin is intermediate between the normal phenotype and major thalassemia, and mild anemia results.
minor thalassemia
result from the interactions of many genes. Although all the genes contribute to the phenotype without being dominant or recessive to each other, each gene has its own characteristics, such as multiple alleles or incomplete dominance.
polygenic trait
haploid gametes are produced that have one chromosome from each of the homologous pairs of chromosomes. Therefore, gametes have one-half the number of chromosomes and one-half as many alleles as the original diploid cells.
meiosis
is a failure of structure, function, or both as a result of abnormalities in a person’s genetic makeup—that is, his or her DNA. Humans may have a variety of genetic disorders
genetic disorder
In most cases, the specific cause of a mutation cannot be determined. Once a mutation has occurred, however, the abnormal trait can be passed from one generation to the next.
mutagen
The failure of chromosomes to separate during meiosis
nondisjunction
When the gametes are fertilized, the resulting zygote has either 47 chromosomes or 45 chromosomes, rather than the normal 46
aneuploidy
trisomy 21, is a type of aneuploidy in which three chromosomes 21 are present
Down syndrome
is a set of signs and symptoms occurring together as the result of a single cause, such as a single mutation or one extra chromosome (a trisomy).
syndrome
One hypothesis of aging suggests the existence of this, after a certain passage of time or a certain number of cell divisions, results in the death of a given cell line.
Cellular clock
Another hypothesis suggests that there are “death genes,” which turn on late in life, or sometimes prematurely, causing cells to deteriorate and die.
Death genes
Other hypotheses suggest that, through time, DNA is damaged, resulting in cell degeneration and death.
DNA damage
which are atoms or molecules with an unpaired electron.
free radicals
are traits affected by genes on the sex chromosomes
Sex-linked traits
re affected by genes on the X chromosome
X-linked traits
are affected by genes on the Y chromosome. In humans, the X chromosome is much larger than the Y chromosome.
Y-linked traits
The specific location of a gene on a chromosome is its
Locus
If an albino (aa) mates with a person homozygous for normal pigment (AA)
All the offspring are normal but carriers.
In humans, somatic cells have ____ chromosomes, while reproductive cells (gametes) have ____.
46; 23
A mutation involving a single nucleotide change is
point mutation
