principle of genetic inheritance Flashcards
genes
segments of DNA in a chromosome
locus or loci (plural)
a gene’s location on a chromosome
chromatid
one of two identical copies of a chromosome
centromere
connects identical sister chromatids
telomere
region at the end of a chromosome, used for stability
somatic cells
all cells other than germ-line cells; diploid, 2 copies- one from each parent– 23 pairs of different chromosomes, (22 pairs of autosomes and one pair of sex chromosomes) 46 total– diploid
homologous chromosomes
pairs of chromosomes
polymorphisms
DNA sequence variants that are more common in populations; “many forms” describing multiple alleles at a locus — loci that contain multiple alleles are called polymorphic
autosomes
chromosomes common in both genders, one from each parent – 22 pairs
karyotype
the entire set of a persons chromosomes; 46 chromosomes (of a karyotype) are in each diploid cell of a patient ;
normal karyotype is written as: 46XY and 46XX
genotype
an individuals genetic constitution at a locus
phenotype
what is actually observed physically
germ-line mosaicism
occurs when all or part of a parent’s germ-line is affected by a disease-causing mutation, but the somatic cells are not– it elevates the recurrence risk for offspring of the mosaic parent
the parent carries the mutation in his/her germ-line, but does not express the disease because the mutation in absent in other cells of the body
from lecture: a condition in which cells from a patient have different genotypes (& karyotypes)
- down’s syndrome: some 46XX, some 47XX, +21
- Klinefelter syndrome: some 46XY, some 47XXY
- turner syndrome: some 46XX, some 46XO
lyonization
X-inactivation; the choice of which X chromosome to be inactivated is random
during which phase of the cell cycle are chromosomes duplicated?
Interphase (G1, S, G2)
what is the result of mitosis in somatic cells?
two identical diploid daughter cells
result of meiosis in germ-line cells
meisosis reduces the total number of chromosomes by half, producing 4 gametes (haploid)
homologous recombination
in meiosis, it can produce new combinations of genes
two ways in which meiosis creates genetic diversity
random segregation of homologs & homologous recombination (cross-over exchange)
polyploidy
presence of a complete set of extra chromosomes in cells
aneuploidy
cells with missing or additional individual chromosomes– result of non-disjunctions
ex: monosomy, trisomy
translocations
non-homologous chromosomes exchange genetic material
reciprocal translocation
an exchange of material between nonhomologous chromosomes
Robertsonian translocation
long arm of two acrocentric chromosomes combined, short arm typically lost
pleoitropy
individuals with the same genotype can have multiple phenotypes (ex: PKU)
variable expressivity
the range of phenotypes that vary between individuals with a specific genotype
example: neurofibromatosis, patients have cafe-au-lait spots - pigmented areas the color of coffee with cream, spots differ in number, shape, size, and position
locus heterogeneity
single disorder, trait, or pattern of traits caused by mutations in genes at different chromosomal loci
ex: osteogenesis imperfecta – brittle bone disease, mutations in collagen genes (two loci: chromosome 7 and 17), either mutation exhibits the same phenotype
polygenic
traits in which variations are thought to be caused by the combined effects of multiple genes
