Karyotype
an ordered display of the pairs of chromosomes from a cell
Homologous chromosomes
2 chromosomes in each pair, same shape and same genes
Diploid cell
has 2 sets of chromosomes (2n). Normal eukaryotic organism. Humans have 46
Haploid cell
half the number of chromosomes
Gamete
(sperm or egg) contains a single set of chromosomes and is thus a haploid cell. Only type of human cells produced by meiosis, rather than mitosis
Zygote
Fertilized egg
Meiosis 1
Separates homologous chromosomes
Meiosis 2
Separates sister chromatids
Meiosis
reduces the number of chromosome sets from two (diploid) to one (haploid), producing cells that differ genetically from each other and from the parent cell
Mitosis
conserves the number of chromosome sets, producing cells that are genetically identical to the parent cell
Crossing over
occurs between prophase 1 and metaphase 1 and is the process where homologous chromosomes pair up with each other and exchange different segments of their genetic material to form recombinant chromosomes
Recombinant chromosomes
combine DNA inherited from each parent
True breeding
plants that produce offspring of the same variety when they self pollinate
Hybridization
mating of 2 contrasting, true-breeding varieties
The law of segregation
states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization
Allele
Alternative version of a gene
Independent assortment
each pair of alleles segregates independently of any pair of alleles during gamete formation
Incomplete dominance
the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties. Not blending because recessive genotype/phenotype can be separated
Codominance
two dominant alleles affect the phenotype in separate, distinguishable ways
Pleitophy
multiple phenotypic effects
-cystic fibrosis and sickle cell anemia
Epistasis
expression of a gene at one locus alters the phenotypic expression of a gene at a second locus
Quantitative characters
are those that vary in the population along a continuum. Uses polygenic inheritance
Polygenic inheritance
an additive effect of two or more genes on a single phenotype
Carrier
heterozygous individuals who carry the recessive allele but are phenotypically normal
Aminocentesis
the liquid that bathes the fetus is removed and tested
Chorionic villus sampling
a sample of the placenta is removed and tested
Chromosome theory of inheritance
Identifies chromosomes as the carrier of genes
- Sutton and Boveri
Nondisjunction
Pairs of homologous chromosomes do not separate normally during meiosis
-as a result, only one gamete receives two of the same types of chromosome, and another gamete receives no copy
Aneuploidy
results from the fertilization of gametes in which nondisjunction occurred
- offspring with this condition have an abnormal number of a particular chromosome - aneuploid condition
Mono sonic zygote
Has only one copy of a particular chromosome
Trisomic zygote
has 3 copies of a particular chromosome
-ex trisomy 21, Down syndrome
Polyploidy
a condition in which an organism has more than two complete sets of chromosomes
- triploidy: 3 sets - tetraploidy: 4 sets
Deletion
Removes a chromosomal fragment
Duplication
Repeats a segment
Inversion
Reverses orientation of a segment within a chromosome
Translocation
Moves a segment from one chromosome to another
Genomic imprinting
Phenotype variation, the phenotype depends on which parent passed along the alleles for those traits