Heredity Flashcards
Character
A heritable feature in an organism
Trait
Variants of a character
True-breeding
A scenario where self-pollination always produces the same organism
P generation
True-breeding parental generation
F1 generation
Direct hybrids of true-breeding generation
F2 generation
Self-pollination of F1 generation
Dominant trait
A trait that is expressed over the recessive trait
Alleles
Alternative version of genes
Somatic cell
Body cell (non-sex cell)
Law of segregation
Two alleles for a character segregate during meiosis and arrive at different gametes
Homozygous
Pair of identical alleles
Heterozygous
Pair of different alleles (dominant one is expressed)
Phenotype
Physical appearance of a gene
Genotype
The genetic makeup
Testcross
A cross between recessive and an unknown organism to determine if the genotype is homozygous dominant or heterozygous
Monohybrid cross
Cross of two organisms that are hybridized for one trait (3:1 phenotypic ratio)
Dihybrid cross
Cross of two organisms that are hybridized for two traits (9:3:3:1 phenotypic ratio)
Law of independent assortment
Pairs of allele segregates independently of other pairs during gamete formation
Complete dominance
Heterozygotes exhibit no phenotypic trace of the recessive allele
Incomplete dominance
Heterozygotes have a mixture, or blending, of both alleles
Codominance
Heterozygotes exhibit both alleles at once
Tay Sachs disease
Disease with improperly functioning enzymes that lead to lipid accumulation in the brain; requires two alleles to manifest, but just one allele produces mediocre enzymes
Blood types
A, B, AB, O (describing surface carbs of a blood cell)
Pleiotropy
A condition where a gene is affected by multiple phenotypes
Epistasis
Phenotypic expression of one gene alters expression of a second gene
Polygenic inheritance
Phenotype is influenced by multiple genes
Multifactorial genes
Character influenced by genetic and environmental factors
Pedigree
Family tree describing traits of parents and descendants
Carriers
Heterozygotes who carry recessive alleles for a condition without expressing them
Cystic fibrosis
A disease preventing proper chloride ion transport in certain cells, causing thick mucus buildup
Sickle cell disease
A condition resulting in warped blood cells which cannot hold oxygen well
Sickle cell trait
The heterozygotic condition of sickle cell disease; results in some sickled and some regular blood cells
Huntington’s disease
A late-onset disease that is passed onto offspring well before it manifests
Amniocentesis
Fetal testing using cultured amniotic cluid
Chorionic villus sampling
Fetal testing using cultured placenta tissue
PKU
A disorder that prevents breakdown of phenylalanine
Benefits of Drosophila in experiments
Short generation time, plenty of offspring, four pairs of chromosomes
Sex-linked gene
A gene present on a sex chromosome
Systems of sex chromosomes
X-Y: gamete in sperm dictates sex
Z-W: gamete in egg dictates sex
X-0: males have one sex chromosome
Haploid-diploid: females are diploid, males are haploid
SRY
A gene on the Y chromosome that causes testes to form
Hemizygous
Describes a male with one allele present on the Y chromosome
Barr body
Condensed remnant of inactivated X chromosome
Linked genes
Occur near each other on the same chromosome
Recombinants
Offspring with different traits from the parents
Recombination frequency
Percent of offspring with recombinant type
Crossing over
Produces recombination
Linkage map
A representation of recombination frequencies
Nondisjunction
Failure of homologous chromosomes to separate
Aneuploidy
Abnormal number of a single chromosome
Monosomy
A chromosome is missing from a pair
Trisomy
A chromosome is added to a pair
Polyploidy
An entire set of chromosomes is replicated
Deletion
Chromosome fragment is lost
Duplication
Chromosome fragment is duplicated
Inversion
Chromosome segment is reversed
Translocation
Chromosome segment moves to another, non-homologous chromosome
Trisomy 21
Down’s syndrome, results in developmental delays and physical aberrations
Klinefelter syndrome
XXY, sterile male sex organs
Turner syndrome
Monosomy X, sterile female sex organs
