Genetics Flashcards
gene
DNA segment located on a specific chromosome site containing info for specific protein production (polypeptide)
allele
alternative form of gene
- pair
- one from each parent
genotype
specific alleles related to a particular (set of) trait(s) (phenotypes)
polymorphism
used to indicate different versions of genes
homozygous
2 copies of same allele
heterozygous
different alleles of a given gene
dominant allele
expressed, masks recessive gene (TT/Tt)
recessive allele
only expressed when there are 2 of this (tt)
phenotype
observable traits
law of segregation
gamete formation: 2 alleles/chromosome separate as homologous chromosomes move toward opposite ends of cell (meiosis)
- each chromosome inherited independent of other chromosomes
gregor mendel
- how single genes inherited from parent to offspring
- first used one-trait crosses
- two-trait (dihybrid) crosses
dominant alllele
produces a functional protein that recessive allele does not
albinism
ability to produce melanin is lacking
- recessive allele produces nonfunctional tyrosinase
codominance
effects of both alleles are apparent in a heterozygote
- eg blood type AB (A+B alleles_
incomplete dominance
- trait expression in heterozygous individual is in between of a homozygous dominant/recessive- eg sickle-cell
plieotropy
one gene resulting in many problems
eg: sickle cell anemia
polygenic inheritance
variation in a trait independent of environmental influences (involves 2(+) genes, often on different chromosomes)
- eg height
x/y-linked inheritance
allele carried on the X/Y chromosome
- most sex-linked are x-linked
x-linked disorders
most are recessive
- color blindness
- muscular dystrophy
- hemophilia
nondisjunction
- both members of a homologous pair go into same daughter cell during meiosis 1
- sister chromatids fails to separate in meiosis 2
