2.5 - inheritance Flashcards
what’s a gene
length of DNA on a chromosome that codes for the production of one or more polypeptide chains + functional RNA
define genotype
genetic constitution of an organism
define phenotype
expression of an organisms genetic constitution, combined with/ its interaction within the environment
what’s a locus
fixed position on a DNA molecules occupied by a gene
what’s an allele
different forms of particular gene, found at same locus on chromosome
single gene can have many alleles
define homozygous
having two identical alleles of a gene
e.g: FF or ff
define heterozygous
faving two different alleles of a gene
e.g: Ff
what’s a dominant allele
- allele always expressed
- represented w/ capital letter, e.g: F
what’s a recessive allele
- allele only expressed in absence of dominant allele, only expressed if 2 copies present
- represented w/ small letter, e.g f
what’s meant by codominant alleles
2 dominant alleles that both contribute to phenotype, either by showing blend on both characteristics, or characteristics appearing together
what’s an autosome
chromosome not an X or Y chromosome
what’s a sex chromosome
chromosome determining sex of an organisms
e.g: X + Y chromosomes in humans + other mammals
what’s the F1 generation
first generation of offspring resulting from cross of 2 individuals in parental generation
what’s the F2 generation
second generation of offspring resulting from cross of 2 individuals in F1 generation
define monohybrid inheritance
where one phenotype characteristic is controlled by a single gene
what’s mendels first law of inheritance
- law of segregation
- alleles separate randomly into gametes
- each parent passes one allele to their offspring
what’s mendels second law of inheritance
- law of independent assortment
- alleles of genes assortment independently of other genes during gamete formation
PKU is a recessive condition
two heterozygous parents have offspring
predict proportion of offspring that will have PKU
75% chance of normal phenotype
25% chance of PKU phenotype
what’s the purpose of a test cross
used to determine whether an individual w/ dominant trait is heterozygous or homozygous domiannt
describe how a test cross is carried out
- individual of unknown genotype bred w/ homozygous recessive individual
- offspring phenotypes observed to determine genotype of unknown individual