genetic crosses theory Flashcards
what is a gamete
haploid cells capable of fusion
what is fertilisation
fusion of two gametes to form a single cell with a diploid number known as a zygote
define locus
the location of a gene on a chromosome
define allele
different variations of the same gene
what’s a dominant allele
the allele prevents the working of the recessive allele, this trait is then expressed in offspring
what’s a recessive gene
the allele is prevented from working by the dominant allele
what are progeny
the offspring produced
define genotype
the genetic make up of an organism
define phenotype
the physical apperance of an organism
define homozygous
two alleles are the same e.g BB TT GG
define heterozygous
two alleles are different e.g Bb Tt Gg
what is incomplete dominance
neither allele is dominant or recessive. they work in heterozygous genotype to produce an intermediate phenotype
how are male chromosomes represented
xy
how are female chromosomes represented
xx
explain mendel’s first law of segregation
characteristics are controlled by pairs of factors but only one factor can be carried in a gamete
explain mendel’s second law of independant assortment
where two or more characterisitcsare concerned the factors for these enter the gametes independantly of each other
when would a cross not obey mendel’s second law
if the cross is sex linked as there is no independant assortment
when wold a cross obey mendel’s second law
if the corss is not sex linked as the alleles separate from eachother and can combine with any allele from another pair
define linkage
means that genes are located on the same chromosome
explain a sex linked disorder and how to treat it
haemophilia - blood doesnt clot when exposed to air, treated by ingecting clotting proteins
