Inherited Change Flashcards
Dihybrid crosses
involves inheritance of 2 genes which often control different characteristics
eg. RrYy is heterozygous
R - round
Y - yellow
What is the ratio of offspring phenotypes for the F1 generation in a dihybrid cross for both heterozygotes?
9:3:3:1
What is Mendel’s law of assortment?
each member of a pair of alleles may combine randomly with either of another pair
How is a gene sex-linked?
If it is carried on either the X or Y chromosome
Females have XX, males have XY
Why do X linked genetic disorders appear more frequently in males?
X much longer than Y, so no equivalent homologous portion of Y for parts of X. So characteristics controlled by recessive alleles on non-homologous portion will appear more frequently in males
-> lack of dominant allele on Y portion, no second X chromosome
What is haemophilia? What is it caused by?
X linked genetic disorder, blood clots slowly + may be slow persistent bleeding around joints
- caused by recessive allele w/ altered nucleotide sequence, codes for faulty protein
What is the use of pedigree charts?
Can trace inheritance of sex-linked characters like haemophilia
What is autosomal linkage?
Autosome is one of the remaining 22 chromosomes.
Where two or more genes are carried on the same autosome
What gametes are produced if genes A and B are linked and if they were on separate chromosomes?
linked- AB, ab
mixed alleles - AB, Ab, aB, ab
Assuming no crossing over, why do all linked genes remain together in meiosis and so pass into gametes?
They do not segregate in accordance w/ Mendel’s law of independent assortment
What is the equation for the chi-squared test?
How do you obtain the degrees of freedom?
sum of (O-E)^2 /E
d.f = n-1
What is the null hypothesis of the Chi-squared test?
There is no difference between observed and expected results/characteristics
