week 6, mar 14th - 18th - midterms Flashcards
What is a dihybrid cross
Two varieties that differ for two traits (ex colour and shape)
What is the first generation from a pure breed dihybrid cross
Always heterozygous
How many gametes does a dihybrid cross from
4 different gametes
What is the F2 phenotypic ratio
9 - both traits looking dominant
3 - 1 dominant & 1 recessive
3 - 1 recessive & 1 dominant
1 - both recessive
What is mendels second law
Law of independent assortment = two traits were independently inherited
*probability
What is epistasis
When one gene interferes (allows or prevents) with the expression of another gene
Give an example of epistasis
Labrador dogs
Gene B=black b=chocolate
Gene E=normal pigment e=mutated pigment (yellow)
What kind of phenotypic ratio will Labrador dogs (epistasis) produce
9:3:4
What is polygenic inheritance
Many genes code for one phenotype resulting in a gradient of phenotypes
Many genes —> one phenotype
Give an example of polygenic inheritance
Skin colour
What is pleiotropy
One gene affects expression of may different phenotypes
One gene —> many phenotypes
Give an example of pleiotropy
One mutated gene in a tiger can cause albinism and blindness
How do you solve a genetics problem
1) read text and make genotype/phenotype table
2) write genotypes of parents
3) gametes of parents (punnet square)
4) read punnet square for answer and write it down (percentage/ratio or whatever question wants)
How many pairs of chromosomes do humans have
23
How many chromosomes are of autosomal inheritance
22 (they are the same for men and women)
Describe autosomal recessive
Homozygous dominant = not affected
Heterozygous = carriers
Homozygous recessive = affected
Give examples of autosomal recessive disorders
Cystic fibrosis
Tay sachs
Albino
Describe autosomal dominant
Homozygous dominant & heterozygous = affected
Homozygous recessive = not affected
Give examples of autosomal dominant disorders
Dwarfism
Huntingtons
Extra digits
Rare mutations
What are the 23rd pair of chromosomes
Sex chromosomes
23rd chromosome pair of women
XX
23rd chromosome pair of men
XY
Describe sex-linked recessive
X^M X^M = not affected X^M X^m = not affected **carrier X^m X^m = affected X^M Y = not affected X^m Y = affected
How to solve a pedigree
1 = is the affliction recessive or dominant?
if recessive it skips a generation
2 = is it sex-linked
–> make genotype/phenotype table
–> do punnet squares for each couple
–> if all children are possible it is sex-linked
–> if not possible then its autosomal recessive
