week 6, mar 14th - 18th - midterms

Question 1

What is a dihybrid cross

Answer 1

Two varieties that differ for two traits (ex colour and shape)

Question 2

What is the first generation from a pure breed dihybrid cross

Answer 2

Always heterozygous

Question 3

How many gametes does a dihybrid cross from

Answer 3

4 different gametes

Question 4

What is the F2 phenotypic ratio

Answer 4

9 - both traits looking dominant
3 - 1 dominant & 1 recessive
3 - 1 recessive & 1 dominant
1 - both recessive

Question 5

What is mendels second law

Answer 5

Law of independent assortment = two traits were independently inherited
*probability

Question 6

What is epistasis

Answer 6

When one gene interferes (allows or prevents) with the expression of another gene

Question 7

Give an example of epistasis

Answer 7

Labrador dogs
Gene B=black b=chocolate
Gene E=normal pigment e=mutated pigment (yellow)

Question 8

What kind of phenotypic ratio will Labrador dogs (epistasis) produce

Answer 8

9:3:4

Question 9

What is polygenic inheritance

Answer 9

Many genes code for one phenotype resulting in a gradient of phenotypes
Many genes —> one phenotype

Question 10

Give an example of polygenic inheritance

Answer 10

Skin colour

Question 11

What is pleiotropy

Answer 11

One gene affects expression of may different phenotypes

One gene —> many phenotypes

Question 12

Give an example of pleiotropy

Answer 12

One mutated gene in a tiger can cause albinism and blindness

Question 13

How do you solve a genetics problem

Answer 13

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)

Question 14

How many pairs of chromosomes do humans have

Answer 14

23

Question 15

How many chromosomes are of autosomal inheritance

Answer 15

22 (they are the same for men and women)

Question 16

Describe autosomal recessive

Answer 16

Homozygous dominant = not affected
Heterozygous = carriers
Homozygous recessive = affected

Question 17

Give examples of autosomal recessive disorders

Answer 17

Cystic fibrosis
Tay sachs
Albino

Question 18

Describe autosomal dominant

Answer 18

Homozygous dominant & heterozygous = affected

Homozygous recessive = not affected

Question 19

Give examples of autosomal dominant disorders

Answer 19

Dwarfism
Huntingtons
Extra digits
Rare mutations

Question 20

What are the 23rd pair of chromosomes

Answer 20

Sex chromosomes

Question 21

23rd chromosome pair of women

Answer 21

XX

Question 22

23rd chromosome pair of men

Answer 22

XY

Question 23

Describe sex-linked recessive

Answer 23

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

Question 24

How to solve a pedigree

Answer 24

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