Inheritance, linkages, and epistatis simple

Question 1

What are the ratios expected in the F2 generation for monogenic, dihybrid, and codominant

when parents are all homozygous dominant and homozygous recessive?

Answer 1

• monogenic
  
  • 3:1
  • dominant:recessive
• dihybrid
  
  • 9:3:3:1
  • dominant both : dominant 1st recessive 2nd : recessive 1st dominant 2nd : recessive both
• codominant
  
  • 1 : 2 : 1
  • homozygous one alel: heterozygous : homozygous for other

Question 2

Why would you not get the expected ratio?

Answer 2

• sex linkage
• autosomal linkage
• epistasis

Question 3

When is a gene said to be sex linked

Answer 3

when it is located on a sex chromosome

Question 4

WHy are men more likely than femals to show recessive phenotypes for genes that are sex linked?

Answer 4

• Y smalled, most genes carreid on X chromosome
• males have one copy, only have one allele for sex linked genes
• they express the characteristic even if its recessive

Question 5

What is an autosome?

Answer 5

chromosome that isnt a sex chromosome

Question 6

Why are genes on the same autosome said to be linked? when does linkage not occur?

Answer 6

• staytogether during independant assortment
• pass onto offspring together
• only reason this wont happen is if if corssing over occurs

Question 7

How is closeness of genes determined?

Answer 7

• more closely linked the closer the are
• crossing over less likely to split them up

Question 8

WHat does an epsistatic gene do?

Answer 8

• mask expression of another gene

Question 9

What are the expected ratios for epistasis when you cross a homozygous recessive parent with a homozygous dominant parent in the F2 generation?

Answer 9

• recessie epistatic allele
  
  • 9 : 3 : 4
  • dominant both : dominant epistatic recessive other : recessive epistatic
• dominant epistatic allele
  
  • 12 : 3 : 1
  • dominant epistatic : recessiver epistatic other : recessive both

Question 10

What does it mean if the critical value is larger or equal to the value at 0.05?

Answer 10

• there is a significant difference between the observed and expected results
• something other than chance is caysing the difference
• null hypothesis can be rejected
• 5% probability that the difference betweem the observed and expected results is due t chance