Sex determination

1
Sex determination
2
(No Transcript)
3
(No Transcript)
4
(No Transcript)
5
(No Transcript)
6
(No Transcript)
7
Problem

• Colour blindness is rarely observed in females
  while 1/8 men have some form of it. Describe how
  this phenomenon can be explained.

8
Problem
9
Cytoplasmic inheritance
10
Problem

• Describe an experiment that can be used to
  determine the mode of inheritance of eye colour
  (red white) in Drosophila melanogaster.
• Use inbred lines, cross and make reciprocal cross

11

• Red (?) x white (?) White (?) x red (?)
• IF AUTOSOMAL
• Progeny of both crosses will have red eyes
• IF CYTOPLASMIC
• All offspring of cross 1 will have red eyes
  cross 2 will have white eyes
• IF SEX LINKED
• All offspring of cross 1 will have red eyes in
  cross 2 you will get white ? and red ?

12
Pedigree analysis
13
Pedigree analysis
14
Pedigree analysis
15
Pedigree analysis
16
Pedigree analysis
17
Pedigree analysis
18
KC 4.24 (p102)

• A husband and wife have normal vision, but both
  have fathers which were red-green colour blind
  (red-green colour blindness is an X-linked
  recessive condition). What is the probability
  that their first child will be
• a) A normal boy?
• b) A normal daughter?
• c) A colour blind son?
• d) A colour blind daughter?

19
Dad ? XRGY Mom ? XRGXrg
20

• a) A normal son? ½
• b) A normal daughter? 100
• c) A colour blind son? ½
• d) A colour blind daughter? 0

21
KC 15.3 (p410)

• A plant may have green, white or variegated
  leaves, depending on the mutation in the
  chloroplasts. Predict the results of the
  following crosses