Chapter 15 The Chromosomal Basis of Inheritance

1
Chapter 15The Chromosomal Basis of Inheritance
2
Chapter 15The Chromosomal Basis of Inheritance

• Mendelian inheritance has its physical basis in
  the behavior of chromosomes during meiosis.

3
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan

4
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• In the early 1900s, he was the first scientist
  to want different varieties of fruit flies to
  study.

5
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• A white-eyed mutation showed up in his
  laboratory.

6
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• He bred his white-eyed fruit flies with wild
  type red-eyed fruit flies.

7
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• F1 all offspring had red eyes
• (therefore red is dominant)

8
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• F2 redwhite 31
• (as expected)

9
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• F2 redwhite 31
• But all the white-eyed flies were male. (very
  surprising)

10
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• F2 redwhite 31
• But all the white-eyed flies were male. (very
  surprising)
• F2? red 100
• F2? redwhite 11

11
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• Therefore the gene for white eyes is on the X
  chromosome.

12
Chapter 15The Chromosomal Basis of Inheritance

• Thomas Hunt Morgan
• XX red-eyed female
• XX red-eyed female
• XY red-eyed male
• XY white-eyed male.

13
Chapter 15The Chromosomal Basis of Inheritance

• Recombination

14
Chapter 15The Chromosomal Basis of Inheritance

• Recombination
• Linked genes tend to be inherited together
  because they are on the same chromosome.

15
Chapter 15The Chromosomal Basis of Inheritance

• Recombination
• Independent assortment of chromosomes and
  crossing over produce genetic recombinations.

16
Chapter 15The Chromosomal Basis of Inheritance

• Recombination
• Recombination can be used to map genes on the
  chromosome.
• 1 centimorgan 1 recombination.

17
Chapter 15The Chromosomal Basis of Inheritance

• Sex Chromosomes

18
Chapter 15The Chromosomal Basis of Inheritance

• Sex Chromosomes
• Several patterns exist.
• XX vs. XY
• XX vs. X
• ZW vs. ZZ
• diploid vs. haploid.

19
Chapter 15The Chromosomal Basis of Inheritance

• Barr Bodies

20
Chapter 15The Chromosomal Basis of Inheritance

• Barr Bodies
• A mammalian cell needs only one active X
  chromosome.
• In females, one of the two Xs is inactivated.

21
Chapter 15The Chromosomal Basis of Inheritance

• Genomic Imprinting

22
Chapter 15The Chromosomal Basis of Inheritance

• Genomic Imprinting
• Individual genes may also be inactivated. Often
  this is done preferentially to the maternal or to
  the paternal copy of the gene.

23
REPRODUCTIVE COMPETITION BETWEEN MALES AND
FEMALES

• DAD DAD
• MOM MOM MOM
• KID KID KID KID KID KID

24
Easygoing kids make moms job easier. Mom has
more kids.

• DAD DAD
• MOM MOM MOM
• KID KID KID KID KID KID

25
Difficult kids make moms job harder. Moms have
fewer kids. Dads kids do better.

• DAD DAD
• MOM MOM MOM
• KID KID KID KID KID KID

26
Genomic imprinting allows genes to have different
effects based on whether they are passed through
mom or through dad.

• DAD DAD
• MOM MOM MOM
• KID KID KID KID KID KID

27
Chapter 15The Chromosomal Basis of Inheritance

• Chromosomal Mutations

28
Chapter 15The Chromosomal Basis of Inheritance

• Chromosomal Mutations
• Alterations in chromosome number or structure
  cause some genetic disorders.

29
Chapter 15The Chromosomal Basis of Inheritance

• Chromosomal Mutations
• Aneuploidy
• Abnormal chromosome number.

30
Chapter 15The Chromosomal Basis of Inheritance

• Chromosomal Mutations
• Polyploidy
• More than two complete sets of chromosomes.

31
Chapter 15The Chromosomal Basis of Inheritance

• Chromosomal Mutations
• Deletion
• Duplication
• Inversion
• Translocation.

32
Chapter 15The Chromosomal Basis of Inheritance

• Extranuclear Genes

33
Chapter 15The Chromosomal Basis of Inheritance

• Extranuclear Genes
• Mitochondria and chloroplasts contain some genes

34
Chapter 15The Chromosomal Basis of Inheritance

• Extranuclear Genes
• Mitochondria and chloroplasts contain some genes.
• These exhibit non-Mendelian inheritance (mother
  line only).
• .