Lecture # 20

 

Chromosomal sex

 

karyotying

 

Chromatin bodies

 

Barr bodies

 

Normal human females (XX)

have one chromatin body.

 

Normal human males (XY)

have no chromatin body.

 

A chromatin body is an

inactive X-chromosome.

 

Females with Turner’s

Syndrome (X) have no

chromatin body.

 

Individuals with 3 X-

chromosomes have 2

chromatin bodies.

 

Individuals with

Klinefelter’s Syndrome

(XXY) have one

chromatin body.

 

Inactivation of all but

one X-chromosome in

a cell.

 

Amniotic fluid

 

Chromatin bodies appear

in human embryos only

after the 16th day of

development.

 

X-chromosomes are

inactivated randomly.

 

Mosaic patterns in adult

organisms

 

Calico cats

Tortoise shell coat

      pattern in mice

 

Sex-linked traits

 

AY if on the X-chromosome

XB if on the Y-chromosome

 

Sex-linked traits on the

X-chromosome in males

are inherited from the

mother’s side of the

family.

 

Heterozygous females are

carriers of the recessive

expression.

 

The father determines

the sex of a child.

 

Sex-linked traits were

discovered with

white-eyed fruit flies.

 

Sex-linked traits in

humans on the

X-chromosome:

Hemophilia (“bleeder’s

            Disease”)

Colorblindness

 

Sex-linked traits in

humans on the

Y-chromosome:

Hairy earlobes

 

Sex-influenced traits are

inherited by genes on

the autosomes but the

expression of the trait

is influenced by the sex

of the individual.

 

Hormones are the basis

for the expression of

most sex-influenced traits.

 

4. Multiple Alleles

 

Allelomorphic expressions

 

Allelomorphs

 

Allele

 

If there are more than

two alleles for a locus,

the condition is called

multiple alleles.

 

Superscripts

 

DA > DB > DC > d

 

DBDC vs. DADB = DADC

 

Human hairdresser genes:

kinky>curly>wavy>straight

 

Coat color in rabbits:

wildtype>chinchilla>

  Himalayan>albino

 

Immunology

 

Antibody  

 

An antigen is an

ANTIbody GENerator.

 

Blood Type       Antigens

     AB            both A and B

     A                        A

     B                        B

     O            neither A nor B

 

IA     IB     i

 

Blood Type    Genotype

     AB                   IAIB

     A                IAIA or IAi

     B                IBIB or IBi

     O                       ii

 

Blood typing can be good

negative evidence.

 

1900               Landsteiner

 

 Blood

 Type      Antigens          Antibodies

    AB    both A and B    neither a nor b

    A             A                         b

    B              B                          a

    O     neither A nor B     both a and b

 

The reaction that occurs

between the donor’s

antigens and the

recipient’s antibodies

 

Type AB blood is the

universal recipient.

 

Type O blood is the

universal donor.

 

Rejection

  

Rh system

 

Rh      rh

 

Rhesus monkeys

 

Rh-positive: RhRh or Rhrh

Rh-negative: rhrh

   

In the second and

subsequent children born

to an Rh-positive man

and an Rh-negative woman.

   

Erythroblastosis fetalis

   

Rhogam

   

Inbreeding is the mating

of closely related

individuals.

   

Outbreeding is the mating

of unrelated individuals.

 

Heterosis or Hybrid Vigor