Genetics: Multiple Alleles

Genetics: Multiple AllelesBiology 12

Joke of the day:

Multiple Alleles Many genes have

more than two alleles An individual does

not have more than two alleles for each trait but different individuals can have different pairs of alleles when multiple alleles exist

Example: Multiple AllelesHuman blood type is controlled by three

alleles : IA, IB and i. Alleles IA and IB are dominant over i IA and IB are codominant

Phenotype (blood type) GenotypesA IA IA or IAiB IB IB or IBi

AB IA IB

O ii

http://www.pennmedicine.org/health_info/images/19450.jpg

Problem: Multiple Alleles Show the cross between a mother who has type O

blood and a father who has type AB blood.

- IAi (2) IBi (2)- ratio 1:1

- type A blood (2); type B blood(2)- ratio 1:1

GENOTYPES:

PHENOTYPES:

i i

IA

IB

IAi

IBi

IAi

IBi

Problem2: Multiple AllelesShow the cross between a mother who is

heterozygous for type B blood and a father who is heterozygous for type A blood.

- IAIB (1); IBi (1); IAi (1); ii (1)- ratio 1:1:1:1

- type AB (1); type B (1) type A (1); type O (1)- ratio 1:1:1:1

GENOTYPES:

PHENOTYPES:

IA i

IB

i

IAIB

ii

IBi

IAi

http://duongchan.files.wordpress.com/2007/05/abobloodsystem.jpg

http://image.wistatutor.com/content/feed/tvcs/blood_type5B15D.jpg

Rhesus Factor The Rhesus factor, also

known as the Rh factor, gets its name from experiments conducted in 1937 by scientists Karl Landsteiner and Alexander S. Weiner.

Involved Rabbits which when injected with the Rhesus monkey’s red blood cells, produced an antigen present in the red blood cells of many humans http://content9.clipmarks.com/blog_cache/latimesblogs.latimes.com/img/E0C83714-56E5-4757-B9F1-604FCE5643C3

Rhesus Factor: The Rhesus factor is an

antigen (a protein) that exists on the surface of red blood cells. If a person has either two

(+) genes for Rh or one (+) and one (-) Rh gene, they will test Rh(+).

A person will be negative only if they have 2 (-).

It is very important in terms of babies Example: An Rh(-) mother has a Rh (+)

baby, she will make antibody against the Rh(+) fetus

Relevance of Rh Factor & ABO Typing?

To do: Blood type WS Genetics: Multiple Allele Traits WS