Class Notes (835,581)
Canada (509,259)
Biology (116)
BIOL 1010 (39)

LEc 28

3 Pages
Unlock Document

BIOL 1010
Igor Kovalchuk

Mendelian Genetics Lecture 28 Polygenic inheritance of skin color  Three separately inherited genes affect the darkness of skin.  For each gene, an allele for dark skin is incompletely dominant to an allele for light skin  Thus, an individual who is heterozygous for all three genes (AaBbCc) has inherited three “units” of darkness Polygenic inheritance  Human polygenic traits include o Height o Weight o Eye Color o Skin Color o Many forms of behavior Pleiotropy  Pleiotropy is the effect of a single gene on more than one characteristic  The primary result of this gene is the production of defective feathers  Secondary results are both good and bad; good include increase adaptation to warm temperatures, bad include increase metabolic rate, decreases egg-laying.  Sickle-cell anemia is a human disease originating in warm lowland tropical areas where malaria is common  Sickle-cell individuals suffer from a number of problems, all of which are pleiotropic effects of the sickle-cell allele The chromosomal basis of Mendel’s laws  The arrangements of chromosomes at metaphase I of meiosis and their movement during anaphase I account for the segregation and independent assortment of the alleles for seed color and shape  The alternatives are equally likely; F1 plants will produce numbers of eight kinds of gametes.  In the F2 generation, we see the physical explanation for Mendel’s 9:3:3:1 ratio of phenotypes Finding the genes  Between 1884 (the year Mendel died) and 1888; o Details of mitosis and meiosis were reported o The cell nucleus was identified as the location of the genetic material o “Qualities” were even proposed to be transmitted on chromosomes to daughter cells at mitosis  In 1903 Walter Sutton and Theodore Boveri formally proposed that chromosomes contain the genes  The Chromosome Theory of Inheritance is one of the foundations of genetics and explains the physical reality of Mendel’s principles of inheritance.  The location of many genes (Mendel’s factors) was determined by Thomas Hunt Morgan and his coworker in the early 1990s.  Morgan experimental organism was the fruit fly  Fruit flies are ideal organisms for genetics, having a small size, ease of care, susceptibility to mutation and short (7-9 day) generation time  The role of chromosomes in determination of sex was deduced by Morgan from work on fruit flies  During Metaphase I, homologous chromosomes will line up. o A karyotype can be made by cutting and arranging photomicrographs of the homologous chromosomes thus revealed at Metaphase I o Two types of chromosome pairs appear  Autosomes resemble each other in size and placement of centromere, for example pars of chromosome 21 are the same size, while pairs of chromosome 9 are different size from pair 21  Sex Chromosomes may differ in their size, depending on the species of the organism they are from.  In humans and fruit flies, males have smaller sex chromosomes, termed the Y, and a larger one, termed the X.  Males are thus XY and termed heterogametic  Females are thus XX, and termed homogametic  Morgan disc
More Less

Related notes for BIOL 1010

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.