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Exam 1 next week, 9/19, 9/20 in testing center. Covers chapters 1 through 4, with emphasis on material: from lectures through 9/13, from “Monk in the garden”, and from lab. Part multiple-choice, part short answer - emphasis on problem-solving. No time limit, but must finish that day so choose a 2-3 hr. time block. Closed book; bring calculator, #2 pencils and BLUE BOOK.
**Review sessions next week in lecture and in lab. Bring your questions!
“Problem set 2” answers due Friday, 9/13 at start of class. Also practice Ch.4 problems this week (but do not turn in): 1, 7, 16, 27, 31.
3. re. printing power point slide files: when in computer room of Brooks, please choose “handout” when asked print what and
print 6 slides/page. Do not print 1 slide per page.
The LM and LN alleles at the MN blood group locus exhibit codominance. Give the expected genotypes and phenotypes (with their ratios) of progeny from the following crosses:
a) LMLM x LMLN
b) LMLN x LNLN
A woman of blood group AB marries a man of blood group A whose father was group O. What is the probability that:
a) their 2 children will both be group A?
b) one child will be group B and the other child group O?
3. In snapdragons, red flower color (R1) is incompletely dominant to white (R2); the R1/R2 heterozygotes are pink. A red-flowered snapdragon is crossed to a white colored one. Determine the ratios of the flower colors in the progeny from a cross of an F1 with the red parent.
2 points each question part for 10 points total
Review of last lecture work.
I. Chi-square revisited: small deviation from expected yields small X2 value; this correlates with high probability that deviation is due to chance and you should NOT reject your hypothesis
II. Pedigree analysis- recessive vs. dominant traits
- solving pedigree problems
Outline of Lecture 7 work.
In all crosses discussed so far, one of two traits for a character has been dominant to the other. ie. according to Mendel’s second postulate of dominance/ recessiveness. Does the expression of all genes occur in this way? ex. Are there only two colors of hair for humans with one clearly dominant to the other? NO
I. Alleles alter phenotypes in different ways; a variety of symbols are used for alleles
II. Incomplete dominance - where neither allele is dominant
III. Codominance - both alleles in a heterozygote are expressed
IV. Multiple alleles of a gene are studied in a population
V. Lethal alleles - recessive or dominant
VI. Modification of the 9:3:3:1 ratio
Gene Symbol Conventions work.
II. Incomplete Dominance work.
III. Codominance work.
ABO Blood Groups work.
A - A antigen only
B - B antigen only
AB - Both A and B antigens
O - Neither antigen
ABO, continued work.
Biochemical Basis of ABO work.
Complexity with ABO blood groups: work. The Bombay Phenotype
HhI work. AIO HhIAIB
Bombay Phenotype: hh masks the expression of ABO (Epistasis)
About 80% of human population have the A and B antigens present in various body secretions - not only in blood.
Genetics - dominant allele, Se (Se/Se or Se/se)
In what societal application would the secretor locus have significance?
Forensic science - ABO blood typing can be performed on tissue samples other than blood.
Multiple alleles - a second example blood type
White locus in Drosophila - over 100 alleles may occupy this locus. This results in an allelic series of eye colors ranging from pure white, to light buff to yellowish pink to deep ruby.
(Table 4.3 in text)
V. Lethal Alleles blood type
Mouse coat colors blood type
Agouti x agouti
Yellow x yellow
Agouti x yellow
2/3 yellow, 1/3 agouti
1/2 yellow, 1/2 agouti
AY is dominant to A
AAY is yellow, but
AYAY is lethal
Results in 2:1 monohybrid ratio
Ex. 2 humans heterozygous for albinism and are blood type AB