MBG 3060 Study Guide - Winter 2018, Comprehensive Midterm Notes - Locus Genetics, Allele, Genotype
12 Oct 2018
School
Department
Course
Professor
MBG 3060
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Defined basic terminology
•
Recognized that genes come in different forms (alleles) and diploid organisms
has 2 alleles for each inherited characteristic
•
Each spermatozoa and oocyte carry one allele for each characteristic since
allelic pairs segregate during meiosis
•
When two alleles are different, one is expressed and one is masked
•
Mendel:
There are alternate forms of genes
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For each inherited characteristic, an organism has 2 alleles
•
Laid groundwork for modern day genetics
○
= oversimplified view!
•
Law of Segregation: allelic pairs segregate during gametic formation and the paired
condition is restored by random fusion of gametes at fertilization
Most overworked word
•
Locus (location on chromosome) with 2 alleles in diploid organisms
○
An allele or variant of a gene
○
Can mean….
•
"Gene"
Used to represent possible inheritance of alleles
•
Punnet Square
Female
B
b
Male
B
=BB
=Bb
b
=Bb
=bb
Female
F(B)=0.5
F(b)=0.5
Male
F(B)=0.6
F(BB)=0.30
F(Bb)=0.30
1. Mendelian Genetics
Monday,*January*9,*2017
11:07*AM
find more resources at oneclass.com
find more resources at oneclass.com
F(b)=0.4
F(Bb)=0.20
F(bb)=0.20
F1: Bb (x Bb)
F2: 1 BB: 2 Bb: 1 bb
Ex. Homozygotes: BB x bb
Demonstrates polymorphism or difference in alleles in the DNA sequence at a
locus in the organism's genome
•
B vs. b
Phenotypic ratio is 3:1
○
If B is dominant to b:
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WW is lethal
Ww: ww = 2:1 genotypic/phenotypic ratio
Ex. In horses, there is a lethal white overo locus in the Paint/Pinto colour
pattern
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If one genotype is lethal:
•
When two or more loci are independent of each other
○
Gametes: AB, Ab, aB, ab (1/4 each)
Offspring: 1:2:1 = AA:Aa:aa = BB:Bb:bb
F(AABB) = 1/4 X 1/4 = 0.0625 (1/16)
□
F(AaBb) = 1/2 X 1/2 = 0.25 (1/4)
□
Frequency of Genotype Combinations:
Ex. Aa Bb x AaBb
○
Used to calculate the probability or frequency of multiple different
genotypes (ex. Getting Bb or bb)
= rule of addition
Used to calculate the probability or frequency of a specific
genotype (ex. Getting AA and Bb)
= rule of multiplication
Law of Independent Segregation:
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Disrupting the "classic" 1:2:1:
Where one genotype affects multiple phenotypes
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Ex. A locus involved in insulin regulation can result in
hypoglycemia and from that condition many phenotypes can be
expressed (diabetes, peripheral circulation issues…etc)
Ex. Deafness and white coat colour in cats
Can occur with a locus that is involved with a housekeeping pathway
•
Pleiotropy
1.
Major factors affecting the expression of phenotypes from multiple genotypes:
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Recognized that genes come in different forms (alleles) and diploid organisms has 2 alleles for each inherited characteristic. Each spermatozoa and oocyte carry one allele for each characteristic since allelic pairs segregate during meiosis. When two alleles are different, one is expressed and one is masked. Law of segregation: allelic pairs segregate during gametic formation and the paired condition is restored by random fusion of gametes at fertilization. For each inherited characteristic, an organism has 2 alleles. Locus (location on chromosome) with 2 alleles in diploid organisms. Demonstrates polymorphism or difference in alleles in the dna sequence at a locus in the organism"s genome. In horses, there is a lethal white overo locus in the paint/pinto colour pattern. When two or more loci are independent of each other. F(aabb) = 1/2 x 1/2 = 0. 25 (1/4) Used to calculate the probability or frequency of multiple different genotypes (ex. Used to calculate the probability or frequency of a specific genotype (ex.
