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AU / Biology / BIOL 3000 / What were the pea characteristics that mendel studied?

What were the pea characteristics that mendel studied?

What were the pea characteristics that mendel studied?


School: Auburn University
Department: Biology
Course: Genetics
Professor: Michael wooten
Term: Fall 2018
Tags: crosses
Cost: 25
Name: Week Three Note
Description: Mendelian Genetics
Uploaded: 09/09/2018
6 Pages 151 Views 4 Unlocks

Week Three Notes: Mendelian Genetics 

What were the pea characteristics that mendel studied?

I. Intro- Yohan Mendel, but took the name Gregor when he joined the  monastery

A. Late 1800’s 

B. Took care of the monastery garden to help him out of depression C. Observed the different characteristics of pea plants 

D. Made a nice soup! 

E. Waited for almost 3 years, observing nearly 10 generations F. True breeding- making controls (the most important samples)  II. Mendel’s Control Experiments 

A. True breeding (pure breeding)- always passes down certain phenotypic traits to its offspring; every time you mate two specific parents, you  aways get the same result  

B. Reciprocal cross- cross between male of one strain and female of  another, and vice versa  

What does the punnett square method show?

C. Parental generation= P, Round( smooth)= R, Wrinkled= r D. Filial Generation= F1- related to one’s first offspring Don't forget about the age old question of Why do unstable isotopes happen?

E. Mendel predicted he would get blended inheritance- inherited trains  are determined randomly from a range defined by the two parents F. Mendel was lucky to pick peas because 

1. The pea traits he observed were independent

Don't forget about the age old question of What is the role of strategic marketing management?

G. Characteristics Mendel Studied in Peas

What refers to the discreet particle of inheritance?

H. First Trial 

1. One round X one wrinkled = all round F1 

I. Second Trial 

1. Crossed two offspring of the F1 from trial one (Self Cross)= some  wrinkled but most round F2

2. Mendel counted the F2 peas (3:1) 

a) 5474 round peas  We also discuss several other topics like What is the curse of tutankhamun?

b) 1850 wrinkled peas 

3. Also tallied the other traits of the peas 

a) Pod shape- 882 inflated, 299 constricted => 2.95 : 1 

b) Flower color- 705 purple, 224 white => 3.15 : 1 

c) Seed color- 6022 yellow, 2001 green => 3.01 : 1 

4. Genetic characters which control phenotypes must exist in pairs Dominance 

a) Diploid(2n)- offspring inherits one allele from each parent  b) Parents- RR x rr = Rr 

c) F1 generation- Rr x Rr = RR Rr Rr rr


s (both Rr)









We also discuss several other topics like What are the four groups around an atom?

5. Punnett Square Method We also discuss several other topics like In human biology, genetic recombination allows what?

a) 3:1 round peas 

b) Works great for very simple simple crosses, but not for multiple  traits being crossed at once…

 6. Probability Method 

a) Multiplication rule- probability of two or more independent  events(such as using multiple characteristics) occurring together is calculated by MULTIPLYING their independent probabilities (1) Used when attempting to find the probability of several  independent alleles  

(2) Look for key words such as “and” 

b) Addition rule- probability of any one of multiple exclusive events  occurring is calculated by ADDING their independent  


(1) Used when attempting to find the probability a specific event (2) Look for key words such as “or” We also discuss several other topics like What is”snipped” during vasectomy?

(3) Often used in dihybrid crosses 

c) Rr x Rr 

(1) R 1/2 x R 1/2= RR 1/4 

(2) R 1/2 x r 1/2= Rr 1/4 

(3) r 1/2 x R 1/2= Rr 1/4 

(4) r 1/2 x r 1/2= rr 1/4 

d) Results 

(1) 3/4 were round 

(2) 1/4 were wrinkled  

(3) 3:1 round peas 

e) Mendel got the results, then wrote the manuscript  

(1) He did not develop the hypothesis until after the experiment  (2) The science professionals told him to redo the paper, first  giving a hypothesis, then conducting the experiment  

(3) He then crossed the rr peas through each of the round ones  to add more to his text

III. Genetics Terminology

A. Gene- discreet particle of inheritance/ DNA sequence 

1. No such thing as a “dominant gene” 

2. Dominance is used for phenotype and trait, not genes or allele  (which are simply information

B. Allele- alternative forms of a gene ( R vs. r) 

C. Locus- physical location of any gene on a chromosome 

D. Loci- physical location of any two or more genes on a chromosome E. Genotype- combination of alleles an individual has (ex. RR, Rr, rr) F. Phenotype- physical appearance of a trait (ex. Round, wrinkled)  G. Homozygote- individual having the same alleles (RR or rr) H. Heterozygote- individual having different alleles (Rr) 

I. Dominant- phenotype 1 is dominant to phenotype 2 if the F1  heterozygote has phenotype 1 (one allele overpowers the other and is  usually characterized by a uppercase letter)

J. Recessive- phenotype 2 is recessive to phenotype 1 if the F1  heterozygote has phenotype 1 (this allele is not shown if coupled with  the other allele)

K. Mendel’s First Law- Segregation of Alleles; every individual has two  alleles for a trait (diploid). During formation of gametes, the alleles  separate and offspring randomly receive an allele from each parent.  

L. Mendel’s Third Law- Idea of Dominance; the trait from one allele will  mask the trait of another allele  

M. Monohybrid Cross- mating between two individuals with different  alleles at a single locus= one characteristic; R on one chromosome X r  on one chromosome

IV. Mendel’s Big Six- for any given allele, there are one SIX possible crosses 

Parent’s Alleles





Pure A

All AA

All AA (Dom.)

aa x aa

Pure a

All aa

All aa (Rec.)

AA x aa


All Aa

All Aa (Dom.)

Aa x Aa

F1 cross

1 AA : 2 Aa : 1 aa

3 Dom. : 1 Rec.

Aa x aa

Backcross recessive

1 Aa : 1 aa

1 Dom. : 1 Rec.

AA x Aa

Backcross dominant

1 Aa : 1 AA

All A_ (Dom.)


VI. Mendel’s Laws 

A. Mendel’s First Law

1. A single trait is controlled by a pair of alleles and those alleles are  distributed independently to the offspring

B. Mendel’s Third Law  

1. A single trait controlled by one allele can mask the trait being  controlled by another allele  

C. Mendel’s Second Law- Independent Assortment; during gamete  formation, when two or alleles are inherited, individual alleles assort  independently of one another giving different traits an equal  opportunity of occurring together

1. A total random passing of genes 

2. One gene does not affect the other 

3. Breeding multiple alleles 

4. True breeding plants for multiple traits in order to create controls results in all homozygous offspring  

5. Dihybrid cross- crossing two sets of traits 

6. Mathematician 

a) Mendel’s work on genetics reflects the Laws of Probability b) Segregation of alleles into gametes is basically like a coin toss equal probability 

c) Cystic Fibrosis  

d) For a dihybrid cross- the chances that two independent events  will occur together is the the product of their chances occurring  separately (crossing two GgFf)

(1) Gg x Gg  

(a) Chance of having Green pods (GG or Gg)- 3/4 

(b) Chance of having a Yellow pods (gg)- 1/4 

(2) Ff x Ff 

(a) Chance of having Full pods (FF or Ff)- 3/4 

(b) Chance of having Constricted pods (ff)- 1/4 

(3) Phenotypic results 

(a) Green Full= 3/4 x 3/4= 9/16 

(b) Green Constricted= 3/4 x 1/4= 3/16 

(c) Yellow Full= 1/4 x 3/4= 3/16 

(d) Yellow Constricted= 1/4 x 1/4= 1/14 

e) Trihybrid cross (RrFfPp x RrFfPp) 

(1) Chances of having Round seeds (RR or Rr)- 3/4 

(2) Chances of having Wrinkled seeds (rr)- 1/4 

(3) Chances of having Full pods (FF or Fr)- 3/4

(4) Chances of having Constricted pods (ff)- 1/4 

(5) Chances of having Purple flowers (PP or Pp)- 3/4 

(6) Chances of having White flowers (pp)- 1/4 

(7) Phenotypic results 

(a) Round and Full and Purple= 3/4 x 3/4 x 3/4= 27/64 (b) Round and Full and White= 3/4 x 3/4 x 1/4= 9/64 (c) Wrinkled and Constricted and White= 1/4 x 1/4 x 1/4=  1/64 

(d) Etc.  

7. Tips and Tricks  

a) Break bigger, more difficult problems down into smaller pieces b) Remember Mendel’s Big Six Crosses 

c) Identify the “given” in word problems first and fill in all known  information  

d) Determine Segregation Rule (genotypes) first, then multiply to  get Assortment Rules (phenotypes)

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