Chapter 11: Mendelian Genetics Flashcards Preview

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Flashcards in Chapter 11: Mendelian Genetics Deck (52):

Mendel studied inheritance in ___?

-pea plants


Mendel's peas: What three things did he note in the pea plants he studied ?

1. many varieties 2. distinct heritable characteristics 3. different traits


Mendel's peas: Mendel cross pollinated what kind of breeding pea varieties?

- true breeding


Mendel's peas: What kind of breeding are the Parental generations?

- true breeding


Mendel's peas: How would you describe the F1 generation offspring from the crossing of the P1's?

- hybrid


Mendel's peas: F1 hybrids will ____ to produce the F2 generation?

- self pollinate


Mendel's peas: Quantitative analysis of the F2 generation of plants revealed two fundamental principles of heredity which were what?

1. law of segregation 2. law of independent assortment


Principle of uniformity encompasses what kind of breeding?

true breeding/pure breeding


What is cross fertilization called?



What is self fertilization called?



Monohybrid cross?

A monohybrid cross is a mating between individuals who have different alleles at one genetic locus of interest. The character being studied in a monohybrid cross are governed by two alleles for a single locus.

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What is a reciporical cross? 

In genetics, a reciprocal cross is a breeding experiment designed to test the role of parental sex on a given inheritance pattern.[1] All parent organisms must be true breeding to properly carry out such an experiment. In one cross, a male expressing the trait of interest will be crossed with a female not expressing the trait. In the other, a female expressing the trait of interest will be crossed with a male not expressing the trait...aka reciporical 



genetic constituiton of an organism 



- an observable trait or set of traits (structural and functional) of an organism produced by the interaction between its genotype and the environment. 


The characteristics of an individual are called?

- traits/characters which are heritable...they are transmitted from generation to generation....these are under the control of genes. 



- genotype only gives the potential for developing a particular phenotype (range) and the extent to which one exhibits it is determined by an interaction with the environment which places it on that range. 

- relevence of the environment varies 


True breeding or pure breeding strains?

- strains in which the trait under investigation remained unchanged from parent to offspring for many generations 


Recessive alleles? 

Dominant alleles? 

- the phenotype of these alleles only show up if the organism is  a double homozygous for these alleles

-the phenotype of these alleles will be expressed as long as one is present thereby masking the recessive can also be present homozygously 


Homozygous vs heterozygous for an allele?

- individuals that contain two copies of the same specific allele of a gene are said to be this for that gene. 

- individuals that have two different alleles of a particular gene are said to be this. 


What the heck is a punnett square?Do you even know? 

The Punnett square is a diagram that is used to predict an outcome of a particular cross or breeding experiment

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Punnett squares show the various possibilities of the union of ____ gametes and of ___gametes.

- parental, F1


Do we ever do a punnett square larger than a monohybrid one?

- nope and if you do you're cray


Mendel conclusions from crosses:

- Reciprocal cross results were always the same

- F1 progeny will exhibit traits of one of the parents indicating the dominance of one allele (100% heterozygous)

- In the F2 progeny the parental trait that disappeared in the F1 generation reappeared. The rait seen in the F1 (the dominant trait) was always found in the F2 generation at about 3x as common vs the recessive trait. aka progeny showed all parental traits. 

(1:2:1 for genotype) 


Describe the principle of segregation!

- recessive traits which are masked in the F1 from a cross between two true breeding strains reappear in a specific proportion in the F2. 

- aka two members of a gene pair (alleles) seggregate (separate) from each other during the formation of meiosis. As a result half of the gametes carry one allele and the other half have the other allele. The progeny are created by the random combinations of gametes from the two parents. 



- specific location of a gene on a chromosome 


Gene segregation parallels the what?

separation of homologus pairs of chromosomes at anaphase 1. 


Probability Formula #1: 

-If you wanted to know what the chances were for you to have a girl how would you calculate this? 

- what about picking a club from a deck of cards?

** express the formula and explain the variables**

Probability= a(number of favourable cases)/ n( total number of possible cases) 

1. P(girl)= 1/2=0.5=50%

2. P(club)= 13/52=1/4=25%


What the heck is the Hardy-Weinberg equation?

- name the formula 

- describe it using alleles A and a 

H-W equation: 

  • p2+2pq+q2= 1 
  • p=  frequency of allele A in the population
  • p2=  represents the frequency of the homozygous genotype AA 
  • q2= represents the frequency of the homozygous genotype aa 
  • 2pq= represents the frequency of the heterozygous genotype Aa 
  • furthermore..... p+q=1 .... the sum of the allele frequencies for all the alleles at the locus must be 1 
  • If the p and q allele frequencies are known, then the frequencies of the three genotypes may be calculated using the Hardy-Weinberg equation. In population genetics studies, the Hardy-Weinberg equation can be used to measure whether the observed genotype frequencies in a population differ from the frequencies predicted by the equation. 


The H-W equation calcualtes what? (general)

genetic variation of a population at equilibrium



What does the H-W equlibrium principle state? 

the amount of genetic variation in a population will remain constant from one generation to the next in the absence of disturbing factors.


What is the Sum rule ? (Probability Rules) 

L> either or rule

- probability of either one of several mutually exclusive events occuring is the SUM of their individual probabilties.  

aka: P(A or a)= P(A) + P(a) 


Experiment 1:   A single 6-sided die is rolled. What is the probability of rolling a 2 OR a 5? [single die]Probabilities:  

P(2)  =  1/6

P(5)  =  1/6

P(2 or 5)  =  P(2)  +  P(5)   =  1/6  +  1/6  


= 1/3



Rules of Probability: 

-Product Rule?

L> And rule

- probability that two independent events will BOTH occur, is the product of their individual probabilities  

L> ex: If you role a die twice, what is the probability of getting a six and a four (in that order) ? 

p= (1/6)(1/6) = 1/36


Rules of Probability: 

-Binomial Theorem? 

L>equation?(when do you use it as well)

- porbability that some arrangement will occur in which the final order is NOT SPECIFIED. 

- used for unordered events 

  • P=(n!/s!t!)psqt 
  • != factorial
  • s+t=n
  • p+q=1


Rules of probability: 

-Binomial Theorem? 

ex: What is the probability that a family with 6 kids will have 5 girls and 1 boy?


 != factorial;  


P= (6x5x4x3x2x1/([5x4x3x2x1][1x1]))(1/2)5(1/2)

P= (720/120)(1/2)6 

P= 6(1/2)6 

P= 6/64


What is the probability that a family with 6 kids will have 4 girls and then 1 boy and then 1 girl? (ordered hint)

- product rule 

- P= (1/2)x(1/2)x(1/2)x(1/2)x(1/2)x(1/2)= 1/64



- a cross of an individual expressing the dominant phenotype with an unknown genotype with a homozygous recessive individual to determine its genotype 

ex: A = dominant, a= recessive

A- x aa = geneotype found via exammining offspring  

F1= 1:1 = Aa and aa aka unknown parent= Aaheterozygous 


F2: all Aa..therefore uknown parent was homozygous AA


Loss-of function mutation?

- mutation in agene causes the protein product of that gene to be absent, partially functional, or nonfunctional then the associated biological function is likely to be lost or decreased significantly (usually these are recessive)


null mutation?

- mutation that results in no protein or a protein with no function 


Explain the Principle of independent assortment!

-the factors for different pairs of traits assort independently of one another. aka pairs of alleles for a gene on different chromosomes will segregate independently in the formation of gametes.



- when the F1 generation are heterozygous for two pairs of alleles at two different loci.A cross between two of these individuals is called a dihybrid cross

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what is the phenotype ratio for dihybrid crosses? (normally)



Dihybrid test cross?(ratio?)

- used to find the genotype of an individual 

ex: S-Y- x  ssyy 

1:1:1:1 ratio


Trihybrid crosses?

-used for when three pairs of alleles are segregating in other crosses.  

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Whats the formula for finding out how many phenotypic classes will be present in the F2 generation? 

- formula?





n= the number of independently assorting, heterozygous gene pairs 

mono: Ss x Ss = 21= 2

di: SsYy x SsYy = 22= 4

tri: SsYyCc x SsYyCc = 23= 8


What is the formula for finding genotypes? 





n= number of independently assorting heterozygous genes 

- mono: 31= 3

di: 32= 9

tri: 33= 27 


Formula for finding phenotypes and genotypes of multiple heterozygous F1 used in a test cross?

- the number of genotypes = the number of phenotypes 


2n= phenotypes and genotypes 

- di: AaBb x AaBb.... n=2 ...22= 4....there are four phenotypes and four genotypes ( AaBb, Aabb, aaBb, aabb)


The formulas to find genotypes and phenotypes expected from self crosses of heterozygotes can only be used if what is present?

genes show complete dominance 


Chi-square (x2) test??(theory)

- test the significance of any deviation of the observed results from the expected as predicted by the null the significance due to chance or something other than chance?


Chi-square test:

What is the Goodness of fit test?

X2= Σ(O-E)2/E

O= observed phenotypes 

E: expected number of phenotypes to be seen (based on phenotype test cross: 1:1:1:1.....di: 9:3:3:1......3:1 mono)

- assumptions: 

1.each allele is dom or recessive 

2. segregation of alleles 

3.independent assortment 

4. fertilization is random 


Chi-square test:

Samples are distributed among ___ categories. X2 values are not___? What distribution curve do you use for this test?

- discrete categories

- not probabilities 

- Chi square distribution curve: degrees of feedom (# categories - 1)


What does a chi-square table include? (calculations)

- observed phenotypes

- expected phenotypes

- difference between the two ( O-E) 

- difference squared 

- difference divided by expected 

- totals of osberved , expected and difference. 


Rejection rule for Chi-square test?

If the probability of obtaiing the observed Chi square is greater than 5/100...aka alpha= 0.05.... P>0.05.... the deviation is not statistically sig and the Ho is retained....(the observed data  does not differ significantly from the expected)