day 11 february 16th chapter 6 + 7

8/3/2019 Day 11 February 16th Chapter 6 + 7

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February 16th

Chapter 7

Presidents Day 2/21 (no class)

Exam 2 2/23 (Chapters 3, 5, 6, firsthalf of 7)



Turner Syndrome: X_

98% of the time this condition occurs the fertilized egg is spontaneously

aborted long before a baby can come to term



Klinefelt er Syndrome: XXY



XYY Males



XXX Females



A non-disjunction is caused by a failure of chromosomes t o separat e properly during

meiosis. Which non-disjunction list ed below will cause deat h of t he zygot e in t he womb?

1. Three copies of chromosome 21(small chromosome)

2. Two copies of t he X chromosome

3. Two copies of t he Y chromosome4. Three copies of chromosome 1

(large chromosome).



Chapter 7: Mendelian Inheritance

Family resemblance: how traits are inherited

Lect ures by Mark Mant euffel, St . Louis Communit y College; Clicker Questions by K rist en Curran, Universit y of Wisconsin-Whit ewat er



(note the hand position of each twin)



Where do we begin

and our parents end?



Selective Breeding: Observing Heredit y

Observations are easy figuring out how is hard!!!



Are any human traitsdetermined by a single gene?

Traits that are determined by theinstructions a person carries at onegene are called single-gene traits.

9,000 human traits



Other traits, such

as height, hair

color, and eye

color, are a bit

trickier.



What did scientists know, at the time?

Made observations

Previous science

Did experiments

Made predictions

Nature of Science



Sexist view of science?



Plants could be self-fertilized or

cross-fertilized



True-Breeding



Mendel f igured out t he rules of genetics byworking wit h pea plant s. Why were t hese

plant s a good t ool for Mendel t o use t oanswer his questions about inherit ance?

1. Individual plant s could be self-fertilized orcross-fertilized wit h ot her individuals.

2. They grew quickly (short generation time).

3. Clearly def ined t rait s (yellow vs. green) were

observed.

4. A ll of t he above.



7.4 Segregation: youve got two

copies of each gene but put onlyone copy in each sperm or egg.



A dominant t rait

masks t he effect of a recessivet rait .



Three Ideas Mendel Used for ExplainingThis Patt ern of Inherit ance

1) Each parent put s int o every sperm or egg it makes a single set of inst ructions forbuilding t he t rait .

2) Offspring t hus f ind t hemselves wit h t wocopies of t he inst ructions for any t rait (called alleles).

3) The act ual t rait produced by an individual

depends on t he t wo copies of t he gene t hat t hey inherit from t heir parent s.

homozygous and het erozygous



Which answer below is an

example of a het erozygousplant ?

1. Two copies of t he purple allele2. Two copies of t he whit e allele

3. One copy of t he purple allele and one

copy of t he whit e allele4. 1 and 2

5. A ll of t he above



7.5 Observing an individuals

phenotype is not sufficientfor determining its genotype.



Phenot ypes and Genot ypes

The out ward appearance of an individual is called t heir phenotype.

Underlying t he phenot ype is t hegenotype.

This is an organisms genetic composition.



Surprise???



How do we analyze and predict t heout come of crosses?

A ssign symbols t o represent t he different variant s of a gene.

Generally we use an uppercase lett er for t hedominant allele and lowercase for t herecessive allele.

If we dont know which of the two possible

genotypes the pigmented individual is, we canwrite A _, where the _ is a placeholder for theunknown second allele, whose identity we arentcertain of.



Probabilit y has a cent ral role ingenetics for t wo reasons:

The f irst is a consequence of segregation.

The second reason is t hat fertilization, t oo,

is a chance event .

7.6 Chance is important in genetics.



Probabilities

A ny gamet e produced by an individual het erozygous for a t rait has a 50%probabilit y of carrying t he dominant allele

and a 50% probabilit y of carrying t herecessive allele.



Probabilities

If a male is het erozygous for albinism ( A a)and a female is homozygous for albinism(aa), what is t he probabilit y t hat t heir childwill be homozygous for albinism (aa)?



If an albino woman marries a man t hat ishet erozygous for albinism, what is t he

probabilit y t hat t hey will have an albinochild?

1. 0%

2. 25%

3. 50%

4. 75%5. 100%



A nalyzing Which Individuals Manifest t heTrait and Which Do Not



Why do breeders value pedigreed horses and dogs

so much?



7.10 Whats your blood type?

Some genes may have morethan two alleles.

It can be O, A, B, or AB



Multiple A llelism

in which a single gene has more t han t woalleles

each individual still carries only t wo alleles



Inherit ance of t he A BO Blood Groups

A , B, and O alleles

The A and B alleles are bot h complet ely

dominant t o O.

The A and B alleles are codominant t o eachot her.

Individuals can be one of four different bloodt ypes: A , B, A B, and O.

day 11 february 16th chapter 6 + 7

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