day 11 september 28 chapter 7 scribd

8/4/2019 Day 11 September 28 Chapter 7 Scribd

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September 28 Chapter 7

Our 2nd Exam will be Friday, Oct 7th


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Chapter 7: Mendelian Inheritance

Familyresemblance: how traits are inherited

Lectures by Mark Manteuffel, St. Louis Community College; Clicker Questions by Kristen Curran, University of Wisconsin-Whitewater


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(note the hand position of each twin)


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Where do we begin

and our parents end?


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Selective Breeding: Observing Heredity

Observations are easy

figuring out how is hard!!!


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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


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Other traits, suchas height, hair

color, and eye

color, are a bit

trickier.


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What did scientists know, at the time?

Made observations

Previous science

Did experiments Made predictions

Nature of Science


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Plants could be self-fertilized or

cross-fertilized


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True-Breeding


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7.4 Segregation: youve got two

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


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Adominant trait

masks the effectof a recessivetrait.


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Three Ideas Mendel Used for ExplainingThis Pattern of Inheritance

1) Each parent puts into every sperm or egg itmakes a single set of instructions forbuilding the trait.

2) Offspring thus find themselves with twocopies of the instructions for any trait(called alleles).

3) The actual trait produced by an individual

depends on the twocopies of the gene thatthey inherit from their parents.

homozygous and heterozygous


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7.5 Observing an individualsphenotype is not sufficientfor determining its genotype.


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Phenotypes and Genotypes

The outward appearance of an individualis called their phenotype.

Underlying the phenotype is thegenotype.

This is an organisms genetic composition.


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Surprise???


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How do we analyze and predict theoutcome of crosses?

Assign symbols to represent the differentvariants of a gene.

Generally we use an uppercase letter for thedominant allele and lowercase for therecessive 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.


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Probability has a central role ingenetics for two reasons:

The first is a consequence of segregation.

The second reason is that fertilization, too,

is a chance event.

7.6 Chance is important in genetics.


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Probabilities

Any gamete produced by an individualheterozygous for a trait has a 50%probability of carrying the dominant allele

and a 50% probability of carrying therecessive allele.


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Probabilities

If a male is heterozygous for albinism (Aa)and a female is homozygous for albinism(aa), what is the probability that their child

will be homozygous for albinism (aa)?


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Take-home message 7.6

Chance plays a role in fertilization too.

All of an individuals sperm or eggs are

different.

Any of these gametes may be the gamete

involved in fertilization.


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Y t i t d l lli t t


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You mate a pigmented male alligator to afemale albino alligator. The clutch of babyalligators includes both pigmented andalbino individuals. What is the genotype ofthe father?

1. MM

2. Mm

3. mm

4. 1 and 2 are equally possible.

Y t i t d l lli t t


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You mate a pigmented male alligator to afemale albino alligator. The clutch of babyalligators includes both pigmented andalbino individuals. What is the genotype ofthe father?

1. MM

2. Mm

3. mm

4. 1 and 2 are equally possible.


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Analyzing Which Individuals Manifest theTrait and Which Do Not


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Why do breeders valuepedigreed horses and dogs

so much?


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7.10 Whats your blood type?

Some genes may have morethan two alleles.

It can be O, A, B, or AB


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Multiple Allelism

in which a single gene has more than twoalleles

each individual still carries only two alleles


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Inheritance of the ABO Blood Groups

A, B, and O alleles

The A and B alleles are both completely

dominant to O.

The A and B alleles are codominant to eachother.

Individuals can be one of four different bloodtypes: A, B, AB, and O.


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Why are people with type Oblood considered universaldonors? Why are those with type AB considered

universal acceptors?

day 11 september 28 chapter 7 scribd

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