Genetics and heredity
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Genetics and Heredity. Traits and Genes. A trait is a specific characteristic, such a eye color or height, that varies from one individual to another Today scientists call the chemical factors that determine traits genes. Are these inherited traits?. Your eye color.

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Genetics and heredity

Genetics and Heredity


Traits and genes

Traits and Genes

  • A trait is a specific characteristic, such a eye color or height, that varies from one individual to another

  • Today scientists call the chemical factors that determine traits genes


Are these inherited traits

Are these inherited traits?

Your eye color

Your hair color and texture

Your height


Are these inherited traits1

Are these inherited traits?

Your personality

Your musical, athletic, and artistic abilities


Think about this

Think about this….

  • “My parents have brown eyes, why are mine blue?”

  • “My brother is tall. Why am I short?”

  • “Why does my sister have blonde hair while mine is brown?”


Alleles

Alleles

  • The different forms of a gene are called alleles. For example, the alleles for a tall plant could be TT or Tt

  • The principle of dominance states that some alleles are dominant and others are recessive.


These are questions that gregor mendel tried to answer

These are questions that Gregor Mendel tried to answer..

  • Born in 1822 in Austria

  • 1843 – Studied Theology

  • 1846-Studied Science at the University of Vienna

Father of Genetics


Mendel s studies led to

Dominant (H)

Homozygous (HH or hh)

Genotype (HH, Hh or hh)

Purebred (HH or hh)

Recessive (h)

Heterozygous (Hh)

Phenotype (blonde, brown, red)

Hybrid (Hh)

Mendel’s studies led to:


Mendel s studies led to1

Fertilization- during sexual reproduction, male and female reproductive cells join

True breeding- when allowed to self-pollinate, they would produce offspring identical to themselves.

Mendel’s studies led to:


Theory of heredity

Theory of Heredity

Inherited allele for purple P

Inherited allele for purple P

HOMOZYGOUSpurple flower PP


Theory of heredity1

Theory of Heredity

Inherited allele for purple flower (P)

Inherited allele for pink flower (p)

HETEROZYGOUS purple flower (Pp)


Theory of heredity2

Theory of Heredity

Inherited for pink flower (p)

Inherited for pink flower (p)

HOMOZYGOUS pink flower (pp)


Predicting heredity

PREDICTING HEREDITY


Probability

The likelihood that a specific event will occur

Probability = # of 1 times event occurs number of possible outcomes

Example: What is the probability that a tossed coin will be heads?

½ or 50%

Probability


Probability1

The First Law of Probability: the results of the first trial of a chance event do not affect the results of later trials of the same event.

In other words, no matter how many times a flipped coin lands on tails, every flip still has a ½ chance of tails.

Probability


Probability2

Second Law of Probability: The probability of two or more independent events occurring together is the product of their separate probabilities.

What is the probability that a couple will have four boys?

½ x ½ x ½ x ½ = 1/16

Probability


Punnett squares

Punnett squares can be used to predict and compare the genetic variations that will result from a cross.

Punnett Squares!


Monohybrid cross a cross that shows the possible offspring for one trait

A

a

AA

A

Aa

a

Aa

aa

Monohybrid Cross:a cross that shows the possible offspring for one trait

Aa x Aa

A: White fur

a: Brown fur

Genotypic Ratio: 1:2:1

Phenotype: 3 white:1 brown


Practice

A

A

A

a

Practice!

Cross a HOMOZYGOUS dominant female with a HETEROZYGOUS male using the same trait.

What is the genotypic ratio?

AA

AA

2:2 or 50%

What is the phenotypic ratio?

Aa

Aa

4 white fur


Dihybrid crosses cross that shows the possible offspring for two traits

BR

Br

bR

br

BR

BBRR

BBRr

BbRR

BbRr

Br

BBRr

BBrr

BbRr

Bbrr

bR

BbRR

BbRr

bbRR

bbRr

br

BbRr

Bbrr

bbRr

bbrr

Dihybrid Crosses:cross that shows the possible offspring for two traits

BbRr x BbRr

  • This shows a cross between parents hybrid for two traits: BbRr x BbRr

Fur Color: B: Black b: White

Coat Texture: R: Rough r: Smooth


Dihybrid crosses

BR

Br

bR

br

BR

BBRR

BBRr

BbRR

BbRr

Br

BBRr

BBrr

BbRr

Bbrr

bR

BbRR

BbRr

bbRR

bbRr

br

BbRr

Bbrr

bbRr

bbrr

Dihybrid Crosses

Phenotypic Ratio: # dom/dom : # dom/rec : # rec/dom : # rec/rec

  • How many of the offspring would have a black, rough coat? (#dom/dom)

  • How many would have a black, smooth coat? (#dom/rec)

  • How many would have a brown, rough coat? (#rec/dom)

  • How many would have a brown, smooth coat? (#rec/rec)

16

Phenotypic Ratio: 9:3:3:1


Dihybrid crosses1

BR

Br

bR

br

BR

BBRR

BBRr

BbRR

BbRr

Br

BBRr

BBrr

BbRr

Bbrr

bR

BbRR

BbRr

bbRR

bbRr

br

BbRr

Bbrr

bbRr

bbrr

Dihybrid Crosses

  • If mouse #1 were crossed with mouse #16, what would their offspring look like?

1

16


More complex patterns of heredity

More Complex Patterns of Heredity

  • Incomplete Dominance

  • Codominance

  • Multiple Alleles

  • Polygenic Traits

  • Sex-Linked Traits


Incomplete dominance

Incomplete Dominance

RR

WW

RW

One allele is not completely dominant over the other. The heterozygous phenotype is somewhere in between the two.


Codominance two dominant alleles are expressed at the same time

Codominance:two dominant alleles are expressed at the same time

CRCR

CWCW

CRCW


Codominance

Codominance

  • Sickle-Cell Anemia is another codominant trait.

NA

NA

NSNA

NSNA

NS

NA=Normal RBC

NS=Sickle Cell RBC

NANA

NANA

NA


Multiple alleles traits with more than 2 alleles

Multiple Alleles:traits with more than 2 alleles

  • Blood type has 3 alleles: A, B, O

  • A and B are codominant over O

  • O is recessive


Polygenic traits

Polygenic Traits

Often show a wide range of phenotypes.

For example, the wide range of skin color in humans comes about partly because more that for different genes probably control the trait.

Traits controlled by two or more genes


What are sex linked traits

What are Sex-Linked Traits?

Traits that are located on one of the sex chromosomes (XY)

Hemophilia: Failure of blood to clot

Alix and Nicholas II

Muscular Dystrophy: wasting away of muscles


Can i inherit a sex linked disease

Can I inherit a sex-linked disease?

Fathers (XY) can only pass disorders to daughters (XX)

Mothers (XX) can pass disorders to both sons (XY) and daughters (XX)

Most disorders are carried on the X chromosome, so males are more likely to inherit them.


How can i tell if i have a genetic disorder

How can I tell if I have a genetic disorder?

  • Karyotypes are a “map” of all 46 (23 pair) of chromosomes.


What s wrong with this karyotype

What’s wrong with this Karyotype?

Is this a male or a female?


Pedigree analysis

Pedigree Analysis

A pedigree shows inheritance of genetic traits over several generations

Marriage

male

female

Female Carrier

Offspring


Royal hemophilia pedigree

Royal Hemophilia Pedigree

http://www.sciencecases.org/hemo/hemo.asp


Pedigree for colorblindness

Pedigree for Colorblindness


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