7.1 Chromosomes and Phenotype Set up Cornell Notes on pg. 81 Topic: 7.1 Chromosomes and Phenotype: Autosomal Genetic Disorders Essential Questions: 1.Why

7.1 Chromosomes and PhenotypeSet up Cornell Notes on pg. 81

•Topic: 7.1 Chromosomes and Phenotype: Autosomal Genetic Disorders

•Essential Questions:

1.Why is it impossible to have a “carrier” of an autosomal dominant disorder?

2.1 Atoms, Ions, and Molecules

7.1 Chromosomes and Phenotype: Autosomal Genetic Disorders

KEY CONCEPT The chromosomes on which genes are located can affect the expression of traits.

1. Why is it impossible to have a “carrier” of an autosomal dominant disorder?

7.1 Chromosomes and Phenotype

P. 80 Video Notes

Autosomal Recessive Disorder

Albinism

Treacher-Collins Syndrome


KEY CONCEPT The chromosomes on which genes are located can affect the expression of traits.


• Many human genetic disorders are caused by autosomal genes, and can be predicted the same as flower color, or Pea shape

• Autosomal genetic disorders: disorders that have no relation to the sex of an individual• Can be male or female in equal proportions

Ex: Albinism


• Any offspring with two recessive genes (cc) will have the disease/disorder

C c

C

c cc

Cc

Cc

CC Ex: Cystic Fibrosis


– A carrier is heterozygous (Cc) for a recessive disorder and does not show any signs or symptoms, but can pass on the disorder to their offspring

– Please label each box with: Carrier/Disorder/Normal

C c

C

c cc

Cc

Cc

CC*carrier

*carrier Disorder

Ex: Cystic Fibrosis

Normal


Video: Autosomal Recessive Disorders (4m52s)

Pg. 80 Take at least 10 bullets


– Albinism is a autosomal recessive disorder characterized by a lack of pigment in skin, hair, and eyes (race/gender does not matter!!!!)

– Can affect ANY animal in the animal kingdom





A a

A

A

A a

a

a

Genotype:Phenotype:Carriers?:Albinism?:Are either of the parents albino?

Genotype:Phenotype:Carriers?:Albinism?:Are either of the parents albino?

mom mom

dad dad

Please label: normal/carrier/disorder


A a

A

A

A a

a

a

AA Aa*carrier

AA Aa*carrier

Genotype: AA, AaPhenotype: •O% albino•100% non-albinoCarrier?: 50% carrierAlbinism?: 0% albinoParents?: Neither parent is albino

Aa*carrier

aa*disorder

Aa*carrier

aa*disorder

Genotype: Aa, aaPhenotype: •50% albino•50% non-albinoCarrier?: 50% carrierAlbinism?: 50% albinoParents?: Father is albino


Both Mom and Dad have to either have the disorder or be carriers for offspring to be affected with an autosomal recessive disorder!


Video: ABC’s Special Report: Albinism- Caught between light and dark (6m54s)

• 5-7 bullets• NON TRADITIONAL NOTES

– Social issues?– Physical/Health issues?– Any other notations you make


• Autosomal DOMINANT Disorders: any offspring with a dominant allele will have the disorder– Dominant disorders are uncommon– No carriers! ( Hh- would show the trait)

H h

H

h

*anywhere there is an H the child will have the disease


Huntington’s disease is a autosomal dominant disorder in which nerve cells in certain parts of the brain waste away, or degenerate. The disease is passed down through families.

Causes•Huntington disease is caused by a genetic defect on chromosome 4. The defect causes a part of DNA, called a CAG repeat, to occur many more times than it is supposed to. Normally, this section of DNA is repeated 10 to 28 times. But in persons with Huntington disease, it is repeated 36 to 120 times.•As the gene is passed down through families, the number of repeats tend to get larger. The larger the number of repeats, the higher your chance of developing symptoms at an earlier age. Therefore, as the disease is passed along in families, symptoms develop at younger and younger ages.

Normal brain HD brain


Huntington’s Disease

H h

H

h


Genotype:

Phenotype:


Huntington’s Disease

H h

H

h


HH Hh

Hhhh

Disorder

Disorder

Disorder

Genotype:HH, Hh, hh

Phenotype:75% Huntington’s Disease25% non-H’s D


Treacher Collins Syndrome is an autosomal Dominant disorder.It can lead to the person having no cheekbones or very small cheekbones (so the eyes droop), and they may also have a cleft palate, under developed ears, and an very small jaw.


If Mom or Dad have the disorder 50/50 chance the offspring will also have the disorder.

T t

t

t

Tt*disorder

tt

Tt*disorder

tt

Genotype: Tt, ttPhenotype:•50% will have TCS•50% non-TCS

Genotype:Phenotype:


Video: Ashley’s Story- Treacher Collins Syndrome (5m11s)

• 5-7 bullets• NON TRADITIONAL NOTES

– Social issues?– Physical/Health issues?– Any other notations you make


How did Ashley inherit the disease if neither of his parents had it?

• This condition is caused by a change in a single gene. The Treacher Collins syndrome gene is on chromosome 5. Over 50 different changes in the gene are known to cause Treacher Collins syndrome.

• In about 60% of people with Treacher Collins syndrome the change in their gene happened for the first time in them. This means that there is little chance of this person’s parents or brothers or sisters having any children with Treacher Collins syndrome.

In about 40% of people with Treacher Collins syndrome one of their parents also has the same gene chance.

7.1 Chromosomes and PhenotypeSet up Cornell Notes on pg. 83

•Topic: 7.1 Chromosomes and Phenotype: Sex-linked Genes

•Essential Questions:

1. Describe how Sex-linked genes are expressed differently in men than women.

2.1 Atoms, Ions, and Molecules

7.1 Chromosomes and Phenotype: Sex-linked Genes

1. Describe how Sex-linked genes are expressed differently in men than women.


• 82Punnett Square work


Gene expression is often related to whether a gene is located on an autosome or a sex chromosome

– Sex chromosomesSex chromosomes: determine gender• Y chromosome genes in mammals are responsible for male

characteristics.• X chromosome genes in mammals affect many traits.

– Autosomes: all other chromosomes- no relation to gender• All genes that Mendel studied were autosomes• Most traits are the result of autosomal genes

REVIEW


• Because the X and Y chromosomes have different genes, sex-linked genes have a pattern of expression that is different from autosomal genes

Crossing 2 heterozygous

• 25% will have white eyes as expected (similar to autosomal findings)

• BUT ALL will be male!


• Female mammals have an XX genotype.

– Expression of sex-linked genes is similar to autosomal genes in females.

X XX X

X X

A A

A

aa

a

*carrier

*disorder


– Males have no second copies of sex-linked genes, so ALL of a male’s sex-linked genes are expressed

– Even if all the sex-linked genes of a male are recessive, they will be expressed

– There is no second “X” to mask the recessive gene

X YX Y

A

a

*disorder


Genes on sex chromosomes are called sex-linked genes.

X XX

X

Y

X

X X

X Y YX

A A

A A A A A

A A

• % chance of male offspring showing recessive trait?

• % chance of female offspring showing recessive trait?



X XX

X

Y

X

X X

X Y YX

A A

A A A A A

A A


• 0%• % chance of

female offspring showing recessive trait?

• 0%



X XX

X

Y

X

X X

X Y YX

A a

A A A A a

A a





X XX

X

Y

X

X X

X Y YX

A a

A A A A a

A a


• 50%


• 0%


Examples of sex linked disorders

• Color-blindness• Hemophilia• Muscular Dystrophy


Color blindness is a recessive sex-linked trait.

A non-colorblind man marries a woman who is a carrier for color blindness. Predict the heredity of their offspring. (Use “b” to show color blindness)

Phenotypes:

Male-______% colorblind______% Non-colorblind______% Carrier

Female-______% colorblind______% Non-colorblind______% Carrier


Color blindness is a recessive sex-linked trait.

A non-colorblind man marries a woman who is a carrier for color blindness. Predict the heredity of their offspring. (Use “b” to show color blindness)Phenotypes:

Male- 50% Colorblind50% Non-CBNO CARRIERS

Female- 0% Colorblind100% Non-CB50% carrier

X X

X

Y

B b

BX X X X

X XY Y

B B

B

B b

b


Sex Linked Inheritance (5m15s)

• https://www.youtube.com/watch?v=H1HaR47Dqfw


A white-eyed male fly mates with a red eyed female fly to produce: 24 white-eyed males, 27 white-eyed females, 26 red-eyed males, and 23 red-eyed females. Can this trait be sex-linked? Prove your answer by completing 2 Punnett squares. (r=white eyes)

Phenotypes:

Male-____% Red eyes____%White eyes

Female-____% Red eyes____%White eyes


A white-eyed male fly mates with a red eyed female fly to produce: 24 white-eyed males, 27 white-eyed females, 26 red-eyed males, and 23 red-eyed females. Can this trait be sex-linked? Prove your answer by completing 2 Punnett squares. (r=white eyes)

Phenotypes:

Male- 100% Red eyes0% White eyes

Female- 100% Red Eyes0% White eyes

X X

X

Y

R R

rX X X X

X XY Y

R r

R

R r

R

White eyes is a recessive sex-linked trait.


White eyes is a recessive sex-linked trait.A white-eyed male mates with a red eyed female to produce: 24 white-eyed males, 27 white-eyed females, 26 red-eyed males, and 23 red-eyed females. Can this trait be sex-linked? Prove your answer by completing 2 Punnett squares. (r=white eyes)

Phenotypes:

Male- 50% Red eyes50% White eyes

Female- 50% Red Eyes50% White eyes

X X

X

Y

R r

rX X X X

X XY Y

R r

R

r r

r


Sex Linked Genes (8m9s-10m17s)

• https://www.youtube.com/watch?v=CBezq1fFUEA


Sex Linked inheritance Penny Lab

BackgroundThe relationship between genotype and phenotype in sex-linked genes differs from that in autosomal genes. A female must have two recessive alleles of a sex-linked gene to express a recessive sex-linked trait. Just one recessive allele is needed for the same trait to be expressed in a male.

PurposeTo model the inheritance pattern of sex-linked genes based on probability

MaterialsCoins (2) – prelabeled Genetic cross (given by teacher)


Sex Linked inheritance Penny LabProcedure

1) One coin represents the egg cell and the other coin represents the sperm cell. In the Data/Results section of your lab, record the genetic cross you were given. 2) Fill in the Punnett square for the given genetic cross. 3) Determine the expected genotypic and phenotypic ratios. Use the key: A = does not have trait a = has the trait 4) Flip the two coins and record the genotype of the “offspring” in the count (tally marks) row of the data table under the appropriate given possible genotype. 5) Repeat step 4 until you have modeled 100 genetic crosses.

6) Calculate the total number of each genotype and the % of each type in your data table.


– X chromosome inactivation randomly “turns off” one X chromosome

– Ensures that females, like males, have one functional copy of the X chromosome in each body cell

– Like a flip of a coin to determine which “X” turns off

P. 83


X Inactivation (6m22s)

• https://www.youtube.com/watch?v=Y9vXhmI5FXM


X

• X Chromosome inactivation example: Tortoiseshell and Calico Cats (tend to always be female)

• The female cats have white fur; and black (b) oror orange fur (B) alleles on their X Chromosomes- these will be expressed randomly

• Males have white fur; and one sex-linked gene for either black (b) or orange (B) fur


Males only have one X chromosome so one color will be present

Female cats have two X chromosomes.

•Each patch of fur can be different depending on which X chromosome “turns off”

X YR

X YB

X X X X X XB B R R B R

B R B R


X X

X

Y

B B

R X X

B RX-chromosome inactivation

Black


X X

X

Y

B B

R X X

B RX-chromosome inactivation

Orange


X X

X

Y

B B

R X X X X

X Y X Y

B R RB

B B

Calico Calico

Black Black


X X

X

Y

B R

B

Answer the following questions:


• What are the chances of getting a black cat?• What are the chances of getting an orange, male cat?• What are the chances of a male cat being black? • What are the chances of a female being calico?

Answer the questions about your cat cross:


X X

X

Y

B R

B X X X X

X Y X Y

B B RB

B R

CalicoBlack

Black Orange


• What are the chances of getting a black cat?• 50%• What are the chances of getting an orange, male cat?• 50%• What are the chances of a male cat being black?• 50% • What are the chances of a female being calico?• 50%

Answer the questions about your cat cross:


Sex Linked Inheritance Worksheet

Documents

7.1 Chromosomes and Phenotype Set up Cornell Notes on pg. 81 Topic: 7.1 Chromosomes and Phenotype: Autosomal Genetic Disorders Essential Questions: 1.Why