7.1 chromosomes and phenotype set up cornell notes on pg. 77 topic: 7.1 chromosomes and phenotype:...

7.1 Chromosomes and PhenotypeSet up Cornell Notes on pg. 77

•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

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 porportions

Ex: Albinism


– Autosomal recessive disorder: Any offspring with two recessive genes (cc) will have the disease/disorder

C c

C

c cc

Cc

Cc

CC

Disorder

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

C c

C

c cc

Cc

Cc

CC*carrier

*carrier Disorder

Ex: Cystic Fibrosis


Video: Autosomal Recessive Disorders (4m52s)

Pg. 76 Take at least 10 bullets


– Albinism is a autosomal recessive disorder characterized by a lack of pigment in skin, hair, and eyes.


A a

A

A

A a

a

a

Fill out these punnett sqs. What is the probability that the offspring will have albinism?

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

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

mom mom

dad dad


A a

A

A

A a

a

a

AA Aa*carrier

AA Aa*carrier

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

Aa*carrier

aa*disorder

Aa*carrier

aa*disorder

Genotype: AaPhenotype: •50% albino•50% non-albinoCarrier?: 50% carrierParents: 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)


• 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

Hh hh

Hh hh

Disorder

Disorder


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


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)

7.1 Chromosomes and PhenotypeSet up Cornell Notes on pg. 79•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.


Genes on sex chromosomes are called sex-linked genes. – Y chromosome genes in mammals are responsible for

male characteristics.– X chromosome genes in mammals affect many traits.


• Gene expression is often related to whether a gene is located on an autosome or a sex chromosome– Sex chromosomesSex chromosomes: determine gender– Autosomes: all other chromosomes- no relation to gender

• All genes that Mendel studied were autosomes• Most traits are the result of autosomal genes


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


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

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

Only 1 Y, and 1 X


• Female mammals have an XX genotype.

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

– 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


X

• X Chromosome inactivation example: Tortoiseshell and Calico Cats (always 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


X X

X

Y

b b

B X X

B bX-chromosome inactivation

Black


X X

X

Y

b b

B X X

B bX-chromosome inactivation

Orange


X X

X

Y

b b

B X X X X

X Y X Y

B b bB

b b


Males only have one X chromosome so one color will be present (recessive OR dominant)

Female cats have two X chromosomes. •Each patch of fur can be different depending on which X chromosome “turns off”


X X

X

Y

B b

b X X X X

X Y X Y

B b bb

B b

Calico Black


• What are the chances of getting a black cat?• 50% black cats• What are the chances of getting an orange, male cat?• 25% orange male cat• What are the chances of a male cat being orange? • 50% male orange cat• What are the chances of a female being calico?• 50% female calico

Answer the questions about your cat cross:


Color blindness is a recessive sex-linked trait.

A normal 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 normal 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% Colorblind50% Non-CB50% carrier

X X

X

Y

B b

BX X X X

X XY Y

B B

B

B b

b


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 test crosses. (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 test crosses. (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 1-2 test crosses. (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

7.1 chromosomes and phenotype set up cornell notes on pg. 77 topic: 7.1 chromosomes and phenotype:...

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