7.1 Chromosomes and Phenotype Set up Cornell Notes on pg. 81 Topic: 7.1 Chromosomes and Phenotype:...
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Transcript of 7.1 Chromosomes and Phenotype Set up Cornell Notes on pg. 81 Topic: 7.1 Chromosomes and Phenotype:...
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
7.1 Chromosomes and Phenotype
KEY CONCEPT The chromosomes on which genes are located can affect the expression of traits.
7.1 Chromosomes and Phenotype
• 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
7.1 Chromosomes and Phenotype
• Any offspring with two recessive genes (cc) will have the disease/disorder
C c
C
c cc
Cc
Cc
CC Ex: Cystic Fibrosis
7.1 Chromosomes and Phenotype
– 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
7.1 Chromosomes and Phenotype
Video: Autosomal Recessive Disorders (4m52s)
Pg. 80 Take at least 10 bullets
7.1 Chromosomes and Phenotype
– 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
7.1 Chromosomes and Phenotype
7.1 Chromosomes and Phenotype
7.1 Chromosomes and Phenotype
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
Both Mom and Dad have to either have the disorder or be carriers for offspring to be affected with an autosomal recessive disorder!
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
• 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
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
Huntington’s Disease
H h
H
h
*anywhere there is an H the child will have the disease
Genotype:
Phenotype:
7.1 Chromosomes and Phenotype
Huntington’s Disease
H h
H
h
*anywhere there is an H the child will have the disease
HH Hh
Hhhh
Disorder
Disorder
Disorder
Genotype:HH, Hh, hh
Phenotype:75% Huntington’s Disease25% non-H’s D
7.1 Chromosomes and Phenotype
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.
7.1 Chromosomes and Phenotype
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:
7.1 Chromosomes and 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
7.1 Chromosomes and Phenotype
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.
7.1 Chromosomes and Phenotype
• 82Punnett Square work
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
• 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!
7.1 Chromosomes and Phenotype
• 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
7.1 Chromosomes and Phenotype
– 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
7.1 Chromosomes and Phenotype
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?
7.1 Chromosomes and Phenotype
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?
• 0%• % chance of
female offspring showing recessive trait?
• 0%
7.1 Chromosomes and Phenotype
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?
7.1 Chromosomes and Phenotype
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?
• 50%
• % chance of female offspring showing recessive trait?
• 0%
7.1 Chromosomes and Phenotype
Examples of sex linked disorders
• Color-blindness• Hemophilia• Muscular Dystrophy
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
Sex Linked Inheritance (5m15s)
• https://www.youtube.com/watch?v=H1HaR47Dqfw
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
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.
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
Sex Linked Genes (8m9s-10m17s)
• https://www.youtube.com/watch?v=CBezq1fFUEA
7.1 Chromosomes and Phenotype
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)
7.1 Chromosomes and Phenotype
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.
7.1 Chromosomes and Phenotype
– 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
7.1 Chromosomes and Phenotype
X Inactivation (6m22s)
• https://www.youtube.com/watch?v=Y9vXhmI5FXM
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
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
7.1 Chromosomes and Phenotype
X X
X
Y
B B
R X X
B RX-chromosome inactivation
Black
7.1 Chromosomes and Phenotype
X X
X
Y
B B
R X X
B RX-chromosome inactivation
Orange
7.1 Chromosomes and Phenotype
X X
X
Y
B B
R X X X X
X Y X Y
B R RB
B B
Calico Calico
Black Black
7.1 Chromosomes and Phenotype
X X
X
Y
B R
B
Answer the following questions:
7.1 Chromosomes and Phenotype
• 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:
7.1 Chromosomes and Phenotype
X X
X
Y
B R
B X X X X
X Y X Y
B B RB
B R
CalicoBlack
Black Orange
7.1 Chromosomes and Phenotype
• 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:
7.1 Chromosomes and Phenotype
Sex Linked Inheritance Worksheet