Download Sex-linked Traits - Perry Local Schools

Wednesday, January 2
Bell Work:
What would be the percentage of
offspring with type O blood if one
parent is type A and one Type B, both
heterozygous?
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Options for Next Year
Dual Credit Chemistry (55 on Compass Alegbra I)
Chemistry (C or higher in Biology)
Geology (C or higher in Biology)
Integrated Physical Science (Pass Biology) Good if math skills are not really good.
Eco­science (Pass Biology) Not College Prep!
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Environmental Influences
• Effects of genes can be altered by the environment
• organism’s surroundings
• The genetic make­up of an organism at fertilization determines only the organisms potential to develop and function in a certain way.
• As it develops many factors can influence whether genes are expressed or how they’re expressed
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Types of Environmental Influences
• Two types: internal and external
• Internal: varies between males and females because of hormones and structural differences • Examples Include: temperature, nutrition, genetic disease, and Cleft chin
• Age can affect gene function because internal environment changes with age.
• External: temperature, nutrition, light, chemicals and certain diseases can influence gene expression.
• Internal and External can be related!
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Environmental Influences: Examples
• External:
• Siamese cats and artic foxes coat color is affected by the temperature
• Leaves­thickness, shape, and size all depend on the amount of light they receive
• Internal:
• Feather color in peacocks
• Male­pattern baldness
• Horn­size in mountain sheep
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Boy or Girl??
• The genes on chromosomes determine the sex of a baby.
• Sex chromosomes are the only pair of chromosomes that do not always match…
• Females (XX) Males (XY)
• Females only have X’s so all eggs contain only one X
• (remember gametes or sex cells have half the number of chromosomes) • Males have 2 different sex chromosomes so ½ will be Y’s and the other half of the sperm will be X’s.
• Therefore, it is the sperm that determine the sex of the baby..
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X­Chromosome Inactivation
Since males have one ___ and one ___, they express all of Y
X
the _______________ on both chromosomes.
genes
Even if males have all ___________________ genes, they will recessive
still be ___________________.
expressed
In females (_______) one of the XX
_________________________ is turned off, this is X-chromosomes
_________________________________.
X-chromosome inactivation
Because one X­chromosome is randomly turned off, females are a ____________________ of two types of cells. One mixture
type with an active X­chromosome from ___________ and mom
one with an active X­chromosome from __________.
dad
Examples: _________________________________________________
Tortioseshell and calico cats
___________
Female calico cats have white fur and alleles for black and orange fur that are expressed randomly in some cells.
Since males have only 1 X chromosome they can have black or orange.
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Sex­Linked Traits
• Sex­linked traits are traits that are passed from parent to child on a sex chromosome
• (ALLELES ARE CONNECTED TO THE X­CHROMOSOME OR THE Y­CHROMOSOME)
• Can still have dominant and recessive alleles
• Some traits occur more often in one sex than the other
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Sex­Linked Genes cont.
• If a trait is carried on the x­chromosome and they guy receives that x­chromosome
• He inherits that trait
• Example: red/green colorblindness, more males than females have this
• X­chromosome recessive trait
• dangerous because you can not see
the colors of traffic signals.
• Common colorblindness test­chart
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• Carrier­a person who has one recessive allele for a trait and one dominant allele.
• Sex­linked traits can be hidden on carriers and passed on to the offspring.
• In the case of sex­linked traits, only females can be carriers. (If a male has the trait…he’s got the disease)
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REMINDER: Sex-Linked Traits ARE TRAITS EXPRESSED FROM A GENE LOCATED ON A SEX CHROMOSOME; (ALLELES ARE CONNECTED TO THE X­
CHROMOSOME OR THE Y­CHROMOSOME)
Examples: Hemophilia (blood disease) and colorblindness
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Practice Problems:
The human blood clotting disorder is a recessive trait (must receive both recessive alleles to express trait) which is found on the X chromosome.
XH XH and XH Xh = females without hemophilia
Xh Xh = female with hemophilia
XH Y = male without hemophilia
Xh Y = male with hemophilia
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1. A woman who is heterozygous for hemophilia mates with a male without hemophilia. What % of female offspring will be a carrier for hemophilia (heterozygous) and describe the phenotypes of the boy offspring.
% female offspring carriers: ______________
male offspring phenotypes: ______________
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2. A woman who is a carrier mates with a male with hemophilia. Will any girls have hemophilia?
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Complete Practice Problems
3 and 4
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Below is a chart listing some alien sex­linked characteristics. Use the chart to solve the genetics problems below.
• A male with yellow eyes mates with a red­eyed female. What is the chance that this couple will have a baby boy with red eyes?
Probability of baby boy having red eyes: _______ %
• A female, heterozygous for the body color trait mates with a pink male. What is the chance that these aliens will give birth to a purple­skinned girls?
Purple­skinned Girl: _______ %
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