Download Boy or Girl?? - Perry Local Schools

Bell Work:
A royal blue betta fish mates with a green betta fish. What is the phenotypic ratio of their offspring? Look in your notes under incomplete dominance.
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.
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
• 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
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: ______________
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
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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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Genetic Disorder
• An abnormal condition that a person inherits through genes or chromosomes
• caused by mutations or changes in a person’s DNA
• Mutations can occur during meiosis or can be passed from parent to child through an already­existing mutation.
• Mutation­a sudden change in characteristics
What’s the difference between a treatment and a cure?
• A cure eliminates the symptoms and the disease.
• A treatment controls the symptoms without eliminating the disease.
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Cystic Fibrosis
• A genetic disorder that causes thick mucus to build up in a person’s lungs and intestines­
making it hard to breathe.
• Bacteria grow in mucus and can cause infection/lung damage
• Mucus makes digestion in intestines difficult
• Affects the whole body, oftentimes leads to an early death
• Avg. life span is 37.4 years
• Other symptoms include: poor growth and poor weight gain despite a normal food intake, accumulation of thick, sticky mucus, frequent chest infections and coughing, and sinus infections.
• Can be diagnosed using a genetic test, even before birth
• Recessive • Most common in people from Northern Europe
• Currently no cure exists but treatments exists • for lung infections: medications, breathing treatments • Sometimes lung transplants are also necessary
• physical therapy is available to help break down the mucus
• Important for them to stay active
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Sickle Cell Anemia
• Genetic disorder that affects the blood
• Shape of cells always serves a purpose
• RBC are usually disc shape so that they can move easily through the vessels in your body
• Sickle cell anemia patients have sickle or half­moon shape RBC causing them to get stuck in narrow blood vessels.
• The mutation that causes the disorder affects the production of an important protein called hemoglobin
• Carries oxygen to all parts of your body • Oxygen levels are very low in people who have sickle cell anemia.
• It is a co­dominant allele with the normal one.
• African ancestry is most common place for disease (1 in 12 are carriers).
• Pain, weakness, and lack of oxygen are all symptoms.
• A person with two sickle cell traits will have the disease, • person with one allele will be a carrier and produce ½ sickle cells, ½ normal and generally they do not have any health issues.
• No cure but given drugs to help with pain and prevent blockage in blood vessels.
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Huntington’s Disease
• Lethal genetic disorder by a rare dominant allele in which certain parts of the brain start to break down.
• This causes uncontrolled movements, emotional disturbance, lack of concentration, eventually they have trouble feeding themselves and swallowing
• Onset doesn’t usually occur until 30­50 years old
• there is no way to stop or reverse the course of HD
• Medications do exist to help with muscle control and emotional problems Inheritance of Huntington’s
• We now have a test that can be done to determine whether or not you have the allele • The disease runs in families
• passed from parent to child through a mutation in the normal gene. • Each child of an HD parent has a 50­50 chance of inheriting the HD gene. • If a child does not inherit the HD gene, he or she will not develop the disease and cannot pass it to subsequent generations 10
Hemophilia
• Genetic disorder in which a person’s blood clots very slowly or not at all • they lack the proteins necessary for clotting
• Could bleed to death from a minor cut or scrape
• Doesn’t bleed at a faster rate, just for longer periods of time
• Recessive allele on x­chromosome (sex­linked) • more common in males than females
• Can lead normal lives but advised to avoid contact sports and other activities that could cause internal injuries
Down Syndrome
• A genetic disorder in which a person’s cells have an extra copy of chromosome 21
• Can see this by doing an amniocentesis or looking at baby when born
• An error occurs during meiosis
• chromosomes fail to separate
• Occurs when mothers are older when they have kids
• People with this genetic disorder have a distinctive physical appearance (flattened face, upward slanted eyes) and some degree of mental retardation, heart defects are also common but most can be treated, infertile.
• Physical genetic limitations of Down syndrome cannot be overcome, but education and proper care will improve quality of life.
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Friday, December 9
Bell Work:
A woman who has hemophilia marries a
man without hemophilia. What is the
probability that their children will have
hemophilia?
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Diagnosing Genetic Disorders
• Years ago Dr.’s relied on pedigrees and punnett squares to help predict whether a child might have a genetic disorder
• Today doctors use tools such as amniocentesis and karyotypes to help determine genetic disorders.
• Amniocentesis­a long needle is inserted into the mother’s belly to remove a small amount of fluid that surrounds the developing baby…why?
• Because cells from the baby will be found there and then they use that to make a karyotype
Karyotype
• karyotype­ a picture of all the chromosomes in a cell
• arranged in pairs by length and location of the centromeres • Reveals whether a baby has the right number of chromosomes (would show genetic disorders)
• you can also tell whether it is a boy/girl 13
Karyotyping Activity
Diagnosis…analyzing karyotypes and determining the sex and the disease.
Genetic Counseling
• A couple with a concern about genetic disorders may turn to a genetic counselor for advice.
• Age­related
• Family history
• Genetic counselors might run tests to see if the parents are carriers for a particular genetic disorder.
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Pedigrees
• To study patterns of inheritance in humans you would need to trace the inheritance of traits through many generations in a number of families
• An important tool that geneticists use to trace the inheritance of traits in humans is a pedigree
• Pedigree­ a chart or “family tree” that tracks which members of a family have a particular trait.
• You can use pedigrees for any kind of trait…including sex­linked.
Pedigrees Continued…
understanding the symbols
Scientists use a bunch of symbols that help us to simplify the actual ‘charts’.
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More pedigree symbols
Pedigree symbols cont.
• The generations are identified in sequence by Roman numerals
• Each individual is also given a number to make conversations and studies easier to understand
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Practice with A6: Interpreting Information in a Pedigree
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Pedigree mini­project
­their own family
­already designed family
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