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Published byΧθόνιος Μαρκόπουλος Modified over 5 years ago
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Sex-Linked Traits and Chromosomal Disorders
EQ: Why do some people inherit certain traits?
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Chromosomes Sex Chromosomes- chromosomes that determine the sex of an organism Autosomes- all other chromosomes Both males and females can be carriers Humans have 2 sex chromosomes X & Y and 44 autosomes
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Karyotype Can tell if the person is missing or have extra chromosomes as well as gender Can’t see single gene mutations
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Sex-linked traits Sex chromosomes carry genes that are either on the X or Y chromosome These traits show up in different percentages in males and females because they move with the sex chromosome
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Y-linked genes Genes that are specifically carried on the Y chromosome
Y-linked genes ONLY show up in males Example: Hairy ears
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X-linked Genes Carried on the X chromosome
X-linked recessive disorders show up more frequently on males than females because males have only one X chromosome Females can be carriers of recessive traits
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Or Males ONLY HAVE ONE X They either have the They are disorder normal
DEFECTIVE NORMAL They either have the disorder They are normal Or
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Females have one normal gene that works.
FEMALES HAVE TWO X CHROMOSOMES DEFECTIVE NORMAL DEFECTIVE Females have one normal gene that works. Females __________ defective recessive alleles to show the disorder need 2
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Example of x-linked recessive disorders
Hemophilia Cause: Mutations in genes for blood clotting proteins carried on X chromosomes Blood clotting proteins are missing so a person with this disorder can’t stop bleeding when injured Can bleed to death from minor cuts or suffer internal bleeding from bruises or bumps Treatment: Injections of normal clotting proteins to stop bleeding More common in males because it is X-linked, but females with 2 recessive alleles will also show the traits 1 in 10,000 males have hemophilia
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Examples of x-linked recessive disorders
Color Blindness Cause: Mutation in one of three genes for color vision carried on X chromosome People with this disorder have trouble distinguishing colors Red-Green colorblindness is the most common Seen in 1 in 10 males and 1 in 100 females
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Chromosomal Disorders
1 infant in 200 newborns has a chromosomal disorder 28% of first trimester miscarriages have a severe chromosomal abnormality Chromosomal mutations- change in the structure or number of chromosomes
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Nondisjunction During Anaphase, the homologous chromosomes fail to separate during meiosis. Since it happens to a sperm or egg cell, the new baby can end up with trisomy (3 copies) or monosomy (one copy) of the chromosome.
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Nondisjunction
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Example of Chromosomal Disorders
Down Syndrome Cause: three copies of the 21st chromosomes Most common chromosomal disorder (1 in 800 births) 50% have heart defects that need surgery to repair Mild to severe mental deficiencies Increase chances of having other diseases
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Down Syndrome
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