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Sex Linked Traits

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Sex Linked Traits What do you think sex linked means??? Traits that are controlled by genes located on the sex chromosomes. What are the sex chromosomes? – PowerPoint PPT presentation

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Title: Sex Linked Traits


1
Sex Linked Traits
  • What do you think sex linked means???
  • Traits that are controlled by genes located on
    the sex chromosomes.
  • What are the sex chromosomes?
  • XX for female, and XY for males

2
Chromosomes and Sex Linked Traits
  • The chromosomal theory of inheritance
  • Chromosomes carry ______ (the units of heredity)
  • Each chromosome contains many different genes
  • Paired chromosomes segregate during _______. Each
    sex cell or gamete has ____ the number of
    chromosomes found in a somatic cell
  • Chromosomes assort __________ during meiosis.
    This means that each gamete receives one member
    from each pair of chromosomes, and that each
    chromosome pair has no influence on the movement
    of any other chromosome pair.

3
Chromosomes and Sex Linked Traits cont.
  • Females have two __ chromosomes, while males have
    one __ and one __ chromosome
  • Sex linked traits are controlled by genes located
    on the sex chromosomes. A recessive trait located
    on the X chromosome is more likely to express
    itself in males than in females since males need
    only one copy of the recessive allele while
    females need two

4
Sex Linked Traits Info
  • Genes found on X chromosome, but not on Y
    chromosome
  • Females (XX) with one recessive and one dominant
    trait will display the dominant trait
  • Males (XY) with one recessive trait will display
    the recessive trait because they do not have a
    dominant trait to display

5
Sex Linked Traits in Humans
  • 1. Hemophilia the defective allele prevents
    the synthesis of a factor needed for blood
    clotting.
  • 2. Colour Blindness A condition where not all
    colours in the spectrum are visible.
  • 3. Duchennes muscular dystrophy A condition
    where muscles begin to degenerate in childhood.

6
Sample Problem
  • A man with hemophilia maries a homozygous normal
    woman. Predict the possible genotypes and
    phenotypes of their children.
  • XH X chromosome with normal dominant allele
    (non-hemophilia)
  • Xh X chromosome with recessive hemophilia allele
  • Y Y chromosome (does not contain comparable gene)

7
Sample Problem
  • Step 1 Determine the genotypes of the parents
  • Step 2 Determine the gamete genotypes produced
    by each parent
  • Step 3 Set up a Punnett square using the gamete
    genotypes
  • Step 4 Combine the gamete genotypes of one
    parent with those of the other parent to show all
    possible offspring genotypes
  • Step 5 State the genotype and phenotype ratios
    of the offspring

8
Human Pedigrees
  • The tool we would use to demonstrate the passing
    on of traits within a family from generation to
    generation.
  • The pedigree uses different symbols and numbers
    that we need to be aware of in order for us to
    read it.

9
Symbols in a Pedigree (142)
10
Example
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