Transcript Human Genetics and Sex

Human Genetics and SexLinked Traits
Human Chromosomes

Humans have 46 (23 pairs) of chromosomes

These 46 chromosomes contain over 100,000 genes

Human chromosomes come in homologous pairs –
one from mom, one from dad – they are similar in
size, shape and the genes they contain
Determination of Gender

Sex chromosomes are the only pair of chromosomes
in which the members of a pair do not always match
together

Sex chromosomes = X and Y
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All other chromosomes = autosomes
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The presence of the Y chromosome determines
“maleness”
Turner Syndrome
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One X chromosome, no other
sex chromosome

Individuals with Turner
Syndrome are physically female
but never develop physically past
childhood
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XXY

Other Sex
Chromosome
abnormalities
XXX

Less facial and body hair

XXXX

Usually less muscular due to less
testosterone being produced

XYY – 1/1000 male births;
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XXYY
Klinefelter Syndrome

Usually infertility is a symptom
Sex – Linked Traits

The X chromosome is large and
carries many genes

The Y chromosome is small
with few genes

If an allele is on an X
chromosome and not the Y, then
a man will express that allele –
regardless of whether it is
dominant or recessive
Sex – Linked Traits
Colorblindness

XN = color vision

Xn = color blind

In females:
 XNXN = Normal vision
 XNXn = normal vision (carrier)
 XnXn = color blind

In Males:
 XNY = normal vision
 XnY = color blind
Hemophilia

Hemophilia is a blood clotting
disorder where the blood does
not clot (at all)

1/10,000 men

1/100,000,000 women
Muscular Dystrophy

A disorder in which the muscles
degenerate over time

Caused by a problem with a
gene that codes for a certain
muscle protein

Located on the X chromosome