Transcript 7 1 Sex Linked Traits

Monday, November 7, 2011
Something to think about…READ it, write a paragraph. 
When you’re in a crowd, look around at all the different people.
Notice their clothes, faces, hair, sizes. Look at their gestures and
movements, noticing if they are loose, stiff, or free. Just take it
in, without judgment, as if you were looking at a garden of
people. Then see them all as energy fields, the same as you.
Just energy. As you continue watching, think to yourself, Every
person here has had to live every day, decide what to wear, face
loss, success, hurt, shame, just like me. Everyone fell down
while learning to walk, everyone probably felt anxious on their
first day of school, just like me. Each person has a story to tell.
Some of the chapters are heroic. Some of them are about loss,
some about fear, some about achievement or joy, just like my
story. When you encounter someone, remember that you are a
moment in their story. Make it a story that doesn’t leave a scar.
7.1 KEY CONCEPT
The chromosomes on which genes are
located can affect the expression of
traits.
Remember, you get two copies of
each autosomal gene & that affects
your phenotype.
• all chroms other than
sex chroms.!!
• Mendel studied
autosomal gene traits
• Ex-hair color
Autosomal gene expression!!
• PHENOTYPES!
2 alleles work
together, EXPRESS
the trait!!!
DD = dimples 
Inheritance of autosomes:
(dominant)
Carriers:
heterozygous for a recessive
disorder
Use “A”s…because
Cs are really hard to tell
Apart (C and c look
Similar!)
Why are the heterozygotes called
“carriers” if the gene is for a
disorder?
• They “carry” one recessive allele for the
disorder, but they don’t express the
phenotype because …
• It’s recessive!
• You need TWO alleles (homozygous) to
express a recessive phenotype!!
SEX CHROMOSOMES:
MOM: XX
Can give an X
DAD: XY
Can give an X or Y
Sex-linked traits
• genes on sex chromosomes (X, Y)
– Y chromosome genes = male traits only
– X chromosome genes in mammals affect many
traits, males and females have them
Expression in males!!
– Only get ONE copy
of X...
– Whatever they get
from mom is
expressed, no 2nd X
allele to mask 1st!
Expression in females!!
– Get 2 copies of X...
– Recessive traits
only expressed if
BOTH X’s have it
Let’s Try this out...
• Punnett Practice with Sex-Linked Genes
SMART file…click me!