BICH107GENE105 9182007

1
BICH107/GENE105 9-18-2007
Features of a chromosome
From Figure 13.6, pg. 245, Human Genetics 6th
edition by R. Lewis Human chromosomes 1-22 are
AUTOSOMES. We inherit one set from Mom and one
set from Dad. The X and Y chromosomes are SEX
CHROMOSOMES. We also inherit these from our
parents. Male offspring inherit one X and one Y.
Female offspring inherit two X chromosomes.
What is the function of a telomere? What is the
function of a centromere?
2
Vertical transmission of genetic information Most
higher eukaryotes propagate through sexual
reproduction that forms a new individual from two
haploid sex cells (gametes).
Meiosis - (pronounced my-o-sis) a process to
convert a diploid cell to a haploid gamete, and
cause a change in the genetic information to
increase diversity in the offspring Here is a
link to the Biology Project at the University of
Arizona and a tutorial on meiosis http//www.biol
ogy.arizona.edu/cell_bio/tutorials/meiosis/main.ht
ml
Horizontal transmission of genetic information -
will cover in detail next week
Mitosis - (pronounced my-toe-sis) a process that
divides duplicated genetic material in the
nucleus plus cytokinesis (division of the cell)
to produce two identical daughter cells Here is
a link to the Biology Project at the University
of Arizona with a figure and animation depicting
a cell undergoing mitosis http//www.biology.arizo
na.edu/cell_bio/tutorials/cell_cycle/cells3.html
3
Inheritance of sex chromosomes from parents to
offspring
Genotype of sex chromosomes
XX
XY
All are X
1/2 are X and 1/2 are Y
Possible gametes
Punnett Square
Gametes from the male
X
Y
XX
XY
X
Gametes from the female
XX
XY
X
4
Gregor Mendel studied the inheritance of stable
traits with two easily distinguishable forms,
like plant height (tall and short) in pea plants
Tall phenotype is dominant over short
The short phenotype reappears in crosses with
hybrid tall parent
Tt
Tt
Tt
Tt
Expect two hybrid tall plants and two short plants
Expect all hybrid tall plants
Tt
Tt
tt
tt
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BICH107/GENE105 9-18-2007
Inheritance of Recessive Disorders One Chance in
Four
N
d
NN
Nd
N
Nd
dd
d
From http//www.hhmi.org/genetictrail/
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BICH107/GENE105 9-18-2007
Inheritance of Dominant Disorders A Fifty-Fifty
Chance
D
n
Dn
nn
n
Dn
nn
n
From http//www.hhmi.org/genetictrail/
7
BICH107/GENE105 9-18-2007
Inheritance of X-Linked Disorders Males are at
Risk
X
Y
XX
XY
X
XX
XY
X
From http//www.hhmi.org/genetictrail/
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Human traits that determined by inheritance of
alleles that have simple dominant and recessive
characteristics
ability to roll the tongue is dominant
(R) non-rolling is recessive (r)
Widows peak is dominant (W) a straight hairline
is recessive (w)
ear lobes hang free is the dominant (E) attached
earlobe is recessive (e)
A straight thumb is dominant (S) a bent thumb is
recessive (s)
little fingers bend away is dominant (B) straight
little fingers are recessive (b)
mid-digital hair is dominant (H) lack of
mid-digital hair is recessive (h)
left thumb is on top is dominant (C) the right
thumb is recessive (c)