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.
What is the function of a telomere?
What is the function of a centromere?
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.
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.biology.arizona.edu/cell_bio/tutorials/meiosis/main.html
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.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html
Inheritance of sex chromosomes from parents to offspring
Genotype of sex
chromosomes:
XX
Possible gametes:
All are X
Punnett Square
Gametes from
the female
XY
1/2 are X and 1/2 are Y
Gametes from the male
X
Y
X
XX
XY
X
XX
XY
Gregor Mendel studied the inheritance of stable traits with two easily
distinguishable forms, like plant height (tall and short) in pea plants
true tall
true short
Hybrid tall
Tall phenotype is dominant over short
true short
The short phenotype reappears in crosses with hybrid tall parent
t
t
t
t
T Tt
Tt
T Tt
Tt
Tt
Tt
tt
tt
T
Expect all hybrid tall
plants
t
Expect two hybrid tall
plants and two short
plants
BICH107/GENE105 9-18-2007
Inheritance of Recessive Disorders: One Chance in Four
N
d
N
NN
Nd
d
Nd
dd
From http://www.hhmi.org/genetictrail/
BICH107/GENE105 9-18-2007
Inheritance of Dominant Disorders: A Fifty-Fifty Chance
D
n
n
Dn
nn
n
Dn
nn
From http://www.hhmi.org/genetictrail/
BICH107/GENE105 9-18-2007
Inheritance of X-Linked Disorders: Males are at Risk
X
Y
X
XX
XY
X
XX
XY
From http://www.hhmi.org/genetictrail/
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)
Widow’s 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)