Transcript 91608Handout

BICH107/GENE105 9-16-2008 pg 1
Features of a chromosome
replication
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.
BICH107/GENE105 9-16-2008 pg 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.biology.arizona.edu/cell_bio/tutorials/meiosis/main.html
Inheritance of sex chromosomes from parents to offspring
Genotype of sex
chromosomes:
XX
XY
Possible gametes: All are X
Gametes from the male
Punnett Square
Gametes from
the female
1/2 are X & 1/2 are Y
X
Y
X
XX
XY
X
XX
XY
BICH107/GENE105 9-16-2008 pg 3
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 9-16-2008 pg 4
Inheritance of Recessive
Disorders: One Chance in Four
N
N NN
d
Nd
d Nd
dd
Inheritance of Dominant
Disorders: A Fifty-Fifty Chance
n
n
D
n
Dn
Dn
nn
nn
Inheritance of X-Linked
Disorders: Males are at Risk
X
X
XX
Y
XY
X
XX
XY
Adapted from http://www.hhmi.org/genetictrail/
Single gene traits of humans
BICH107/GENE105 9-16-2008 pg 5
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 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)