Transcript Slide 1 - Fort Bend ISD

Human Heredity
 There are traits that are controlled by one
gene with 2 alleles. Often, one is
dominant and the other is recessive
 Example:
widow’s peaks and dimples.
Some traits are controlled by a gene with
multiple alleles – 3 or more for a single
trait.
For example: blood types and skin color in
humans.
 There are 44 chromosomes that we call
autosomal chromosomes.
 However, there are 2 chromosomes that
determine our sex and we call them sex
chromosomes.
 These 46 chromosomes all carrier genes
on them that determine our traits.
 Out of our 23 pairs of chromosomes, 1
pair is the sex chromosomes (X and Y).

Female = XX

Male = XY
 Question: What is the probability
that your parents will have a boy
or girl?
 XY (dad) x XX (mom)
X
X
XX
Y
XY
Phenotype:
50% boy
50% girl
X
Genotype:
XX
XY
50% XX
50% XY
Question?
If my parents have 5 boys in a row, what
is the chance they will have a girl the
next time?
50%
Sex-linked gene:
 Some traits are carried on the sex
chromosomes. Genes on the X or Y
chromosomes are sex-linked genes.
 These traits are passes on from parent to
child. Sex- linked genes can be recessive or
dominant.
 MALES are more likely to have a sex-linked
trait because they only have ONE X and Y. The
allele is USUALLY on the X chromosome.
 Ex. colorblindness, hemophilia, hairy ears,
muscular dystrophy
Are you colorblind?
What numbers do you see?
Carrier – person who has one recessive
allele and one dominant allele for a trait or
heterozygous for that trait (only women
can be carriers).
Example
Hemophiliac carrier XHXh
Colorblind carrier XBXb
Sex linked Punnett Squares:
Question:
What is the probability that a carrier female and a
colorblind male will have a girl who is colorblind
(b = colorblind, B = normal)?
Xb
Y
Phenotype:
XB
XBXb
XBY
25% normal boy
25% colorblind boy
25% normal girl
Xb
25% colorblind girl
XbXb
XbY
Try this one on your own
Question:
What is the probability that a homozygous
(normal vision) female and a colorblind male
will have a girl who is colorblind (b = colorblind,
B = normal)?
Parents: XBXB x
Xb
X bY
Y
Phenotype:
XB
XBXb
XBY
XB
XBXb
XBY
50% normal girls
50% normal boys
?
Pedigree
 Simply a family tree describing the
interrelationships of parents and children
across the generations
 Males – square
 Females – circle
 Past and future
 Genotype and phenotype
 Sex-linked or autosomal
 Carriers do not show that particular trait
phenotypically but have a chance to pass
the trait on to their child.
Carrier – half colored
Reading a Pedigree
Task 1: Genotyping a pedigree chart
Task 2:
Take out your pedigree sheet.
Lets do the first one together.
Do # 2.
Sex-linked-Practice on
your own:
 What is the probability of a female carrier
of hemophilia and a normal male having a
boy with hemophilia (X-linked recessive)?
 What is the probability of a man with hairy
ears and a woman having a son with hairy
ears (Y-linked recessive)?
 What is the probability of a carrier woman
and a male with muscular dystrophy
having a girl with muscular dystrophy (Xlinked recessive)?
Genetic
Engineering
Cloning – Ch. 13
 Donor cell taken from original animal
 Fused with egg cell with no nucleus
 Fused with electric shock
 Dolly
 First mammal cloned
 Offspring genetically IDENTICAL to
parent/donor
 CC (Copy Cat)
 http://www.msnbc.msn.com/id/30769
08/
DNA Fingerprinting
 Analyze sections of DNA that have
little or no known function
 Sections that vary widely from one
individual to another
 Positive ID has similar marker to
mother AND father
 Remember you get your chromosomes
from both your mom AND your dad
 Uses gel electrophoresis – gel setup
between two poles; positive charge
on one end and negative on the
other
 Amino acids have different charges
and travel along the gel depending
on that charge
 Figure 14-18: which suspect
matches the evidence?
Human Genome Project
 Scientists working on full set of
chromosomes/DNA sequence of
humans
 Look at haploid set of chromosomes
 Human genome - ~3 billion base
pairs
Stem Cells
 Unspecialized cells with the potential
to become a variety of cells
 Taken from embryos
 Moral and ethical objections
 Immune system may reject stem
cells
 Mouse cells to date