Transcript Genetics Lecture IV

Genetics Lecture IV
Human Genetics
Biology Standards Covered:
• Std 2f ~ students know the role of chromosomes in
determining an individual’s sex
• Std 2g ~ students know how to predict the possible
combinations of alleles in a zygote from the genetic makeup of
the parents
• Std 3c* ~ students know how to predict the probable mode
of inheritance from a pedigree diagram showing phenotypes
Exploring the Human Genome
Human Chromosomes
Let’s Review:



A diploid human cell contains 46
chromosomes
A haploid gamete or sex cell has 23
chromosomes
Chromosomes are a condensed form of
DNA that carries all of the genetic
information that makes up that organism
Human Chromosomes
Scientists have been
analyzing our DNA to see
what makes us human
They take pictures of our
DNA when it is condensed
into the form of
chromosomes
After that they group the 23
pairs into matched pairs
When chromosomes are
arranged like this it is
called karyotyping
(karyotype)
Human Chromosomes
Of the 46 chromosomes that make up
each of our cells two of them are sex
chromosomes
It is our sex chromosomes that
determine whether or not we are female
or male


Two X chromosomes and we are female (XX)
One X and one Y and we are male (XY)
XY Male
Parent
Sex
determination
X
XX
Female
X
Y
XX
Female
XY
Male
XX
Female
XY
Male
Parent
X
Human Chromosomes
The other 44
chromosomes are
known as autosomal
chromosomes or
autosomes
This picture shows what
type of cell? Sex cells or
autosomal cells?
Human Traits
Humans inherit genes according to the
principles that Mendel came up with
Both parents randomly assort their genes
into their sex cells and the two sex cells are
joined in fertilization
Some traits are shown in the phenotype of
the offspring while other traits are masked
until further generations
A Human Pedigree
A pedigree is a chart
that shows how traits
are passed from one
generation to the next
Spheres or circles
represent females while
boxes or squares
represent males
Pedigrees illustrate inheritance
A half-shaded
circle or square
represents a
carrier, a
heterozygous
individual.
Pedigrees illustrate inheritance
I
1
2
II
2
1
3
4
5
III
1
2
4
3
IV
1
2
3
4
5
A horizontal line
connecting a circle
and a square
indicates that the
individuals are
parents, and a
vertical line
connects parents
with their offspring.
Pedigrees illustrate inheritance
I
1
2
II
1
III
IV
1
2
1
3
2
4
4
3
2
5
3
4
5
Each horizontal
row of circles and
squares in a
pedigree
designates a
generation, with
the most recent
generation shown
at the bottom.
Pedigrees illustrate inheritance
I
1
2
II
1
3
2
4
5
III
?
1
2
4
3
IV
1
2
3
4
5
The generations
are identified in
sequence by
Roman
numerals, and
each individual is
given an Arabic
number.
Pedigree
Section 14-1
A horizontal line
connecting a male and
female represents a
marriage.
A circle
represents a
female.
A square
represents a
male.
A vertical line and a
bracket connect the
parents to their
children.
A half-shaded
circle or square
indicates that a
person is a
carrier of the
trait.
A completely shaded circle
or square indicates that a
person expresses the trait.
A circle or square that is not shaded
indicates that a person neither
expresses the trait nor is a carrier of the
trait. Some regular DUDE.
Human Traits
It can be quite difficult to trace an actual
trait through generations of a family
Some believe that you receive your eyes
from one parent and ears from another
Many traits, however, are considered
polygenic ; Meaning: a trait that is
controlled by many genes
Human Traits
The second reason that it
is difficult to determine
where you receive your
physical characteristics
from is because only some
of your genes are
controlled by inheritance
Many traits are strongly
influenced by
environmental, or nongenetic, factors


Nutrition and exercise
Habitat and lifestyle
In arctic foxes
temperature has an
effect on the expression of
coat color.
Human Blood Group Genes
Why is it important to know your blood
type?


If you receive a transfusion of the wrong
blood type there is a very strong chance
that you will die
Each person has a specific blood type and
can receive donor blood specific to the type
of blood that pumps through their veins &
arteries
Human Blood Group Genes
The ABO blood groups are the following:

•
Type A , Type B , Type AB , and Type O
There are three alleles for the ABO blood group
• IA
Phenotype
(Blood Type)
, IB , i
Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
Human Blood Group Genes
IA and IB are codominant

Phenotype
(Blood Type)
This means:
If you have both alleles you will have Type
AB blood
If you have Type A or Type B with the i
allele you will express the dominant trait
of Type A or Type B
Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
Type A Blood
Type A blood is the
result of the genotype
IA IA or IA i
The surface of all of
the Type A blood
molecules is the
same throughout the
body
Type B Blood
Type B blood is the
result of
IB IB or
IB i
All of the blood in a
Type B person has
the same surface
Type AB Blood
The only way to have
Type AB blood is to
have the alleles IA IB
Because it has both
surfaces it can accept
donor blood from all
blood types
Human Blood Group Genes
The i allele is recessive

Phenotype
(Blood Type)
This means:
If it is with any other allele it will be
masked
If someone has both ii they will have Type
O blood
Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
Type O Blood
With two recessive
alleles ii you have the
Blood Type O
Type O blood has a
smooth surface and
because of that it is a
universal donor
Human Blood Group Genes
Blood transfusions are specific


Phenotype
(Blood Type)
Type AB is the universal acceptor
Type AB can ONLY donate to another Type
AB !!
Type O is the universal donor
Type O can ONLY accept another Type O
blood type
Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
Human Blood Group Genes
Human blood is governed by another gene
as well
The Rh Blood group only has two alleles

Rh+ is dominant
Rh+ / Rh+ OR Rh+ / Rh- is positive

Rh- is recessive
ONLY Rh- / Rh- is a negative blood type