Download Dragonfly Chapter 14

Dragonfly Chapter 14
The Human Genome
Section 14-1: Human Heredity
Key Concepts: How is sex determined?
How do small changes in DNA Cause genetic disorders?
I.
Human Chromosomes
A. Karyotype: A picture of chromosomes taken during mitosis and
cut out and arranged into homologous pairs.
Diploid Cell: ________
Two sets of homologous chromosomes
Human diploid cell has ____
46 chromosomes
arranged in ____
23 pairs
The 46 chromosomes contain 6 billion nucleotide
pairs
Mendelian genetics requires that organisms
inherit a single copy of gene from each parent
In humans, _______________
(reproductive cells
the gametes
of egg and sperm) contain a single copy of each
gene (one set of genetic information).
testes
Gametes are formed in the __________
(sperm) and
ovaries
__________(egg)
by meiosis.
Each gamete contains 23 chromosomes (one set) or
haploid number (N) of chromosomes.
__________________
Fertilization
________________
requires the egg and the sperm to
join and produce a ______________
(fertilized egg)
zygote
that contains 46 chromosomes (two sets) or
diploid number
_____________________
(2N).
Humans have 46 total chromosomes
44 _____________
autosomes follow regular Mendelian
genetics
2 _________________
sex chromosomes (X and Y) are sex-linked
A. Pedigree Chart: A pedigree chart shows the
_________________
within a family and can be
relationship
genetic inheritance problems
useful to help with __________________________
within families. It is another __________________
way to predict the
outcome of a particular cross and the genotype of
_________
the family members.
Figure 14-3 A Pedigree
Section 14-1
Pedigree
A circle represents
a female.
A horizontal line connecting
a male and female
represents a marriage.
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 square represents
a male.
A vertical line and a
bracket connect the
parents to their children.
A circle or square
that is not shaded
indicates that a
person neither
expresses the trait
nor is a carrier of
the trait.
Human Traits
Phenotypes are determined by genotype as well as
________________________________.
environmentally influenced
________________________________
on gene
Environmental influences
expression are not inherited, but genes are.
III. Human Genes
The __________________:
Complete set of genetic
human genome
information
Composed of about 30,000 genes
Blood Group Genes
Human Blood comes in a variety of genetically
determined blood groups
There are many different types of blood groups
but the ones associated with the ABO blood
group and the Rh blood groups are best known.
Rh blood groups is controlled by single gene with
________________.
It is another antigen in blood,
Two alleles
first discovered in Rhesus monkeys. The
arrangement of the alleles determines only _______
two
positive
possible types _____________
(+) contains the
antigen, or ___________
(-) doesn’t contain the
negative
antigen. Positive is ______________
over negative.
dominant
Rh-positive is identified with two genotypes:
Rh+/Rh+ or Rh+/RhRh-negative is identified with one genotype:
Rh-/Rh-
ABO Blood Groups: Discovered in 1900 by Karl
Landsteiner. He realized that all blood is classified
into four types: ____,
A ____,
O due to
B ____,
AB and _____
the presence of or absence of specific __________
antigens
in the blood.
o is
Alleles IA and IB are __________________
and
i
codominant
________________
to both IA and IB
recessive
Antigens are ______________________
used by
chemical markers
the immune system. When an unrecognized
antigen is present an immune response takes place
and the cells ____________________________.
clump or agglutinate
Figure 14-4 Blood Groups
Blood Type and Antigen
Interactions
Section 14-1
Phenotype
(Blood Type
Go to
Section:
Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
B. Recessive Alleles: Trait controlled by a
recessive allele. This results in the
disorder being present
___________________________.
only if both alleles are recessive
• Examples include: PKU
(Phenylketonuria), Tay Sachs disease and
Cystic Fibrosis, Albinism, and
Galactosemia (See chart on page 345)
C. Dominant Alleles: Traits controlled by a
dominant allele. This results in the
disorder being present when
only one allele is present
__________________________.
• Examples include: Achondroplasia
(dwarfism), Hypercholesterolemia, and
Huntington’s Disease
Section 14-1
Autosomal Disorders
Autosomol
Disorders
caused by
Recessive
alleles
Dominant alleles
Codominant
alleles
include
include
include
Huntington’s
disease
Sickle cell
disease
Galactosemia
Albinism
Cystic
fibrosis
Phenylketonuria
Tay-Sachs
disease
Achondroplasia
Hypercholesterolemia
Huntington Disease:
It is controlled by a _________________________.
single dominant allele
The gene is located on Chromosome #4.
Genetic degenerative disease that shows no
symptoms until a person is in their
____________________.
It progresses with
thirties or forties
gradual degeneration of their nervous system
leading to loss of muscle control and mental
function until death occurs.
Question? Would you want to know now if you
could potentially get Huntington’s disease when you
are older? Would you want to know if you could
pass the gene on to your offspring before you have
children?
A. Codominant Alleles: controlled by
_______________________________________.
two alleles that share dominance
Sickle Cell Anemia is such a disorder. (This will be
discussed in detail later)
IV. From Gene to Molecule
The link between genetics
______________________
and phenotype
is not easily determined but for several diseases we
have been able to make the connection.
Cystic fibrosis and Sickle
cell disease
For both _____________
________________
single gene
a small change in the DNA of a _____________
affects the ______________________,
causing a
structure of a protein
serious genetic disorder.
A. Cystic Fibrosis: (See figure 14-8 p. 347)
Cystic Fibrosis a.k.a. “CF” is a common genetic
disease. It is most common in people of
Northern European decent.
It is a _______________________
of a gene
Recessive disease
found on the # 7 chromosome and affects
the______________________________
digestive and respiratory systems
It is caused by the____________________
deletion of 3 bases in
the middle of a sequence for a protein and
causes the protein to be ______________
abnormal and
doesn’t allow Chloride ions to transport across
the membrane, as they should. This causes
the cells in a person’s airways to be unable to
transport chloride ions and become
__________________.
clogged with mucus
Figure 14-8 The Cause of Cystic Fibrosis
Section 14-1
Chromosome
#7
CFTR
gene
The most common allele
that causes cystic fibrosis is
missing 3 DNA bases. As
a result, the amino acid
phenylalanine is missing
from the CFTR protein.
Normal CFTR is a chloride
ion channel in cell
membranes. Abnormal
CFTR cannot be transported
to the cell membrane.
The cells in the person’s airways
are unable to transport chloride
ions. As a result, the airways
become clogged with a thick
mucus.
B. Sickle Cell Anemia
The patient’s blood cells were found to be
irregularly shaped, ____________________,
like a sickle
and this is how the disease got its name.
In normal red blood cells the
____________________
oxygen
hemoglobin molecule carries ___________
and distributes it around the body. In sickle cell
disease, the red blood cells are sickle–shaped,
causing the blood hemoglobin to no longer carry
oxygen as well and _____________________
disrupts the normal
functioning of the bodies cells, tissues and
organs
This person is deprived of oxygen and the result is
physical weakness, and damage to the brain,
heart, spleen. It may be fatal.
The cause: A _________________
in the DNA that
single base
codes for Hemoglobin polypeptides is changed.
This substitutes Valine for glutamic acid.
This change makes the hemoglobin less soluble in
blood. This will cause the hemoglobin to come
out of the blood and _______________.
This
crystallize
crystallization causes the ________________
of
sickle shape
the blood cells and the medical consequences.
The genetics: The allele for sickle cell (HS) is
___________
codominant with the allele for normal
hemoglobin (HA).
Heterozygotes (HS HA) are said to be ____
Sickle____
cell
__________
carriers and have some effects of the disorder
because they have both normal and sickle cell blood
hemoglobin.
DNA normal hemoglobin
CAC GTG GAC TGA GGA CTC CTC
Messenger RNA sequence
GUG CAC CUG ACU CCU GAG GAG
Normal hemoglobin amino acid sequence
Val – His – Leu – Thr – Pro – Glu – Glu…
1
2
3
4
5
6
7 …146
DNA Sickle Cell Anemia
CAC GTG GAC TGA GGA CAC CTC
Messenger RNA sequence
GUG CAC CUG ACU CCU
GAG
Val – His – Leu – Thr – Pro –
– Glu…
1
2
3
4
5
6
7 …146
The distribution: Sickle Cell anemia is most
prevalent in people of __________________.
African descent
10% of African Americans and 40% of populations
in Africa and Asia carry the gene for Sickle cell
anemia.
Why? The carriers for the disease have a
___________________,
resistance to Malaria a dangerous disease
caused by a blood parasite found in tropical areas of
the world.
Sickle Cell Anemia is a __________
mutation that has
provided an ____________
in Malaria prone areas
advantage
and in these areas it is favored
_______________________
by natural selection
and therefore Sickle Cell Anemia persists.
HS
HA
HS
HS HS
H S HA
HA
HS HA
H A HA
Section 14-2: Human Chromosomes
Key concepts: Why are sex-linked disorders more
common in males than in females?
What is nondisjunction, and what problems does it
cause?
I. Human Genes and Chromosomes
Human diploid cell contains ______________________
6 billion base pairs of
DNA. All neatly packed into the 46 chromosomes.
__________________
of the DNA actually functions as
Small part
genes.
Genes are located on the chromosomes and each gene
occupies a ______________________
on a
specific place
chromosome.
Genes may exist in ____________________
(alleles)
several forms
Each chromosome contains ______
one of the alleles for each
of its genes
Chromosome #21 and 22 are the ____________
smallest of the
human autosomes. These were the first two
chromosomes whose sequences had been determined.
Both also contain genes for some genetic
disorders like ________________________
Leukemia and
Amyotrophic Lateral Sclerosis (ALS)
___________________________
We also discovered that there are many
_________________________
segments of DNA
non-coding, repeating
Human chromosomes also have
________________
that can cross over just as we
Linked genes
saw in the fruit fly.
II. Sex-linked Genes
Sex Chromosomes
1. _______________________
are the ones that
__________
in males and females
differ
2. Chromosomes that are the ________
in male and
same
females = _______________
autosomes
3. In humans: females = ____
XY
XX and Males = ____
4. The Y chromosome is smaller than the X
A. Sex Determination
1. Female _________
gametes carry an X chromosome
2. _________
gametes can carry either an X or Y
Male
(meiosis segregates the chromosomes; _______
50%
50% of the sperm
of the sperm carry X and ______
carry Y)
3. In humans, _____________________________
males determine the sex
of an offspring
X
Y
Female: XX
X XX
XY
male: XY
X XX
XY
In some animals such as birds, butterflies, and
some fish, the female determines the sex
differing chromosomes.
because she has the __________
Sex-linked Genes
1. In addition to determining the sex of an
individual, the sex chromosomes carry genes
that ____________________
affect other traits.
Sex-linked Genetic Disorders
May be on the X or Y chromosome, but
usually on the X because the Y has very few genes.
males
Most often expressed in ____________because
they only have one X chromosome and thus all the
alleles are expressed even if they are recessive.
Colorblindness is a recessive disorder in which
people can’t distinguish between certain colors.
Red-green
____________________
colorblindness is most
common.
XC and Xc are ________________
for normal and
the alleles
colorblind vision.
XC XC and XC Xc are both normal vision females.
carrier for colorblindness and can
XC Xc is a _______________________
pass the gene on to her sons.
Xc Xc is a colorblind female.
XC Y is a normal male and
Xc Y is a colorblind male.
http://www.toledo-bend.com/colorblind/Ishihara.html
Figure 14-13 Colorblindness
Colorblindness
Section 14-2
Father
(normal vision)
Colorblind
Normal
vision
Male
Female
Daughter
(normal vision)
Son
(normal vision)
Daughter
(carrier)
Son
(colorblind)
Mother
(carrier)
Go to
Section:
Figure 14-13 Colorblindness
Colorblindness
Section 14-2
Father
(normal vision)
Colorblind
Normal
vision
Male
Female
Daughter
(normal vision)
Son
(normal vision)
Daughter
(carrier)
Son
(colorblind)
Mother
(carrier)
Go to
Section:
Hemophilia is a __________________________
recessive sex-linked disorder in
which one is unable to clot their blood.
Also known as “bleeders disease”.
Hemophilia is caused by a defect in a gene and the
protein for normal blood clotting is missing.
Figure 21.12
Page 394
Slide 16
Royal Family and Hemophilia
I
II
III
Albert Victoria
IV
V
VI
Figure 21.13
Page 394
Slide 18
Muscular Dystrophy is another
sex-linked recessive disease.
Here the affected individual inherits a degenerative
__________disorder.
muscle
The gene that codes for a _____________
muscle protein is
defective. They rarely live past early adulthood.
Treatments are being explored that ___________
replace
the defective gene.
III. X-Chromosomes Inactivation
Males survive with only one X chromosome so,
what do females do with 2? They ___________;
shut one off
it becomes inactive. This creates a dense region
in the nucleus known as a ______________.
Barr body
This is seen in coat color in cats. The cells will
randomly shut off the coat color allele in one X
chromosome and turn them off in the other X
chromosome in other cells and this leads to some
areas that are spotted orange and some spotted
black, creating a tricolor cat, ________.
This
calico
only happens in __________
females because males only
have one X chromosome.
IV. Chromosomal Disorders
Whole/sets of chromosome mutations
1. _______________
Nondisjunction = failure of homologous
chromosomes to separate normally during
meiosis
This results in a disorder of __________________
chromosome number
2. Examples of disorders include Down’s
Syndrome, Klinefelter’s, and Turner’s
Syndrome
Section 14-2
Nondisjunction
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
Go to
Section:
Meiosis II
Nondisjunction
Section 14-2
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
Go to
Section:
Meiosis II
Nondisjunction
Section 14-2
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
Go to
Section:
Meiosis II
Nondisjunction
n+1
n+1
n-1
n-1
chromosome
alignments at
metaphase I
nondisjunction
at anaphase I
alignments at
metaphase II
anaphase II
gametes
Figure 21.19
Page 398
Slide 23
2. Examples of disorders include Down’s
Syndrome, Klinefelter’s, and Turner’s
Syndrome
Nondisjunction disorders: Disorders in which
the failure of _____________________
chromosome separation
during one of the stages of meiosis causes a
gamete to have
_______________________________.
too few or too many chromosomes
Nondisjunction can occur in
___________________________.
autosomes or sex chromosomes
Down’s Syndrome: Down’s syndrome is an
example of ____________________________,
nondisjunction of an autosome
specifically chromosome 21.
In Down’s syndrome there is an ___________
extra copy of
chromosome 21 (trisomy 21).
Doing a _____________
karyotype (display of all the
chromosomes in a cell nucleus) and looking at the
chromosomes under a microscope detect the extra
chromosome.
Characteristics of Down’s syndrome include
_________________,
mental retardation physically challenged, facial
irregularities, and often heart defects.
incidence per 1,000 births
Incidence of Down’s Syndrome and mother’s age
20
15
10
5
0
20
25
30
35
40
45
mother's age
Fig. 21.20a,b
Page 399
Slide 24
Turners Syndrome: Nondisjunction of the sex
chromosomes in which a chromosome is missing.
45 XO
They have the chromosome makeup of _________
where “O” represents the missing chromosome.
This individual is female in appearance but does not
develop the female sex organs during puberty and is
sterile.
________.
Klinefelter’s Syndrome: Nondisjunction of the sex
extra X chromosome
chromosomes in which an _____________________
is present.
47XXY
They have the chromosome makeup of ________.
male
They are ___________
in appearance and are also
sterile. May also be 48 XXXY or 49 XXXXY
No nondisjunctions of the sex chromosomes have ever
X chromosome
produced and survived without an ______________.
This is because the X chromosome carries many genes
essential for life.
•XXY condition
•Results mainly from nondisjunction in
mother (67%)
•Phenotype is tall males
–Sterile or nearly so
–Feminized traits (sparse facial hair,
somewhat enlarged breasts)
–Treated with testosterone injections
Nondisjunction of Sex Chromosomes
XX
x
Y
XX
x
X
O
x
Y
x
X
gamete
XX
XXY
(Klinefelter syndrome)
or
nondisjunction
XXX
(“metafemale”)
XX
gamete
O
YO
(not viable)
or
O
meiosis and
possibilities
gamete formation at fertilization
XO
(Turner syndrome)
genotype
(phenotype)
Figure 21.21
Page 399
Slide 25
The impact of the sex chromosome
nondisjunction has led us to understand the
importance of the _____________________
Y chromosome
in determination of sex of an individual.
This has recently been determined to be true
because the Y chromosome has been found
to have a gene that turns on
______________________
male sexual development in the embryo
even if many X chromosomes are present.