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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: ________ of homologous chromosomes
Human diploid cell has ____ chromosomes arranged in ____ pairs The 46 chromosomes contain
Two sets
46
23 6 billion nucleotide pairs
Mendelian genetics requires that organismsof gene from each parent inherit a single copy
In humans, _______________ (reproductive cells of egg and sperm) contain a single copy of each gene (one set of genetic information).
the gametes
Gametes are formed in the __________ (sperm) and __________(egg) by meiosis. Each gamete contains 23 chromosomes (one set) or __________________ (N) of chromosomes. ________________ requires the egg and the sperm to join and produce a ______________ (fertilized egg) that contains 46 chromosomes (two sets) or _____________________ (2N).
testes ovaries
haploid number
zygote
diploid number
Fertilization
Humans have 46 total chromosomes
44 _____________ follow regular Mendelian genetics
2 _________________ (X and Y) are sex-linked
autosomes
sex chromosomes
A. Pedigree Chart: A pedigree chart shows the _________________ within a family and can be useful to help with __________________________ within families. It is another ___________________________ of a particular cross and the genotype of the family members.
relationshipgenetic inheritance problems
outcomeway to predict the
A circle represents a female.
A square represents a male.
A horizontal line connecting a male and female represents a marriage.
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.
Section 14-1
Figure 14-3 A PedigreePedigree
Human Traits
Phenotypes are determined by genotype as well as ________________________________.
________________________________ on gene expression are not inherited, but genes are.
environmentally influenced
Environmental influences
III. Human GenesThe __________________: Complete set of genetic information
Composed of about 30,000 genes
Blood Group GenesHuman 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. .
human genome
Rh blood groups is controlled by single gene with ________________. It is another antigen in blood, first discovered in Rhesus monkeys. The arrangement of the alleles determines only _______ possible types _____________ (+) contains the antigen, or ___________ (-) doesn’t contain the antigen. Positive is ______________ over negative.
Rh-positive is identified with two genotypes: Rh+/Rh+ or Rh+/Rh-
Rh-negative is identified with one genotype: Rh-/Rh-
Two alleles
two positive
negativedominant
ABO Blood Groups: Discovered in 1900 by Karl Landsteiner. He realized that all blood is classified into four types: ____, ____, ____, and _____ due to the presence of or absence of specific __________ in the blood. Alleles IA and IB are __________________ and io is ________________ to both IA and IB
OABBA
codominant
recessive
Antigens are ______________________ used by the immune system. When an unrecognized antigen is present an immune response takes place and the cells ____________________________.
chemical markers
antigens
clump or agglutinate
Phenotype(Blood Type Genotype
Antigen on Red Blood Cell
Safe Transfusions
To From
Section 14-1
Figure 14-4 Blood Groups
Go to Section:
Blood Type and Antigen Interactions
B. Recessive Alleles: Trait controlled by a recessive allele. This results in the disorder being present ___________________________.
• Examples include: PKU (Phenylketonuria), Tay Sachs disease and Cystic Fibrosis, Albinism, and Galactosemia (See chart on page 345)
only if both alleles are recessive
C. Dominant Alleles: Traits controlled by a dominant allele. This results in the disorder being present when __________________________.
• Examples include: Achondroplasia (dwarfism), Hypercholesterolemia, and Huntington’s Disease
only one allele is present
caused by
Section 14-1
includeincludeinclude
AutosomolDisorders
Recessive alleles
Dominant allelesCodominant
alleles
Albinism Galactosemia Tay-Sachs disease
Huntington’s disease
Sickle cell disease
Cystic fibrosis
Phenylketonuria AchondroplasiaHypercholes-
terolemia
Autosomal Disorders
Huntington Disease:
It is controlled by a _________________________. The gene is located on Chromosome #4.
single dominant allele
Genetic degenerative disease that shows no symptoms until a person is in their ____________________. It progresses with gradual degeneration of their nervous system leading to loss of muscle control and mental function until death occurs.
thirties or forties
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 _______________________________________. Sickle Cell Anemia is such a disorder. (This will be discussed in detail later)
two alleles that share dominance
IV. From Gene to Molecule
The link between ______________________
is not easily determined but for several diseases we
have been able to make the connection.
For both _____________ and ________________
a small change in the DNA of a _____________
affects the ______________________, causing a
serious genetic disorder.
genetics and phenotype
Cystic fibrosis Sickle cell disease
single gene
structure of a protein
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 found on the # 7 chromosome and affects the______________________________
Recessive disease
digestive and respiratory systems
It is caused by the____________________ in
the middle of a sequence for a protein and
causes the protein to be ______________ 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
__________________.
deletion of 3 bases
abnormal
clogged with mucus
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.
Section 14-1
Figure 14-8 The Cause of Cystic Fibrosis
B. Sickle Cell Anemia
The patient’s blood cells were found to be
irregularly shaped, ____________________,
and this is how the disease got its name.
In normal red blood cells the
____________________ 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 _____________________
like a sickle
hemoglobin molecule oxygen
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
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 crystallization causes the ________________ of the blood cells and the medical consequences.
single base
crystallize
sickle shape
The genetics: The allele for sickle cell (HS) is ___________ with the allele for normal hemoglobin (HA). codominant
Heterozygotes (HS HA) are said to be ____ ____ __________ and have some effects of the disorder because they have both normal and sickle cell blood hemoglobin.
Sickle cell carriers
DNA normal hemoglobinCAC GTG GAC TGA GGA CTC CTCMessenger RNA sequence
GUG CAC CUG ACU CCU GAG GAGNormal hemoglobin amino acid sequenceVal – His – Leu – Thr – Pro – Glu – Glu… 1 2 3 4 5 6 7 …146 DNA Sickle Cell Anemia CAC GTG GAC TGA GGA CAC CTCMessenger RNA sequenceGUG CAC CUG ACU CCU GAGVal – His – Leu – Thr – Pro – – Glu… 1 2 3 4 5 6 7 …146
The distribution: Sickle Cell anemia is most prevalent in people of __________________. 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 ___________________, a dangerous disease caused by a blood parasite found in tropical areas of the world.
African descent
resistance to Malaria
Sickle Cell Anemia is a __________ that has provided an ____________ in Malaria prone areas and in these areas it is _______________________ and therefore Sickle Cell Anemia persists.
favored by natural selection
HS HA
HS
HA
HS HS HS HA
HS HA HA HA
advantagemutation
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 ______________________ of DNA. All neatly packed into the 46 chromosomes.
__________________ of the DNA actually functions as genes.
Genes are located on the chromosomes and each gene occupies a ______________________ on a chromosome.
Genes may exist in ____________________ (alleles)
Each chromosome contains ______ of the alleles for each of its genes
Chromosome #21 and 22 are the ____________ of the human autosomes. These were the first two chromosomes whose sequences had been determined.
6 billion base pairs
Small part
specific place
several formsone
smallest
Both also contain genes for some genetic
disorders like ________________________
___________________________
We also discovered that there are many
_________________________ segments of DNA
Human chromosomes also have
________________ that can cross over just as we
saw in the fruit fly.
Leukemia and Amyotrophic Lateral Sclerosis (ALS)
non-coding, repeating
Linked genes
II. Sex-linked Genes
1. _______________________ are the ones that
__________ in males and females
2. Chromosomes that are the ________ in male and females = _______________
3. In humans: females = ____ and Males = ____
4. The Y chromosome is smaller than the X
Sex Chromosomes
differ
sameautosomes
XX XY
A. Sex Determination
1. Female _________ carry an X chromosome
2. _________ gametes can carry either an X or Y (meiosis segregates the chromosomes; _______ of the sperm carry X and ______ of the sperm carry Y)
3. In humans, _____________________________ of an offspring
Female: XX
male: XY
gametes
Male50%
X
males determine the sex
X
YX
XX XY
XX XY
50%
In some animals such as birds, butterflies, and
some fish, the female determines the sex
because she has the __________ chromosomes.
Sex-linked Genes 1. In addition to determining the sex of an
individual, the sex chromosomes carry genes
that ____________________
differing
affect other traits.
Sex-linked Genetic DisordersMay be on the X or Y chromosome, but Most often expressed in ____________because they only have one X chromosome and thus all the alleles are expressed even if they are recessive.
usually on the X because the Y has very few genes.males
Colorblindness is a recessive disorder in which people can’t distinguish between certain colors. ____________________ colorblindness is most common. XC and Xc are ________________ for normal and colorblind vision.
Red-green
the alleles
XC XC and XC Xc are
XC Xc is a _______________________ and can pass the gene on to her sons.
Xc Xc is a
XC Y is a
Xc Y is a
both normal vision females.
carrier for colorblindness
colorblind female.
normal male and
colorblind male.
http://www.toledo-bend.com/colorblind/Ishihara.html
Father(normal vision)
ColorblindNormal vision
Mother (carrier)
Daughter(normal vision)
Son(normal vision)
Daughter(carrier)
Son(colorblind)
Section 14-2
Male
Female
Figure 14-13 Colorblindness
Go to Section:
Colorblindness
Father(normal vision)
ColorblindNormal vision
Mother (carrier)
Daughter(normal vision)
Son(normal vision)
Daughter(carrier)
Son(colorblind)
Section 14-2
Male
Female
Figure 14-13 Colorblindness
Go to Section:
Colorblindness
Hemophilia is a __________________________ in which one is unable to clot their blood. Also known as Hemophilia is caused by a defect in a gene and the protein for normal blood clotting is missing.
recessive sex-linked disorder
“bleeders disease”.
Slide 16
Figure 21.12Page 394
Slide 18
I
II
III
IV
V
VI
Albert Victoria
Figure 21.13Page 394
Royal Family and Hemophilia
Muscular Dystrophy is another
Here the affected individual inherits a degenerative __________disorder. The gene that codes for a _____________ is defective. They rarely live past early adulthood. Treatments are being explored that ___________ the defective gene.
sex-linked recessive disease.
muscle
muscle protein
replace
III. X-Chromosomes InactivationMales survive with only one X chromosome so,
what do females do with 2? They ___________; it becomes inactive. This creates a dense region in the nucleus known as a ______________.
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 only happens in __________ because males only have one X chromosome.
shut one off
Barr body
calicofemales
IV. Chromosomal Disorders
Whole/sets of chromosome mutations1. _______________ = failure of homologous
chromosomes to separate normally during meiosis
This results in a disorder of __________________
2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome
Nondisjunction
chromosome number
Homologous chromosomes fail to separate
Meiosis I:Nondisjunction
Meiosis II
Section 14-2 Nondisjunction
Go to Section:
Homologous chromosomes fail to separate
Meiosis I:Nondisjunction
Meiosis II
Section 14-2
Nondisjunction
Go to Section:
Homologous chromosomes fail to separate
Meiosis I:Nondisjunction
Meiosis II
Section 14-2
Go to Section:
Nondisjunction
Slide 23
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 21.19Page 398
Nondisjunction
2. Examples of disorders include Down’s Syndrome, Klinefelter’s, and Turner’s Syndrome
Nondisjunction disorders: Disorders in which the failure of _____________________ during one of the stages of meiosis causes a gamete to have _______________________________.
Nondisjunction can occur in ___________________________.
chromosome separation
too few or too many chromosomes
autosomes or sex chromosomes
Down’s Syndrome: Down’s syndrome is an example of ____________________________, specifically chromosome 21.
In Down’s syndrome there is an ___________ of chromosome 21 (trisomy 21).
Doing a _____________ (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 _________________, physically challenged, facial irregularities, and often heart defects.
nondisjunction of an autosome
extra copy
karyotype
mental retardation
Slide 24
inc
ide
nc
e p
er 1
,00
0 b
irth
s
20
15
10
5
020 25 30 35 40 45
mother's age
Fig. 21.20a,bPage 399
Incidence of Down’s Syndrome and mother’s age
Turners Syndrome: Nondisjunction of the sex chromosomes in which
They have the chromosome makeup of _________ where “O” represents the missing chromosome.
45 XO
a chromosome is missing.
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 chromosomes in which an _____________________ is present.
They have the chromosome makeup of ________. They are ___________ in appearance and are also sterile. May also be 48 XXXY or 49 XXXXY
extra X chromosome
47XXY
male
No nondisjunctions of the sex chromosomes have ever produced and survived without an ______________. This is because the X chromosome carries many genes
X chromosome
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
Slide 25
Figure 21.21Page 399
XX
XX
O
XX
O
O
XX
Y
Y
X
X
x
x
x
x
XXY
XXX
YO
XO
gamete
nondisjunction
gamete
or
or
meiosis and gamete formation
possibilities at fertilization
genotype (phenotype)
(Klinefelter syndrome)
(“metafemale”)
(not viable)
(Turner syndrome)
The impact of the sex chromosome nondisjunction has led us to understand the importance of the _____________________ 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 ______________________ in the embryo even if many X chromosomes are present.
Y chromosome
male sexual development