Download Chapter 13 - Pierce Public Schools

Chapter 12
Advanced Genetics
Mutations
• Mutation: a change in __.
– May involve :
• an entire __
• a specific __
– may take place in __ cell
• When a mutation takes place the DNA is
changed which affects the production of __.
This may affect metabolism, development, or
result in a new phenotype.
Mutations in reproductive cells
• Germ cell mutation - occurs in the __ cells.
– This does not affect that organism but may be passed on
to the __.
• If this cell takes part in __, the altered gene would
become part of the genetic makeup of the offspring.
Mutations in reproductive cells
result in:
• A __ mutation - the embryo does not survive.
• A __ that does not work correctly.
• In some rare cases it may have a __ effect.
Mutations in body
cells
• __ mutations - mutations in body cells
– Ex)
• This mutation would __ be passed on to offspring.
Mutations in body
cells result in:
• Impairing the __ of the cell.
• When that cell divides, the new cells also will have
the same mutation.
• Affecting genes that control __.
– Cells may grow and divide rapidly, producing __
Types of Mutations
• A) __: a change in a single base pair in DNA.
– A single nitrogen base is __ by another
• This may have __ noticeable affect or it can change
the entire structure of a __ because a change in a
single amino acid can affect the shape of the protein.
The effects of point
mutations
Normal
mRNA
Stop
Protein
Replace G with A
Point mRNA
mutation Protein
Stop
• B) __: mutation in which a single base is added or
deleted from DNA.
– Results in every __ after either the added or deleted base to
be different.
• This mutation would cause nearly every __ in
the protein after the __ to be changed.
Frameshift mutations
Deletion of U
Frameshift mRNA
mutation Protein
• C) __: Structural changes in chromosomes.
– Occur during __
– can be either changes in the __ of a chromosome or a __ of
an entire chromosome.
– Are more __ types of mutations.
– __ are passed on to the next generation because the zygote
usually dies.
– In cases where the zygote lives and develops, the mature
organism is often __.
Types of Chromosomal
Alterations
• 1) Deletion- __.
– It breaks off and all that information is now lost.
A B C D E
F G H
A B C E
Deletion
F G H
Chromosomal
Alterations
• 2) Duplication (__)- When part of a chromatid breaks
off and attaches to its sister chromatid.
• The result is a duplication of genes on the __
chromosome.
A B C D E
F G H
A B C B C D E
Insertion
F G H
Chromosomal
Alterations
• 3) Inversion- When part of a chromosome breaks off
and __.
A B C D E F G H
A D C B E FGH
Inversion
Chromosomal
Alterations
• 4) Translocation- When part of one chromosome
breaks off and is added to __.
AB C D E F GH
WXY Z
WXAB C DE F GH
Y Z
Translocation
Causes of
Mutations
• 1) __ mutations: mutations that just seem to happen
• How?
– Errors in __ (mistake in base pairing)
– Errors in __
Causes of
Mutations
• 2) __: Any agent that can cause a change in the __
(mutation)
• These are environmental factors such as:
– a) __: such as X rays cosmic rays, ultraviolet light, and
nuclear radiation.
– The energy they contain can damage or break apart __.
Causes of
Mutations
– b) __ mutagens: include dioxins, asbestos, benzene, and
formaldehyde.
• Usually cause substitution mutations
– c) __
*__- Procedure used to identify mutagenic substances.
Repairing DNA
• __ proofread the DNA and replace incorrect
nucleotides with correct nucleotides.
• However, the __ the exposure to a mutagen such as
UV light, the __ likely is the chance that a mistake
will not be corrected.
Pedigrees illustrate inheritance
• Pedigree: a graphic representation of __
inheritance.
– Like a __.
• It is a diagram made up of a set of __ that identifies
individuals affected by the trait being studied, and
family relationships.
Male
Parents
Female
Siblings
Affected
male
Affected
Known heterozygotes
female for recessive allele
Mating
Death
Pedigrees
illustrate
inheritance
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Female
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Male
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4
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Pedigrees
illustrate
inheritance
• In a pedigree, a
__ represents a
female; a __
represents a
male.
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Pedigrees
illustrate
inheritance
• Highlighted circles
and squares
represent
individuals showing
the trait being
studied.
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Pedigrees
illustrate
inheritance
• Circles and squares
that are not
highlighted
designate
individuals that do
not show the trait.
Pedigrees illustrate inheritance
• A half-shaded
circle or square
represents a __: a
heterozygous
individual.
Pedigrees illustrate inheritance
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• A horizontal line
connecting a circle
and a square indicates
that the individuals
are parents (__ line),
and a vertical line
connects parents with
their offspring (__
line).
Pedigrees illustrate inheritance
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IV
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• Each horizontal
row of circles and
squares in a
pedigree designates
a __, with the most
recent generation
shown at the
bottom.
Pedigrees illustrate inheritance
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IV
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2
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• The generations
are identified in
sequence by __,
and each
individual is given
an Arabic number.
Detecting Genetic Disorders
• 1) __: an examination of a persons genetic
makeup.
– This may involve:
• A) Blood test - looks for the presence or absence of certain __
Detecting Genetic Disorders
• B) Karyotype- __.
– Procedure: remove __ from a cell
– stain and photograph chromosomes
– cut out each chromosome
– match it with its __
Detecting Genetic Disorders: In a fetus
• 1) __- uses high-frequency sound waves to
produce an image of a fetus on a moniter
– image is called a __
• 2) Amniocentesis- __.
– Use a needle and syringe to remove some amniotic fluid.
– Make a __ and analyze.
Detecting Genetic Disorders: In a fetus
• 3) Chorion villi sampling- analyze a sample
of the chorion villi (tissue that grows between
the __.)
– villi has the same __as the fetus.
• 4) __- a visual procedure for observing disorders in
the fetus.
– Uses an instrument called an __
– can: observe fetus’ development, take skin and blood
samples for analysis, do blood transfusions, and remove
excess fluid from the brian.
Simple Recessive Heredity
• Most genetic disorders are caused by __ alleles.
1) Cystic fibrosis
• Due to a defective __ in the cell membrane.
• Results in the formation and accumulation of thick
__ in the lungs and digestive tract.
• Common among __. (1 in 28 carries the allele, 1 in
2500 inherits the disorder)
• Average lifespan: __ yrs.
2) Tay-Sachs disease
• Tay-Sachs (tay saks): a recessive disorder of the __.
• Results in the absence of an __ that normally
breaks down a __ produced and stored in tissues of
the central nervous system.
• Therefore, lipids accumulate in the cells.
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Typical
Pedigree
for
Tay-Sachs
3) Phenylketonuria
• Phenylketonuria (fen ul kee tun YOO ree uh): (PKU)
the absence of an __ that converts one amino acid,
phenylalanine, to a different amino acid, tyrosine.
• Phenylalanine and its by-products accumulate in
the body resulting in severe damage to the __.
• A PKU test is normally performed on all __ a few
days after birth.
• Infants affected by PKU are given a diet that is low
in __ until their __ are fully developed.
Phenylketonuria
• New Problem: If a female who is homozygous
recessive for PKU becomes __, the high
phenylalanine levels in her blood can damage her
__ - the developing baby.
• This problem occurs even if the fetus is __ and would
be phenotypically normal.
Phenylketonuria
Phenylketonurics: Contains Phenylalanine
Simple Dominant Heredity
• A single dominant allele inherited from __ parent is
all that is needed for a person to show the dominant
trait.
Simple dominant traits:
• 1) __
• 2) widow’s __
• 3) hitchhiker’s thumb
• 4) almond shaped __
• 5) thick lips
• 6) presence of __ on the
middle section of you
fingers
Huntington’s disease
• A __ genetic disorder
• Caused by a rare __ allele.
• Results in a breakdown of certain areas of the __.
• Symptoms: __ and irritability,
eventually lose
of __ control, uncontrollable physical __, severe
mental illness, and eventually __.
Huntington’s disease
• Usually occurs between the ages of __
– An individual may already have had children
before knowing whether he or she is affected.
• __: a short section of __ that indicates the presence
of an allele that codes for a trait.
– __of people with this marker have a chance of
developing HD
– can test before they have __.
Typical Pedigree of Huntington’s Disease
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Question 1
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What does
this
pedigree tell
you about
those who
show the
recessive
phenotype
for the
disease?
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1
The pedigree
indicates that
showing the
recessive
phenotype for the
disease is __.
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Genetic Patterns
• Thomas Hunt __ (early 1900’s)
– Began a series of breeding experiments with Drosophila
melanogaster (__) Why use fruit flies?
• Easy to maintain in a laboratory
• have a generation time of only __ days
• produce __ of offspring from each mating
• have easily distinguishable __ characteristics
• have only __ chromosomes
Genetic Patterns
• He discovered that __ pair of chromosomes were
different in males and females.
– In females: all pairs were __
– In males: the __ pair was different
• He called the large chromosome in the 4th pair the “__”
chromosome and he called the short hooked one the
“__” chromosome.
• The same applies to __.
– Other organisms differ
Sex determination
• In humans the __ number of chromosomes is 46, or 23
pairs.
• __ chromosomes: Chromosomes that determine an
individual’s sex. They are the __ pair in humans and
they differ in males and females.
• __: A chromosome that is not a sex chromosome. There
are __ pairs of homologous autosomes in humans. They
all look alike.
Sex determination
• If you are __, your 23rd
pair of chromosomes
are homologous, __.
X
X
Female
• If you are __, your 23rd
pair of chromosomes
__, look different.
X
Male
Y
Sex determination
• Males: Produce two kinds of __, X and Y.
• Females: Produce only __ gametes.
• It is the __ gamete that determines the sex of the
offspring.
Sex
determination
X
X
XX
Female
XY
Male
Y
XX
Female
XY
Male
XX
Female
XY
Male
X
Sex-linked inheritance
• __ hypothesized that some traits were always
associated with one __ or the other.
– Ex) Most fruit flies have __ eyes
• crossed a white-eyed male with a red-eyed female
• F1 - all had red eyes
• Next he crossed the F1 generation
• expected a __ratio. He got it BUT…..
• Noticed all white-eyed flies were __. (in this example)
• His hypothesis: The allele for eye color in fruit
flies must be carried on the __ chromosome.
Sex-linked inheritance
• Sex-linked traits: Traits controlled by genes
located on the __.
• The alleles for sex-linked traits are written as __
of the X or Y chromosomes.
• The __ chromosome has no corresponding allele
to one on the X chromosome and no __ is used.
(Since X and Y are not homologous)
• Therefore, any __ allele on the X chromosome of
a male will __ be masked by an allele on the Y
chromosome.
Sex-linked inheritance
White-eyed male
(XrY)
F2
Females:
all red
eyed
Males:
Redeyed
female
(XRXR)
1/2 red
eyed
F1 All red
eyed
1/2 white
eyed
Sex-Linked Traits in Humans
• Many human traits are determined by genes that are
carried on the __; most of these genes are located on
the __ chromosome. (Not the Y)
• These traits are more common in __. WHY?
– The __ chromosome does not carry a gene for these
traits so whatever allele is on the X chromosome is what
trait will be expressed. (Dominant or recessive)
– Sons inherit these traits from their __ since that is who
they are receiving the __ chromosome from.
Sex-Linked Traits in Humans
• Females, who are XX, pass one of their X
chromosomes to __ child.
Male
Female
Female
Sperm
Eggs
Eggs
Male
Sperm
FemaleFemale Male Male Female Male Female Male
Example: __color blindness
• Caused by a __ allele
• These people can’t
differentiate between red or
green.
• __of males are color blind.
• Is __ in females.
Example: Hemophilia
• Hemophilia A: The __ does not clot properly
because it lacks a __ essential for clotting.
• __: about one in every 10 000 has hemophilia. __:
only about one in 100 million inherits it.
– Females would need __ recessive alleles to inherit
hemophilia.
– Males inherit it from their carrier __. (One allele will
cause the disorder in males.)
Polygenic inheritance
• Polygenic inheritance: is the inheritance pattern of
a trait that is controlled by __.
• Genes may be on the __ chromosome or on __
chromosomes. (Each gene may have two or more
alleles.)
• All heterozygotes are __ in phenotype.
– Phenotypes show a continuous range of variability.
– Ex) Plants:
• aabbcc - 4cm tall
• AABBCC - 16cm tall
•
Polygenic Inheritance in Humans
• Examples:
– __
– __
– __
– __
__: A polygenic trait
• Scientists found that when light-skinned people mate
with dark-skinned people, their offspring have __
skin colors.
• The __ genes, the __ ranges of skin color.
Skin color: A polygenic
trait
Number of
individuals
Number of Genes Involved in Skin Color
Observed
distribution
of skin
color
Light
Expected
distribution1 gene
Range of skin
color
Expected
distribution4 genes
Expected
distribution3 genes
Right
• This graph shows
the expected
distribution of
human skin color
if controlled by
one, three, or
four genes.
Studying Human Genetics
• Problem:
– May take __ years to produce 3 generations of humans.
– Each generation will produce only a __ individuals.
– Because of ethical __, scientists are prevented from using
same procedures they would use on other organisms.
• Human inheritance patterns are very
complicated. Their chromosomes contain atleast
__ genes (7 times more than Drosopohila)
– SO……. How do scientists go about it?
Studying Human Genetics
• 1) Population sampling: __
– use carefully formulated statistical rules to select
members of a sample to ensure they get accurate results.
– Ex) Used to estimate the percentage of people in the U.S.
who could __ the chemical phenylthiocarbamide (PTC)
– “Tasters” - detect a bitter taste to PTC (65% of pop.)
– “Nontasters” do not detect any taste (35% of pop.)
Studying Human Genetics
• 2) __: Geneticists study __ twins to distinguish
between genetic and environmental influences on
certain traits.
– Identical twins - have the same __ information.
Differences may result from environmental influences
(home life, education, etc…) Is more easily studied if
raised by __ families.
• 3) __: Shows how traits have been passed down
through the __.
Environmental Influences
• The genetic makeup of an organism only determines
the organism’s __.
• As the organism develops, many factors can
influence how the __ is expressed, or even if it is
expressed at all.
• Two influences are:
– 1) __ environment
– 2) __ environment
Influence of external environment
• A)
• B)
• C)
• D)
• E)
Influence of external environment
• In arctic foxes __
has an effect on the
expression of coat
color.
Influence of external environment
• External influences can also be seen in leaves.
Leaves can have different sizes, thicknesses, and
shapes depending on the amount of __ they receive.
Influence of internal environment
• A) __-influenced trait:
trait that is influenced by
the presence of male or
female sex __. Males and
females have different
hormones therefore __ are
expresses differently.
– Ex) __ pattern baldness
• __ in males
• __ in females
• B) __ can also affect
gene function.
__ in Humans
• Both alleles are __ expressed in the heterozygous
offspring.
• Example: Sickle-cell disease (Sickle-cell anemia)
Sickle-cell disease
• A - dominant allele, produces normal __
• A` - codominant allele, produces abnormal
hemoglobin. (affects ability to carry __)
• AA` - have both __ and __ hemoglobin
– The defective hemoglobin changes the shape of the __.
• Normal red blood cells are __-shaped
• Abnormal red blood cells are shaped like a __, or half-moon.
Sickle-cell disease
• The change in shape occurs in the body’s narrow __
after the hemoglobin delivers oxygen to the cells.
Normal
red blood
cell
Sickle
cell
Sickle-cell disease
• Results in : 1) Impairing the flow of __ 2) Slows __
flow, 3) __ clots, 4) Tissue damage and __ 5) __, 6)
__, 7) Eventually failure of vital __.
Normal
red blood
cell
Sickle
cell
Sickle-cell disease
• Affects mainly __ population.
– In U.S. __ of Black population carry the sickle-cell allele
– In Africa as many as __ carry it.
• Advantage to being a carrier:
• The parasite responsible for __ cannot survive in sickle cells,
therefore, they are more likely to survive malaria.
Huntington’s Disease (HD)
• Cause by a __ allele.
• Symptoms: Forgetfulness, irritability first.
Eventually loss of muscle control, uncontrollable
physical spasms, severe mental illness, eventually
death.
• Problem: Carriers do not know they have the disease
until after they’ve had __.
• __: a short section of __ that indicates the presence
of an allele that codes for a trait.
– Ex) __of people with this marker develop HD
Changes in Chromosome Numbers
• __: when a replicated chromosome pair fails to
separate during cell division.
• One daughter cell receives an __ chromosome and
the other daughter cell __ a chromosome.
Abnormal numbers of autosomes
• Trisomoy: Cells that have an __ autosome (they
have __ of a particular chromosome instead of two.)
– Results in __ chromosomes
• Monosomy: Cells that are __ an autosome. (they
have __ of a particular chromosome instead of
two.)
– Results in __ chromosomes
__ syndrome: Trisomy 21
• Results from trisomy of chromosome __.
• Individuals who have Down syndrome have at least
some degree of __ retardation, folds of skin above
the __, weak __, enlarged tongue, a rounder, fuller
face, and are __ in height.
• The incidence of Down syndrome births is higher
in older mothers, especially those over __.
Down syndrome: Trisomy 21
• Down syndrome is
the __ autosomal
trisomy in which
affected individuals
__ to adulthood.
• It occurs in about
one in __ live
births.
Abnormal numbers of sex
chromosomes
• Klinefelters Syndrome:
– caused by __
– results in a __ of XXY
– is a __ with mental retardation, and low fertility
– occurs 1:1000 births
• __ Syndrome:
– caused by nondisjunction
– results in a __ of XO
– is a __ with immature physical development, sterility, and
webbed neck.
– Occurs 1: 10,000 births
Mapping and Sequencing the
Human Genome
• Genome: __.
• Human __ Project (HGP): organized by scientists in
the United States in __.
– It is an international effort to completely __ and
sequence the approximately 35,000-40,000 __ on the 46
human chromosomes. (human genome)
Mapping and Sequencing the
Human Genome
• In February of 2001, the HGP published its working
draft of the __ base pairs of __ in most human cells.
Applications of the Human
Genome Project
• Improved techniques for prenatal diagnosis of human
__, use of __ therapy, and development of new
methods of __ detection are areas currently being
researched.
Linkage maps
• Linkage map (__): Shows the relative locations of __
on a chromosome.
– These genes are usually __ together
– Exception: __
• These maps are made by studying the __data
Linkage maps
• Example using Drosophila
– wing shape/eye color: linked 90% of the time, crossed
over __ of the time.
– Wing shape/body color: linked 93% of the time, crossed
over __ of the time.
– Eye color/ body color: linked 83% of the time, crossed
over __ of the time.
• This information is used to create a linkage map.
(Atleast __ traits must be compared)
Linkage maps
• __: A unit in chromosome mapping equal to a __
occurrence of crossing over.
• Example: If wing shape and eye color cross over 10
% of the time then they are __ map units apart.