Download The Human Genome - Animo Venice Biology

The Human Genome
& Human Heredity
January 6th/7th, 2008
Human Chromosomes
46 total (23 from mom and 23 from dad)
Key Terms
Sex Chromosomes – two of the 46 total
chromosomes. Determine whether a baby
will be a boy or a girl.
• If a baby gets an X from its mom and a Y
from its dad, it will be a boy.
• If a baby gets an X from its mom and an X
from its dad, it will be a girl.
Autosomal Chromosomes – the remaining
44 chromosomes. Where most of your
inherited traits come from.
Different Types Of Inheritance
Sex Linked Inheritance- applies specifically
to genes located on the X chromosome.
•Females – because they have two X chromosomes – are
more likely to be carries and not show defective trait. This is
because they would need the mutated gene on both
chromosomes.
•Males – because they only have one X chromosome – are
more likely to express the disease. This is because there are
really no genes on the Y chromosome to cover the effects of
the abnormal X chromosome.
Sex Linked Inheritance- ex. Color blindness.
Male (XY) are more
likely to be affected and
show the trait because
they only have one X
chromosome.
Males can pass gene only
to daughters. Why?
Practice
1. How is color blindness transmitted?
Different Types Of Inheritance
Sex Linked Inheritancew
Are You Color Blind?
25. Everyone should see this.
29. People who are
RED/GREEN color blind will
not see anything.
Are You Color Blind?
45. People who are color blind
will not see anything.
56. Even people who are color
blind should see this.
Some Autosomal Disorders in Humans
Type of Disorder
Disorder
Major Symptoms
Disorders caused by
Albinism
Lack of pigment in skin, hair, and eyes.
recessive alleles
Cystic fibrosis
Excess mucus in lungs, digestive tract, liver;
increased susceptibility to infections.
Galactosemia
Accumulation of galactose (a sugar) in tissues;
mental retardation; eye and liver damage.
Phenylketomuria (PKU)
Accumulation of phenlalanine in tissues; lack
of normal skin pigment; mental retardation.
Tay-Sachs disease
Lipid accumulation in brain cells; mental
deficiency; blindness; death in early childhood
Disorders caused by
Achondroplasia
Dwarfism (one form)
dominant alleles
Huntington disease
Mental deterioration and uncontrollable
movements; symptoms usually appear in
middle age
Hypercholesterolemia
Excess cholesterol in blood; heart disease
Sickle cell disease
Misshapen, or sickled, read blood cells;
damage to many tissues
Disorders caused by
codominant alleles
Practice: Human Inherited Disorders
Autosomal Dominant and Autosomal Recessive Traits
1. In autosomal recessively inherited disorders, do heterozygotes (also called
“carriers”) show the genetic disorder? Why or why not?
2. In a recessive disorder, what is the probability of an offspring having the disorder
when two carriers mate? Prove it.
3. What are two examples of recessive inherited disorders? Briefly explain the
symptoms of each of the disorders.
4. Why are males more likely to have a recessive disorder than females?
5. What are the chances two carriers of Huntington’s disease will pass the trait to
their offspring? Prove it.
Nondisjunction
Normally Chromosome pairs are
pulled to opposite ends during
Anaphase I and II. Nondisjunction
is when chromosomes do not
properly separate. Gametes with the
wrong number of chromosomes
usually do not survive.
A few exceptions…
• Down’s syndrome-Trisomy 21 (47
chromosomes)
• Turner syndrome X 0 (45 chromosomes)
• Klinefelter;s syndrome – XXX (47
chromosomes)
Activity: Looking at Karyotypes
Questions to answer:
1. Circle the sex chromosomes.
2. Male or Female? _____
3. Normal or Abnormal? _________
4. If abnormal, circle the
abnormality and tell what disease
is present.
Activity: Looking at Karyotypes
Questions to answer:
1. Circle the sex chromosomes.
2. Male or Female? _____
3. Normal or Abnormal? _________
4. If abnormal, circle the
abnormality and tell what disease
is present.
Activity: Looking at Karyotypes
Questions to answer:
1. Circle the sex chromosomes.
2. Male or Female? _____
3. Normal or Abnormal? _________
4. If abnormal, circle the
abnormality and tell what disease
is present.
Activity: Looking at Karyotypes
Questions to answer:
1. Circle the sex chromosomes.
2. Male or Female? _____
3. Normal or Abnormal? _________
4. If abnormal, circle the
abnormality and tell what disease
is present.
Home Work: Genetic Practice
1.
In fruit flies, normal wings (W) are dominant to dumpy wings (w). Two normalwinged flies were mated and produced 298 normal-winged and 100 dumpy-winged
flies. What were the parents’ genotypes?
2.
Hemophilia is an X-linked trait. A normal male person has children with a normal
female who carries the hemophilia allele. What is the probability their offspring will
have hemophilia? What is the probability their daughters will have hemophilia?
What is the probability their sons will have hemophilia?
3.
Color-blindness is an X-linked trait. A male who is colorblind mates with a normal
female. What is the probability their offspring will have color-blindness? What is
the probability their daughters will have color-blindness? What is the probability
their sons will have color-blindness?
4.
In fruit-flies, white eyes are a recessive X-linked trait. If a male mates with a
female and the offspring came up as follows, what were the parents’ genotypes?
Male, White-Eyed
Male, Red-Eyed
Female, White-Eyed
Female, White-Eyed
98
102
99
101
Pedigrees
January 8th/9th, 2008
Human Traits
Pedigree – a chart that shows the relationships
within a family.
A square represents a male.
A horizontal
line connecting
a male and a
female
represents a
marriage.
A shaded circle
or square
indicates that a
person expresses
the trait.
A circle represents a female.
A vertical line and
a bracket connect
the parents to their
children.
A circle or
square that is
not shaded
indicates that
a person does
not express
the trait.
In humans, dimples (D) is dominant to no dimples (d). Complete the pedigree
below. For each individual, list the possible genotypes and the phenotype of each.
dd
Dd
no
dimples
dimples
Dd
Dd
Dd
Dd
DD
dimples
dimples
dimples
dimples
Dd
DD
dd
Dd
DD
Dd
DD
dimples
no
dimples
dimples
dimples
dd
Dd
no
dimples
dimples
dd
Dd
no
dimples
dimples
Problem Solving: Using a Pedigree
Introduction:
Imagine that you are a genetic counselor. The pedigree shown illustrates the
inheritance of albinism – a condition in which a person’s skin, hair, and eyes lack
normal coloring – in three generations of a family. A couple from the family has
come to you for advice about how the trait is inherited. Your task is to determine
whether the allele for albinism is dominant or recessive.
Question to be answered:
1. Based on your analysis of the pedigree, is albinism caused by a dominant or
recessive allele and how do you know?
Procedure:
Inside each circle or square on the pedigree below, label each person with his or her
phenotype: normal pigmented skin (NP) or albino (A). Then, inside each circle or
square, write down each individual’s possible genotype.
Albino
Male
Female
Normal
pigmented skin
Extra Credit
• Office Hour Work – Blood Types
Blood Groups
Multiple AllelesMore than just two
forms of a gene. Much
more realistic but
much more
complicated. Ex.
Blood types 3 alleles
IA,IB,i
Sample Blood type crosses.
Directions: Cross the requested parents on the following pages. For each cross, list
genotypes and genotype ratios; phenotypes, and phenotype ratios.
Type A mom with a Type O Dad.
Genotypes
Genotype Ratios
Genotypes
Genotype Ratios
Phenotypes
Phenotype Ratios
Phenotypes
Phenotype Ratios
Type AB mom with a Type B Dad.
Genotypes
Genotype Ratios
Genotypes
Genotype Ratios
Phenotypes
Phenotype Ratios
Phenotypes
Phenotype Ratios
Type B mom with a Type A Dad.
Genotypes
Genotype Ratios
Phenotypes
Phenotype Ratios
Genotypes
Genotype Ratios
Phenotypes
Phenotype Ratios
Genotypes
Genotype Ratios
Genotypes
Genotype Ratios
Phenotypes
Phenotype Ratios
Phenotypes
Phenotype Ratios