Transcript Ch. 14 The Human Genome

Ch. 14 The Human
Genome
Ch. 14 Outline
 14-1: Human Heredity
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Human Chromosomes
Human Traits
Human Genes
From Gene to Molecule
Ch. 14 Outline
 14-2: Human Chromosomes
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Human Genes and Chromosomes
Sex-linked Genes
X-Chromosome Inactivation
Chromosomal Disorders
 14-3: Human Molecular Genetics
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Human DNA Analysis
The Human Genome Project
Gene Therapy
Ethical Issues in Human Genetics
Human Chromosomes
 Karyotypes:
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A picture of chromosomes arranged by
homologous pairs
 Humans have 23 pairs (46 total) chromosomes.
 Two of the 46 chromosomes are called sex
chromosome because they determine and
individual’s sex.
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In Human’s:
 Female –
 Male –
Human Chromsomes
 Autosomes: the remaining 44
chromosomes. They do not determine
the sex of the organism.
 All Human egg cells carry a single X
chromosome.
 Half of all sperm cells carry an X
chromosome and half carry the Y.
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This is why the ratio of males to
females is 50/50.
Human Traits
 Scientists use a pedigree chart to help
study how a trait is passed from one
generation to the next.
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Pedigree: chart that shows the
relationships within a family.
How to read a 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.
Pedigrees
 These Charts are used to infer the
genotypes of family members. They can
reveal if traits are sex-linked, dominant
or recessive.
Human Genes
 Blood Group Genes
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Knowing a person’s blood group is
important during transfusions.
Two blood groups:
 Rh
groups
 ABO groups
The Rh Blood Group
 The Rh blood group is determined by a
single gene with two alleles: Positive
and negative
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Rh+ is dominant to Rh-
 The Rh factor is named after the Rhesus
Monkey where the factor was first
isolated
 Very important for females to know
during pregnancies.
ABO Blood Groups
 There are three alleles for the ABO
Blood Group:
 IA , I B ,
I
 “i” is the recessive allele. ii  type O
blood
 IAIB are codominant  type AB blood
 IAIA or IAi  type A Blood
 IBIB or IBi  type B Blood
ABO Blood Groups
Phenotype
(Blood Type
Genotype
Antigen on
Red Blood Cell
Safe Transfusions
To
From
Antigens and Blood
Disorders in Humans
 Genetic Disorders may be caused by:
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Recessive Alleles
 Ex.
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CF, PKU, Tay-Sachs
Dominant Alleles
 Huntington’s
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Disease
Codominant Alleles
 Sickle
Cell Anemia
Concept Map
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
Sex-Linked Genes
 Sex-linked genes: Genes Located on
the sex chromosomes
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Many genes are located on the X
chromosome
 Sex-linked disorders are caused by
genes on the X or Y chromosome
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Colorblindness, Hemophilia
X-Chromosome Inactivation
 Females have two X chromosomes but
males only have one. How do females
cells “adjust” to having an extra X if
males can survive with just one?
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One of the X chromosomes in female cells
are randomly switched off. Those are
called Barr bodies.
Chromosomal Disorders
 Nondisjunction: failure of
chromosomes to separate correctly in
meiosis
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This leads to an abnormal number of
chromosomes in gametes
 Ex:
Down Syndrome (3 copies of
chromosome 21  “trisomy”)
Nondisjunction
Homologous
chromosomes
fail to separate
Meiosis I:
Nondisjunction
Meiosis II
The Human Genome Project
 A research project to sequence (identify
in order) all the bases in Human DNA
~3.2 BILLION pairs!
 Some discoveries:
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A large amount of DNA does not code for
proteins
Humans only have 30,000-40,000 genes
(scientists expected 100,000)
The Human Genome Project
Website
 http://www.genome.gov/
 Really interesting Information about the
Human Genome Project. It might help
you understand stuff better.
 EDUCATE YOURSELF!
Gene Therapy
 Information about the human genome
might be used to cure genetic disorders
though the use of gene therapy.
 Gene therapy: the process of changing
a gene that causes a genetic disorder
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It replaces the faulty gene with a normal,
working gene
Ethical Issues
 If Human cells can be manipulated to
cure disease, should biologists try to
engineer people with specific traits?
 What will happen to the human species if
we design our own bodies?
 Should we clone humans?