Transcript Unit 8: Inheritance & Human Genetic Patterns

Inheritance & Human Genetic
Patterns
Chapter 12-13
Thomas Hunt Morgan
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Early 1900’s
Used fruit flies, Drosophila
melanogaster to identify genetic
patterns.
Observed that only male fruit flies
had white eyes
WHY??
Linkage groups
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A group of genes located on one
chromosome.
These genes are usually inherited
together.
Example:
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Fruit flies have 4 pairs of chromosomes
& four linkage groups.
How many linkage groups do humans
have?
Sex Determination
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Sex Chromosomes
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X&Y
Located in 23rd position (human)
XX – female
XY - male
Autosomes
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All other
chromosomes
Sex Linkage
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Traits that are linked to sex
chromosomes.
Gene Maps
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Show the
relative
locations of
each known
gene on an
organisms’
chromosome.
Mutations
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Change in DNA
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Germ cell mutation
Occurs in gametes
 Do no affect the organism
 May be passed on offspring
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Somatic cell mutation
Occurs in body cells
 Not passed to offspring
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LETHAL MUTATIONS: cause death
usually before birth
Gene mutations
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Involve a single nitrogen
base or larger segment of
DNA.
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Point Mutations
 Substitution, addition, or
removal of a single nitrogen
base
Mutagen
 Environmental factor that
damages DNA
 Ex. Carcinogens, tobacco,
tars, UV radiation
Chromosome Mutations
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Deletion
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Loss of a piece of chromosome
Inversion
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Chromosome section breaks off &
reattaches in reverse orientation.
Chromosome Mutations cont…
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Translocation
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Chromosome section
breaks off & reattaches
to another, nonhomologous
chromosome
Nondisjunction
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Failure of a
chromosome to
separate during
meiosis.
Results of Nondisjunction
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Monosomy
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Zygote with 45 chromosomes
Turners Syndrome (XO)
Trisomy
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Zygote with 47 chromosomes
Down Syndrome (Trisomy 21)
Klinefelters Syndrome (XXY)
Trisomy 21
Genetic Traits & Disorders
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Single Allele Traits
(dominant)
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Huntington’s Disease,
Achondroplasia (Dwarfism),
Cataracts, Polydactyly
Single Allele Traits
(recessive)
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Albinism, PKU, Cystic Fibrosis,
Hereditary deafness, Sickle cell
anemia
Genetic Traits continued…
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X-linked Traits
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Multiple Allele Traits
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Blood Types
Polygenic Traits
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Colorblindness, hemophilia, muscular
dystrophy, ichthyosis simplex
Skin, hair, & eye color; foot size, nose length,
height
Sex-influenced Traits
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Male pattern baldness
Detecting Human Genetic Disorders
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Genetic Screening
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Genetic Counseling
Amniocentesis
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Examination of person’s genetic
makeup
Removal of amniotic fluid from mother
Chorionic Villi Sampling
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Villi contain same genetic makeup of
fetus
Continued…
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Karyotype
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Ultrasound
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Picture of an organisms’ chromosomes
Bouncing sound waves off fetus to
create an image
Pedigree
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Family record that shows how traits are
inherited over several generations
Pedigree
DNA Technology
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Genetic Engineering
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Used to identify genes for specific traits
Transfer genes for a specific trait from
one organism to another organism.
Uses of DNA Technology
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Cure diseases
Treat genetic disorders
Improve good crops
Transplanting Genes
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Isolate a gene (ex. Insulin)
Produce recombinant DNA
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Clone DNA
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A combination of DNA from 2 or more
sources.
Allow bacteria time to reproduce
Transgenic animal: A host
organism receiving recombinant
DNA
The Human Genome Project
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Goals:
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To determine the
nucleotide
sequence of the
entire human
genome (approx.
3 billion nucleotide
pairs or 100,000
genes)
To map the location
of every gene.
Gene Therapy
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Treating a disorder by introducing a
gene into a cell or by correcting a
gene defect in a cell’s genome.