Transcript Section Objectives

Human Genetics
and the
Pedigree
Section Objectives
• Understand how different
mutations occur.
• Be able to identify different
diseases and disorders.
Causes of Mutations
• Some mutations seem to just happen,
but many mutations are caused by
factors in the environment.
• Any agent that can cause a change in
DNA is called a mutagen. Mutagens
include radiation, chemicals, and
even high temperatures.
Human Traits are Affected By:
• 1. Dominant and recessive genes that are
inherited
• 2. Environmental Factors like diet and
exercise
Mutations in Reproductive Cells
• Gamete: Sex Cells
• Zygote: Fertilized egg
• Human diploid cell has 46 chromosomes
• Human Haploid cell has 23 chromosomes
Mutations in reproductive cells
• Occurs by changing the sequence in a sperm
or an egg cell.
• If this cell is involved in fertilization, the
offspring has the mutation.
• The mutation may produce a new trait or it
may result in a protein that does not work
correctly. Sometimes, it is nonfunctional, and
the embryo may not survive.
Mutations in body cells/autosomes
• A cell’s DNA is changed, this mutation would
not be passed on to offspring.
• Damage to a gene may impair the function of
the cell. Some mutations of DNA in body cells
affect genes that control cell division. This can
result in the cells growing and dividing rapidly,
producing cancer.
Sex linked Traits/Disorders
• Carried on either the X or the Y
chromosome
• Different diseases
–Colorblindness: Caused by genes
on the X chromosome, causes
people not to make pigments in the
eye needed for color
Sex Linked Traits/Disorders
• Colorblindness: Most people with this
disorder cannot distinguish between reds
and greens
• Why does this affect mostly males?
• 8% of males less than 1% of females
Sex Linked Traits/Disorders
• Hemophilia: free bleeders, people that
lack a factor for normal blood
clotting
• 1:10,000 males
• 1:100,000,000 females
Sex Linked Traits/Disorders
• Muscular Dystrophy: progressive wasting
of skeletal muscle. A defective gene that
codes for a muscle protein dystrophin and
is located on the X chromosome
Chromosomal and Gene Mutations
• A mistake on one or more of the
segments in DNA in either the gene
or the chromosome
• Types: deletion, inversion,
translocation and nondisjunction
Nondisjunction
•In nondisjunction, both chromosomes of
a homologous pair move to the same pole
of the cell during meiosis I anaphase.
•Types:
•Down Syndrome (trisomy 21): mental retardation,
extra 21 chromosome
•Klinefelter Syndrome: extra X chromosome with
the Y chromosome (male)
•Turner Syndrome: missing X chromosome (female)
Nondisjunction
• Turner Syndrome: appear female but are
sterile (XO) no second sex chromosome
present 1:1,000 births
• Klinefelter Syndrome: male in
appearance but are sterile (XXY) there is
a second X chromosome present 1:1,000
births
Nondisjunction
• Down’s Syndrome: nondisjunction of
autosomes (trisomy 21) There is an extra
copy of chromosome 21. Results in
Mental Retardation mild to severe, short
neck, eyes spaced apart, short webbed
fingers
Tests to Detect Chromosomal
Abnormalities
• 1. Amniocentesis – remove a small
amount of amniotic fluid
• 2. Chorionic Villus Biopsy – sample of
embryo cells from the choroin (placental
tissue)
Inherited Traits
• Blood Types: A, B, AB, O
• RH Factor: + or – ( used to determine the
risk of hemophilia)
• A has the A antigen on red blood cells
and the B antibody in plasma
• B has the B antigen on red blood cells
and the A antibody in plasma
Blood Types Cont:
• AB has bot A and B antigens in red blood
cells but neither A or B antibodies in
plasma
• O has neither A or B antigens in red
blood cells but has both A and B
antibodies in plasma
Blood Donation Rules
• Negative Blood is given to negative
blood type
• Positive Blood or negative blood can be
given to positive patients
• Universal red blood cell Donor is O• Universal plasma donor is AB+
Sickle Cell Anemia
• Red blood cells are moon shaped and
deprive organs of oxygen
•Can result in death
•Mostly in African Americans
10% African Americans
40% of African Population
Other Genetic Disorders
• Huntington Disease: nervous system
disorder with loss of muscle control,
mental deterioration and death starts
from age 30 to 40.
•Cystic fibrosis: thickening of mucus
lining in lungs.
•PKU: can develop into retardation
(prevented if caught at birth)
Polygenic Traits
• Traits controlled by many genes
Examples: height, weight, skin color
• This is why children of 1 couple skin
color height and weight may vary
Section Objectives:
• Interpret a pedigree.
• Identify human genetic disorders
caused by inherited recessive
alleles.
• Analyze the pattern of sex-linked
inheritance.
Pedigrees illustrate inheritance
• A pedigree is a diagram made up of a
set of symbols that identify males and
females, individuals affected by the
trait being studied, and family
relationships.
• Carriers (have 1 copy of the recessive
allele)
Male
Parents
Female
Siblings
Affected
male
Affected
female
Mating
Known
heterozygotes
for recessive
allele
Death
Pedigrees
illustrate
inheritance
Section Objectives:
• Discuss new methods in
genetic technology.
Genetic Engineering
• A new
form of manipulation
that biologists created where
they can engineer a set of
genetic changes directly into
an organisms DNA
CLONING
The production of
organisms with identical
genes
Human Genome Project
• Determines
what genes are
carried on each chromosome of
the human
•Helped in diagnosis of many
inherited diseases and will lead
to many advances in our future