Download BIOLOGY CLASS NOTES UNIT 8 Human Heredity PART 2

Unit 8:
Human Heredity
Mrs. Howland
Biology 10
Rev. Feb 2016
What can be INHERITED?
TRAITS
Why LOOK at inheritance?
Can predict DISORDERS
Pedigree analysis
Inheritance patterns
Phenotypes  Genotypes
Information about INHERITANCE
Inheritance may be studied by looking at:
Karyotypes
Pedigrees
Physical traits to determine genotypes
Patterns: sex-influenced, X-chromosome
inactivation
Heterozygous advantage
Mistakes in meiosis (nondisjunction)
Prenatal genetic screening
PEDIGREES
A pedigree is a diagram that tracks inheritance
of a trait through multiple generations of
offspring in a family
Information From Pedigrees
Genotypes of individuals
Determination of trait
inheritance:
Autosomal or X-linked?
Dominant or recessive?
Interpreting a pedigree…
Helpful Videos ~ Pedigrees
Overview of pedigrees:
https://www.youtube.com/watch?v=YhRxoA_49m8
Interpreting a pedigree: https://www.youtube.com/watch?v=Ztzi6pAh5M
TIPS
TIPS
Remember! Recessive disorders can skip a generation!
Example:
PRACTICE! Pedigrees
Complete the following:
Detecting Genetic Disorders
GENETIC SCREENING allows for early detection
of chromosomal disorders in fetuses
Carried out during 1st or 2nd trimester of
pregnancy
Can be used for karyotyping
Amniocentesis
Chorionic Villus Screening (CVS)
Genetic Screening
Amniocentesis = Medical procedure used to
diagnose chromosomal abnormalities
Needle aspirates sample
of amniotic fluid (the fluid
contains particles of fetal
tissues). Ultrasound is
used as visual guide for
needle insertion.
Genetic Screening
Chorionic Villus Sampling (CVS) = Medical test
that samples placental tissue through the cervix
or abdomen
X-Chromosome Inactivation
Males have only ONE “X” chromosome, while
females have TWO
EACH X chromosome has ~1000 genes
It could be a problem if those genes are
expressed TWICE!
Dosage compensation= X-chromosome
inactivation “turns off” one X chromosome
in females
X-Chromosome Inactivation
Which X chromosome gets shut off?
It is randomly selected!
FUN FACT: Some marsupials
preferentially inactivate the father’s X
chromosome!
WHEN does this occur? EARLY in life
~ during embryonic development
ANIMATION:
https://highered.mheducation.com/sites/9834092339/student_view0/chapter13/x_inactivation.html
Barr Body
With X-chromosome inactivation, what happens
to the INACTIVE X chromosome?
INACTIVE X chromosome condenses into a Barr
body, which maintains a silent state
Blood Type Inheritance
ABO blood type is inherited by multiple alleles
Overview of Blood Types
Blood Type Inheritance
ABO blood type is inherited by multiple alleles
Rh blood type (+ or -) is inherited independently
of ABO blood type
Coded by TWO genes: RHD and RHCE
Rh+ is DOMINANT
Rh is also an antigen on the surface of the red
blood cell
Rh Incompatibility
Some of baby’s blood may enter mother’s
bloodstream
Sometimes, mother and child differ in Rh blood
type
May result in ‘rejection’
Blood Type Compatibility
Who can donate/receive blood?
Epigenetics
Genes do not change once they are inherited
Gene expression may be influenced by
environment or stages of life
Epigenetics studies differences in gene
expression (nature vs. nurture) NOT due to
changes in DNA
Epigenetics ~ What can be learned?
VIDEO: https://www.youtube.com/watch?v=kp1bZEUgqVI
ACTIVITY: Diverging Twins
Heterozygote Advantage
Why might it be a GOOD THING to be a carrier
for a disease or disorder?
VIDEO: https://goo.gl/n0VIUG
Heterozygote Advantage
EXAMPLE: Malaria & Sickle Cell Anemia
How MALARIA affects the body
What’s the connection between BLOOD and MALARIA?
SOURCE:
http://www.niaid.nih.gov/topics/malaria/pages/lifecycle.aspx
Heterozygote Advantage
Heterozygote advantage = Individuals with
heterozygous genotypes (two different alleles) is
more ‘fit’ than those with homozygous
genotypes
Natural selection maintains existence of both
copies of alleles
EXAMPLES:
Sickle cell / malaria (sickle cells inhibit reproduction of
parasite)
Cystic fibrosis and cholera (cystic fibrosis prevents
dehydration)