Download Chapter 12: Genetics and Health

Science
24
Chapter 12: Genetics and Health
In this chapter you will learn:
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How physical characteristics are
inherited in humans
How chromosomes determine the
sex of a child
How genetic information is
organized in the cells of your body
About human diseases that result
from changes to genetic make-up
About ethical and social issues
related to genetic research
Mrs. Sample
Holy Cross Collegiate
Science 24
Chapter 12: Getting Ready
1. What characteristics have been passed from one generation to another in your
family?
2. What environmental factors might affect the development of a fetus?
3. What determines whether a baby will be a girl or a boy?
4. How does overexposure to the Sun affect cells?
5. What is the Human Genome Project?
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12.1
Structure of DNA
_________________ is the study of how _____________________________________
are passed on from parents to offspring.
The Structure of DNA
DNA is organized in the shape of a ____________________,
often referred to as a ___________________. The rungs of
the ladder are arranged in a very specific way.
Chemical compounds called __________ make up the rungs.
One ________ of bases makes up each rung. One molecule
of DNA contains about __________________ base pairs.
Different genes are made up of different arrangements of
these base pairs. The _______________ of the base pairs
determines the traits you inherit.
There are four different bases:
___________ which always pairs with ____________
___________ which always pairs with ____________
Chromosomes
Human body cells contain 46 chromosomes arranged
in 23 pairs that hold all the genetic information. One
chromosome of each pair comes from the
______________ and the other chromosome of each
pair comes from the _____________.
When scientists study chromosomes, they group them
into pairs, and organize them by _________,
beginning with the ______________. The ________
chromosome pair is always last.
In humans, there are two types of sex chromosomes, X and Y.
Human males have _______ chromosomes, and females have _______ chromosomes.
The DNA of all people on earth is _________% identical. It is only very small
differences that make each of us unique!
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12.2
Inheritance and Genetics
_________________ is the passing of characteristics from parents to offspring. It can
often help to explain why you share some of your mother’s characteristics, and some of
your father’s characteristics, but yet you look different from your siblings.
Gregor Mendel’s Pea Plants
Gregor Mendel, an Augustinian monk, experimented with pea plants to show that
__________________________________________________________. He noticed
that pea plants vary in height, and so crossed tall and short plants together to see how
height would be affected in the offspring.
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Recording Inherited Traits
Since chromosomes come in pairs, genes for traits do too. Many traits are controlled by
only one pair of genes, others by two or more pairs. For traits controlled by one pair of
genes, geneticists use two letters to represent the _________________ or combination
of genes.
_______________________ represent _______________ genes. For example, the
letter T could represent the dominant gene for tallness, which is the tall gene.
_______________________ represent _______________ genes. For example, the
letter t could represent the recessive gene for tallness.
During reproduction, chromosomes separate so each sperm or egg cell gets one
chromosome of each kind, so one gene for each trait is passed on from each parent.
Punnett Squares
Punnett squares are used to predict the probability of offspring inheriting certain traits.
Punnett Squares of Mendel’s Pea Plants
Pedigrees
Family trees or pedigrees are used to trace traits in a family. A pedigree is a diagram
that shows the history of a trait from generation to generation. Pedigrees show traits
with different characteristics such as long eyelashes or short eyelashes, through many
generations. Plant and animal breeders use the information from pedigrees to increase
the chances of breeding plants and animals with only desirable traits.
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12.3
Genetic Changes
________________ are changes in genetic information because of an abnormal
gene. These changes may be beneficial, harmful, or neither. Mutations can occur in
several ways.
Helpful mutations: _______________________________________________________
_______________________________________________________________________
Harmful mutations:_______________________________________________________
_______________________________________________________________________
Neither helpful/harmful mutations:___________________________________________
_______________________________________________________________________
Any environmental factor or substance that causes mutations is called a ____________.
Some examples of mutagens are: ___________________________________________
_______________________________________________________________________
_______________________________________________________________________
Genetically, mutations are caused by errors in the ______________________________.
Most of these errors do not pass from one generation to the next, but there are some
exceptions.
_________________________ are disease or illness caused by alterations to
genes that affect their normal functioning.
Mutagens and Their Effects on Human Embryos
Mutagen
Effect
Exposure to alcohol
Exposure to
prescription and
illegal drugs
PCBs
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Some Inherited Genetic Disorders
Disorder
Features
Chromosomal Mutations
 affects males who have an additional X chromosome
Klinefelter’s
 no physical effects until puberty, when they fail to develop normal sexual characteristics
syndrome
(XXY)
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Trisomy X
syndrome
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(XXX)
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Turner’s syndrome
(XO)
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diabetes mellitus
(Type I)
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phenylketonuria
(PKU)
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galactosemia
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often sterile
possible learning disabilities
treatment with male sex hormones at puberty
affects females who have three X chromosomes
one out of every 1000 female births has Trisomy X syndrome
often remains unnoticed because affected individuals appear normal, experience puberty,
and are usually fertile
often no treatment necessary
affects females who are missing or have a damaged X chromosome
short stature
lack secondary sexual characteristics and may be infertile
affects ears, eyes, heart, kidneys; may result in diabetes or high blood pressure
possible learning disabilities
treatment with sex hormones and injections of human growth hormone before growth is
completed
specific gene mutations that cause the disease have not been found
affects people unable to produce insulin due to a genetic defect; symptoms result from
too much glucose in the blood
causes severe hunger and thirst, excessive urination, fever, headaches, unconsciousness,
confusion, difficulty breathing, dry skin, fatigue, muscle weakness, blurry vision, nausea
and vomiting, heart palpitations, gangrene, convulsions, coma
controlled by diet, exercise, and medication
affects people who inherit two mutant genes
one of the most common genetic disorders
caused by high levels of phenylalanine that result from not having enough of an enzyme
to break it down. (Phenylalanine is an amino acid found in meat, eggs, fish, and milk,
including breast milk.)
if untreated, causes brain damage that leads to irreversible mental retardation
treatment involves a diet low in phenylalanine; when treated early, children can function
within the normal range of ability
affects people who inherit two recessive genes, one from each parent
caused by high levels of galactose (a sugar found in milk) in the blood because there is
not enough liver enzyme to break it down
causes vomiting, enlarged liver, jaundice, bacterial infections
if undiagnosed, can cause liver, brain, eye, and kidney damage
treatment involves stopping breast-feeding and eliminating galactose and lactose,
possibly for life
Sex-linked Disorders
 affects males who inherit a recessive gene from their mother
muscular
 causes progressive weakness and wasting of the muscles
dystrophy
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hemophilia
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physical therapy and corrective surgery may be necessary to improve the quality of life
currently no cure
affects males who inherit a recessive gene from their mother
blood does not clot; minor injuries may cause severe bleeding and blood loss
people with hemophilia bleed at the same rate as anyone else — only longer
treatment involves taking clotting factor concentrates; some are made using genetic
engineering
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12.4
Issues in Genetic Research
The _____________________________________ was established in 1989, with the
goal of mapping the human genome. They achieved this goal in April 2003, meaning
that they successfully mapped out where each gene belongs on each of the 46 human
chromosomes.
This kind of information has many benefits
Benefit
Identifying the source of thousands of
genetic disorders
Examples
Developing new drugs and treatments
Helping people make lifestyle choices
Genetic Technologies
______________________________________________________: a process
developed in the last 30 years to move pieces of _________ from the ______________
one cell to another. This process has allowed the movement of genes with
_________________________________ from one organism to another. This process is
referred to as a ___________________________.
Genetic Engineering leads to questions like:
 Does biotechnology “tamper with nature”?
 Are there unknown harms to the environment, people, or other organisms that come
with specific biotechnologies?
 What new opportunities and ways of solving problems will advances in science
bring?
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Biotechnology in Medicine
Many developments have been made in medicine through the use of biotechnology.
 ____________________________________________________________________
____________________________________________________________________
__________________
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Because of development, animals do not have to die to produce the need proteins.
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A procedure called amniocentesis is used to determine the chromosomal make-up of
a fetus. The test shows whether the fetus may have a _______________________.
Amniocentesis involves using a large, hollow needle to withdraw
_________________________ from the uterus.
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