Transcript Unit 5 - Notes

A Brief History
In the past, people did not understand
how traits were inherited, but there
were many guesses based on things
that could be observed.
Two theories emerged….
Blending Theory - offspring are a
straight mix
Particulate Theory - traits are
inherited as "particles", offspring
receive a "piece" from each parent,
some pieces may hide the others
Golden Doodle
Who was Gregor Mendel?
He was known as the “FATHER OF GENETICS”
He discovered how traits were inherited
GENETICS – study of
heredity
HEREDITY – the
passing of traits from
parents to offspring
Mendel’s Peas
Mendel did his study on pea plants
which have many traits
• tall/short
• purple /white flowers
• round/wrinkled seed
Pea plants can be self-fertilized or
cross-fertilized
True-Breeding Plants - always
create plants that look like
themselves
Hybrids – offspring of truebreeding plants
Tall x Short = Hybrid
Some traits are dominant over others.
Tall x Short = all tall offspring (hybrids)
*Tall is the dominant trait
* Short is recessive
Mendel discovered that each trait is
controlled by two factors (alleles)
Genes – factors that
determine your traits
Genes are located on
chromosomes
Quick Check 1 - What do we know so far?
1. The “Father of Genetics” is ____________
2. Genetics is the study of _____________, which is how traits are passed
from _________ to ____________
3. Mendel studied what organism? ____________
4. If one trait covers up another one, we say that it is ______________,
the one that is covered up is ______
5. A “true-breeding” plant is one that can only produce plants like itself a)
true b) false
6. If a tall and a short plant are crossed, it will create a
a) zygote
b) gene
c) hybrid
Explaining the Cross
When a parent makes sperm or eggs, their
genes separate
(PRINCIPLE OF SEGREGATION)
The GAMETES (egg or sperm) contain either
a T allele (tall) or a t allele (short)
Mendel’s Experiments
Draw the crosses
GENOTYPE - what genes, letters,
the organism has (TT, Tt, tt)
PHENOTYPE - what it looks like (tall
or short)
• Quick Check 2 - What do we know so far?
1. The passing of traits from parents to offspring is
known as ____________________
2. Who was the father of genetics? _________
3. Genes are located on _______________
4. Every gene is made of two
a. genotypes b. alleles
c. cells
5. The organism’s outward appearance, such as wrinkled
seeds are referred to as the
a) phenotype
b) genotype
6. The letters (ex. RR) that represent the traits are referred to as
the a) phenotype
b) genotype
7. An organism that has two different alleles, or letters, such as Rr
is: a) homozygous
b) heterozygous
8. 7. An organism that has two of the same alleles, or letters, such
as RR is: a) homozygous
b) heterozygous
9. Which of the following sets would represent Mendel’s Parent (P)
generation?
a) RR x RR
b) Rr x Rr
c) RR x rr
10. When two different alleles occur together, such as R r, the one
that is expressed is a) dominant b) recessive
11. What is the diagram shown below called?
What does
this letter
actually
represent?
Human Chromosomes
●Karyotype = picture of chromosomes
arranged in pairs & organized by size
●Humans have 46 chromosomes
●2 of these are sex chromosomes
XX = female XY = male
●The other 44 chromosomes are known as
autosomes
NONDISJUNCTION
Failure of chromosomes to separate in
meiosis – results in an egg (sperm) with too
many or too few
●Down Syndrome (extra #21)
●Klinefelter Syndrome (XXY)
●Turner Syndrome (XO)
●Supermale (XYY)
Down Syndrome
- caused by an extra chromosome 21 (trisomy 21)
Edward Syndrome
- caused by an extra chromosome 18 (trisomy 18)
Median life
expectancy is 4
days. However,
about 5-10%
survive beyond
one year
Trisomy – 3 chromosomes
Monosomy – 1 chromosome
Checking in 1:
1. A picture of a person's chromosomes is called a _____.
2. In this pictures, chromosomes are arranged in
pairs according to their ___________.
3. Humans have ______ pairs of chromosomes.
4. The last set of chromosomes is the _____ chromosomes.
5. Males have what sex chromosomes? ______
6. A person who has an extra chromosome #21 has what disorder?
__________
7. If a person has XXY for sex chromosomes, he has what
disorder? _________________
8. As a woman gets _______, her risk for having a child with down
syndrome increases.
9. A human has 2 sex chromosomes, the other 44 chromosomes
are called ______________.
10. When chromosomes fail to separate during
meiosis, ___________ has occurred.
Human Traits
●To study inheritance, biologists use
pedigree charts
oShows relationships within a family
Not all Human Traits can be traced back to
a single gene
Many traits are strongly influenced by
environmental factors
(ex: height, weight, personality)
Human Genome
●Our complete set
of genetic info
●Includes thousands
of genes
●Base sequences of
many genes
identified
BLOOD TYPES
Genes controlling blood types were 1st
genes to be identified
ABO & Rh blood groups ( + and - )
ABO Blood Group
Multiple Allele Trait
●Controlled by 3 alleles: A, B, O
●A and B are codominant
●O is recessive to both A and B
●The blood type is the phenotype
Genotype
Blood Type
AA, AO
Type A
BB, BO
Type B
AB codominant
Type AB
(universal recipient)
OO recessive
Type O
(universal donor)
Blood Types Practice
Mom has type A blood (genotype AO), dad
has type AB blood. What blood types are
possible among their children?
Mom has type B blood (genotype BO), dad
has type O blood. What blood types are
possible among their children?
Human Genetic Disorders
Phenylketonuria (PKU)
Tay – Sachs disease
Albinism
* all recessive
Other animals can be albino too..
Sickle-Cell Disease
codominant (AA, Aa, aa )
heterozygous is resistant to malaria
Achondroplasia
(dwarfism)
Huntington’s disease
* Both dominant
• Checking in 2:
1.
2.
3.
4.
Achondroplasia is another name for ____________
What are the four possible blood types? _______
Is albinism dominant or recessive? _________
If two people are both heterozygous for sickle cell trait, what is
the chance they they will have a child with sickle cell disease?
5. If a person with type A blood is married to person with type O
blood, what blood types are possible in their children?
6. The human _______ describes all the genes found in humans.
7. What type of chart is used to study a trait in a family? __
Genes located on sex
chromosomes follow
different patterns of
heredity. Males are more
likely to be affected by
these genes.
ALL GENES ARE LOCATED ON
CHROMOSOMES
Some genes are located on the SEX
CHROMOSOMES ( X and Y)
Genes on the X chromosome may
affect boys different from girls
These are called SEX-LINKED GENES
EXAMPLES: SEX LINKED GENES
Coat color in cats: Black, Orange, Calico
X B X B = black, female
X O X O = orange, female
X B X O = calico, female
X B Y = black, male
X O Y = orange, male
REMEMBER: TH
E Y IS WIMPY! No
letters (genes) are
attached to it.
CROSSES
X B X B (black female)
x
This explains why all calico
cats are female!
ALSO: in any given cell,
one of the X's becomes
inactive, which randomizes
the pattern or orange and
black
X OY
(orange male)
COLORBLINDNESS IS ALSO SEX LINKED
Look what happens when a woman who is a CARRIER
(b) marries a normal man (B)
X BX b
x
XBY
What happens when a colorblind man marries a normal
woman?
X BX B
x
XbY
COLORBLIND TEST
Young children are given pictures
instead of numbers
HEMOPHILIA - "bleeder's disease"
Blood will not clot normally, small
injuries can be life threatening
Females can be carriers:
What happens if Mom is a carrier?
DUCHENNE MUSCULAR DYSTROPHY
- causes progressive
weakening and loss of
muscle tissue
Females can be carriers:
X DX d
• Checking in 3:
1. Sex-linked genetic traits are on the _______ chromosome.
2. Are females or males more likely to be affected by a sex-linked
traits? _______
3. _________ can be carriers of sex-linked traits.
4. What are two examples of sex-linked traits?