Genetics NOTES - Grants Pass School District 7

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Transcript Genetics NOTES - Grants Pass School District 7

Genetics: The Science of Heredity
“I can explain the difference between asexual and sexual
I. Reproduction
A. Asexual Reproduction
1. Only one parent is
needed for
2. Parent cell divides into
two by mitosis and the
new cell is an exact
copy of the parent cell
3. Examples: yeast,
bacteria, protist (ie.
Paramecium – binary fission
Yeast -Budding
Bacteria Binary Fission
B. Sexual Reproduction
1. Two parents (egg and
sperm cell ) join
together to form a new
2. Sex Cells (gametes)
a. Sperm- male sex cell
b. Egg- female sex cells
Sperm Cell
Human Egg Cell
Egg and Sperm Join
3. Sex Cells are different than
other cells:
a. Normal human body cells have
46 “double” chromosomes
b. Sex cells only have 23
chromosomes (half the usual
c. Egg and sperm cell have only
one chromatid out of each
homologous pair
d. When sperm and egg cell unite
to form a new individual each
parent only donates one half of
a homologous pair. Ensuring
the human offspring will
receive a normal number- 46
chromosomes in a body cell
4. Examples: plants, animals,
fungi, and some protists
Bread Mold Sexual Reproduction (Fungus)
“I can describe how genes are inherited, and how traits are the result of gene
C. Chromosomes and Inheritance
1. Chromosome Theory- genes are carried from parents
to offspring on chromosomes
2. Chromosome- the cell structure made of condensed
chromatin containing DNA or genetic code
3. Genes are located on chromosomes
4. Genes carry genetic information one from each parent
5. Humans have 46 chromosomes -23 matching pairs
6. Chromosomes control inherited characteristics
– Eye color, hair color, skin color, certain diseases
7. Many genes are located on each chromosome
Genes located on chromosome
“I can describe how genes are inherited, and how traits are the result of gene combinations.”
II. Details of Genetics
Genes – a set of instructions
donated by each parent
1. Genes are located on the
2. Genes are made of DNA
3. Each characteristic of an
organism has two sets of
instructions one from each
parent. (double strand)
Ex. Hair color, skin color,
ear lobe, flower color, etc.
*Draw a picture in the space below showing how genes are passed from
parents to offspring.
“I can explain DNA and its structures and explain they are located on the
B. What do genes look like?- DNA Connection
1. Discovery of DNA
a. Watson and Crick (&
Franklin) came up
with a model for DNA
showing how the
nucleotides fit
together in a pattern
DNA resembles a twisted
ladder called a double helix
Watson and Crick
2. DNA (deoxyribonucleic acid): and
proteins make up chromosomes
a. DNA must be able to:
 Supply instructions for cell
 Build cell structures
 Control the production of
 Be copied each time a cell
divides – ensuring that each
cell has an identical set of
b. DNA is made of nucleotides
DNA Connection (cont.)
3. Nucleotide- the subunits of
a. Nucleotide bases consists of 3
materials : sugar, phosphate,
b. DNA molecule is made of four
nucleotides bases:
 Adenine (A)
 Thymine (T)
 Guanine (G)
 Cytosine ( C)
c. Nucleotides are identical
except for the bases and have
slightly different shapes
4. Rules for Building DNA
a. These 4 nucleotide bases form
the rungs of the DNA ladder
structure (double helix)
b. Rungs of the ladder are
composed of a pair of
nucleotide bases
c. Adenine on one side always
pairs up with thymine on the
other side: the number a A
always = T
d. Guanine always pairs up with
cytosine in same way: the
number of G always = C
e. The upright part of the ladder
is made with alternating sugar
and phosphoric acid
Rules for Building DNA (cont.)
f. One side of DNA molecule is
complimentary to the other
– Ex. ACCG always binds to the
sequence TGGC (allowing the
DNA to make a copy and
replicate itself)
– DNA molecules replicate by
splitting down center of ladderthe one side of the ladder can
be used as a pattern for a new
complimentary side
g. Each gene consists of a string
of bases: the order of the
bases give the cell information
about how to make each trait
“I can explain the difference between phenotype and genotype.”
Details of Genetics (cont.)
C. Alleles- forms of a gene for a trait or characteristic
Fertilized egg has two forms (alleles) of the same gene for every
D. Genotype- inherited combination of alleles (shown with letters)
– Ex. Tt, TT, PP, Pp
E. Phenotype- organisms appearance (shown with words)
-Ex. Tall, Short, Purple, White
“I can describe how genes are inherited, and how traits are the result of
gene combinations.”
III. History of Genetics
A. Genetics- The study of heredity or the
passing on of traits from parents to
i. Geneticist- scientist who studies
B. Gregor Mendel- “Father of Genetics”
1. His studies gave scientists the basic
ideas for genetics
2. Mendel studies pea plants: grow
quickly, self-pollinate (plants carry
both male and female reproductive
parts), and come in many varieties
3. Mendel developed a method know as
cross-pollination: Anthers of one plant
are removed so that the plant can’t
self-pollinated; pollen from another
plant are used to fertilize the plant
without anthers
4. Mendel performed pea-plant crosses to study
the seven characteristics below:
Pod Shape
Pod Color
Dominant Trait
Along Stem
Recessive Trait
At Tip
C. Parental Generation- Ppassing
of traits (genes) from parents to
offspring ( babies )
D. First Generation F1 (offspring
from first cross):
Cross between two traits of each
characteristic- one trait always
another vanished
ex. Purple flower X White
flower = Purple Flower
Details of Genetics (cont.)
H. Second Generation F2:
Mendel allowed the F1 generation
plant with dominate trait; to selfpollinate = recessive trait showed
up again -some white flower
plants came back
– ex. Purple flower
dominant plants
produced 3 purple
flowered plants and 1
white flowered plant
“I can explain how dominant and recessive genes work.”
E. Dominant Trait- Trait that appeared = a stronger
trait (shows up in offspring)
1. Symbol used when writing is an upper case letter
ex. T
F. Recessive Trait- Trait that vanished or disappeared
= weaker traits (masked or covered up in
1. Symbol used when writing is a lower case letterex. t
“I can define purebred and hybrid traits giving an example of each.”
G. Purebred (true-breeding or
homozygous) an organism
that has genes (alleles) that
are the same for the trait.
SS, EE, ee, PP, pp, CC, cc
Genotypes= Purebred
TT tall
TT tall
TT tall
TT tall
– Ex. Short plants always
produce short offspring
tt (purebred short). Tall
plants always produce
tall offspring TT
(purebred tall).
tt short tt short
tt short tt short
L. Hybrid (Heterozygous
(different) - an organism that
has different genes (alleles) for
a trait ( a mixture)
– Ex. Hybrid tall plant
receives one tall allele T
and one short allele t (Tt)
*Note- Tt will all be tall plants
because it has a dominant
gene or allele. “T” covers up
or masks the “t”.
Tt, Pp, Ee, Cc, Ss
Genotypes= Hybrid
“I can calculate percentages and probability from a Punnett square.”
IV. Probability
A. Probability-mathematical
chance that an event will
occur. - “What are the
1. Used to predict the results for
genetic crosses
2. Shown as a fraction or
B. Calculating Probability:
Ex. Ten marbles are in a bag, six of
the marbles are red. What is
the probability of getting a red
6 red marbles/ 10 marbles
total= 6/10 or 3/5
C. Ratio Results- approx. 3 dominant traits showed up to 1
recessive trait = ratio 3:1
“I can calculate percentages and probability from a Punnett
“I can complete a Punnett square with a one factor cross to show
genetic variation in offspring.”
Punnett Squares- a special chart used to show all
the possible combinations of allele from their
1. Dominant Alleles- symbolized by capital letters (SS, YY, BB)
2. Recessive Allele -symbolized by lowercase letters
(ss, yy,
B. Practice a Punnett Square
1. Cross purebred (homozygous,
true- breeding) tall plant (TT)
with a hybrid (heterozygous)
tall plant (Tt)
TT x Tt
Punnett Squares Results
• Probability of purebred
(homozygous) tall plant =
2/4 or 50%
• Probability of a hybrid
(heterozygous) all plant
= 2/4 or 50%
• Probability of short plant=
• Probability of a tall plant =
4/4 or 100%
• Genotype = Tt, TT
• Phenotype = Tall
More Punnett Square Practice
2. Cross a purebred (true
breeding, homozygous) white
flower (pp), with a hybrid
(heterozygous) purple flower
Punnett Square Results
• Probability of getting a
hybrid Purple flower = 2/4
or 50%
• Probability of getting a
homozygous (truebreeding) Purple Flower
= 0%
• Probability of getting a
pure-bred (true-breeding)
White Flower= 2/4 or
• Genotype= Pp, pp
• Phenotype = Purple
Flower, White Flower
“I can describe how genes are inherited, and how traits are the
result of gene combinations.”
VI. More News About TraitsExceptions to Mendel’s Rules
A. Co- Dominance- the
alleles are neither
dominant nor recessive
for a trait; both alleles
show up in the offspring.
– Example: Heterozygous
chickens have both black
and white feathers.
– Note: Co-dominant alleles
are written as capital letters
with superscripts FB black
feather and FW for white
Co- Dominance Punnett Square
1. Cross a dominant blackfeathered chicken (____)
with dominant whitefeathered chicken (____)
• Probability of getting a
heterozygous black and
white feathered chicken =
• Genotypes = FBFW
• Phenotypes = Black and
White Feathered
Co-Dominance Punnett Square
2. Cross a co-dominant
heterozygous (hybrid ) black
and white feathered chicken
(FBFW) with a co-dominant
heterozygous (hybrid) black
and white feathered chicken
Co-Dominance Punnett Square
• Probability of getting
heterozygous black and white
feathered chicken = 50%
• Probability of getting
homozygous white feathered
chicken = 25 %
• Probability of getting a
homozygous black feathered
chicken = 25 %
• Genotypes=FBFB, FBFW,
• Phenotypes= Black feathered,
Black and White Feathered,
White Feathered
B. In-Complete Dominance
In-Complete Dominance-
1. Neither allele is fully dominant,
offspring have an intermediate
phenotype, each allele has its
own degree of influence.
2. Show with capital letters and
superscript numbers.
– Ex. Red snapdragon crossed
with a white snapdragon =
pink snapdragon
In-Complete Dominance
Punnett Square
1. Cross a true-breeding R1R1
red snapdragon with a truebreeding W1W1 white
• R 1R 1 X W1W1
In-Complete Dominance
Punnett Square Results
• Probability of pink
flowers = 100%
• Probability of white
flowers = 0%
• Probability of red
flowers = 0%
• Genotype= R1W1
• Phenotype = Pink
C. More Exceptions to the Rule
1. Many genes can influence a
single trait- called Polygenic
a. Traits such as eye, hair, and
skin color are the results of
several genes acting togetherdifficult to determine if a trait is
result of a dominant or
recessive trait
b. Different combinations of
alleles result in slight
differences in the amount of
pigment present
– ex. Different shades of blue
eyes, hair color, skin color,
“I can infer that changes in genetic material may result in making
different proteins, example insertion, deletion and substitution.”
VII. How DNA Works Protein Synthesis
A. The sequence or order of
nucleotides along a gene forms a
code that tells the cell what
protein to produce
How DNA Works (cont.)
B. Protein Synthesis- is the
process of making protein
1. A three nucleotide base
codes for a specific amino
acid (which are the building
blocks of proteins) is built to
form a protein chain
a. The order of the bases
determines the order of the
amino acids in a protein
b. Each gene is a set of
instructions for making a
How DNA Works (cont.)
2. Proteins- acts as
chemical messengers
help determine how tall
you will grow, whether you
have curly or straight hair,
your eye color, skin color,
nail type
a. Human cells contain about
20,000 genes- each genes
spells out a sequence of
amino acids for specific
b. Human body contains
about 50,000 different kinds
of proteins
3. Making of Proteins
(Protein Synthesis)
a. During protein synthesis- cell
uses information from a gene
on a chromosome to make
specific proteins
– Protein synthesis –
takes place on
ribosomes in the
b. Role of RNA
• Messenger RNA
(mRNA)- carries the
genetic code from DNA inside
the nucleus to the ribosomes
• Transfer RNA
(tRNA)- carries the amino
acids and adds them to the
growing protein chain
“I can explain how transcription and translation works to create a protein.”
4. How Protein Synthesis Works:
A. Transcription:
A copy of the section of the DNA
strand containing a gene is
made and carried outside of the
cells nucleus
Messenger RNA molecules take
the genetic information from the
nucleus out into the cytoplasm
In cytoplasm a copy of DNA is
fed though a “protein assembly
line”- this “protein factory” is
found in the ribosomes.
How Protein Synthesis Works
B. Translation:
1. Copy is fed through the
ribosomes three bases at a
time- each group of 3 bases
code for a specific amino
2. Transfer RNA molecules act
as translators of the message
contained in the copy of DNA
(brings the correct amino acid
to ribosomes)
Translation (cont.)
3. Each transfer RNA molecule picks
up a specific amino acid from the
cytoplasm of the cell to the
4. Bases on the transfer RNA
molecule then match up with
bases on the copy of DNA inside
the ribosome
5. Transfer RNA molecules drop off
their amino acid “suitcases” which
are strung together to form a
protein chain
“I can infer that changes in genetic material may result in making
different proteins, example insertion, deletion and substitution.”
“I can define genetic mutations and explain how they occur.”
VIII. Mutations
A. Mutationsa “change” that occurs
in the order of bases in
an organisms DNA
causing an incorrect
protein to be made.
Muscular Hypertrophy
Mutations (cont.)
B. Types of mutations:
1. Deletion- when a base is left out
(ex. White coat on buffalo,
2. Insertion- when a base is added
(ex. Huntington disease, brain
3. Substitution-most commonincorrect base replaces a
correct base- the cell produces
an incorrect protein during
protein synthesis (example:
sickle cell anemia- blood cell
becomes distorted shaped and
get stuck in blood vessels)
Mutations (cont.)
C. If mutation occurs in the sex
cells it can be passed to
D. These mistakes occur in the
genes of a chromosome.
E. If a mutation occurs in a body
cell, such as a skin cell, the
mutation affects the cell that
carries it
F. Mutagens: are environmental
and cause mutations in DNA
(ex. radiation, x-rays,
asbestos, and cigarette
I can give examples of harmful, beneficial and neutral genetic
G. Types of Mutations
1. Helpful- improve an organism’s
chance for survival
– example- insect coloration,
being lactose(milk) tolerant,
new crops- giant strawberries
(add extra chromosome),
seedless watermelon,
2. Neutral- does not affect the
– ex. Flower color, butterfly
markings, insect coloration,
birthmarks, multicolored
3. Harmful- reduces the
organisms’ chances for
– example- an albino, Down
Syndrome, cancer
a. Chromosomes fail to separate
(ex. Down’s Syndrome)
b. The organism’s traits or
phenotype is different
“I can explain the difference between asexual and sexual
IX. Cell Reproduction and Genetic
A. Binary Fission1.
Asexual reproduction where two
daughter cells are formed by
splitting of parent cell.
Prokaryotes (without a nucleus)
the parent cell divides.
Exact replica is made.
B. Mitosis 1. Cell process in which the nucleus
divides to form 2 nuclei that are
identical to each other called
daughter cells.
2. Mitosis is cell division of the
nucleus (in eukaryotes) that
occurs in all other cells in our
body. (ex. Skin cells, hair, blood,
bone etc
C. Meiosis- copying process that makes sex cells with half
the number of chromosomes (NOT the same as mitosis)
1. Chromosomes are copied once, nucleus divides
twice resulting in sex cells with half the number of
2. Only one chromosome pair from each ends up in
each sex cell
3. Meiosis occurs in only the sex cells (sperm and egg)
“I can explain how meiosis produces genetic variation in offspring.”
4. Sexual reproduction involves two
parents, each contributing one gamete.
5. Gametes have half the chromosome
number of other adult cells of an
6. During meiosis sex cells exchange
chromosome pieces which occur in the
first division of this process.
6. This process is called recombination or
crossing over.
7. Recombination is a very important
source of genetic variation
between individuals of sexually
reproducing species, and the driving force
for the process of natural selection.
“I can defend the absence of genetic variation in asexual
D. Asexual reproduction
does not create variation
• With the exception when
a mutation occurs
• Parent cell produces an
exact copy or replica in
the offspring.
E. Sexual reproduction does
create variation
• Traits are passed from
parent to offspring
• Mutations can cause
• New cell have combined
“I can simulate a genetic cross showing sexual reproduction to
produce variations in offspring.”
X. Human Genetics
A. Human InheritanceHumans have 46
chromosomes in the
1. 23 homologous pairs- one
chromatid from each
2. Each gene has matching
gene for each allele/trait
(one from each parent)
1. Ex. Eye color, ear shape
3. Karyotype- a picture of
all the chromosomes in a
B. Male or Female?
1. To be a female all 23
chromosomes match (XX) –
males 22 match but 1 does
not match (XY)
2. Sex chromosomes- carry
genes that determine if an
offspring is male or female
3. Males determine the sex of
offspring- egg cell (female) can
only give (X) to the offspring
male can throw an (X) or (Y). If
male throw and (X) it will be a
girl if male throws the (Y) it will
be a boy.
Male or Female?
4. Cross a male (XY) and a
female (XX)
• Probability of a girl=
• Probability of a boy=
C. Sex- Linked Genes
1. Sex-linked Traitcharacteristics that are
carried on the X and Y
a. X’s carry several different
b. Y’s carry only a few- some
forms or traits are not found
on Y (ex. Color vision)
c. Can have both dominant
and recessive traits on both
X and Y
Sex- Linked Traits (cont.)
d. Dominant traits mask
recessive: if a recessive
trait on an X is paired with
a dominant X, then no
problem- but, if a
recessives trait on an X is
paired with a Y, then there
is nothing to mask so
disorders can occur
e. Carrier- Person who has
the one dominant and one
recessive allele but not the
disorder but can pass the
trait to offspring (only
females can be carriers)
f. Punnett Square Sex- Linked
Cross XC Xc (normal, color blind
carrier Mom) with XC Y(normal
• Chance offspring will be color
blind= 25 %
• The only way a girl can be
color blind is if dad has it and
mom is a carrier or is color
• Examples of Sex-linked
Disorders: hemophilia, high
blood pressure, muscular
dystrophy, progress muscle
disorder, fragile “X” syndrome,
red- green color blindness
“I can interpret a pedigree.”
XI. Pedigrees
A. Tool for geneticist to trace or map out
the inheritance of traits through a
B. Pedigree is a chart or “family tree”
Dominant Inheritance
Punnett Square Hemophilia
X- Linked Dominant Disorder
Cystic Fibrosis Pedigree
• Disease caused from a
recessive allele.
• Occurs most often in
individuals of Northern
European descent.
• Mucus builds up in
lungs/intestines making it hard
to breathe and difficult for
• 4 babies a day born with this
disorder- no cure.
Sickle-Cell Anemia Pedigree
*Helpful mutation in Africa- do not get
XII. Environment and the effects
on your genes.
A. Importance of Environment
Things in your environment effect
how you grow and develop
1. Eat a healthy diet,
exercise, be drug free and
alcohol free, limit caffeine,
energy drinks and fast
Ex. If your genes indicate you
will be tall but you eat
poorly and do drugs as you
grow you may not reach
your full potential