Homologous glossary Diploid glossary Haploid glossary Meiosis Tetrad glossary Crossing Over glossary Zygote glossary Section 4 Meiosis Standards 4C1 4C3 Objectives Summarize the events of meiosis ID: 915401
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Slide1
Chapter 11Genetics
Slide211.4 Vocabulary
Homologous - glossary
Diploid - glossary
Haploid - glossary
Meiosis
Tetrad - glossary
Crossing Over - glossary
Zygote - glossary
Slide3Section 4
Meiosis
Standards: 4C.1, 4C.3
Objectives:
Summarize the events of meiosis.
Explain the reduction in chromosome number that occurs during meiosis.
Analyze the importance of meiosis in providing genetic variation.
Compare/contrast mitosis and meiosis.
Slide4REVIEW
Slide5Asexual Reproduction
Cell copies itself through
MITOSIS
Cells divide producing more cells
Chromosomes inherited from a single parent genetically identical to offspring same DNA
Occurs in all organisms
Budding in Yeast
Slide6Sexual Reproduction
DNA is combined from two different sources through
MEIOSIS
½ DNA from each parent
Produces genetically different cells
Increases beneficial mutations faster than asexual reproduction
Occurs in many organisms
Slide7DNA, Genes, & Chromosomes
Trait
– characteristics (hair color, height, eye color)
Chromosomes contain instructions for traits
DNA on chromosomes is arranged in segments (
genes
) which control the production of proteins.
Each chromosome contains thousands of genes determines characteristics and functions of cells.
Slide8Human Body Cells
46 chromosomes arranged in 23 pairs
23 chromosomes from each parent
Every body cell contains a complete set of chromosomes
Homologous Chromosomes
– pair of chromosomes; one chromosome from each parent
Same length
Same centromere position
same genes (different traits)
Slide946 Human Homologous Chromosomes
Slide1023 Human Nonhomologous Chromosomes
Slide11Maintaining Chromosome Number (n)
Autosomes
– non-sex chromosomes (44 total)
Diploid
– 2 sets of each chromosome (2n)
Gametes
– sex cells
sperm and egg
involved in reproduction½ the number of chromosomes (23 total)Not in pairs; each carries different genetic info.Haploid – 1 set of each chromosome (n)
Slide12Fertilization
Fertilization
– process of sperm and egg joining
Fertilized egg
zygote
Haploid + Haploid = Diploid
n + n = 2n
Each gamete gives 23 chromosomes to offspring 23 + 23 = 4623 pairs of chromosomes, 46 total chromosomes
Slide13How Are Gametes Formed?
NOT through mitosis
Gametes are formed from diploid cells that start with all 46 chromosomes called
germ cells
. Germ cells go through meiosis.
Males
spermatogenesis
produces 4 sperms cellsFemales
oogenesis produces
1 egg cell
Slide14Review: Comparing Haploid and Diploid
How many chromosomes in ……..
“Normal” Human
Bald Eagles
66 chromosomes in their body cells.
1) n
cells?
2) Diploid cells?
3) Gamete cells?
4) Cells that asexually reproduce?
5) Somatic cells?
6) Sex cells?
7) Haploid cells?
8) 2n cells?
9) Sperm cells?
10) Cells that sexually reproduce?
Slide15Meiosis
Process of cell division that reduces the number of chromosomes by half
“reduction division”
Occurs in reproductive structures to produce gametes sperm & eggs
Sexual reproduction
Produces haploid cells
Two Divisions: Meiosis I and Meiosis II
Slide16Interphase I
Normal metabolic processes: increase size, produce RNA, synthesize proteins, & replicate DNA.
Slide17Prophase I
Nucleus disappears
Centrioles move to opposite poles & spindle apparatus forms.
Replicated chromosomes condense and become visible
each with two sister chromatids.
Synapsis
homologous chromosomes pair up (tetrad)
Slide18Prophase I
Crossing Over
– homologous chromosomes exchange DNA increases genetic variation.
Slide19Prophase I
Slide20Metaphase I
Spindle fibers attach to centromeres of each homologous chromosome.
Pairs of homologous chromosomes line up at the middle (equator) of the cell.
Independent Assortment
– pairs of homologous chromosomes randomly line up
increases genetic variation.
Slide21Metaphase I
Slide22Anaphase I
Homologous chromosomes separate and move to opposite poles.
Reduces chromosome number
each side will receive 23 chromosomes.
Anaphase I
Slide23Anaphase I
Slide24Telophase I
Homologous chromosomes reach opposite poles.
Chromosomes relax
chromatin
Spindle apparatus disappears
Nucleus reappears
Cleavage Furrow
animal cells
Telophase I
Slide25Telophase I
Slide26CytokinesisCytoplasm divides forming two haploid cells.
Plants
cell plate forms
Slide27Cytokinesis (after Meiosis I)
Slide28At the End of Meiosis I
Only halfway through meiosis.
Cell may undergo interphase but DNA is NOT replicated this time.
Slide29Prophase II
Nucleus disappears
Spindle apparatus reappears
Chromosomes condense
visible each still containing two sister chromatids.
Prophase II
Slide30Prophase II
Slide31Metaphase II
Spindle fibers attach to centromere and chromosomes RANDOMLY line up at the center.
Metaphase II
Slide32Metaphase II
Slide33Anaphase II
Sister chromatids separate by the spindle fibers pulling opposite directions.
Single chromosomes move to oppose poles.
Reduce chromosome number each side will receive 23 chromosomes.
Slide34Anaphase II
Slide35Telophase II
Chromosomes reach opposite poles.
Chromosomes relax
chromatin
Spindle apparatus disappears
Nucleus reappears
Slide36Telophase II
Slide37Cytokinesis
Cytoplasm divides forming 4 different haploid cells.
Slide38Cytokinesis (after Meiosis II)
Slide39At the End of Meiosis II
In humans
each cell contains 23 chromosomes.
Daughter cells produced during meiosis are genetically different because of:
DNA from two parents
Crossing over
Independent assortment
Slide40___
___
___
___
___
___
___
___
Review: Sequence Meiosis I and II
Slide41Review: Comparing Mitosis & Meiosis
Mitosis
Meiosis
Produces more cells
Body cells
Produces haploid cells
Sexual Reproduction
Sperm & Egg
Gametes
Genetically
identical cells
Produces diploid cells
Increases genetic variation
Sex cells
Somatic cells
Genetically different cells
Asexual Reproduction
Slide42Review: Comparing Mitosis & Meiosis
Mitosis
Meiosis
TWO divisions
DNA from one parent
Occurs in ALL organisms
“Crossing Over”
Occurs in many
organisms
DNA from two parents
Reduces chromosome number
Maintains chromosome number
ONE division
Produces cells with 23 chromosomes
TETRAD
Skin cells, liver cells, hair cells
Produces
cells with 46 chromosomes
Slide43Review: Comparing Mitosis & Meiosis
Slide44Review: Comparing Mitosis & Meiosis
prophase (I)
metaphase (I)
anaphase (I)
telophase
(I)
Slide4511.1 & 11.2 Vocabulary
Genetics
Fertilization
Trait
Hybrid
Gene - glossary
Allele
Principle of Dominance
Segregation - glossary
Gamete
Probability
Homozygous
Heterozygous - glossary
Phenotype
Genotype
Punnett Square - glossary
Independent Assortment
Slide46Sections 1 & 2
Mendelian Genetics
Standards: 4C.2
Objectives:
Explain the significance of Mendel’s experiments to the study of genetics.
Summarize the law of segregation and law of independent assortment.
Predict genetics of offspring using a Punnett Square.
Slide47Review
Most organisms have diploid cells
Polyploidy
– one or more extra sets of all chromosomes in an organism.
Triploid
3 complete sets of chromosomes 3n
Rarely occurs in animals; humans = lethal
Occurs in flowering plants increased size
Strawberries are 8n
.
Slide4846 Human Homologous Chromosomes
Slide49Review
Sexual Reproduction
: DNA for offspring comes from different individuals
Parents: father & mother
Fertilization
: 1 gamete from each parent fuse to form offspring
Each gamete donates ½ amount of DNA needed
Male gamete = sperm/pollen
Female gamete = egg
Slide50Review
DNA
is divided into units called
genes
Genes code for
proteins
Proteins
control how you look
The passing of this genetic information from parents to offspring is called heredityGenetic Recombination – new combination of genes produced by crossing over and independent assortment.Increases genetic diversity!
Slide51Slide52Gregor Mendel
“Father of Genetics”
Genetics
– study of heredity
1866
published finding of
Inheritance
(traits passed from generation to the next).
Studied pea plants
Slide53Mendel’s Experiments
Mendel studied 7 different pea characteristics.
Characteristic = GENE
Each characteristic had 2 different variations.
Variation =
ALLELE
(different form of a single gene)
TRAITS
Slide54Mendel’s Experiments
Mendel controlled which plants bred with each other through a process called
cross-pollination
.
Self-Pollination
Cross-Pollination
Slide55Mendel’s Experiments
Mendel bred plants with different traits to see what kind of traits the offspring would have.
X
Purple Flowers
White Flowers
X
Purple Flowers
Parent Generation
(P)
Offspring Generation
(F
1
)
Slide56Mendel’s Experiments
Mendel started each experiment with purebred plants expressing a specific trait.
Purebred
– organism that expresses and passes on unchanging traits from generation to generation.
X
X
Purebreds
P Generation
Slide57Mendel’s Findings
Some traits always appeared
Some traits always disappeared
Traits that disappeared would reappear in the next generation IF he let the plants self-pollinate.
Slide58Mendel’s Findings
Purebred
X
X
X
Self-pollinate
Cross-pollinate
Purebred
1
st
Generation (F1)
2
nd
Generation (F2)
Slide59Mendel’s Law of Dominance
Forms of a trait that “disappear” are really hidden by the other form of the trait.
Hidden (or masked) traits
Recessive
lowercase letter
Traits that appear & do the hiding
Dominant
capital letter
Slide60Genes
– factors passed from parent to offspring
Slide61Genotype/Phenotype
Genotype
– genetic makeup
Represented by letters
Phenotype –
physical traits
Slide62Homozygous/Heterozygous
Homozygous
identical alleles for a specific gene
Homozygous Dominant
2 capital letters (AA)
Homozygous Recessive
2 lowercase letters (aa)
Heterozygous different alleles for a specific gene
Heterozygous
1 capital & 1 lowercase (Aa)
Also called Hybrids (different)
Pp
= Heterozygous
Slide63Homozygous/Heterozygous
X
X
X
AA
AA
_____
_____
_____
_____
_____
aa
_____
aa
_____
Slide64Probability
Probability
– likelihood that an event will occur
Chance of T?
Chance of Heads?
Chance of t?
Chance of TALL?
Chance of short?
Slide65Mendel’s Law of Segregation
Chromosomes separate during meiosis II.
Each gamete receives 1 of the 2 alleles (= chance).
During fertilization (sperm & egg unite)
two alleles unite.
Each parent passes one copy of its traits
offspring look similar but not exact.
Slide66Mendel’s Law of Segregation
Slide67Mendel’s Law of Independent Assortment
Each trait has same chance of being inherited
no 1 trait prevents the inheritance of another (
unless genes are linked
).
Genes on separate chromosomes separate independently during meiosis.
Creates many possible combinations of traits.
Slide68Mendel’s Law of Independent Assortment
Slide69Mendel’s Law of Independent Assortment
Slide70Punnett Square
Diagram used to predict probabilities of allele combinations.
Must know parent genotypes
Monohybrid Cross
Inheritance of a single trait.
1 gene, 2 alleles
4 boxes
Dihybrid
Cross
Inheritance of two traits.
2 genes, 4 alleles
16 boxes
Slide71How to Use a Punnett Square
Step 1: List dominant and recessive phenotypes
assign letters.
Always use the same letter for the same gene/characteristic!
Dominant
UPPERCASE Recessive lowercase
Slide72How to Use a Punnett Square
Step 2: What are the parent genotypes?
Think of the possible parent genotypes based on offspring.
Homozygous
(same)
if parent only produces one type of a trait
Heterozygous
(different) if parent produces both types of a trait
Slide73How to Use a Punnett Square
Step 3: Determine what information you are trying to find out.
Offspring genotypes
Offspring phenotypes
Ratios for both
Step 4: Draw Punnett Square
Monohybrid (4 boxes) or Dihybrid (16 boxes)
Slide74How to Use a
Punnett
Square
Step 5: Write alleles or both parents on Punnett square (one on top and one down the side)
Slide75How to Use a Punnett Square
Step 6: Cross Parents
Step 7: Analyze Results
Genotypes
Phenotypes
y
y
y
Y
Y
y
y
y
y
y
y
Y
Slide76Practice: Setting Up Punnett Square
In mice, brown fur is dominant to white fur. If a pure-bred brown mouse is crossed with a white mouse, what is the probability that they have brown offspring?
What is the gene?
What are the alleles?
Dominant allele =
Recessive allele =
What are the parent genotypes?
Pure-bred brown =
White =
Slide771) Monohybrid Practice
In dogs, black fur is dominant to white fur. If you cross a homozygous male black dog to a heterozygous female black dog, what are the possible genotypes and phenotypes of the offspring?
Genotypes
Phenotypes
Slide782) Monohybrid Practice
In cabbage butterflies, white wings are dominant to yellow wings. A heterozygous butterfly is crossed with a homozygous yellow butterfly.
Genotypes
Phenotypes
Slide793) Monohybrid Practice
In dogs, there is a hereditary type of deafness caused by a recessive gene. Two dogs who carry the gene for deafness but have normal hearing are mated.
Genotypes
Phenotypes
Slide804) Monohybrid Practice
In guinea pigs, short hair is dominant over long hair. A homozygous short haired one is crossed with a homozygous long haired guinea pig.
Genotypes
Phenotypes
Slide815) Dihybrid Practice
Black hair is dominant over blonde hair and brown eyes are dominant over blue eyes. Father is heterozygous for black hair and brown eyes and mother has blonde hair and blue eyes.
Slide82Slide83Slide846) Dihybrid Practice
Black hair is dominant over blonde hair and brown eyes are dominant over blue eyes. Both parents are heterozygous for both traits.
Slide85Slide86Slide8711.3 Vocabulary
Incomplete Dominance
Codominance
Multiple Allele
Polygenic Trait
Slide88Section 3
Other Patterns of Inheritance
Standards: 4C.2
Objectives:
Distinguish between various complex inheritance patterns.
Analyze sex-linked and sex-limited inheritance patterns.
Slide89Complex Inheritance
Not all genetics shows simple patterns of inheritance
exceptions to Mendel’s principles.
Genes may have more than 2 alleles
Many traits controlled by more than one gene
Complex Inheritance:
Incomplete Dominance
Codominance
Multiple Alleles
Polygenic Traits
Sex-Linked Traits
Slide90Gene Linkage
Genes close on the same chromosome are “linked” and travel together during meiosis
inherited together
.
Linked genes do not segregate independently exception to independent assortment
Slide91Slide92Incomplete Dominance
Neither allele is completely dominant
Blend of both the dominant & recessive alleles
Slide93Practice Incomplete Dominance
Straight hair is dominant to curly hair and the blend of both is wavy hair. Use “S” and “C”. Cross two wavy haired people.
Use “S”. Cross two wavy haired people.
Slide94Codominance
Heterozygous
both alleles act dominantly and are expressed in phenotype
Roan Cows
Sickle-Cell Disease
Slide95Multiple Alleles
More than two alleles for a specific trait (or gene)
Example
Blood Type
Red blood cells (RBC) are covered in proteins called
antigens
that help cells identify each other.
3 Types of alleles (A, B, O) exist for blood
4 Blood Types:Type AType B
Type ABType O
Type O
Universal Donor
Type AB
Universal Receiver
Slide96Blood Type
Possible Allele Combinations
A
i
A
i
A
(homozygous)
i
A
i
(heterozygous)
B
i
B
i
B
(homozygous)
i
B
i
(heterozygous)
AB
i
A
i
B
(heterozygous)
O
i i
(homozygous)
Blood Types
Slide97Blood Typing Practice
What are the possible offspring blood types if mom is homozygous Type A and dad is homozygous Type B?
Slide98Blood Typing Practice
What are the possible offspring blood types if mom is heterozygous Type A and Dad is heterozygous Type B?
Slide99Blood Typing Practice
What are the possible offspring blood types if mom is Type AB and dad is Type O?
Slide100Polygenic Traits
Traits controlled by interaction of multiple genes
Polygenic = many genes
Results in high level of variation
Shows bell shaped curve when graphed
Examples: skin color, height, eye color, fingerprint
Slide101Environmental Influences
Genes provide plan for development but how the plan unfolds also depends on environment.
Environment can affect how a gene functions.
Phenotype partially determined by genotype.
Environment has an effect on phenotype:
Sunlight & Water
Temperature
Diet & Nutrition
Ecological Factors (weather, soil nutrients, toxins)
Slide102Environmental Influences
Summer
Autumn
Western White Butterfly
Slide103Heredity or Environmental Influences?
How do you determine if the expression of a certain trait is a result of heredity or environmental influences?
Scientists study identical twins
same genetics inherited traits will be expressed in both individuals.
Traits that appear frequently Heredity
Traits expressed differently Environment
Slide104Chapter 14Human Heredity
Slide10514.1 & 14.2 Vocabulary
Genome
Karyotype – picture of a complete set of chromosomes arranged in order of decreasing size
Sex Chromosome - glossary
Autosome - glossary
Sex-Linked Gene
Pedigree – glossary
Nondisjunction – glossary
Gel Electrophoresis - glossary
Slide106Sections 1 & 2
Human Chromosomes & Genetic Disorders
Standards: 4C.2, 4D.1
Objectives:
Analyze genetic patterns to determine dominant or recessive inheritance patterns.
Summarize examples of dominant and recessive disorders in humans.
Construct human pedigrees from genetic information.
Slide107Human Chromosomes
Genome
– an organism’s full set of genetic info.
Karyotype
– picture of a complete set of chromosomes arranged in order of decreasing size
Homologous chromosomes arranged in pairs
Shows type and number of chromosomes
Individual 1
Individual 2
Slide108Karyotype
Male or Female?
Slide109Review: Karyotype
Match each organism with its karyotype:
Mouse
40 chromosomes
Dog
78 chromosomes
Normal
Human Male
Normal
Human Female
Slide110Sex Determination
Sex Chromosomes
– determines gender; X and Y
Autosomes
– any chromosome that is NOT a sex chromosome
Normal Humans have 46 chromosomes:
44 autosomes and 2 sex chromosomes
Female has XX and Male has XY
Slide111X and Y Chromosome
X chromosome
1200 genes
Y chromosome
140 genes
Slide112Sex Determination ProblemWhat is the probability of a man and woman having a baby girl?
Slide113Sex-Linked InheritanceSex-Linked Gene
– gene located on sex chromosome
Sex-Linked Traits
– characteristic controlled by genes on the X or Y chromosome
X Linked
traits found on the X chromosome;
expressed in males & females
Y-Linked
traits found on the Y chromosome; expressed only in males
passed from father to son
Slide114Dominant X-Linked Traits
Trait is expressed
in females and males, if they have 1 copy of the dominant allele.
Male
X
A
Y
Female XAXA or XA
Xa
Trait is NOT expressed
if male has 1 copy of the recessive allele and female has 2 copies of the recessive allele.
Male
X
aYFemale XaXa
Slide115Recessive X-Linked Traits
Trait is expressed
only in
females
that have 2 copies of the recessive allele.
Female
X
aXa Trait is expressed only if males have 1 copy of the recessive allele
Male X
a
Y
Slide116Sex-Linked Trait Practice
Circle those affected by a
dominant
X-linked trait
.
X
B
Xb XcY XdX
d XRX
R
X
N
Y
Circle those affected by a recessive X-linked trait
.XaXa XLY X
T
X
t
X
Z
X
Z
X
p
Y
Slide117Sex-Linked Trait Practice
The trait for red-green colorblindness is a recessive X-linked trait. The mother is a carrier for colorblindness and the father is not color blind, what is the probability that they will have a child that will be color blind?
Slide118Sex-Linked Trait Practice
Hemophilia is a recessive X-linked disorder of the blood. Two normal parents have a son that has hemophilia, what is the probability that they will have a daughter that has hemophilia?
Slide119Sex-Linked Trait Practice
Hairy ears is inherited as a Y-linked trait. A man with hairy ears marries a woman with normal ears. What is the probability that they will have a female child with hairy ears? Male child with hairy ears?
Slide120Sex-Linked Trait Practice
This disease is inherited as
an X sex-linked
dominant disease? An affected male marries a homozygous recessive female. What is the probability that they will have an affected daughter? Affected son?
Slide121Changes in DNA = Changes in Phenotype
Changes in a gene’s DNA sequence can change proteins by altering their amino acid sequences, which may directly affect one’s phenotype.
Genetic disorders caused by changes in genes
changes proteins.
Slide122Recessive Genetic DisordersA recessive allele codes for a faulty protein.
Carrier
– an individual that is heterozygous for a recessive disorder.
50% chance of passing recessive allele to child
AA
no disorder
Aa
no disorder but a carrier for it
aa disorder
Slide123What is the % a child could have a recessive genetic disorder?
Slide124Recessive Genetic Disorders
Slide125Cystic Fibrosis (CF)
Slide126Dominant Genetic Disorders
A dominant allele codes for a faulty protein.
Only
one parent
needs to have
one copy
of the defective allele in their gametes to pass the disorder to their children.
AA and
Aa disorderaa no disorder
Slide127PedigreePedigree
– chart that shows traits, diseases, or disorders within a family across several generations.
Used to infer genotypes by observing phenotypes.
Tracks dominant, recessive, and sex-linked traits.
Dominant traits easier to recognize.
Accurate records of family history
predict effects in future offspring.
Slide128Males
Squares
Females
circles
Expresses Trait
filled
No Trait
unfilled
Carrier for Trait
partially filled
Roman Numerals
generations (P1, F1, F2)
I, II, III
Numbers
birth order of offspring
1, 2, 3
Slide129Pedigree
Slide130Pedigree
white lock of hair - dominant
Slide131Recessive or Dominant?
Slide132Recessive or Dominant?Sex-Linked Trait?
Slide133Recessive or Dominant?Sex-Linked Trait?
Slide134Recessive or Dominant?
Sex-Linked Trait?
Slide135Albinism – Recessive Trait
Phenotypes?
AA = ___________________________
Aa
= ___________________________
aa = ___________________________
Draw a
punnett
square & record the genotypes:
Slide136Albinism – Recessive Trait
Children?
Gender of children?
Generations?
Carriers?
Assume the 3
rd
child mated with an albino male, how likely is it that their child will be albino?
Slide137Albinism – Recessive Trait
Record genotypes.
Children from original couple?
Grandchildren?
Grandchild gender?
Carriers?
Slide138Dwarfism
Affected individuals?
Dominant or Recessive Trait?
Genotype of A, B, C, D?
Generations?
dd
DD
Slide139Nondisjunction
Nondisjunction
– homologous chromosomes fail to separate properly during meiosis
cells having abnormal number of chromosomes chromosomal disorders.
Normal = 46
Any number other than 46 = Abnormal
Only 1 chromosome copy =
monosomy
3 chromosomes of one type =
trisomy
Nondisjunction = serious disorders often fatal
Slide140Nondisjunction
Slide141Down Syndrome
Also called Trisomy 21
Nondisjunction of chromosome #21
Symptoms: distinct facial features, mental retardation, short stature, heart defects.
Affects 1/800
Frequency increases with mother’s age.
Slide142Nondisjunction
Can occur with autosomes and sex chromosomes.
Turner’s Syndrome – female is missing X chromosome
Triple X Syndrome – female with 3 X chromosomes
Klinefelter’s
Syndrome – male with XXY
Death – male just receives Y chromosome & no X
Slide143Fetal Testing
Tests that provide genetic information on developing fetus.
Benefits
diagnosing chromosomal abnormalities early
Risks
miscarriage & infection