mitosis: what occurs during mitosis? what are the products ... · asexual reproduction 1. requires...

Bell Work Mitosis: • What occurs during mitosis? • What are the products of mitosis? • What is the purpose of mitosis?

3/8/18

Bell Work: Complete the pre-assessment on your Anchor Activity Unit 6 sheet. Get out your notebooks for Meiosis notes.

3/9/18

REPRODUCTION: THE NATURAL PROCESS BY WHICH NEW ORGANISMS ARE GENERATED

Asexual Reproduction

1. Requires only 1 parent

2. Offspring are identical to parent

3. Examples: Binary Fission (bacteria), Budding (Hydra and yeast)

A Hydra

budding

Sexual Reproduction

1. Requires 2 parents which each:

provides a gamete – sperm or egg

Give DNA to offspring

2. Two gametes fuse to create a new organisms → Fertilization

3. Offspring are different from both parents

4. Example: Meiosis

FERTILIZATION: Male & female reproductive cells (GAMETES) fuse to form a new cell (ZYGOTE) that develops into a new organism.

Gametes: • Have 1 copy of each

chromosome or gene • Haploid, n

Zygotes: • Have 2 copies of each

chromosome (1 from each parent)

• Diploid, 2n

haploid haploid

diploid

Somatic Cells: a. Have 2 copies of each gene – diploid b. Make up most of the cells in your body

MEIOSIS

Making the Reproductive Cells: Starts with Germ Cells

1. Interphase: • DNA replication

2. Prophase I: • Homologous chromosomes pair up • Crossing over occurs

Interphase and Meiosis I

HOMOLOGOUS CHROMOSOMES

• A pair of chromosomes, one from each parent

• Carry the same genes

• Are identical in shape

Sister Chromatids

Homologous Chromosomes

Crossover

Crossing Over: Homologous chromosomes exchange pieces

3. Metaphase I Homologous chromosomes line up at metaphase plate

4. Anaphase I Homologous chromosomes pulled to opposite ends of cell

5. Telophase I Nuclear envelope reforms

6. Cytokinesis 2 daughter cells with ½ number of chromosomes as parent.

End of Meiosis I: 2 new cells each with 2 copies of 1 chromosome (from only 1 parent)

1. Prophase II Nuclear envelope breaks down

2. Metaphase II Chromosomes line up at metaphase plate

Meiosis II

3. Anaphase II Sister chromatids pulled to opposite ends of cell

4. Telophase II: Nuclear envelope reforms

5. Cytokinesis: 4 daughter cells with 1 copy of each chromosome

4 Haploid Cells each genetically different

DNA replication

Meiosis I

Diploid Cell

Meiosis

Meiosis II

MITOSIS MEIOSIS

DNA Replication

Number of cell divisions

Number of daughter cells and genetic

composition

Role in the body

Once in Interphase Once in Interphase

One Two

2, diploid, identical to

parent

4, haploid, different from

parent

Growth & Repair Reproduction

Bell Work 3/12/18

Make a Venn Diagram comparing Mitosis and Meiosis

Complete your Meiosis on the Table

When you have completed your modeling of meiosis on the

whiteboard your options are:

1. Complete the Meiosis worksheet – due tomorrow

2. Take notes from the slides on the website (#21 to #26).

3. Do the Google Classroom Assignment (Chromosomes and

Karyotypes) – due Thursday

4. Work on “Identifying Genetic Disorders with Karyotypes” – due

Thursday

Bell Work 3/13/18

Make a Venn Diagram comparing Mitosis and Meiosis

2. Independent Assortment: Chromosomes are randomly segregated & sorted during metaphase I

Sources of Diversity in Meiosis & Sexual Reproduction

1. Crossing Over during Prophase I

3. “Random” Mating Combination of sperm & egg that form the zygote is random.

Chromosome Mutations

Deletion of a part of a chromosome

Duplication of a part of a chromosome

Inversion of a chromosome

Translocation between 2 different chromosomes

Breakage of a chromosome caused by errors in cell division or damaging agents such as radiation.

Mistakes during Meiosis

Nondisjunction: An error that can occur during meiosis in which chromosomes DO NOT separate.

Human Fruit fly Karyotypes: • a photograph of

chromosomes grouped as homologous pairs

• Can be used to determine gender and diagnose disease

Sex Chromosomes: • All organisms have 1 pair, X

and Y • X and Y have different

genes • Females have 2 X

chromosomes • Males have 1 X & 1 Y

Autosomal Chromosomes: • Paired – 1 from each

parent • Each pair has the same

genes

Bell Work 3/14/18

1. What is the gender of the individual shown on the right?

2. Is the Karyotype normal? If not, where is the abnormality?

XYY Syndrome: • Male • Taller • Sexually normal • Increased risk of

learning disabilities

Turner Syndrome: • Short • Infertile • Female

Down’s Syndrome: Intellectual disability Weak muscle tone Increased risk of

other medical conditions

Edwards Syndrome • Low birth weight •Heart defects •Often die before

birth or in 1st month

Patau Syndrome • Severe intellectual

disabilities • Physical abnormalities • Small eyes • Extra fingers or toes • Many infants die in 1st

days

Klinefelter Syndrome: •Male •Produce less

testosterone •Delayed puberty •Breast enlargement • Sterile

Bell Work 3/14/18

1. What is the gender of the individual shown on the right?

2. Is the Karyotype normal? If not, where is the abnormality?

Triple X Syndrome: • Female •Often infertile •Otherwise normal

2. Independent Assortment:

What are 3 events that occur during meiosis and zygote formation that contribute to genetic diversity in a species?

1. Crossing Over during Prophase I

3. “Random” Mating

Bell Work 3/15/18

• Alleles: Different sequences of the same gene

Mendelian Genetics - Vocabulary

Alleles are either dominant or recessive

• Homozygous: both alleles in the organism are the same; Homozygous Dominant and Homozygous Recessive

• Heterozygous: each allele for a gene in the organism is different.

• Genetics: Study of heredity • Heredity: passing of traits from parent to offspring

• Genotype: the alleles an organism has for each gene

• Phenotype: the outward appearance of the genotype

• Trait: characteristic that varies from person to person, depends on

combination of alleles for each gene • Punnett squares:

diagram showing the allele combinations that MIGHT result from the fusion of 2 gametes to form a zygote.

R = violet, dominant r = white, recessive Genotype Phenotype Genotype ratio Phenotype ratio

RR = violet 1 Rr = violet 2 3 rr = white 1 1

R r male / sperm

R

r

fem

ale

/ e

ggs

Sample Cross:

Rr x Rr

R R

r r

R

R

r

r

Gregor Mendel (1822-1884)

• Austrian monk. • Studied inheritance of traits in

garden peas. • 1866: Defined the laws that govern

inheritance of traits.

Mendel’s Pea Plant Experiments

• Pollen – produced by the

stamen, contains the sperm

(male reproductive cell).

• Flower – contains the ovary or

egg (female reproductive cell).

a. Self-pollinated: pollen and ovary

from same flower fertilize

b. Cross-pollinated: pollen and

ovary from different flowers

fertilize

• Plants can be:

• Generations in breeding:

1. P1: Parental generation.

2. F1: 1st generation offspring (from breeding individuals in

P1 generation).

3. F2: 2nd generation offspring (from breeding individuals in

F1 generation).

• Observation: Offspring retain traits of

parents.

• Conclusion: Physical traits are inherited

as particles

• Mendel studied 7 traits in pea plants by:

1. Allowing plants to self-pollinate for

many generations to create a pure

strain (homozygous)

2. Cross-pollinating plants w/ different

traits

• Types of Genetic Crosses a. Monohybrid: Cross involving a single trait (for example

flower color). b. Dihybrid: Cross involving 2 traits (for example flower color

and plant height)

male / sperm

fem

ale

/ e

ggs Genotype:

Phenotype:

P1 Cross

Monohybrid

Trait: Seed Shape

Alleles: R – Round; r – Wrinkled

Cross: Round seeds x Wrinkled seeds

(RR x rr)

Genotype ratio:

Phenotype ratio:

male / sperm

fem

ale

/ e

ggs

Genotype:

Phenotype:

F1 Cross

Monohybrid

Trait: Seed Shape

Alleles: R – Round r – Wrinkled

Cross: Round seeds x Round seeds

(Rr x Rr)

Genotype ratio:

Phenotype ratio:

yellow round

green round

yellow wrinkled

green wrinkled

F1 Generation

Dihybrid cross – P1 generation

YYRR yyrr yr yr yr yr

YR

YR

YR

YR

YyRr

YyRr

YyRr

YyRr YyRr YyRr YyRr

YyRr YyRr YyRr YyRr

x

YyRr

YyRr YyRr YyRr

YyRr

Dihybrid cross – F1 generation

YyRr YyRr

YR Yr yR yr

YR

Yr

yR

yr

YYRR YYRr YyRR YyRr

YYRr YYrr YyRr Yyrr

YyRR YyRr yyRR yyRr

YyRr Yyrr yyRr yyrr

x yellow round

green round

yellow wrinkled

green wrinkled

F2 Generation

true-breeding yellow, round peas

true-breeding green, wrinkled peas

x

YYRR yyrr

YyRr

100% F1 generation

yellow, round peas

self-pollinate

F2 generation

9/16 yellow round peas

9:3:3:1

3/16 green round peas

3/16 yellow

wrinkled peas

1/16 green

wrinkled peas

Y = yellow

R = round

y = green

r = wrinkled cross-pollinate

Dihybrid Crosses

Mendel’s Laws of Inheritance:

1. Law of Dominance:

Some alleles are dominant and some are recessive – the dominant

alleles mask the recessive alleles.

2. Law of Segregation:

During gamete formation the 2

alleles that determine trait

separate from each other and

at fertilization are recombined.

3. Law of Independent

Assortment:

Alleles for different traits

are sorted randomly

during Metaphase I.

Each pair of alleles segregates into gametes independently

Gametes with different combinations of alleles are produced in equal amounts

YyRr

Yr Yr yR yR YR YR yr yr

Trait: Seed Shape and plant height

Alleles: R – round r – wrinkled

T – tall t - short

Cross: 1 round seed, tall plant

1 wrinkled seed, tall plant

(RrTt x rrTt)

Phenotype Ratio:

Bell Work 3/16/18

Bell Work 3/19/18

How do Mendel’s observations of the pea plant offspring support the Law of Dominance?

Corn Snake Genetics

Correction on the handout:

Under Albino snake, change the genotype:

It is NOT Bbrr – it SHOULD be bbrr

Bell Work 3/20/18

To determine the true genotype of your new ‘wild’ corn snake (B_R_), you cross it with an albino corn snake (bbrr). 1. What offspring phenotypes

are possible for each possible genotype?

2. How will this tell you what the genotype of your snake is?

BbRr

br

br

br

br

BBRR

BBRr

BbRR

Sex Chromosomes: Chromosomes with genes that determine gender. X-Linked Traits: Genes carried on the X Chromosome

Autosomes: Chromosomes with genes that do not determine gender. Autosomal Traits: Genes carried on these chromosomes

There are 2 types of chromosomes:

Gene notation for X-linked traits:

Xupper-case letter : For the dominant

allele on X-chromosome (XH)

Xlower-case letter : For the recessive

allele on X-chromosome (Xh)

Y : For the male chromosome

Females have 2 X chromosomes:

XX with allele shown by upper- or lower-case letter for each

X. Heterozygous female: XRXr

Males have 1 X which is paired with 1 Y chromosome:

XY with allele shown by upper- or lower-case letter on the

X. Male with recessive trait: XrY

Male with dominant trait: XRY

Offspring Ratios

Gender:

Genotype:

Phenotype:

In Fruit Fly, eye color is X-linked:

Xr = white eyed (recessive)

Cross white-eyed female fruit fly w/ red-eyed male fruit fly:

White-eyed female genotype:

Red-eyed male genotype:

Practice

Cross a female carrier of Hemophilia and a normal male

1. Normal (XH) is dominant over hemophilia (Xh)

2. Parent Genotypes

Mom:

Dad:

3. Offspring ratios

Gender:

Genotype:

Phenotype:

Hemophilia is an X-linked Trait: Practice

Background: Sickle cell Anemia is a recessive trait carried on chromosome 11. In regions where malaria is common, individuals who are heterozygous for sickle cell anemia have a 60% survival advantage compared to individuals who are homozygous dominant (AA). Individuals who are homozygous recessive for sickle cell anemia (SS) live on average to ~45 years.

Problem: Two heterozygous parents living in Madagascar have children. What is the probability that they will have children who will survive to the age of 65 years?

Bell Work 3/22/18

Co-dominant Alleles:

Alleles – B and W

BB = Black

WW = white

BW = Multi-colored

Both alleles contribute to the

phenotype B B

W

W

BW

BW

BW

BW

In some chickens neither black nor white

feathers is dominant – chickens with

both alleles are checkered

Blood Type has 3 alleles: IA, IB, i

IA and IB: co-dominant

i: recessive

Multiple Alleles

Genes with more than 2 alleles

These alleles represent the antigens that are expressed on the

surface of your red blood cells

Antibodies in your

plasma will attack only

those red blood cells

(RBCs) with an antigen

different to the one on

your own RBCs.

Blood Type and

Blood donors

Red Blood Cell

antigen Plasma

antibody

Blood

type

Genotypes

IA IA

IA i

IB IB

IB i

IA IB

i i

Phenotype

A

A

B

B

AB

O

RBC*

Antigen

A

A

B

B

A & B

none

Plasma

Antibody

B

B

A

A

None

A & B

Malaria and the Inheritance of Sickle Cell Anemia

Sickle Cell is an example of a co-dominant trait:

Individuals w/out the disease have 2 normal alleles – AA

Individuals w/ 1 diseased allele have the “trait” – AS

Individuals w/ 2 diseased alleles have the disease – SS

The Ghost in Your Genes

Bell Work: 4/2/18

About 70% of Canadians get a bitter taste from the chemical phenyl

thiocarbamide (PTC), while the other 30% do not. The ability to taste PTC (T)

is a dominant characteristic, while ‘taste-blindness’ to it is recessive (t).

Tongue-rolling is dominant (R); inability to roll the tongue is recessive (r).

A tongue-rolling woman who is taste-blind for PTC has a father who could

not roll his tongue but could taste the PTC chemical. She marries a man

who can taste PTC but cannot roll his tongue. His mother was taste-blind to

the chemical. Show the possible children this couple could produce. Use a

Punnett square to illustrate your answer.

Daughter Genotypes:

Her Fathers Genotypes:

Husband Genotypes:

His Mothers Genotypes:

A tongue-rolling woman who is taste-blind for PTC has a father who could not roll his tongue but could taste the PTC chemical. She marries a man who can taste PTC but cannot roll his tongue. His mother was taste-blind to the chemical. Show the possible children this couple could produce. Use a Punnett square to illustrate your answer.

Daughter Genotypes: Her Fathers Genotypes:

Husband Genotypes: His Mothers Genotypes:

Offspring Genotype Ratio: Offspring Phenotype Ratio:

Incomplete dominance:

One allele is not completely

dominant over another

Some flowers show incomplete

dominance in flower color:

Alleles – R and W

RR = red

WW = white

RW = pink

Polygenic Inheritance:

The inheritance pattern is controlled by two or more

genes each with two alleles.

• Polygenic inheritance shows up as a range of variation such has height, skin color or hair color.

• The results of an average population will yield a bell-shaped curve.

Height is an example of an incompletely dominant trait that is

determined by more than one gene.

TTHH: very tall TtHh: med.

TtHH or TTHh: tall

TtHh, ttHH, TThh: med.

tthh: short

What is the probability that 2 medium

height parents will have tall or very tall

children?

Example of inheritance of height: keeping it simple, we will only

consider only 2 genes (T & H).

Eye Color in Humans: Polygenic Trait • At present, three gene pairs controlling human eye color are known.

• Two of the gene pairs occur on chromosome pair 15 and one occurs

on chromosome pair 19.

• One gene, on chromosome 15, has a brown and a blue allele.

• The second gene, located on chromosome 19, has a blue and a green

allele.

• The third gene, located on chromosome 15, is a central brown eye

color gene.

Bell Work

A

B

1. What is happening in diagram A?

2. What phases of meiosis does diagram A

represent?

3. What is happening in diagram B?

4. What phases of meiosis does diagram B

represent?

4/3/18

Metaphase I Anaphase I

Metaphase II Anaphase II

Essential Question Notecard: What is the role of meiosis in sexual reproduction and genetic variation?

Bell Work 4/4/18 & 4/5/18

Possible vocabulary: Crossing over, Random mating, Haploid, Diploid, Gametes, Independent assortment

Essential Question Notecard: How can the ratio of offspring be predicted from patterns of inheritance?

Bell Work 4/5/18 & 4/6/18

Possible vocabulary: Allele, co-dominance, Punnett Square, gametes, trait, dominance, recessive, genotype, incomplete dominance, phenotype

Essential Question Notecard: How does the environment influence the expression of genetic traits?

Bell Work 4/6/18 & 4/9/18

Pedigree Charts

Show how a trait is passed from one generation to the next.

Can be used to

Infer the genotypes of family members

Study the inheritance of genetic disorders

Parts of a Pedigree Squares: males Circles: females Horizontal lines: breeding

couples Vertical lines: connect

parents to children

Shading: individuals with the trait being studied

Diagonal line: death Roman numerals: generations Numbers: identify individuals

in a generation

Half shading or a dot: “carriers” of the trait

No shading: individuals without the trait being studied

Interpreting Pedigrees

1. Is the trait dominant or

recessive?

• Trait skips a generation?

Most likely Recessive

• Trait occurs every

generation?

Most likely Dominant

2. Is the trait autosomal or

sex linked?

• Affects males & females

equally? Autosomal

(i.e. Aa)

• Affects one sex more

than the other (i.e.

mostly males)? Sex-

linked (XAXa, XaY)

Pedigree Chart for Eye Color (autosomal)

What are genotypes of individuals 8 & 9?

Huntington’s Disease Autosomal Dominant (H, h)

What is genotype of individuals 1, 2, 3, & 4?

1 2

3

4

Hemophilia: X-linked recessive trait (Xh)

What are the genotypes of the following individuals:

1:

5:

7:

8:

Individuals with hemophilia are shaded

The pedigree chart shows the blood types of three generations of family members. Some of the phenotypes are shown.

Bell Work 4/9/18

1. What is the genotype of individuals 1 -6?

2. Give the probable genotype of all other family members.

Building a Pedigree Chart: The father, Tom, & mother, Diane, have 3 children. The 2 oldest children are

Anna and Mary and the youngest is Teddy. The oldest, Anna, is married &

has an older son, Will, and a younger daughter, Vanessa. Mary is also married

and has a son, Patrick. Teddy is not yet married. Everyone in this family is

right-handed except the father, the oldest daughter, and the granddaughter.

Right-handedness is dominant.

Cystic Fibrosis: What is the pattern of inheritance? What are the Genotypes of the individuals?

Hypercholesterolemia (H, h) Autosomal or X-linked trait? Dominant or Recessive? What are the Genotypes of the individuals?