SBI3UO genetic continuity

SBI 3UO LESSON PLANS

Unit 2: Genetic Continuity (17 hours)

Students will demonstrate an understanding of the role of meiosis and genes in transmitting hereditary characteristics according to Mendelian inheritance. Laboratory studies of meiosis will be performed and analysis made of the results of genetic research related the laws of hereditary. Students will understand some of the technological advances in the field of genetics and will demonstrate an awareness of some of the corresponding social and political issues.

Ontario Curriculum objectives:
U=understanding concepts (U1-U7)
D=developing skills (D1-D4)
R=relating science (R1-R3)

Text: Biology 11
Addison-Wesley

Lesson One

Summary:(U1,D3)
-define mitosis, cytokinesis
-describe chromosomes, chromatids, centromeres
-work on long sheet on mitosis

Homework:
-read p. 120-122
-do p.130 #1

CELL DIVISION

-Cells make copies of themselves with identical DNA

Mitosis:
-equal distribution of DNA from one parent to two daughter cells
Cytokinesis:
-splitting of one parent cell into two daughter cells

-a limited number of cell divisions occur in multicellular organisms for the following reasons:
-growth of new cells (to keep surface area : volume ratio low)
-repair of damaged cells
-replacement of dead cells

-an unlimited number of cell divisions occur in In unicellular organisms for the following reason:
-reproduction of organisms

chromosome:
-one double helix of DNA on own
-chromosomes must double in size before mitosis occurs

Interphase:
-stage in cell life when chromosomes copy themselves to double in size
-the two copies are held together by a protein called a centromere
-each half is now called a chromatid and the pair is called a chromosome

Lesson Two

Summary:(U1)
-describe interphase
-describe mitosis after completion
-examine cells undergoing mitosis

Homework:
-read p.122-126
-do p.130, #2-4

INTERPHASE

-before mitosis occurs, the cells must go through interphase
Interphase:
G1 -cell spends 20% of its time in this phase
-cell grows, carries out life functions and animal cells replicate centrioles
S -cell spends 50% of its time in this phase
-cell doubles the size of the chromosomes
G2 -cell spends 20% of its time in this phase
-cell grows, continues to carry out life functions

Mitosis and Cytokinesis take the remaining 10% of the cell’s time
-one cell makes two cells with identical DNA to the parent cell

Do long sheets on mitosis

Lesson Three

Summary:(U1,U4)
-describe cancer, differentiation
-do mitosis microviewer
-describe meiosis
-define diploid, haploid

Homework:
-read p. 126-128, 129-132
-do p.130 #5,6

CELL DIVISION (continued)

Cancer:
-uncontrolled mitosis (cells with fixed number of divisions divide out of control)
-treatments for cancer include surgery, radiation, chemotherapy

Differentiation/Specialization:
-in the first three months after conception (in humans), cells turn on certain genes
-the function is of these cells is determined at this time
-after this point, a cells fate as a certain cell type or tissue is generally fixed

Do “animal mitosis” microviewers

MEIOSIS

Sex cells are produced by the process of meiosis
Meiosis:
-one cell divides into four cells with half the parent’s chromosomes
-only sexually reproducing organisms do this, in order to make sperm or egg (gametes = sex cells)
-cells start of this division with a diploid number of chromosomes (two sets of homologous chromosomes)

Homologous Chromosomes:
-each chromosome has a matching chromosome with the same size, centromere location and genes
-they may differ in the trait on those genes, however
eg. -two chromosomes are same size, centromere location, and genes for hair colour and eye colour
-one has genes for blonde hair and blue eyes, the other has the genes for brown hair and brown eyes

Diploid # = 2n# = 46 chromosomes in humans (23 pairs)
   = 48 chromosomes in chimps (24 pairs)
    = 8 chromosomes in fruit flies (4 pairs)
   = 92 chromosomes in corn (46 pairs)

-every somatic (body) cell in animals and plants has a diploid number of chromosomes
-after meiosis, gametes (sperm, egg) only have a single set of chromosomes (one of each homologous pair)
-haploid number is number of chromosomes in single set

Haploid # = 1n# = 23 chromosomes in human gametes
   = 24 chromosomes in chimp gametes
    = 4 chromosomes in fruit fly gametes
   = 46 chromosomes in corn gametes

Lesson Four

Summary:(U4,D1,D3)
-describe synapsis
-do long sheets on meiosis

Homework:
-read p.132-135
-do p. 130, #3-5

MEIOSIS (continued)

-meiosis is the production of gametes with half the normal number of chromosome
-these gemetes join during fertilization to make a complete set of chromosomes in a cell

-a large variety of gametes are produced by each parent
-one way variety is increased in gametes occurs during Prophase I, first stage in meiosis

Synapsis:
-joining of homologous chromosomes (occurs in prophase I)
-homologous chromosomes join at points to form a tetrad (4 chromatids)
-DNA on the two chromosomes is randomly exchanged (recombination”/“crossing over”) at points called “chiasmata”
(eg. gene for blue and brown eyes could be exchanged between two chromatids, but all other genes remain unaltered)
-see figure 5.18, p. 134
-after crossing over occurs the chromosome pairs separate at most points (pair is called a “bivalent”)
-do long sheets on meiosis

Lesson Five

Summary:(U3,U4,D3)
-describe independent assortment
-describe sperm and egg formation

Homework:
-read p. 136-138
-do p. 142 #8

MEIOSIS (continued)

Meiosis:
first division -one diploid cell produces two haploid cells with chromosomes each consisting of two chromatid
second division -two haploid cells produce four haploid cells with chromosomes half the size of the original

Independent (random) Assortment:
-what one pair of homologous chromosomes does is independent of the other pairs
-this contributes to the wide variety of gametes being produced
(see p. 135, teacher will describe with coloured markers or chalk)

-the two meiotic divisions in males produce four equal sized cells

-the first meiotic division in females produces two cells of different sizes
-the large cell has most of the nutrients,cytoplasm and the smaller cell is called a “polar body”
-the second meiotic division in females results in the large cell again splitting to form a polar body and a large egg
-the first polar body may or may not divide
-the polar bodies now degrade
-the egg is now larger than the sperm, as it has more cytoplasm and nutrients (p. 38, fig. 5.22)

-work on pipe cleaner practice sheets for mitosis and meiosis

Lesson Six

Summary:(U4)
-complete pipe cleaner activity
-describe asexual, sexual reproduction

Homework:
-read p. 143-145
-do p. 146, #2,5,6

-complete pipe cleaner activity

REPRODUCTION

asexual reproduction:
-one cell splits into two "clone" cells with the same DNA as the parents (mitosis)

METHOD	DESCRIPTION	EXAMPLE
binary fission	-one cell splits into two equal sized cells	-amoeba, bacteria
budding	-one cell splits into two unequal sized cells	-yeast
vegetative propagation	-part of a plant grows into a new organism	-spider plant
fragmentation	-animal body parts grow into new organism	-flatworms
spore formation	-hard cased cell is produced by mitosis and then released	-fungus, ferns

-variety in offspring arises by random changes to the DNA called mutations

advantages of asexual reproduction:
-consistent offspring, good at survival in stable environment, little energy is needed
disadvantages of asexual reproduction:
-little variety produced makes environmental change more devastating

sexual reproduction:
-two cells with half the normal DNA join to make a diploid cell with amount of DNA
-done in animals, plants
-gametes join to form a zygote (fertilization), which divides into a blastula
-specialization then occurs (embryo) as genes are turned on in certain cells
-a growth stage follows (fetus)

-variety in offspring arises by mutation, crossing over, independent assortment, fertilization

advantages of sexual reproduction:
-large amount of variety produced ensures better adaptability to environmental change
disadvantages of sexual reproduction:
-much energy is expended looking for a mate
-variety produces some offspring which are less successful than their parents

Lesson Seven

Summary:(U4)
-genetic terms
-do meiosis microviewer

Homework:
-read p. 156-157
-do p. 157 #2,3,4

GENETICS

-review genetics survey

Genetics is the study of hereditary information with respect to its coding and method of transmission from one generation to the next

Gene:
-a units of hereditary information
-a gene is now known as pieces of DNA responsible for production of one protein
-the letter chosen to represent the gene is best if capital and small case letters are easily distinguished
Allele:
-alternate form of the same gene
e.g. the gene for hair colour has brown and blonde alleles

Dominant:
-when two different alleles are present the one that is expressed is dominant
e.g. brown is dominant to blonde, indicated with capital letter (B)
-dominant alleles are not always the most common trait
Recessive:
-when two different alleles are present the one that is not expressed is recessive
e.g. blonde is recessive to brown, indicated with a lower case letter (b)

Homozygous:
-when an organism has two identical alleles for one gene
e.g. BB (dominant) or bb (recessive)
Heterozygous:
-when an organism has two different alleles for one gene
e.g. Bb (the dominant trait is expressed)

Genotype:
-the symbolic representation of the alleles for the trait
e.g. BB, Bb, bb
Phenotype:
-the physical result of the genotype
e.g. Brown, Blonde

Gametes:
-cells resulting from meiosis and are haploid (one set of chromosomes) e.g. sperm and egg
Somatic cells:
-regular body cells and are diploid (two sets of chromosomes)
Zygote:
-fertilized egg, diploid because it is formed by the fusion of two haploid cells

Progeny:
-another term for offspring

Diploid Number:
-a double set of chromosomes (normal number found in somatic cells)
e.g. humans 2n# = 46, chimps 2n# = 48, fruit fly 2n# = 8
Haploid Number:
-a single set of chromosomes (normal number found in gametes)
e.g. humans 1n# = 23, chimps 1n# = 24, fruit fly 1n#=4

Monohybrid Cross:
-a mating looking at one gene and two alleles
e.g. BB X bb uses the gene for hair colour, alleles are brown and blonde
Dihybrid Cross:
-a mating looking at two genes and four alleles
e.g. BBRR X bbrr uses the genes for hair colour and eye colour, alleles are brown/blonde hair, brown/blue eyes

Parental (P) Cross:
-a mating of any two parents
First Filial (F₁)Generation:
-offspring of P cross
F₁ cross:
-mating of first filial generation
(not done in humans too often...generally frowned upon because the danger of two rare deleterious recessives combining is high in siblings)
Second Filial (F₂) Generation:
-progeny of F₁ cross

-work on meiosis microviewers...quiz on meiosis and mitosis stage next class

Lesson Eight

Summary:(U1)
-describe Mendel’s work
-introduce monohybrid crosses

Homework:
-read p. 160-161
-do monohybrid cross sheet

GREGOR MENDEL

Gregor Mendel was the first to study genetics scientifically
-he was a monk who worked with peas in the mid 1800’s

Why work with peas? -can be self pollinated, easy to control parental crosses (p. 155, fig. 6.4)
   -grow quickly
   -produce many seeds, improving statistics
   -have many obvious, contrasting traits (p. 156, fig. 6.5)
Mendel’s experiments with peas led him to the following conclusions:
1. inheritance of traits was determined by genes...these genes are found in pairs (diploid)
2. one gene of each pair is in a gamete (haploid)
3. gametes unite randomly

Mendel’s Laws:
Law of Dominance:
-if two different alleles are present for one gene (heterozygous), one allele will be expressed (dominant) and the other hidden (recessive)
Law of Segregation:
-gametes contain one gene of each pair, which segregate randomly
eg. Bb will form gametes with B and b in a 1:1 ratio

MONOHYBRID CROSS

When genetics problems arise a certain form is used to predict offspring
eg. A heterozygous (hybrid) purple flowered male pea is mated to a white flowered pea
What offspring will be produced?
This is a monohybrid cross, which involves one gene with two alleles
determine what trait is dominant:
-in a heterozygous organism, only the dominant trait is expressed
-purple must be dominant
give name of organism and gene studied:
PEAS, flower colour
write a legend showing dominant and recessive genes:
Q = purple (dominant)
q = white (recessive)
write the phenotype of the parents:
             Purple male             X             White female
write the genotype of the parents:
             Qq male                 X             qq female
write the gametes produced by each parent:
             Q     q                                      q             q
Place gametes around a Punnett square, find offspring:

male gametes down side, female gametes along top

gametes	q	q
Q	Qq	Qq
q	qq	qq

Genotype ratio of F₁:
1 Qq : 1 qq

Phenotype ratio of F₁:
1 purple : 1 white

Lesson Nine

Summary:(D1,R1,R3)
-research biology project

Homework:

BIOLOGY PROJECT

-research biology project

Lesson Ten

Summary:(U7,D2,D4)
-genetics monohybrid tutorial

Homework:
-do genetics tutorial

GENETICS TUTORIAL

-complete genetics wheel

-review monohybrid crosses

-do genetics tutorial
-click here to download: crosses

Lesson Eleven

Summary:(U3,U7,D2)
-describe dihybrid crosses
-describe independent assortment

Homework:
-read p. 158-159, 164-165
-do monohybrid cross sheet
-do dihybrid cross sheet

DIHYBRID CROSSES

Dihybrid crosses:
-a genetic cross studying two genes and four alleles
eg. A heterozygous tall, green pea is mated with a short, heterozygous yellow female pea

organism/genes:

Pea: height, colour

legend:
B = tall (dominant)
b = short (recessive)
E = yellow (dominant)
e = green (recessive)

P phenotypes:
hetero. tall, green male X short, hetero. yellow female

P genotypes:
Bbee X bbEe

gametes formed:

Be Be be be bE be bE be

Punnett square:

gametes	bE	be	bE	be
Be	BbEe	Bbee	BbEe	Bbee
Be	BbEe	Bbee	BbEe	Bbee
be	bbEe	bbee	bbEe	bbee
be	bbEe	bbee	bbEe	bbee

g ratio of F₁:
4 BbEe: 4 bbEe: 4 Bbee: 4 bbee
or
1 BbEe: 1 bbEe: 1 Bbee: 1 bbee

p ratio of F₁:
1Tall, Yellow: 1 Short, Yellow: 1 Tall, Green: 1 Short, Green

Mendel’s law of Independent Assortment:
-one gene behaves independently of another gene during gamete formation
-this works if genes are on separate chromosomes chromosome
(different chromosome pairs separate independently during meiosis)
-this also works if the genes are far apart on the same chromosome
(genes far apart have a large number of crossovers between them during prophase I of meisosis)
-Mendel knew none of these reasons

eg. gametes formed for BbEe are BE, Be, bE, be

Cross BbEe X BbEe as practice:
p ratio of F₁ should be 9 Tall, Yellow: 3 Tall, Green: 3 Short, Yellow: 1 Short, Green

Lesson Twelve

Summary:(U7,D2)
-describe hazards of inbreeding
-do dihybrid crosses

Homework:
-review p. 210-211
-do 167, #2,8

INBREEDING

Inbreeding:
-most families have deleterious (dangerous) recessive alleles hidden in their genes by dominant genes
-the chance of an unrelated person having this same recessive is slim
-if a person mates with a direct relative the chance of the same two deleterious recessive genes coming together (being homozygous) in their offspring is higher than with random mating
-these recessive genes are expressed only when homozygous
-this holds true for most species
eg. dog breeding is monitored in order to prevent inbreeding (kennel clubs)

Work on dihybrid crosses sheet

Lesson Thirteen

Summary:(U2,U6,D2)
-describe sex-linked traits
-describe Barr bodies
-do sex-linked worksheet

Homework:
-read p. 190-192
-do p. 200, #4

SEX LINKED TRAITS

In humans, sex is determined by the X and Y chromosomes
X chromosome:
-large chromosome containing many genes (called sex-linked genes)
Y chromosome:
-small chromosome that contains few genes, triggers genes responsible for male traits

XX = female
XY = male

-in birds, the opposite is true
-in reptiles, sex is determined by egg temperature
-many organisms determine sex in different ways

The chance of a human couple having a male or female baby is 50%

eg. XY x XX

Punnett square:

gametes</