1 dec opener: what does a karyotype show us? agenda review karyotypes meiosis meiosis puzzle ...
TRANSCRIPT
1 Dec
Opener: What does a
karyotype show us?
Agenda Review
Karyotypes Meiosis Meiosis puzzle Meiosis drawing
Homework none
Human female karyotype
46 chromosomes23 pairs
XX
diploid = 2 copies2n
46 chromosomes23 pairs
XY
Human male karyotypediploid = 2 copies2n
Do we make egg & sperm by mitosis?
46 46+ 92
egg sperm zygote
What if we did, then….
Doesn’t work!
No!
Meiosis Meiosis
special cell division in sexually reproducing organisms
reduce number of chromosomes Diploid (2 sets of chromosomes
haploid or monoploid (1 set ) makes gametes- sex cells
sperm, eggs
gametes
How do we make sperm & eggs? Must reduce 46 chromosomes 23
must halve the number of chromosomes haploid
23
2346
egg
sperm
46
meiosis 46
fertilization
23
23
zygote
Meiosis makes sperm & eggs
46 chromosomes to 23 chromosomes halve the number of chromosomes
23
2346
egg
sperm
46
meiosis
haploiddiploid
Steps of meiosis
1. Cell copies its DNA2. Chromosomes that code for the same
information pair-up and some of their information is transferred (crossing-over)
3. Cell divides once, yielding 2 cells4. Each of the 2 cells divide again, yielding
4 gametes.
2 Dec
Opening question If neither parent
has a genetic disease, can a child have it?
Agenda: Hand back work Fire drill/lock
down procedures Genetics
discussion questions
Pedigree Basics Class activity
HW: none
Genetics Discussion Questions
1. Where do you get your traits?2. How do you get your traits?3. Are your traits just a blend of your
parents’?4. Is it possible to have a trait that neither of
your parents have?5. Besides function, what is the difference
between sex cells (sperm & egg) and body cells (skin, liver, brain)?
6. Can humans reproduce asexually?
Pedigree basics
Male/female Marriage line Offspring line Generations Shading Questions:
How many males? How many matings? How many generations? How many kids were made from 2nd generation? How many people with the disease? Does the disease have a pattern?
Pedigree basics
Questions: How many males? How many matings? How many generations? How many kids were made from 2nd generation? How many people with the disease? Does the disease have a pattern?
Pedigree Class Regroup
Does this disease affect malesmore than females? If the parent has this disease, does that mean the kids are going to have it? If the parents don’t have it,
can their kids have it? Any ideas on how this disease is passed
on through families by their genes?
3 Dec
Opener: Agenda Finish Pedigree
worksheet Homework
4 Dec
Opener Think about the pedigrees
from yesterday. When can we tell someone’s genetic make-up by observing them?
Agenda: Review Meiosis Why sex? Sources of
variation
Homework
Meiosis Review
Meiosis Review
http://media.pearsoncmg.com/bc/bc_0media_bio/bioflix/bioflix.htm?8apmeiosis
Crossing over-
Crossing over
Asexual vs. Sexual reproduction
Asexual Reproduction Sexual ReproductionAdvantages:- Can reproduce very quickly- No need to look for mate- If well suited to environment, no
changes are made
Advantages:- Increases genetic variation - Easier for population to adapt to
changing environmental conditions
Disadvantages:- No variation generated - Difficult for population to adapt
to changing environment
Disadvantages:- Energy expended looking for
mates- No mates = no reproduction
5 Dec
Opener Agenda Generation of
Variation Meiosis Review
Pop Beads White Board
Participation Quiz
Homework
Natural selection There is heritable variation
within populations More offspring are born
than can survive This leads to a competition
for limited resources Some survive/reproduce
based on favorable adaptationsCharles Darwin
Where does the Variation come from?
Generation of variation
Where does that variation in offspring come from?
Mutations & Epigenetics Crossing over Independent assortment of
chromosomes into gametes Random fertilization or combination
of gametes
On your whiteboard…
Show the complete process of meiosis from parent cell to gamete.
Pretend your organism’s diploid number of chromosomes is six.
Be sure to have a small, medium and large set of homologous chromosomes.
Make sure to include the following terms: Diploid Haploid Gamete Crossing over Homologous pair
Participation Quiz
1. What is the main advantage of sexual reproduction over asexual reproduction?
2. What type of cells are produced via meiosis?
3. In meerkats, a diploid cell contains 36 chromosomes. How many chromosomes does a meerkat egg contain?
4. T/F: All the gametes produced from meiosis are genetically identical to one another.
5. How many chromosomes did you get from your mother?
8 Dec
Opener: If a couple (of humans)
were going to have a baby, what are the chances of them having a girl? How do you know?
Agenda Genetics Vocab Punnett Squares
Homework Punnett Square
Problems
Genetics vocabulary
Allele- different versions of a gene Dominant- an allele that masks the effects of
another. Only need one copy to show the trait. Usually represented as a capital letter
Recessive- need two copies to show the trait. Usually represented with a lower case letter
Homozygous- two copies of the same allele (dominant or recessive) Ex. RR, tt, EE, qq
Heterozygous- one copy of each allele. Also, called carriers Ex. Rr, Tt, Ee, Qq
Genetics Vocab (cont.)
Genotype- an organism’s genetic make-up ex. Tt, rr, Qq
Phenotype- the physical trait- “what is seen” Ex. Attached earlobes, blood type, eye
color
You can’t always tell a genotype by looking at the phenotype
Solving genetic problems
1. Write out genotypes
2. Write out cross
3. Make a Punnett square
4. Answer the question
Gregor Mendel
In pea plants, Yellow seeds (E) are dominant over green (e) seeds.
What are the possible genotypes for a yellow- seeded plant?
green-seeded? If two heterozygotes were crossed, what
could be the possible outcomes?
EE or Eeee
Use a Punnett Square
Punnett square : a chart that shows the predicted outcomes of a genetic cross
Punnett squaresEe x Ee
male / sperm
fem
ale
/ e
gg
s EE
Ee ee
EeE
e
E eNow try:
EE x ee
Ee x ee
Let’s try a problem…
In a certain species of daisy, purple flowers are dominant to white flowers. A heterozygote and a homozygous recessive plant are crossed. What percent of their offspring would you expect to be white?
1. R= purple flowers r= white
2. Rr x rr
3.
Rr rr
Rr rr
R r
r
r
4. 2/4= 50%
9 Dec
Opener: In lynx, striped fur is dominant over solid fur. If you were presented with a striped lynx, how could you determine its genotype (without doing a genetic test)?
Agenda Participation
quiz Non-
Mendelian Genetics
Homework none
Participation Quiz
In a certain species of daisy, purple flowers are dominant to white flowers. A heterozygote and a homozygous recessive plant are crossed.
1. Write a key for this problem2. Show the cross3. Draw the Punnett square.4. If 36 offspring are produced from this
cross, how many of their offspring are expected to be purple?
What traits in humans obey Mendel’s Law of Dominance?
Tongue curling- dominant Free Ear lobe- dominant Widow’s peak- dominant Hitchhiker’s thumb- recessive Shorter big toe than 2nd toe-
dominant
Polydactyly (D)
Breaking the Law of DominanceAccording to the law of dominance what
should happen when you cross a purebred/homozygous white snapdragon plant with a purebred/homozygous red snapdragon?
All the F1 generation should be red but...
Incomplete Dominance
Heterozygotes show a blending of the two parental traits
Red is incompletely dominant over white so pink snapdragons are produced
According to the Law of Dominance what should happen when you cross a red and white horse?
All red or all white horses should be produced, but…
CODOMINANCE-
Both parental phenotypes are shown in heterozygotes
White and red color in horses are codominant so a white and red horse is produced.
The same is true in cows!
Multiple Alleles
Many genes have more than just two alleles
If there are three or more alleles for a trait, it is called multiple alleles
Example: Human Blood typeAlleles: A gene B gene O gene
Polygenic inheritance Some phenotypes determined by
additive effects of 2 or more genes on a single character phenotypes on a continuum human traits
skin color height weight intelligence behaviors
Example of a polygenic trait
Eye color There are genes for
Tone of pigment (what color it is) The amount of pigment Position of pigments (look at people’s eyes-
there are many different patterns in the iris)
Sex-linked inheritance
Alleles carried on sex chromosomes (usually “X” chromosome)
Gender influences phenotype
Examples:
Hemophilia
Red-green color-blindedness
Male pattern baldness
A woman who is a carrier for hemophilia mates with a man who does not have hemophilia.
XH = Normal (dominant allele)
Xh = hemophilia (recessive allele)
Y = no allele for this trait XHXh x XHY
XH Y
XH XHXH XHY
Xh XHXh XhYFem
al
eMale
Environmental Effects
The environment can influence the expression of genes
Remember Epigenetics?
Example of effect of temperature Ptarmigan in the tundra- change color
depending on the temperature and weather
Soil acidity and hydrangea