Transcript Genetics ppt

Take out a sheet of paper,
and put your name on it.
1. Who is known as the father
of genetics?
A. Felix Mendelssohn
B. Gregor Mendel
C. Dr. Reginald Punnett
D. Albert Einstein
2. What did this person study?
A. rabbits
B. Trees
C. Dogs
D. Pea plants
3. The offspring of a pure, truebreeding generation are called:
A. F1 generation
B. F2 generation
C. P generation
D. Q generation
4. Different forms of a single
gene are called
A. Traits
B. Alleles
C. Phenotypes
D. Genotypes
5. Outward expression of
traits is a
A. genotype
B. Trait
C. Phenotype
D. Recessive
6. Which of these is
heterozygous?
A. TT
B. tt
C. TZ
D. Tt
7. Which of these will NOT show
brown eyes, if B is dominant for
brown?
A. BB
B. Bb
C. bb
D. bB
8. What gametes will be formed
from a plant with the genotype of
Yy?
A. Y
B. y
C. Yy
D. Both A and B
9. The previous question
described Mendel’s law of
A. Segregation
B. Independent assortment
C. Hybrids
D. dominance
10. Fill in the Punnett square
showing the cross of Bb and Bb:
11. What is the ratio of brown
eyes to blue eyes, if brown is
dominant? (from #10)
A. 3:1
B. 1:3
C. 4:1
D. 1:4
12. What is the genotype ratio
from the cross in #10?
A. 3:1
B. 1:2:1
C. 2:2
D. 1:3
When you’re done with the
traits chart:


Work on Drawing the “senior portrait”
for your offspring! Make sure to include
every trait, write the offspring’s name,
and the name of the parents (you!)
Work on the questions in the packet
Mendelian Genetics
MAIN IDEA: Mendel
explained how a dominant
allele can mask the presence
of a recessive allele.
“Father of Genetics”



Gregor Mendel – Austrian monk
and plant breeder
Studied inheritance in pea plants
Pea plants – usually self-fertilize,
but he cross-pollinated to study
traits
Mendel’s work



Pea plants have only 2 forms of
each trait
True-breeding plants produce
offspring with only one form of
each trait – ex: always green seeds
PF1F2
Do Now:

Take out Simple Genetics Problems
packet and complete it
Parental (P) Generation


Mendel crossed 2 true-breeding
plants with opposite traits. Ex:
green seed X yellow seed
(Only monitor one trait at a time –
others the same – controlled)
First Filial Generation (f1)




Offspring of P generation
100% showed only ONE of the
parent’s traits.
Ex: yellow seeds X green seeds –
produced ALL yellow seeds
Where did the green seeds go?
Second Filial Generation (F2)




Self-pollinated plants from F1
Results: 6022 yellow seeds and
2001 green seeds
3:1 ratio
Studied 7 traits total, all with same
results
Mendel’s Conclusions





Must be 2 forms of each trait
Each form called an allele –
alternative form of one gene
Dominant vs. recessive alleles
Homozygous vs. heterozygous
(hybrid)
Genotype vs. phenotype
Law of Segregation

During meiosis, 2 alleles for each
trait separate
Answer This!
Parent plants: YY and yy
(yellow=dominant, green=recessive)
 How do we set up the cross?
 What genotype possibilities are
there for the offspring?
 What are the resulting ratios for
genotype and phenotype?
 Repeat for the F1 generation.

Law of Independent
Assortment


During meiosis and gamete
formation, alleles are distributed
randomly.
Genes on separate chromosomes
sort independently during meiosis.
Do Now




What are Mendel’s 2 laws of genetics?
What is the probability of flipping a
coin, and it landing on heads?
What is the probability of flipping 2
coins, and both are heads?
What is the probability of flipping 2
coins, and getting heads & tails in any
order?
Example



Alleles in parent cell: TtGg
What are the possible gametes
from this parent?
Use FOIL to find out!
FOIL TtGg






F = first  TtGg = TG
O = outer  TtGg = Tg
I = inner  TtGg = tG
L = last  TtGg = tg
Possible gametes:
TG, Tg, tG, tg
There’s an equal chance of each
gamete combination (1/4 chance)
Monohybrid vs. Dihybrid
(Don’t Copy)


Monohybrid – cross only one trait
Dihybrid – cross 2 traits (dihybrids
are heterozygous for both traits)
Cross 2 dihybrids





TtGg X TtGg
Set up a 16 box Punnett Square
Write the possible gametes across
the top and side
Fill in the offspring
Determine the phenotype ratio
Probability


Punnett squares give PROBABLE
(predicted) outcomes
Actual data MAY NOT always match
the predicted outcomes
Example


When you flip a coin, what is the
chance it will land on heads?
If you flip a coin 10 times in a row,
how many times would you predict
it to land on heads?
Rules of Probability


A larger sample size will give
results more accurate to predicted
outcome than a smaller sample.
Ex: Mendel used thousands of
plants! Only using a few would not
have been as accurate.
Rules of Probability


In determining the probability of 2
independent events occurring at the
same time, you multiply the
probability of each.
Ex: The probability of a coin landing
heads up is ½. The probability of 2
coins landing heads up at the same
time is ½ x ½ = ¼.
Rules of Probability

The probability of an event
occurring any one of several
possible ways is the sum of their
individual probabilities.
Rules of Probability

Example: If you flip 2 coins (a
nickel and a penny), there is a ¼
chance of the nickel being heads
and the penny being tails. There is
also a ¼ chance of the opposite.
There is a ½ chance (1/4 + ¼) of
one coin being heads and one
being tails.
Probability Examples



What’s the chance of parents
having a girl as opposed to a boy?
If a couple has 2 children, what’s
the chance of them both being
girls?
What’s the chance of them both
being boys?
Probability Examples



If a couple has 3 children, what’s
the chance of them all being girls?
If a couple has 2 children, what’s
the chance of the oldest being a
boy and the youngest being a girl?
What’s the chance of them having
a boy and a girl in any order?
Do Now
What is the probability of a couple
having a girl?
 What is the probability of a couple
having 2 girls in a row?
 Set up the following Punnett
Square: FFTt x Fftt

10.3: Gene Linkage and
Polyploidy
MAIN IDEA: Crossing
over of linked genes is a
source of genetic variation.
Genetic Recombination

When new combinations of genes
are made by:
Crossing over
 Independent assortment


Occurs during meiosis
Independent Assortment



Number of possible gene
combinations = 2n
n = # of chromosome pairs
Ex: how many gene combinations
are possible in an organism with 3
gene pairs?
After Fertilization…



Number of possible gene
combinations = 2n x 2n
How many possible gene
combinations are possible in an
organism with 3 chromosome pairs
AFTER fertilization?
Crossing over increases possibilities
even more!
Gene Linkage




Each chromosome has many genes
If genes are close together on one
chromosome, they are linked
Linked genes DO NOT segregate
independently during meiosis
Separation only happens during
crossing over; more likely in far
apart genes
Chromosome Map



Shows order of genes on a
chromosome
Distance between genes –
estimated by how often crossing
over occurs between them
More crossing over = farther apart
Figure out the Order
Genes
D-F
G-D
E-G
E-D
G-F
E-F
Frequency of C.O.
15%
2%
8%
10%
17%
25%
Polyploidy




Cells have one or more extra sets of
chromosomes
LETHAL in humans
Seen in some animals (earthworms,
goldfish) and flowering plants
Useful to make bigger, stronger food
plants (wheat, oats, strawberries)
DO NOW
Which of these is NOT equal to the
others?
 25%
 1:3
 1:4
 1/4