Similar to 01b254bbc2da9e7e7bdf1044ee763265793749d75e0189e5e0c40579d3a76907_LF 111 Lecture 2_Mendelian genetics Recap and implications 01 March 2024.ppt (20)
01b254bbc2da9e7e7bdf1044ee763265793749d75e0189e5e0c40579d3a76907_LF 111 Lecture 2_Mendelian genetics Recap and implications 01 March 2024.ppt
1. Lecture 2: 01 March 2024
(final part pg Mendelian genetics)
LIF111/101
https://www.youtube.com/watch?v=B_PQ8qYtUL0&t=12s&ab_channel=FrankGregorio
https://www.youtube.com/watch?v=Mehz7tCxjSE&ab_channel=TED-Ed
You can play this simple animation for Mendelian genetics
Introduction to Genetics
2. Law of segregation
Alleles (factors) representing a given trait
segregate (separate) during gamete formation,
and randomly unite at fertilization.
What is
assumed here?
How this
inference was
drawn?
RECAP Assumption
:
For each
trait there is
one pair of
alleles
An interpretation based on
first & second law of
probability:
Each gamete receive only
one of the two alleles
(factors)
How to read ? Example
http://en.wikipedia.org/wiki/Mendelian_inheritance
3. RECAP This is also called a
monohybrid cross.
Why??
4/21
4. Test cross
Purple X White
Pp pp
??
What does this
cross reveal?
Explain the
design/purpos
e of this cross
RECAP
5/21
5. Let’s consider inheritance of two different pairs of factor
Character : texture of the seeds
Traits smooth (R ) and rough ( r)
Character : color of the seeds
Traits yellow (Y) and green (y)
Which one is
dominant?
If a plant is true breeding smooth and yellow – how
can we represent its genotype?
If a plant is true breeding rough and green – how can we
represent its genotype?
RRYY
rryy
What
does R
and r
mean?
6. What will be the
consequence if a true
breeding smooth and yellow
plant is crossed with another
true breeding plant which is
rough and yellow?
RRYY X rryy
P1
8/21
7. Why this is called
law of
independent
assortment
Second,
speculate
the
outcome if
factors of
original
parent
segregate
together
F2
F1
First, find
the types
of
gametes
that are
possible
X YyRr
What happens in the F2 generation?
8. Law of Independent assortment
(This law tells how different Mendelian factors are
distributed following segregation)
The Law of Independent
Assortment states that segregating
alleles of different genes assort
independently of one another
during gamete formation.
10/21
10. Explain why did Mendel took two contrasting
factors to demonstrate this rule of inheritance,
namely, the law of segregation?
What is the modern term for Mendelian
factors?
11. Use the following words to complete the sentence below.
dominant, homozygous, non-identical, heterozygous, identical
All non-reproductive cells contain two alleles of each gene. When
those alleles are ____________, the cell is said to be _____________.
When those alleles are _____________, the cell is said to be
_______________, in which case the cell’s (or organism’s) phenotype is
dictated by the _____________ allele.
17/21
12. 1. One gene has alleles A and a. another has allele B and b.
For each of the four genotypes below, what type(s) of
gametes will form? Assume independent assortment
occurs.
a. AABB
b. AaBB
c. Aabb
d. AaBb
Which set of
gametes display
evidence of
independent
assortment?
Parental
genotype
Gamete types formed
AABB AB
AaBB AB (1/2) & aB(1/2)
Aabb Ab (1/2), ab(1/2)
AaBb AB (1/4), Ab (1/4)
aB (1/4), ab (1/4)
Explain why there
are four types of
gametes
19/21
13. 2. What will be the genotypes of offspring from the following matings?
Indicate the frequencies of each genotype among
a. AABB x aaBB
b. AaBB X AABb
c. AaBb X aabb
d. AaBb X AaBb
Step 1: In each case, first identify the types gametes formed by each parent
Step 2: Place these gametes at the designated position in a Punnett square
Step 3. Display the genotypes of the products of fusion of these various gametes
in the Punnett square
Step 4. Describe the phenotypes of the genotype of the progeny and their ratios
Home work
20/21
14. Use the following words to complete the sentence below
allele(s), diploid, gamete(s), gene, haploid
A ______organism contains two _____ of each ______ in all cells
except its _________which are _________ and contain only one.
16/21
15. vestigial mutant
Allele symbol: Vg
Information: mutant is recessive
Wild type
What should
be the mutant
allele symbol?
vg
What should be the genotype of the mutant fly?
Fruit fly, Drosophila
vg/vg
What could be the genotype of the wild type fly Vg/Vg Vg/vg
X
16. vestigial mutant
Wild type
Cross wild type
&
vg mutant
Step 1
Write their
genotype
vg/vg
Vg/Vg
Step 2
Write
genotypes of
their gametes
vg
Vg
Step 3
Write
genotypes the
F1 progeny
Vg/vg
Step 4
Mention the
phenotype of F1
progeny
X
17. vestigial mutant
Wild type
F1 progeny
50% 50%
X
How would you
explain this
outcome?
What was the
genotype of this
parent
19. Does understanding Mendelian genetics make
practical sense to our life?
Why marriage
amongst near relative
is not a good idea?
What is inbreeding?
What is
consanguineous
marriage
Thalassaemia
20. Can you inherit genes that may give rise to a disease
later on?
On average, a woman with a BRCA1 or BRCA2 gene mutation
has up to a 7 in 10 chance of getting breast cancer by age 80. If
you have inherited a mutated copy of either gene from a parent,
you have a higher risk of breast cancer.
Breast Cancer Gene Testing Kits
The first FDA-approved breast cancer gene test kit supplied by
23andMe, a company that is popular for producing reports that
identify a person’s ancestry
23andMe Holding Co. is a publicly held
personal genomics and biotechnology
company based in South San Francisco,
California
21. Cancer prevention treatment
On February 16, 2013, the 37-year-old Jolie underwent a
preventive double mastectomy after learning she had an 87 percent risk of
developing breast cancer due to a defective BRCA1 gene.
Her maternal family history warranted genetic testing for BRCA mutations: her
mother, actress Marcheline Bertrand, had breast cancer and died of ovarian cancer
, while her grandmother died of ovarian cancer. Her aunt, who had the same
BRCA1 defect, died of breast cancer three months after Jolie's operation. The
mastectomy, which lowered her chances of developing breast cancer to under five
percent.
Two years later, in March 2015, after annual test results indicated possible signs of
early ovarian cancer, she underwent a preventive removal of an ovary and its
fallopian tube, as she had a fifty percent risk of developing ovarian cancer due to
the same genetic anomaly.
Application of these
understanding of
Mendelian genetics in our
own life
22. Mendel explained inheritance in pea in 1865 – it was not called a law in those
days – it was hardly noticed. The physical basis of Mendelian inheritance
became evident when chromosomes were discovered and their transmission
in somatic cells (by Mitosis) and Gametes (Meiosis) was understood in the
early 1900s
Summary of our current
understanding
24. Entire set of chromosomes in humans arranged in pairs
Why are these
chromosomes
in pairs
Are these
cells diploid
or haploid?
Are these
cells somatic
or germ cells
How male
and females
are
different?
25. Which one of the two
germ cells may carry Y
chromosome?
Sperm
Egg
26. 1. How many sets of chromosome do we carry?
2. How many versions (alleles) of a gene can
we carry if every chromosome is in pair?
3. What happens during the gamete (sperm or
egg) formation (meiosis) ? Do the allele pairs
stay together?
