topic about Gregor Mendel

1. MENDEL, GENETICS &
MEIOSIS

2. Gregor Mendel’s
Discussions
Meiosis
Genetics
Credits

3. 10.1 MENDEL’S LAWS OF
HEREDITY
I. WHY MENDEL SUCCEEDED
 Gregor Mendol – father of genetics
 1st studies of heredity – the passing of
characteristics to offspring
 Genetics – study of heredity
 The characteristics passed on called traits

5. 1. MENDEL CHOSE HIS
SUBJECT CAREFULLY
 Used garden peas to study
 Have male & female gametes (sex cells)
 Male & female same flower
 Know what pollination & fertilization mean
 He could control the fertilization process
 Not many traits to keep track of

7. 2. MENDEL WAS A CAREFUL
RESEARCHER
 USED CAREFULLY CONTROLLED
EXPERIMENTS
 STUDIED ONE TRAIT AT A TIME
 KEPT DETAILED DATA

8. II. MENDEL’S MONOHYBRID
CROSSES
 MENDEL STUDIED 7 TRAITS CAREFULLY
 Pg. 262 – figure 10.3
 Mendel crossed plants w/ diff. traits to see
what traits the offspring would have
 These offspring are called hybrids –
offspring of parents w/ different traits
 A monohybrid cross is one that looks at
only one trait (let’s look at plant height –
tall or short)

9. A. THE 1ST GENERATION
 Mendel crossed two plants – 1 tall & 1
short (they came from tall & short
populations)
 These plants are called the parental
generation (P generation)
 The offspring were all called the 1st filial
generation (F1 generation)
 All the offspring were tall (the short plants
were totally excluded)

10. B. THE 2ND GENERATION
 Next, Mendel crossed two plants from the
F1 generation
 The offspring from this cross are called
the 2nd filial generation (F2 GENERATION)
 Mendel found that ¾ of the offspring
were tall & ¼ were short (the short plants
reappeared!!!!!!)

12. TO GO ANY FURTHER, WE
MUST UNDERSTAND ALLELES,
DOMINANCE, & SEGREGATION
 Genes – a section of DNA that codes for
one protein
 These genes are what control & produce traits
 The genes Mendel studied came in two
forms (tall/short - round/wrinkled -
yellow/green…….etc.)
 Alternate forms of a gene are called alleles
 Alleles are represented by a one or two
letter symbol (e.g. T for tall, t for short)

14. ALLELES CONT’D
 THESE 2 ALLELS ARE NOW KNOWN TO BE
FOUND ON COPIES OF CHROMOSOMES –
ONE FROM EACH PARENT

15. THE RULE OF DOMINANCE
 A dominant trait is the trait that will always be
expressed if at least one dominant allele is
present
 The dominant allele is always represented by
a capital letter
 A recessive trait will only be expressed if both
alleles are recessive
 Recessive traits are represented by a lower
case letter

16. DOMINANCE CONT’D
 LET’S USE TALL & SHORT PEA PLANTS
FOR AN EXAMPLE
 WHICH OF THESE WILL SHOW THE
DOMINANT & RECESSIVE TRAIT?
TT Tt tt
DOMINANT TRAIT RECESSIVE TRAIT

17. THE LAW OF SEGREGATION
 MENDEL ASKED HIMSELF……..”HOW DID
THE RECESSIVE SHORT PLANTS
REAPPEAR IN THE F2 GENERATION?”
 HE CONCLUDED THAT EACH TALL PLANT
FROM THE F1 GENERATION CARRIED
TWO ALLELES, 1 DOMINANT TALL ALLELE
& ONE RECESSIVE SHORT ALLELE
 SO ALL WERE Tt

18. SEGREGATION CONT’D
 HE ALSO CONCLUDED THAT ONLY ONE
ALLELE FROM EACH PARENT WENT TO
EACH OFFSPRING
 HIS CORRECT HYPOTHESIS WAS THAT
SOMEHOW DURING FERTILIZATION, THE
ALLELES SEPARATED (SEGREGATED) &
COMBINED WITH ANOTHER ALLELE
FROM THE OTHER PARENT
 The law of segregation states that during
gamete formation, the alleles separate to
different gametes

19. F1 GENERATION
FATHER MOTHER
T t T t
T T T t t t
F2 GENERATION
- the law of dominance explained the
heredity of the offspring of the f1
generation
- the law of segregation explained the
heredity of the f2 generation

22. PHENOTYPES & GENOTYPES
PG. 264
 PHENOTYPE – THE WAY AN ORGANISM
LOOKS AND BEHAVES – ITS PHYSICAL
CHARACTERISTICS (i.e. – TALL, GREEN,
BROWN HAIR, BLUE EYES, ETC.)
 GENOTYPE – THE GENE COMBONATION
(ALLELIC COMBINATION) OF AN
ORGANISM – (i.e. – TT, Tt, tt, ETC.)
 HOMOZYGOUS – 2 ALLELES ARE THE SAME
 HETEROZYGOUS – 2 ALLELES DIFFERENT

23. MENDEL’S DIHYBRID CROSSES
 MONOHYBRID – MENDEL LOOKED AT
ONE TRAIT
 IN HIS DIHYBRID CROSSES – HE LOOKED
AT 2 TRAITS
 WANTED TO SEE IF TRAITS ARE
INHERITED TOGETHER OR
INDEPENDENTLY

24. DIHYBRID CROSS
 TOOK TWO TRUE BREEDING PLANTS FOR
2 DIFFERENT TRAITS (ROUND/WRINKLED
SEEDS ------- YELLOW/GREEN SEEDS)
 1ST GENERATION
 WHAT WOULD HAPPEN IF HE CROSSED JUST
TRUE BREEDING ROUND W/ TRUE BREEDING
WRINKLED (ROUND IS DOMINANT)
ALL THE OFFSPRING ARE
ROUND

25. DIHYBRID CROSS – 1ST
GENERATION CONT’D
 SO WHAT DO YOU THINK HAPPENED
WHEN HE CROSSED TRUE BREEDING
ROUND/YELLOW SEEDS WITH TRUE
BREEDING WRINKLED/GREEN SEEDS
ALL THE F1 WERE ROUND
AND YELLOW

26. DIHYBRID CROSS – 2ND
GENERATION
 TOOK THE F1 PLANTS AND BRED THEM
TOGETHER (PHENOTYPE WAS
ROUND/YELLOW X ROUND/YELLOW)
 2ND GENERATION
 FOUND ROUND/YELLOW - 9
 FOUND ROUND/GREEN - 3
 FOUND WRINKLED/YELLOW - 3
 FOUND WRINKLED/GREEN - 1
( 9 : 3 : 3 : 1 RATIO)

27. EXPLANATION OF 2ND
GENERATION
 MENDEL CAME UP W/ 2ND LAW – THE
LAW OF INDEPENDENT ASSORTMENT
 GENES FOR DIFFERENT TRAITS ARE
INHERITED INDEPENDENTLY FROM EACH
OTHER
 THIS IS WHY MENDEL FOUND ALL THE
DIFFERNENT COMBONATIONS OF TRAITS

28. PUNNETT SQUARES
 A QUICK WAY TO FIND THE GENOTYPES
IN UPCOMING GENERATIONS
 1ST DRAW A BIG SQUARE AND DIVIDE IT
IN 4’S

29. PUNNETT SQUARE
CROSS T T X Tt

30. CONT’D
T T X T t
T T
T
t
T T T T
T t T t

31. DIHYBRID CROSSES
 A LITTLE DIFFERENT
 H h G g X H h G g
 MUST FIND OUT ALL THE POSSIBLE
ALLELIC COMBONATIONS
 USE THE FOIL METHOD LIKE IN MATH

32. H h G g X H h G g
1. HG
2. Hg
3. hG
4. hg
FOIL – FIRST, OUTSIDE, INSIDE, LAST
BOTH PARENTS
ARE THE SAME

33. NOW LET’S DO A DIHYBRID
CROSS
H h G g X H h G g
HG Hg hG hg
HG
Hg
hG
hg
HHGG HHGg HhGG HhGg
HHGg HHgg HhGg Hhgg
HhGG HhGg hhGG hhGg
HhGg Hhgg hhGg hhgg

34. WHAT ARE THE PHENOTYPIC
RATIO’S?
H h G g X H h G g
HG Hg hG hg
HG
Hg
hG
hg
HHGG HHGg HhGG HhGg
HHGg HHgg HhGg Hhgg
HhGG HhGg hhGG hhGg
HhGg Hhgg hhGg hhgg
DD:
Dr:
rD:
rr:
9
3
3
1

35. PROBABILITY
 WILL REAL LIFE FOLLOW THE RESULTS
FROM A PUNNETT SQUARE?
 NO!!!!!! – A PUNNETT SQUARE ONLY
SHOWS WHAT WILL PROBABLY OCCUR
 IT’S A LOT LIKE FLIPPING A COIN – YOU
CAN ESTIMATE YOUR CHANCES OF
GETTING HEADS, BUT REALITY DOESN’T
ALWAYS FOLLOW PROBABILITY

36. 10.2 MEIOSIS
 GENES, CHROMOSOMES, AND NUMBERS
 CHROMOSOMES HAVE 100’S OR 1000’S OF
GENES
 GENES FOUND ON CHROMOSOMES

37. DIPLOID & HAPLOID CELLS
 ALL BODY CELLS
(SOMATIC CELLS)
HAVE
CHROMOSOMES
IN PAIRS
 BODY CELLS ARE
CALLED DIPLOID
CELLS (2n)
 HUMANS HAVE
THE 2n # OF
CHROMOSOMES

38. DIPLOID AND HAPLOID CELLS
CONT’D
 HAPLOID CELLS
 ONLY HAVE 1 OF EACH TYPE OF
CHROMOSOME (DIPLOID CELLS HAVE 2 OF
EACH TYPE)
 SYMBOL IS (n)
 SEX CELLS HAVE THE n # OF
CHROMOSOMES

39. HOMOLOGOUS CHROMOSOMES
 HOMOLOGOUS CHROMOSOMES ARE THE
PAIRED CHROMOSOMES THAT CONTAIN THE
SAME TYPE OF GENTIC INFORMATION, SAME
BANDING PATTERNS, SAME CENTROMERE
LOCATION, ETC.
 THEY MAY HAVE DIFFERENT ALLELES, SO NOT
PERFECTLY IDENTICAL
 WHY DO THEY HAVE DIFFERENT ALLELES?
CAME FROM DIFFERENT
PARENTS

40. WHY MEIOSIS?
 MITOSIS – RESULTS IN GENETICALLY
IDENTICAL OFFSPRING – INCLUDING THE
# CHROMOSOMES
 WHAT WOULD HAPPEN IF THE EGG AND
SPERM HAD THE SAME # OF
CHROMOSOMES AS THE BODY CELLS?
EGG = 46 CHROMOSOMES SPERM = 46 CHROM.
ZYGOTE = 46 + 46 = 92 CHROMOSOMES =
NOT HUMAN

41. MEIOSIS
 A TYPE OF CELL DIVISION WHICH
PRODUCES GAMETES CONTAING HALF
THE NUMBER OF CHROMOSOMES AS THE
BODY CELLS
 2 STAGES – MEIOSIS I & MEIOSIS II
 START W/ 1 DIPLOID CELL, END UP W/ 4
HAPLOID CELLS (GAMETES)
 4 DAUGHTER CELLS ARE GENETICALLY
DIFFERENT FROM EACH OTHER AND
MOTHER CELL

42. INTRO TO MEIOSIS CONT’D
 SPERM – MALE GAMETE (n)
 EGG – FEMALE GAMETE (n)
 FERTILIZATION PRODUCES A ZYGOTE
(2n)
 THIS TYPE OF REPRODUCTION IS
CALLED SEXUAL REPRODUCTION

43. STAGES OF MEIOSIS
 MEIOSIS I
 PROPHASE I, METAPHASE I, ANAPHASE I,
TELOPHASE I (PMAT)
 MEIOSIS II
 PROPHASE II, METAPHASE II, ANAPHASE II,
TELOPHASE II (PMAT)

44. Cell Division
(Meiosis)
1. A process
of cell division
where the
number of
chromasomes is
cut in half
3. Makes
gametes

45. IMPORTANT THINGS TO KNOW
 CROSSING OVER – OCCURS DURING
PROPHASE I
 CREATES GENETIC VARIABILITY (RECOMBINATION
OF GENES)
 IN MEIOSIS I, HOMOLOGOUS CHROMOSOMES
SEPARATE (ANAPHASE I)
 IN MEIOSIS II, SISTER CHROMATIDS SEPARATE
 TETRAD – WHAT THE HOMOLOGOUS
CHROMOSOMES ARE CALLED WHEN THEY PAIR
UP DURING PROPHASE I

46. Genetics
Small sections of DNA are responsible
for a “trait”. These small sections are
called “Genes”.
 Gene - A segment of DNA that codes for
a specific trait
 Trait - A characteristic an organism
can pass on to it’s offspring
through DNA
Gen
e

47. Genetics
The study of heredity, how traits are
passed from parent to offspring
x =
or
o
r

48. Genetic Traits
Earlobes: Free ear lobes (dominant trait) vs. Attached ear lobes (recessive
trait) Free earlobes are those that hang below the point of attachment to the
head. Attached ear lobes are attached directly to the side of the head.
Forelock: White forelock (dominant trait) vs.
No white forelock (recessive trait)
A white forelock is a patch of white hair, usually
located at the hairline.
Widow's Peak (below) is dominant over no
widow's peak hairline.
Dimples: Dimples (dominant
trait) vs. No dimples (recessive
trait)
Dimples are natural dents in the
face to the right or left of the
mouth. If a person has only one
dimple, they should be counted as
having dimples.Cleft chin is
dominant over no cleft.

49. Thumbs: Straight thumb (dominant
trait) vs. Curved thumb (recessive
trait) When viewed from the side as in
the illustration below, curved thumbs
can be seen as part of a circle.
Pinky: Straight pinky
(recessive trait) vs. Bent
pinky (dominant trait)
Mid-digit hair: Mid-
digit hair (dominant
trait) vs. No mid-digit
hair (recessive trait)
Longer 2nd toe is
dominant over 2nd
toe shorter than
big toe.
Tongue-Rolling:
Rolling up edges
(dominant trait) vs
not rolling
(recessive)

50. DNA
D.N.A. - Deoxyribonucleic Acid
Molecule made of:
1. Deoxy Sugar
2. Combination of four nitrogen bases
Either: a. Guanine
b. Cytocine
c. Thymine
d. Adenine
The sum total of
combinations that these
four bases are capable of
creating are greater than
all the stars visible in the
night time sky.

51. DNA
 Nitrogen bases pair up
 Cytosine & Guanine
 Thymine & Adenine
 Pairing creates a ladder shape
 Angle of bonds creates a twist
Ladder and Twist produces the
famous
“Double Helix”

52. DNA
 DNA resides in all cells
 Inside the nucleus
 Each strand forms a chromosome
Cel
l
Nucleus
DNA

53. DNA
DNA is found in all living cells
 It controls all functions
inside a cell
 It stores all the genetic
information for an entire
living organism
 Single cell like an amoeba
 Multi cell like a human

54. Mery ’ Ant Bondad

55. J
u
s
t
i
n
T
a
n

56. Rein Emmie Dela Cruz

57. Mary Rose
Hagupit

58. Mary Bridgette De Veyra

59. Thanks For
Watching
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