Mendel’s Laws of Heredity
Section 10.1 p. 253 - 262
Chapter 10 Mendel and Meiosis
heredity
• Passing on of characteristics from
parents to offspring.
Strong Family Resemblance
Cape Buffalo with her calf
Strong Family Resemblance
Strong Family Resemblance
Strong Family Resemblance
traits
• A characteristic that is inherited
• Can be either dominant or recessive
How can you describe these peas?
Green seeds
Smooth seeds
Green pods
Pod looks rounded
How can you describe these peas?
Green seeds
Wrinkled seeds
Yellow pods
Pod looks constricted
Green seeds
Green seeds
Smooth seeds
Wrinkled seeds
Green pods
Yellow pods
These characteristics are
inherited traits
Green seeds = recessive
Green seeds = recessive
Smooth seeds = dominant
Wrinkled seeds = recessive
Green pods = dominant
Yellow pods = recessive
Pod looks rounded
Pod looks constricted = recessive
= dominant
We will talk more about recessive & dominant tomorrow!
genetics
• Branch of biology that studies heredity.
• Yes, people have studied the traits of pea
plants.
• They have studied the patterns that these
traits show when different appearing parents
are used to produce offspring.
• Can you think of the world’s most famous pea
plant grower and observer?
Not this
guy!
Gregor Mendel
Pictures from 1862, 1868 & 1880
Gregor Mendel
• A 19th century central Austrian monk
scientist who published his ideas about
genetics in 1866 but largely went
unrecognized until 1900, which was long
after his death.
• He acquired his understanding of
genetics mostly through pea plant
breeding experiments.
Gregor Mendel
The garden of the Augustinian
Convent in Brno.
This view is looking towards the
entrance to the garden, with
Mendlovo namesti, Mendel Square,
beyond.
In the shadows in front of the tree
can just be seen part of the
foundations of the greenhouse that
Mendel used.
His peas were planted in the beds
against the building on the left.
Photo taken in the1920’s
gametes
• Male and female sex cells
• Sperm
and
egg
gametes
• Gametes contain a “half” set of chromosomes
• We call them haploid cells (n)
• During sexual reproduction, the two gametes, egg &
sperm, will join and any resulting offspring will have
a full set of chromosomes (2n)
• This is how you got half of your chromosomes from
Mom and the other half from Dad
gametes
SPERM
EGG CELLS
...are produced in much much
higher quantities.
...are produced in comparatively
lower quantities.
...are much smaller than egg
cells.
...are much larger than sperm,
since they contain food for the
embryo.
...are equipped to get from
where they're made to where
the egg cells are.
...pretty much wait in one place
for the sperm to reach them.
...from each starting cell that
divides by meiosis, four
functional sperm are made.
...from each starting cell that
divides by meiosis, one
functional egg cell is made, with
3 tiny polar bodies used to
discard "extra" sets of
chromosomes.
How sperm / gametes are made…
this is actually next section ~ 10.2 Meiosis
What are these
organelles?
Do you have any
idea what they
might have to do
with the production
of sperm?
New research suggests that some
male infertility might be caused by
defective respiratory function in
mitochondria.
(Photo credit: P.M. Motta and T.
Naguro/www.sciencesource.com)
Mitochondria Defect
Joan Stephenson, PhD
•
Research on mice with mutated mitochondria may help explain some
cases of infertility among human males
•
In the study, the researchers created male "mito-mice" with different
levels (from less than 10% to more than 80%) of mutant mitochondrial
DNA. Mice with more than 70% mutant mitochondria had difficulty
undergoing meiosis, the process through which sperm are produced. In
addition, the sperm that the animals did produce had increased
morphological abnormalities and decreased swimming ability.
•
The researchers concluded that mitochondrial respiration activity is
essential for mammalian spermatogenesis and suggested that "some
cases of human male infertility with unknown etiology might result from
mitochondrial respiratory dysfunction."
•
(Nakada K et al. Proc Natl Acad Sci U S A. 2006;103:15148-15153).
fertilization
• Fusion of male and
female gametes.
• When sperm meets
the egg.
zygotes
• Diploid cell (2n)
formed when a
sperm fertilizes an
egg.
• A zygote has a full
set of chromosomes.
• It is a unique
organism with a
combination of
traits from the male
and female gametes.
Before we can go any further…
• We need to remember that plants are
sexual beings.
• We also need to think a little about
their sexual parts.
Plant reproductive organs
More of Tenaglia’s “stupid” ways
to remember things
• Stay man
– Male
– Stamen
• She’s got a gun
– Female
– Pistil
pollination
• From male reproductive organs to
female reproductive organs of plants,
usually within the same species.
pollination
Insects definitely help with
pollination.
And its not just bees and wasps… flies do too…
This orchid has evolved to resemble a female bee.
The male, trying unsuccessfully to mate with the flower, unwittingly
collects and spreads the orchid's pollen.
Drakaea glyptodon
King-in-his-Carriage – Hammer Orchid
This person is helping to pollinate the vanilla plant
• Mendel chose which pea plants he would
allow to fertilize or pollinate one
another and then kept records of the
offspring produced.
Before we can go any further…
• There are a bunch of vocab words we
need to start using.
–
–
–
–
–
Alleles
Dominant
Recessive
Homozygous
Heterozygous