mendel’s laws of heredity

Mendel’s Laws of Heredity

Section 10.1 p. 253 - 262Chapter 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

Smooth seeds

Green pods

Green seeds

Wrinkled seeds

Yellow pods

These characteristics are inherited traits

Green seeds = recessive

Smooth seeds = dominant

Green pods = dominant

Pod looks rounded = dominant

Green seeds = recessive

Wrinkled seeds = recessive

Yellow pods = recessive

Pod looks constricted = recessive

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

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.

gametes

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 glyptodonKing-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