Chapter 13 ~ Meiosis and Sexual Life Cycles Can you pick out the “offspring” for each couple?

Can you pick out the “offspring” for each couple?

In a literal sense, children do not inherit particular physical traits from their parents It is genes that are actually inherited In a literal sense, children do not inherit particular physical traits from their parents It is genes that are actually inherited

Genes are the units of heredity Genes are segments of DNA Genes have specific loci on a certain chromosome One set of chromosomes is inherited from each parent Reproductive cells called gametes (sperm and eggs) unite, passing genes to the next generation

Heredity The transmission of traits from parents to offspring. Comment - Humans have been aware of heredity for thousands of years.

Heredity The transmission of traits from parents to offspring. Comment - Humans have been aware of heredity for thousands of years. Genetics The scientific study of heredity. Comment - Genetics is only about 150 years old.

Remember, genes are on the chromosomes Mitosis produces two cells with the same number of chromosomes as the parent cell. Remember, genes are on the chromosomes

Mitosis of a diploid cell (2n) produces: two. diploid (2n). daughter Mitosis of a diploid cell (2n) produces: two diploid (2n) daughter cells.

If two diploid cells went on to participate in sexual reproduction,

their fusion would produce a tetrapoloid (4n) zygote

Female 46 Male 46 egg 46 sperm 46 Zygote 92 mitosis mitosis

What is the answer?

Meiosis To reduce the number of chromosomes by half. Prevents doubling of chromosome numbers during sexual reproduction.

Homologue Chromosomes - Bio I review words: Homologue Chromosomes - Sex Chromosomes - Autosomes -

Pair of homologous chromosomes Centromere Sister chromatids

Bio I review words: Diploid # - Haploid # -

Bio I review words: Diploid Cell (2n) - Haploid Cell (n) -

Homologue Chromosome - Bio I review words: Homologue Chromosome -

Key Maternal set of chromosomes (n = 3) 2n = 6 Paternal set of Two sister chromatids of one replicated chromosomes Centromere Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set)

Bio I review words: Tetrad -

Individual chromosomes replicate Interphase Individual chromosomes replicate

chromosomes seek out their homologue to form tetrad Prophase I chromosomes seek out their homologue to form tetrad crossing over occurs here

CROSSING OVER

tetrads line up on metaphase plate Metaphase I tetrads line up on metaphase plate

It is random chance as to which chromosome is pulled to a side. Anaphase I tetrads move apart It is random chance as to which chromosome is pulled to a side.

Two nuclear envelopes begin to surround the chromosomes Telophase I Two nuclear envelopes begin to surround the chromosomes

No DNA synthesis occurs. Interkinesis No DNA synthesis occurs. May last for years, or the cell may go immediately into Meiosis II. May appear similar to Interphase of Mitosis.

Prophase II dyad (1/2 tetrad)

dyad (1/2 tetrad) line up on the metaphase plate. Metaphase II dyad (1/2 tetrad) line up on the metaphase plate.

dyads (1/2 tetrad) are separated into individual chromatids Anaphase II dyads (1/2 tetrad) are separated into individual chromatids Sister chromatids end up on each side of the cell

nuclear envelope forms Telophase II nuclear envelope forms cytoplasm divides 4 haploid cells are formed

MEIOSIS

MEIOSIS

of meiosis & fertilization Alternation common to all organisms that reproduce sexually of meiosis & fertilization

these events varies between kingdoms Alternation the timing of these events varies between kingdoms of meiosis & fertilization

gametes only are haploid Animals gametes only are haploid meiosis for production of gametes

multicellular organism is diploid Animals multicellular organism is diploid meiosis for production of gametes

WHAT? Sexual Life Cycles

Fungus gametes are haploid zygote forms

meiosis before the offspring develops Fungus zygote is diploid meiosis before the offspring develops

Fungus offspring are haploid

multicellular organism is haploid this produces haploid cells that divide by mitosis

Fungus gametes by mitosis

1 map unit = frequency % of crossing over

1% = 1 map unit (centimorgan)

multicellular stages are Plants & Algae multicellular stages are diploid & haploid

Plants & Algae spores result from meiosis in sporophyte

multicellular haploid Plants & Algae spore then mitose to form multicellular haploid