Meiosis - Sexual Reproduction Flashcards
Asexual reproduction definition
reproduction requiring only one parent and leads to the production of genetically identical offspring
sexual reproduction definition
reproduction involving two parents and leads to the production of genetically distinct offspring
What are male and female reproductive cells called?
gametes
haploid chromosome state
the reproductive cells that contain 23 unpaired chromosomes
diploid cells chromosome state
diploid cells are somatic, they have 23 paired chromosomes
Examples of gametes
haploid sperm, haploid egg(ovum)
somatic cell examples
brain cells, skeletal muscle, gut, skin, heart
Fertilization
(sperm + egg)
zygote definition
fertilized egg that starts as a single cell but then undergoes mitosis and becomes an embryo
sperm and egg ‘n’ things
sperm (n) + ovum(n) = Zygote (2n)
ploidy
the number of chromosome sets in a cell
How do mitosis and meiosis relate to ploidy?
Mitosis preserves ploidy and meiosis halves ploidy
What are the two outcomes of meiosis?
Genetic reduction and then genetic recombination
What is genetic reduction?
when the daughter cells with 1/2 the number of chromosomes in the parent cell are the result
what is genetic recombination?
the productions of meiosis have different combinations of alleles. This creates genetically different offspring from one another and from their parents.
What are the 3 main steps of meiosis?
Interphase, meiosis I and meiosis II
What happens in interphase in meiosis?
- the preparation for division (DNA replication like in mitosis)
what happens in meiosis I
it is also called reduction
- converts a diploid 2n cell into 2 haploid cells
what happens during meiosis II
the cell separates the contents of the two
What are the divisions of interphase in meiosis?
G1, S, and G2
What is the form of DNA in Interphase in meiosis
chromatin
What happens during S phase in meiosis?
There is a duplication of DNA - NOT CHROMOSOMES
If a cell is 2n = 6, what is the result?
6 chromosomes and 6 DNA molecules AND THEN 12 DNA molecules and 6 chromosomes + dupliation of centrosomes
- the spindle fibers begin to grow out from centrosomes
- the nucleolus and nuclear membrane are still present
Synapsis
the pairing of two chromosomes that occurs during meiosis
where does crossing over occur?
chiasma (chiasmata)
What is crossing over?
segments of chromosomes changing
oogenesis definition
the production of eggs or ova
where does oogenesis take place?
the ovaries of females
what does oogenesis begin with
a diploid cell called an oogonium
Describe maturation process for the ovum
- before birth, the oogonia reproduce by mitosis, and they begin meiosis but stop at prophase I
- meiosis I will continue for one cell each month beginning at puberty
- involves an unequal division of cytoplasm
- the cell that receives most of cytoplasm
- forms a viable egg
- contains a large amount of nutrients that will support the zygote after fertilization
when are the final stages of meiosis of an egg completed?
when the egg is fertilized by a sperm
what is the smaller ovum left after meiosis II called?
the polar body
spermatogenesis definition -
the production of sperm
where does spermatogenesis take place
in the testes of males
what is the diploid cell called is spermatogenesis
spermatogonium
hen does spermatogenesis begin
puberty
how to spermatogonia reproduce
by mitosis
primary spermatocyte…
undergo meiosis to form four haploid cells
