meiosis quiz

meiosis

cells that undergo meiosis do not undergo mitosis!

meiosis produces reproductive cells with half the number of chromosomes from the parent cell. these cells are only from sex organs (ovaries/testes in animals)

only type of cell undergoing meiosis is germ cells

gamete

the egg or the sperm. meiosis creates gametes

prophase I

• chromsomes condense, nucleus dissolves, spindle fibers form

• tetrads form, crossing over occurs

• tetrad=two “Xs” (2 homologous chromosomes) coming together to form a tetrad

• you have two copies of ONE HALF of the genetic material

• it is still diploid

metaphase I

pairs of homologous chromosomes line up on the cell equator

anaphase I

homologous chromosomes are pulled apart (NOT SISTER CHROMATIDS), cytokinesis begins

telophase I

• chromosomes gather at poles as the cell divides into two

• newly forming cells are haploid (n=2), each chromosome has two sister chromatids that are NOT identical (because crossing over just happened)

• chromosomes do not decondense

prophase II

• a new spindle assembly forms around chromosomes

metaphase II

pairs of chromosomes that line up on the cell equator

anaphase II

chromatids move to each pole.

centromeres divide

sister chromatids are finally separated basically

telophase II/cytokinesis 2

• nuclear membrane re-forms

• chromosomes dissolve

• spindle dissolves

• cytokinesis finishes the division of the cytoplasm and 4 haploid daughter cells are created

egg/oocyte + sperm

the two germ cell components needed for a zygote

crossing over

a form of recombination that occurs during prophase I. increases genetic variation.

the genes on a recombinant chromatid are the same as the original chromatid, but the alleles (versions of a gene) are different

variation

differences between organisms due meiosis and how it divides DNA to present different alleles and stuff

homologous chromosomes

chromosomes that are matching, but not identical. so you have 46 chromosomes originally and 23 different types, so 2 for each type. these 2 per type are homologous to each other so they will interact and cross over to create new combinations

sister chromatids

the two chromatids on a chromsome that are identical to each other.

during interphase 1 the chromatid number duplicates so you have enough DNA

asexual reproduction

• one parent

• offspring are clones of parent and have same DNA/parental genes passed down

• less/no genetic diversity, which could be bad if environment changes

• faster

sexual reproduction

• two parents

• egg+sperm=offspring (each parent passes on half their DNA)

• new combinations of genes (not new jeans)

• increase of genetic diversity, so offspring better able to evolve and adapt to changing environment

• more time and energy needed

• egg/sperm produced by meiosis

diploid

“2n”, n=1 set of chromosomes (1 set of genetic material).

1 set refers to 23 chromosomes from the mother or 23 chromosomes from the father. normal cells are diploid because they have 2 sets, or 46 chromosomes total.

cells are diploid until the chromosomes are pulled apart in anaphase I

haploid

“n”, n=1 set of chromosomes (1 set of genetic material).

1 set refers to 23 chromosomes from the mother or 23 chromosomes from the father. normal cells are diploid because they have 2 sets, or 46 chromosomes total.

cells are haploid during meiosis 2 and diploid during most of meiosis 1

chromosomes

a package of condensed DNA containing a part of the genetic code/material of an organism. made of chromatin wrapped around histone proteins

how is the production of gametes different than the replication of somatic (Non-Germ) cells?

gametes undergo meisos, everything else goes through mitosis. mitosis makes direct replicates of the parent cell and meiosis does not

what gets passed on to future generations

DNA

why are babies different than their parents

because you are getting DNA that is different since the chromosomes cross over during meiosis and then the cell divides so that you only have a single set of chromosomes that are a blend of your parents’ dna

what are the important ways of introduction variation into the gametes during meiosis

crossing over, having 2 divisions (idek)

gametes produced by meiosis pair up randomly, producing variation in the offspring

recombinant vs non-recombinant chromosomes

recombinant means chromosomes that have been through crossing over and have a combination of two colors

what are the differences between meiosis and mitosis

• crossing over

• 2 divisions

• in mitosis, during telephase chromosomes decondense, but because meiosis has two divisions, the chromosomes dont decondense in telophase I

what is the chromosome number of a cell in each part of meiosis?

basically, there are 23 chromosomes in a cell when there is one color of chromosomes and 46 when you have two different colors

eukaryotes generally have…

• paired chromosomes

• each chromosome contains many genes, and each gene may have a number of versions called alleles

• all multicellular organisms begin with a single cell

what does meiosis produce

• four haploid cells

• two phases of division for the purpose of sexual reproduction

• one egg and three nursery cells OR four sperm are produced depending on the sex of the organism

germ cells diagram

chromatids vs chromosomes

chromatids=represented by how many “arms” on a chromosome you have

chromosomes=counted by the number of centromeres in a cell