meiosis Flashcards
what is meiosis?
a cell division where gametes are produced
what are gametes?
sperm or oocytes
what is a diploid?
a cell with 2 copies of chromosomes
how many pairs of chromosomes do humans have?
23
what is a replicated chromosome?
a chromosome with 2 identical sister chromatids
what is a haploid?
a cell with a single copy of each chromosome
what is a single stranded chromosome?
a chromosome that was previously a sister chromatid and a centromere
what is a homologous chromosome?
pair of similar not identical chromosomes
mitosis
produces 2 cells, each containing 46 chromosome, daughter cells are identical to the original parent cells, cells are diploid, cell division occurs 1 time
meiosis compared to mitosis
produces 4 cells containing only 23 chromosomes, daughter cells are genetically different from parent cells, cells are haploid
what is the spermatogonia?
each contains 23 pairs of chromosomes total 46 and they are diploid, stem cells that help produce sperm, divide by mitosis and produce a primary spermatocyte
what do sustentacular cells do?
support, protect, and nourish the developing sperm
what are the primary spermatocytes?
has 23 pairs of chromosomes that are diploid, divide by meiosis, after finishing the first meiotic division it forms secondary spermatocytes
what are secondary spermatocytes?
contains 23 chromosomes only that are haploid, after they finish the 2nd meiotic division, they produce spermatids
what are spermatids?
immature sperm that contains 23 chromosomes only that are haploid, spermatids develop into sperm
what is sperm?
will shed cytoplasm from the spermatid and develop the head, mid piece, and tail
what is the acrosome cap?
enzymes on the head of sperm
what is the head?
the head of sperm contains nucleus and DNA
what is the midpiece?
contains mitochondria
what is the SRY gene?
region of Y chromosome that initiates a cascade of genes to induce the development of the testis
what happens when a gonad has the SRY gene?
germ cells in the medulla proliferate to form the testes
what happens when a gonad doesn’t have the SRY gene?
germ cells in the cortex proliferate to form the ovaries
prophase 1
double stranded chromosomes pair up, crossing over occurs
what is crossing over and what does it do?
genetic material is exchanged between homologous chromosomes creating genetic diversity
metaphase 1
pairs of homologous chromosomes form two lines in the middle of the cell, the side where the sperm and egg chromosomes go for each pair is random, and spindle fibers attach to replicated chromosomes
anaphase 1
pairs of homologous chromosomes are separated and pulled to opposite ends of the cell, each chromosome is still replicated and not pulled apart
telophase 1
cell finishes 1st meiotic division producing 2 daughter cells, daughter cells each have 23 replicated chromosomes each chromosome contains 2 sister chromatids, parent cells had 23 pairs of chromosomes but daughter cells have only 23 chromosomes total
metaphase 2
replicated chromosomes align at the center of the cell
prophase 2
replicated chromosomes gather, crossing over does not occur since there are no homologous pairs of chromosome
telophase 2
4 cells produced each have 23 with single stranded chromosomes each chromosome has 1 chromatid, cytokinesis begins, 4 cells are gametes
anaphase 2
sister chromatids pulled apart to opposite ends of the cell, become single stranded chromosomes
what is trisomy?
an extra copy of a chromosome. 3 instead of 2
what is monosomy?
a single copy of a chromosome, absence of one of two sets of chromosomes
