Card Set Information
Haploid gametes in the ovaries and testes in animals, and spores in plants.
- only in sex organs
- produces eggs
- producing sex cells
-produces different cells
What is the difference btwn
: half genetic material, one set of chromosomes, 27 chromosomes in humans
2 sets of chromosomes, complete # of chromosome ( varies depending on species ), 46 chromosomes in humans
Compare Mitosis to meiosis.
: Skin, digestive tract, hair folicle, nails etc, growth and repair, Diploid, Identical
: testes, ovaries, sporangium, sperms and eggs ( gametes ), haploid, genetically different
Define homologous chromosome
same length, centromere in same position, trait they code for is the same
Define Autosomal chromosome
" own body ", homologous chromosomes that code for your own body trait
define sex chromosomes.
not homologous, not autosomal, XY, male, female
male = XY(have 22 homologous chromosomes) female = XX ( have 23 homologous chromosomes )
what is the interphase of meiosis?
results in replication of the genetic material to form chromatids, and an increase in the number of organelles, happens only once
refered to as a "
b/c the homologous chromosomes, they are being separated, 6 to begin with and now 3
refered to as an "
is like mitosis, chromosome # has not changed
What is the prophase of meiosis I ?
chromosomes form, chromatin coling
- nuclear envelope breaks down
- centrosomes and centrioles move to oppisite ends of the cell and form spindle fibers
" coming together " process that brings homologous chromosomes together ( pair up )
" 4 " chromatids, end process(result of) of a synapsis
what happens in Metaphase of meiosis I ? compare to MITOSIS
spindle fibers " change " the position of the tetrads so that they line up in the middle of the cell ( random )
MITOSIS : no synapsis, no tetrad, individually lined up above the other
What is anaphase of meiosis I ? compare to MITOSIS
homologous chromosomes are pulled " apart " to opposite ends of the cell by the shortening of spindle fibres.
MITOSIS: no reduction in #'s, spindle fiber shortens, centromere splits, chromatids separated, dragged to oppisite ends
What happens in telephase of meiosis I ? compare to MITOSIS
- nuclear envelope reforms
- spindle fibers dissapear
- cytoplasm of the cell splits to form 2 haploid cells, each with only one set of homologous chromosomes
MITOSIS : Diploid and identical
What does Meiosis II do? compare to MITOSIS
separates the chromatids and results in four haploid gametes
MITOSIS : diploid cells, and body cells
Summary of MITOSIS and MEIOSIS.
what is the primary source of genetic variations?
- changes in nucleotide sequence
: radiation, chemicals in environment, viruses, errors in DNA replication
how does meiosis form genetically different gametes?
-puts them into different gametes
- different variations and shuffling them
Define Crossing over.
overlap, 2 chromatids overlap
the structure that forms as a result of cross-over, overlap ( x shaped structure )
define recombinant chromosomes.
the x shaped structure breaks and segments are exchanged, end products of cross over
- has maternal + paternal portions to it
Define independent assortment
happens at metaphase I, random arrangement of the homologous chromosomes in the middle of cell
What is the total # of genetic combinations possible by independent assortment in humans?
2^n -> haploid # of chromosomes
2^2 = 4 possible outcomes
Define nondisjunction in meiosis. what are the consequences?
no separation of homologous chromosome or chromatids happening in meiosis I and meiosis II
what is downs syndrome? explain cause and symptoms.
- extra chromosome in sex cells
- 47 chromosome instead of 46
- happens more when women is older and has kid
- also called trisomy 21
- tongue is larger, shorter
- body features anormal
- eyes not round, broader
- face round, flat face
- fingers and toes more stubby
- mental retardation
- 50% never makes it after age 1, kidney, heart problems
Explain the cause and symptoms of Klinefelter syndrome.
- caused by nondisjunction
- individual that is XXy extra sex chromosome present
- testes smaller
- breast partially deveopled
- not much facial or chest hair
- hips larger than average