what does Meiosis
- 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 Haploid and Diploid cell?
- Haploid cells: half genetic material, one set of chromosomes, 27 chromosomes in humans
- Diploid cells: 2 sets of chromosomes, complete # of chromosome ( varies depending on species ), 46 chromosomes in humans
Compare Mitosis to meiosis.
- Mitosis: Skin, digestive tract, hair folicle, nails etc, growth and repair, Diploid, Identical
- Meiosis: 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
why is Meiosis I refered to as a " reduction division " ?
b/c the homologous chromosomes, they are being separated, 6 to begin with and now 3
why is meiosis II refered to as an " equation division " ?
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
- -chromatin porms
- - 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?
- - mutations
- - changes in nucleotide sequence
- causes: 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