Sex Cells Gametes (germ cells) Eggs and Sperm Somatic Cells All other cells.
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Meiosis
Sex CellsGametes (germ cells)Eggs and Sperm
Somatic CellsAll other cells
Types of Human Cells
Autosomes – same number in males and females
Sex Chromosomes – X or Y
Human females: XX
Human males: XY
Testosterone and other hormones from the Y make a male
Types of Chromosomes
46 chromosomes(23 pairs)
Humans
Describes how many sets of different chromosomes a cell has.
n = number of chromosomes in 1 set (haploid number)
Haploid Cells: 1nDiploid Cells: 2nIn humans, n = 23 (the
number of different chromosomes we have)
Ploidy
32/16
62
Figure 13.5
Key
Haploid (n)Diploid (2n)
Egg (n)
Haploid gametes (n 23)
Sperm (n)
Ovary Testis
Mitosis anddevelopment
Diploidzygote(2n 46)
Multicellular diploidadults (2n 46)
MEIOSIS FERTILIZATION
Figure 13.6
KeyHaploid (n)
Diploid (2n)
Gametes
MEIOSIS FERTILIZATION
Zygote
MitosisDiploidmulticellularorganism
(a) Animals
n
n
n
2n 2n 2n2n
2n
n n
n
n n
nn
n
n
nMEIOSIS
MEIOSIS
FERTILIZATION
FERTILIZATION
Mitosis Mitosis
Mitosis
Mitosis Mitosis
GametesSpores
Gametes
Zygote
Zygote
Haploid multi-cellular organism(gametophyte)
Diploidmulticellularorganism(sporophyte)
Haploid unicellular ormulticellular organism
(b) Plants and some algae (c) Most fungi and some protists
Plants and some algae exhibit an alternation of generations.
In crossing over, nonsister chromatids exchange DNA segments.
Each pair of chromosomes forms a tetrad, a group of four chromatids.
Each tetrad usually has one or more chiasmata, X-shaped regions where crossing over occurred.
Crossing Over
Figure 13.11-1Prophase Iof meiosis
Nonsister chromatidsheld togetherduring synapsis
Pair of homologs
Figure 13.11-2Prophase Iof meiosis
Nonsister chromatidsheld togetherduring synapsis
Pair of homologs
Chiasma
Centromere
TEM
Figure 13.11-3Prophase Iof meiosis
Nonsister chromatidsheld togetherduring synapsis
Pair of homologs
Chiasma
Centromere
TEM
Anaphase I
Figure 13.11-4Prophase Iof meiosis
Nonsister chromatidsheld togetherduring synapsis
Pair of homologs
Chiasma
Centromere
TEM
Anaphase I
Anaphase II
Figure 13.11-5Prophase Iof meiosis
Nonsister chromatidsheld togetherduring synapsis
Pair of homologs
Chiasma
Centromere
TEM
Anaphase I
Anaphase II
Daughtercells
Recombinant chromosomes
Down Syndrome
Klinefelter’s Syndrome
Cause: Nondisjunction
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