meiosis & sexual reproduction

chromosomes contain…

genetic information

asexual reproduction is also referred to as…

mitosis

every cell in an organism’s body has the same number of…

chromosomes

diploid is represented by the symbol…

2n

how many chromosomes are in human body cells?

46

DNA _______ during interphase

replicates

haploid is represented by the symbol…

n

egg+sperm cell=

zygote

how many chromosomes can be found in human gametes?

23

sexual reproduction involves ___ parents

2

the gamete from the male parent is referred to as a…

sperm cell

the gamete from the female parent is referred to as a…

egg cell

when the egg and sperm cell are combined, it is called…

fertilization

a picture of a persons’s chromosomes

karyotype

there are __ numbered pairs of chromosomes

22

the 22 numbered pairs of chromosomes are called…

autosomes

females have __ chromosomes

xx

males have __ chromosomes

xy

homologous chromosomes are the same ____, ____, and carry the same genes

size, shape

the process in which different sex cells are formed

meiosis

meiosis is important because it ensures that all produced organisms have the correct number of ________ for their species

chromosomes

genetic variation _____ a population and/or species chances of survival

increases

there are __ cell divisions in meiosis

2

meiosis is a process of ____ ________

cell division

meiosis reduces the chromosome number by ____

half

when meiosis reduces the chromosome number by half, it is known as _______ ________

reduction division

each parent cell produces __ daughter cells

4

interphase- DNA is replicated

(what section of meiosis?)

section a

meiosis 1- homologous chromosomes pair, crossing over occurs. goal is to separate the homologous chromosomes, two cells form.

(what section of meiosis?)

section b

meiosis 2- goal is to separate the sister chromatids. the two cells formed in meiosis divide, forming 4 haploid cells.

(what section of meiosis?)

section c

what are the steps of meiosis?

prophase, metaphase, anaphase, telophase

• homologous chromosomes pair up, condense, and undergo crossing over

• this process exchanges genetic material to increase genetic diversity

(what step of meiosis 1)

prophase 1

• tetrads line up at the cell equator

• MIDDLE

• spindle fibers attach to centromeres

(what step of meiosis 1)

metaphase 1

• disjunction- the tetrads slit APART into 2 separate double chromosomes

• homologous chromosomes separate and double chromosome (sister chromatids) move AWAY to opposite poles of the cell

(what step of meiosis 1)

anaphase 1

• cytoplasm divides, forming 2 new daughter cells with half the number of chromosomes

(what step of meiosis 1)

telophase 1

genetic material is ___ replicated a second time in meiosis 2

not

the results of meiosis 2 will yield __ haploid daughter cells

4

in meiosis 2, DNA does ___ replicate during interphase

not

• spindle fibers begin to form 

• each chromosome consists of sister chromatids attached at the centromere)

(what step of meiosis 2)

prophase 2

• sister chromatids line up at the cell equator

(what step of meiosis 2)

metaphase 2

• identical chromatids SEPARATE and move towards opposite poles of the cell

(what step of meiosis 2)

anaphase 2

• both cells from meiosis 1 divide into 2 new cells, producing 4 daughter cells with the haploid number of chromosomes

(what step of meiosis 2)

telophase 2

the sexes are characterized by their sex organs or ____ (another name for sex organs)

gonads

the male gonad is the _____ and produces ____

testes, sperm

the female gonad is the _____ and produces ____

ovary, eggs

the production of eggs or ova in the ovary is called…

oogenesis

mature eggs develop from oogonia which enlarge to form the primary _______

the primary oocyte undergoes the first meiotic division, producing one secondary oocyte and one smaller _____ ____

polar body

all polar bodies __________

disintegrated

the ootid grows into a mature ___ cell

egg

the ovum contains a small quantity of stored food in the…

yolk

the ovum is _____ because of the unequal dividing of the cytoplasm

larger

meiosis is a source of _______ ________

genetic variation

when homologous chromosomes form tetrads and the strands of chromatids TWIST AROUND each other, it’s called…

crossing over

mitosis daughter cells have the _____ number of chromosomes (full set)

diploid

meiosis daughter cells have the ___ number of chromosomes

haploid

meiosis occurs in only _____ reproducing organisms

sexually

mitosis occurs in ____ asexually and sexually reproducing organisms.

both

in mitosis, cells divide ____, yielding __ cells

once, 2

in meiosis, cells divide _____, yielding __ cells

twice, 4

meiosis:

a. has a pair of homologous chromosomes

b. does not have a pair of homologous chromosomes

a

mitosis

a. has a pair of homologous chromosomes

b. does not have a pair of homologous chromosomes

b