Transcript Meiosis & Sexual Reproduction Lecture 11 ________ Transfer of characteristics from parent to offspring through their genes • ________ - Complete complement of an organism’s DNA. • ___________ - carry genes. • ______

Meiosis &
Sexual
Reproduction
Lecture 11
________
Transfer of
characteristics
from parent to
offspring through
their genes
• ________ - Complete
complement of an organism’s
DNA.
• ___________ - carry
genes.
• ______ – “unit of heredity”
made of DNA.
Chromosomes & Genes
• Cellular DNA is
organized in
______________.
• ______ have
specific places on
chromosomes.
Homologues
Chromosomes exist in homologous pairs in ______
(2n) cells.
Exception: Sex chromosomes (X, Y).
Other chromosomes, known as ___________, they have
homologues.
Ploidy – refers to the number of sets
of homologous chromosomes in cells
● haploid – one copy of each chromosome
– designated as “n” (gametes)
●
diploid – two copies (= pair) of each chromosome
– designated as “2n” (somatic cells)
Diploid organisms receive one of each type
of chromosome from female parent
(maternal chromosomes) and one of each
type of chromosome from male parent
(paternal chromosomes)
A “matched” pair of maternal and
paternal chromosomes are called
___________.
Karyotype
•
A karyotype is the complete set of all
chromosomes of a cell of any living
organism.
•
The chromosomes are arranged and
displayed (often on a photo) in a
standard format: in pairs, ordered by
size.
•
Upper right is a typical karyotype of a
human male.
•
Center is a karyotype showing
duplicated homologous chromosomes.
•
Lower right is a karyotype of a human
sperm.
__________ Reproduction
– Many single-celled
organisms reproduce by
splitting, budding.
– Some multicellular
organisms can reproduce
asexually, produce _____
(offspring genetically
identical to parent).
– Type of cell division?
_______ Reproduction
• Fusion of two ________ to
produce a single zygote.
• Introduces greater genetic
variation, allows genetic
recombination.
• With exception of selffertilizing organisms, zygote
has gametes from two
different parents.
Peter + Lois = Stewie
In humans …
• At fertilization, 23 chromosomes are donated
by each parent.
(total = 46 or 23 pairs).
• Gametes (sperm/ova):
– Contain 22 autosomes and 1 sex chromosome.
– Are haploid (haploid number “n” = 23 in humans).
• Fertilization results in diploid zygote.
– Diploid cell; 2n = 46. (n = 23 in humans)
• Most cells in the body are produced by _________.
• Only gametes are produced by _________.
Mitosis
vs.
Meiosis
• 2n
• 1n
• Clone
• Daughter cells
different from
parent cell and
from each other.
• Same genetic
information in parent
cell and daughter cell.
• Give me another one
just like the other one!
• Daughter cells have
½ the number of
chromosomes as
somatic cell.
• Shuffling the genes
(Mix it up!)
Meiosis - Sex Cell (Gamete) Formation
In meiosis,
there are 2 divisions
of the nucleus:
meiosis I
&
meiosis II
Meiosis
Animations:
http://www.sumanasinc.com/webcontent/animations/content/meiosis.html
http://www.johnkyrk.com/meiosis.html
Meiosis
Animations:
http://www.sumanasinc.com/webcontent/animations/content/meiosis.html
http://www.johnkyrk.com/meiosis.html
Mitosis vs. Meiosis
Meiosis creates genetic variation
_________
• During normal cell growth, mitosis produces daughter cells
identical to parent cell (2n to 2n)
__________
• Results in genetic variation by shuffling of maternal and
paternal chromosomes.
• No daughter cells formed during meiosis are genetically
identical to either mother or father.
• During sexual reproduction, fusion of the unique haploid
gametes produces truly unique offspring.
How is this “shuffling” accomplished?
Genetic shuffling of Meiosis 1
1. Crossing over in Prophase I
2. Independent assortment in Metaphase I.
_______ ______
You will also see the terms “synapsis” & “chaisma” associated with this process.
Homologues break at identical
locations, then rejoin opposite
partners.
This creates new combinations
of the alleles on each
chromosome.
Occurs randomly several times
on every chromosome.
Results in mixing of the genes
you inherited from your
parents.
Crossing over
_________ is the pairing
of two homologous
chromosomes that occurs
during meiosis.
_________ are the sites
of crossing over.
Exchange of genetic
material between nonsister chromatids.
Crossing over produces
recombinant chromosomes.
__________ _________
Meiosis & Sexual Life Cycle
•
_____ ______ = sequence of
stages in organisms reproductive
history; conception to
reproduction.
•
________ cells = any cell other
than gametes, most of the cells
in the body.
•
_________ produced by
meiosis.
Meiosis Practicing
Each kit should have:
- 6 duplicated chromosomes (3 sets of homologues)
- 4 pieces of string
BEFORE you start writing and doing your Meiosis
Worksheet, make sure that you have modeled
the stages of Meiosis with the chromosome kits.
(If your group needs help, raise your hand & I will come over assist.)