Download Chapter 10.2 Notes

Chapter 10.2 Notes
NAME_____________________________________
Honors Biology
Organisms have tens of thousands of genes that determine individual traits
Genes don’t exist free in the nucleus but lined up on a __________________________
Diploid and Haploid Cells
In the body cells of animals and most plants, chromosomes occur in _____________
One comes from ______________ parent, one from _____________ parent
A cell with ______ of each kind of ________________________ is called a ___________________ cell
Contains a diploid, or ________, number of chromosomes
This supports ___________________ idea that we have 2 _____________ for every _____________
A cell containing ________ of each kind of chromosome is called ______________________ cell
Contains a haploid, or ______, number of chromosomes
Homologous chromosomes
______________________ chromosomes are ___ chromosomes of each ________ in a diploid cell
On homologous chromosomes, ___________ are arranged in the ________ order but because there are
different possible alleles for the same gene, the 2 chromosomes in a homologous pair are not always
__________________ to each other.
Every pea plant has ______ copies of chromosome 4 (just an example)
One came from each ______________
Since the _________________ chromosomes in the picture are the ________ for each allele, the plant is
_______________________ for each trait
Why meiosis?
Remember ______________ – cell division results in _____ cells with exactly the same ___________
and kind of ______________________
But if mitosis were the _________ form of cell division, each pea plant parent (_____ chromosomes)
would produce ______________ with a _________________ set of 14 chromosomes
That means that each ______________ formed by fertilization would have ______ the number of
_____________________________ as its parents
F1 would have _____ chromosomes; F2 would have _____ chromosomes…..
That’s a __________________! To solve it------___________________!
Meiosis
________________ – cell division that produces ___________________ containing ________ the
number of ___________________________ as a parent’s body cell
Meiosis is broken down into _____________________ and ___________________________
Meiosis I = _________ cell creates _________ 2n cells
Meiosis II = ________ cell creates two ____ cells
Sexual reproduction is the uniting of sperm and egg to form a _______________
The _________________ sex cells are ___________________ (male is sperm, female is egg)
Phases of Meiosis
Interphase
The cell ____________________ its chromosomes
Now each chromosome consist of 2 ______________ sister chromatids held together by a
________________________
Prophase I
__________ coils up, ________________ forms
_________________________ chromosomes line up with each other and form a _____ part
structure called a ________________
_______________ = 2 homologous _______________________, each made up of 2
_____________ chromatids
They pair so _____________ that _________-sister chromatids from ___________________
chromosomes can actually break and ______________ genetic material = _____________
_______
Estimated that during ________________ in humans an average of ________ crossovers occurs
for each pair of homologous chromosomes
Metaphase I
Centromere becomes attached to _______________ fiber
Spindle fibers pull _____________ into __________________
Anaphase I
Homologous chromosomes _______________________
Each new cell will receive only _______ chromosome from each homologous ___________
Telophase I
Spindle breaks down, chromosomes ____________, and cytoplasm __________ into 2 new cells
Each cell has _________ of the ___________________ information of original cell
Meiosis II
The __________ division is simply a _________________ division of products of meiosis I
Has prophase II, metaphase II, anaphase II, telophase II
Prophase II
Spindle forms, spindle fibers attach to chromosome
Metaphase II
Chromosomes (sister chromatids) pulled to the center of cell
Anaphase II
Each chromosome splits to opposite poles
Telophase II
Nuclei re-form, spindles break down, and cytoplasm divides
All of ____________________ is identical to _______________, except the chromosomes don’t
_________________ before dividing
At the end of meiosis II, ___ ______________ cells are formed
They become ______________, ready to give genetic information to ________________
Genetic Variation
Mitosis results in genetically ______________________ cells
_________ ____________ during meiosis provides a way to __________________ allele
combinations
This means there is an ____________ genetic _____________________ in every generation
Genetic Recombination
How many sperm can a pea plant produce?
Each cell has _____ pairs of chromosomes
The 7 pairs can line up in 2 different ways, 128 different kinds of sperm are possible (2n = 27 =
128)
Factor in the same number for eggs
Now multiply number of possible _______ x number of possible __________ to get the number
of different possible offspring
128x128 = 16,384 possible offspring!!
The genetic combinations very depending on the way __________________ chromosomes line
up during __________________ (randomly)
For humans, n = ________
So possible sperm = 223 = over 8 million
Possible eggs = 223 = over 8 million
Multiplied together gives you over ______ trillion different zygotes that are possible!
_________________ ______________________ – major source of genetic variation among
organisms caused by re-assortment or _______________ _____________ during meiosis
Nondisjunction
Sometimes chromosomes fail to ________________ correctly
This is called ____________________________
Both chromosomes of a homologous pair move to the ___________ pole
Results in one with an ___________ chromosome, and one with a ___________ chromosome
If fertilization of the one with the ____________ chromosome takes place, it results in
___________
In humans, trisomy occurs if chromosome __________ is the one with an extra, and
results in a baby with __________ Syndrome.
If ______________ a chromosome it is called _________________
Offspring usually don’t _________________
_______________ Syndrome is monosomy. Only found in _________________; it is
when they lack one of their ______ chromosomes
Polyploidy
___________________ – organisms with ________ than the usual number of chromosome sets
Rare in _______________, usually results in death of zygote
Frequently occurs in _______________
The flowers and fruits are ______________ and plants are ___________________
An example: ________________ plant