Term
| living organisms are distinguished by thier ability to blank thier own blank |
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Definition
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Term
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Definition
| The study of heredity and variation |
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| transmission of traits from one generation to the next |
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| demonstrated by the differences in appearance that offspring show from parents and siblings |
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| in a literal sense children dont inhereit particular physical traits from their parents. what do they inheret? |
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Definition
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Term
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Definition
| units of heredity and are made of segments of dna |
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Definition
| genes are passed to the next generation through reproductive cells called gametes |
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Each gene has a specific locat ion called a
locus on a certain chromosome |
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Term
| Most DNA is packaged into? |
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Definition
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Term
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Definition
one parent
produces genet ically ident ical offspring by
mitosis |
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Term
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Definition
a group of genet ically ident ical
individuals from the same parent |
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Definition
two parents give
rise to offspring that have unique
combinat ions of genes inherited from the
two parents |
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Term
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Definition
the generat ion- togeneration
sequence of stages in the
reproductive history of an organism |
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Term
| somatic cells? how many do humans have? |
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Definition
any cell other than a
gamete; 23 pairs |
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Definition
an ordered display of the pairs
of chromosomes from a cell |
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Definition
| The two chromosomes in each pair, or homologs |
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Term
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Definition
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Term
| Human females have a __ pair of X chomosomes |
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Definition
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Term
| human males have one __ and one __ chromosome |
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Definition
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Term
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Definition
The 22 pairs of chromosomes that do not
determine sex |
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Term
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Definition
has two sets of
chromosomes |
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Term
| diploid number for humans is |
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Definition
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Term
haploid?
what is the human haploid number? |
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Definition
contains a single set
of chromosomes; 23 |
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Term
| in an unfertilized egg (__) the sex chromosome is __. in a sperm cell the chromosome may be either __ or __ |
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Definition
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Term
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Definition
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Term
| the fertilized egg is called a ___; the __ produces __ cells by mitosis and develops into an adult |
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Definition
| zygote; the zygote, somatic |
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Term
At sexual maturity, the ovaries and testes
produce ? |
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Definition
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Term
| ___ are teh only types of human cells produced by meiosis instead of mitosis resulting in one set of chromosomes in each gamete |
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Definition
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Term
| alternation of generations |
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Definition
| plants and animals exhibit this alternation of generations, including both diploid and a haploid multicellular stage. |
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Term
| the diploid organism in plants and some algae is called __ and makes haploid ___ by meiosis |
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Definition
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Term
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Definition
Each spore grows by mitosis into this haploid
organism. fertilization of gametes results in a dpiloid sporophyte |
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Term
| in most fungi and some protists, the __ stage is the single celled ___; there is no __ diploid stage |
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Definition
| diploid; zygote; multicellular |
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Term
| only diploid cells can undergo __ |
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Definition
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Term
| in all three life cycles, the __ing and __ing of __ contriubtes to genetic __ in offspring |
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Definition
| halving and doubling of chromosomes contributes to genetic variation in offspring |
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Term
Meiosis takes place in two sets of cell
divisions what are the? |
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Definition
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Term
| the two cell divisions in meiosis result in what? |
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Definition
| four daughter cells rather than the two daughter cells in mitosis |
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Term
| what happenes in meiosis I |
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Definition
homologous chromosomes separate resulting intwo haploid daughter
cells with replicated chromosomes; it is
called the reduct ional division |
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Term
| what happens in meiosis II? |
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Definition
sister chromatids separate resulting in four haploid daughter
cells with unreplicated chromosomes; it is
called the equational division |
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Term
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Definition
Prophase I
Metaphase I
Anaphase I
Telophase I and cytokinesis |
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Term
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Definition
more than
90% of the t ime required for meiosis
Chromosomes begin to condense
synapsis |
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Term
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Definition
homologous chromosomes
loosely pair up, aligned gene by gene |
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Term
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Definition
nonsister chromat ids
exchange DNA segments |
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Term
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Definition
X- shaped regions where
crossing over occurred |
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Term
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Definition
tetrads line up at the
metaphase plate, with one chromosome
facing each pole
Microtubules from one pole are at tached
to the kinetochore of one chromosome of
each tetrad
Microtubules from the other pole are
at tached to the kinetochore of the other
chromosome |
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Term
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Definition
- pairs of homologous
chromosomes separate
- One chromosome moves toward each pole, guided by the spindle apparatus
- Sister chromatids remain attached at the
cent romere and move as one unit toward
the pole
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Term
| telophase 1 and cytokinesis |
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Definition
- each half
of the cell has a haploid set of
chromosomes; each chromosome still
consists of two sister chromat ids
- Cytokinesis usually occurs simultaneously,
forming two haploid daughter cells
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Term
| in animal cells a __ __ forms; in plants a __ __ forms |
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Definition
| cleavage furrow; cell plate |
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Term
| why doesnt any chromosome replication occur between the end of meiosis I and the beginning of meiosis II? |
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Definition
| because the chromosomes are already replicated |
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Term
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Definition
- Prophase II
- Metaphase II
- Anaphase II
- Telophase II and cytokinesis
- Meiosis II is very similar to mitosis
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Term
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Definition
- a spindle apparatus forms
- In late prophase II, chromosomes (each still composed of two chromatids) move toward the metaphase plate
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Term
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Definition
the sister chromatids are
arranged at the metaphase plate Because of crossing over in meiosis I, the
two sister chromat ids of each chromosome
are no longer genet ically identical The kinetochores of sister chromat ids
attach to microtubules extending from
opposite poles |
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Term
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Definition
the sister chromatids
separateThe sister chromatids of each
chromosome now move as two newly
individual chromosomes toward opposite
poles |
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Term
| Telophase II and Cytokinesis |
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Definition
the chromosomes arrive at
opposite polesNuclei form, and the chromosomes begin
decondensing |
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Term
| what is produces at the end of meiosis |
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Definition
| four daughter cells each with a haploid set of unreplicated chromosomes |
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Term
| each daughter cell is __ __ from teh others and from the __ cell |
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Definition
| denetically distinct; parent |
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Term
| three events unique to meiosis occurring in meiosis I |
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Definition
- synapsis and corssing over in prophase I: Homologous chromosomes physically connect and exchange genetic information
- at the metaphse plate, there are paird homologous chromosomes (tetrads), instead of individual replicated chromosomes
- at anaphase I, it is homologous chromosomes, instead of sister chromatids that septerate
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Term
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Definition
| changes in an organisms DNA, the orginal source of genetic diversity |
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Term
| mutations create different versions of genes called __ |
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Definition
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Term
| reshuffling of __ during __ reproduction produces __ variation |
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Definition
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Term
| three mechanisms conrtibute to genetic variation. what are they? |
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Definition
- independent assortment of chromosomes
- crossing over
- random fertilization
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Term
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Definition
combine genes
inherited from each parent |
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Term
| when does crossing over occur |
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Definition
very early in
prophase I, as homologous chromosomes
pair up gene by gene |
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Term
| what happens during crossing over |
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Definition
homologous portions of
two nonsister chromatids trade places contributing to genetic
variation by combining DNA from two
parents into a single chromosome |
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Term
| why does random fertilization add to genetic variation? |
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Definition
| because any sperm can fuse with any ovum |
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Term
| natural selection results in the accumulation of genetic variations __ by the __ |
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Definition
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Term
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Definition
| keeps cells in metaphse, making chromosomes easier to count |
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Term
meiosis makes __ cells
mitosis makes __ cells |
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Definition
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Term
| how are autosomes arranged? |
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Definition
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Term
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Definition
| cells that produce gametes, found in overies and testes |
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Term
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Definition
| where crossing over takes place. gene for gene |
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Term
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Definition
| keep sister chromatids together |
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Term
meiosis I only has __ split
meiosis II has __ split |
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Definition
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Term
| describe three events that occur during meiosis I but not mitosis |
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Definition
- synapsis and crossing over during prophase I,
- separating of homologous chromosomes, rather than sister chromatids.
- at the metaphase plate, there are paird tetrads, instead of individual replicated chromosomes
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Term
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Definition
| occurs in meiosis I and results in two haploid daughter cells with replicated chromosomes |
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Term
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Definition
| occurs in meiosis II and results in four hapoid daughter cells with unreplicated chromosomes |
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