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127 Cards in this Set
- Front
- Back
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GENES |
A unit of hereditary information ●consisting of a specific nucleotide sequence in DNA |
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Inherited information is passed on in the form of each gene's specific sequence of ___________. |
DNA nucleotides |
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GAMETES |
Reproductive cells (sperm & eggs) |
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What do gametes do? |
They transport genes from one generation to the next |
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What do gametes do during fertilization? |
They unite to form a diploid zygote (passing on genes of both parents to their offspring) |
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Where is most DNA in a eukaryotic cell located? |
In chromosomes within the nucleus |
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How many chromosomes do humans have? |
46 |
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Somatic cells |
Any cell (in multicellular organisms) except sperm & eggs |
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Each chromosome consists of ... |
A single long DNA molecule coiled in association with various proteins |
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How many genes does 1 chromosome contain? |
Few hundred- a few thousand |
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What is a gene's locus? |
A gene's specific location along the length of a chromosome |
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Asexual reproduction |
One individual is the only parent Passes copies of all its genes w/o the fusion of gametes |
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Sexual reproduction |
2 parents give rise to offspring that have unique combinations of genes inherited from the 2 parents |
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What causes the traits of parents (like hair color) to show up in their offspring? |
Parents pass genes to their offspring; The genes program cells to make specific enzymes & proteins; Whose action produces an individual's inherited traits |
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How do asexualy reproducing organisms produce offspring that are genetically identical to each other and the parent? |
Such organisms reproduce by mitosis, which generates offspring whose genomes are the exact copy of the parent's genome |
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A woman breeds orchids, trying to obtain a plant with a combination of desirable traits. After many years, she finally succeeds. To produce more plants like this one, should she cross-breed it with another plant or clone it? Why? |
She should clone it. Cross-breeding it with another plant would generate offspring that have additional variation, which she no longer wants, now that she has obtained her ideal orchid |
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Life cycle |
The generation-to-generation sequence of stages in the reproductive history of an organism (From conception to production of its own offspring) |
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In humans, each somatic cell has ... chromosomes. |
46 |
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How do chromosomes in meiosis & mitosis differ? |
Size, centromere position, & pattern of bands produced by certain chromatin-binding stains |
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How many types of chromosomes are there? |
23 |
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Karyotype |
Display of the chromosome pairs of a cell arranged by size and shape |
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Homologous chromosomes |
Pair of chromosomes of the same length, centromere position, & staining pattern that possess genes for the same characters at corresponding loci. (One homologous chromosome is inherited from the father, one from mother.) |
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Both chromosomes of each pair carry... |
Genes controlling the same inherited characters |
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If a gene for eye color is at a particular locus on a certain chromosome, then its homolog will... |
Also have a version of the same gene specifying eye color at the equivalent locus |
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Human females have a homologous pair of ... |
X chromosomes (XX) |
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Human males have... |
one X & one Y chromosome (XY) |
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In males, are their X & Y chromosomes the same? |
NO. Only small parts of the X & Y area homologous. Most of the genes carried on the X are not on the Y (vice versa) |
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Why are X & Y chromosomes called sex chromosomes? |
They determine an individual's sex |
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Autosomes |
A chromosome that is not a sex chromosome |
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Heredity |
The transmission of traits from one generation to the next |
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Most genes program cells to... |
Synthesize specific enzymes and other proteins, who is action produces an organism's inherited traits. |
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What is the molecular basis for the transmission of hereditary traits? |
The precise replication of DNA, which produces copies of genes that could be passed from parent to offspring |
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Single-celled eukaryotic organisms can reproduce asexually by... |
Mitotic cell division, in which DNA is copied and allocated equally to two daughter cells |
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When do chromosomes become condensed enough to be distinguished microscopically from each other? |
Mitosis |
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We inherit one chromosome of each pair from... |
Each parent |
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The number of chromosomes in a single set is represented by... |
N |
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Diploid cell |
Any cell containing two sets of chromosomes (2n), one set inherited from each parent |
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What is the diploid number in humans? |
46 (2n=46) ... ( the number of chromosomes in our somatic cells ) |
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In a cell in which DNA synthesis has occurred, and all the chromosomes are duplicated, and therefore each consists of... |
Two identical sister chromatids, associated closely at the centromere and along the arms |
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How many sets of chromosomes do gametes contain? |
ONE (n) |
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Haploid cells |
A cell containing only one set of chromosomes (n) |
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What is the haploid number in humans? |
23 (n=23) |
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What does the set of 23 haploids consist of? |
22 autosomes plus a single sex chromosome |
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What chromosome does an unfertilized egg contain? |
X |
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What kind of chromosomes does a sperm contain? |
X or Y |
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When does the human life cycle begin? |
When a haploid sperm from the father fuses with a haploid egg from the mother |
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Fertilization |
The union of haploid gametes, resulting in fusion of their nuclei |
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Zygote |
The diploid cell produced by the union of haploid gametes during fertilization; A fertilized egg |
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Why is a zygote diploid? |
It contains two haploid sets of chromosomes bearing genes representing the maternal and paternal family lines |
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As a human develops into a sexually mature adult, what generates all the somatic cells of the body? |
Mitosis of the zygote and its descendants cells generate all the somatic cells |
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What is passed on from the zygote to its somatic cells? |
Both chromosome sets and all the genes that carry |
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What are the only cells of the human body not produced by mitosis? |
The gametes |
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Where do gametes develop from? |
Specialized cells called germ cells in the gonads- ovaries in females and testes in males |
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What would happen if gametes were made by mitosis? |
They would be diploid cells. At the next round of fertilization, when to give me its fused, the normal chromosome number of 46 with double to 92. Each generation with double the number of chromosomes yet again |
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Meiosis |
A type of cell division in sexually reproducing organisms. Consists of two rounds of cell division but only one round of DNA replication |
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How many chromosomes result from meiosis? |
Half the number of chromosomes sets of the original cell |
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How does meiosis counterbalance fertilization? |
meiosis reduces the number of sets of chromosomes from 2 to 1 in the gametes, counterbalancing the doubling that occurs at fertilization |
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In animals, where does meiosis only occur? |
In germ cells- which are in the ovaries or testes |
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As a result of meiosis, each human sperm and egg is... |
Haploid... n=23 |
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How does fertilization restore the diploid condition? |
By combining two haploid sets of chromosomes and the human life cycle is repeated, generation after generation |
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Alternation of generations |
Type of life cycle. There is both a multicellular diploid form- the sporophyte and a multicellular haploid form- the gametophyte Plants and some algae. |
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Sporophyte |
Then multicellular diploid stage in alternation of generations |
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Meiosis in the sporophyte produces haploid cells called... |
Spores |
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Unlike a gamete, a haploid spore does not fuse with another cell, but divides mitotically, generating a multicellular haploid stage called the... |
Gametophyte |
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Souls of the gametophyte give rise to gametes by... |
Mitosis |
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Fusion of two haploid gametes at fertilization results in... |
A diploid zygote, which develops into the next sporophyte generation |
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In alternation of generations, the sporophyte generation produces a... as its offspring, and the gametophyte generation produces the next... generation |
Gametophyte, Sporophyte |
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What happens in the life cycle of fungi protists and algae? |
After gametes form a diploid zygote, meiosis occurs without a multi cellular diploid offspring developing. Meiosis produces haploid cells rather than gametes that then divide by mitosis and give rise to either unicellular descendants or a haploid multicellular adult organism. |
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What is the only diploid stage found in the life cycle of fungi protists and algae? |
The single celled zygote |
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Can haploid and diploid cells divide by mitosis? |
Yes, depending on the type of life cycle |
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Can both haploid and diploid cells undergo meiosis? |
No, only diploid cells can. Haploid cells have a single set of chromosomes that cannot be further reduced |
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Meiosis I |
The first division of a two-stage process of cell division in sexually reproducing organisms. Results in cells with half the number of chromosome sets of the original cell |
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Meiosis II |
The second division of a two-stage process of cell division in sexually reproducing organisms. Results in cells with half the number of chromosomes sets of the original cell |
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How many daughter cells do meiosis 1 and meiosis 2 together form? |
4 |
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In an overview of meiosis... for a single pair of homologous chromosomes in a diploid cell, both members of the pair are...... |
Duplicated; And the copies are sorted into 4 haploid daughter cells |
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What holds sister chromatids together? |
Sister chromatid cohesion |
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The two chromosomes of a homologous pair are individual chromosomes that were inherited from... |
Different parents |
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What are the five steps of meiosis 1 and meiosis 2? |
Prophase 1, metaphase 1, anaphase 1, telophase 1, cytokinesis ... Prophase 2, metaphase 2, anaphase 2, telophase 2, cytokinesis |
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During early prophase 1, chromosomes begin to... |
Condense |
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During early prophase 1, homologs _______ along their length, aligned by gene. |
Loosely pair |
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During early prophase 1, how do paired homologs become physically connected to each other along their length? |
Synaptonemal complex; A zipper like protein structure |
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Synapsis |
The pairing and physical connection of duplicated homologous chromosomes during prophase 1 |
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Crossing over |
A genetic rearrangement between non sister chromatids; Involving the exchange of corresponding segments DNA molecules |
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When does crossing over begin and end? |
Begins- during pairing and synaptonemal complex formation Ends- while homologs are in synapsis |
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During prophase 1, synopsis ends with the disassembly of... and the ... in each pair have moved apart slightly. |
The synaptonemal complex in mid prophase; CHROMOSOMES |
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During prophase 1, each homologous pair has one or more X shaped regions called... |
CHIASMATA |
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Where does a chiasmata exist? |
At the point where a crossover has occurred. |
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During prophase 1, what three things occur that also occur in mitosis? |
-centrosome movement -spindle formation -nuclear envelope breakdown |
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At the end of prophase 1, what do microtubules do? |
Microtubules from one pole or the other attach to the 2 kinetochores at the centromeres of the 2 homologs |
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At the end of prophase 1, after the microtubules from opposite poles attached to the to kinetochores, where do the homologous pairs move? |
The homologous pairs move toward the metaphase plate |
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During metaphase 1, pairs of homologous chromosomes are now arranged at the..... with one chromosome in each pair facing each pole. |
Metaphase plate |
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During metaphase 1, both chromatids of one homolog are attached to ... from one pole. Those of the other homolog are attached to ... from the opposite pole. |
Kinetochore microtubules; Microtubules |
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During anaphase 1, what allows homologues to separate? |
Proteins responsible for sister chromatid cohesion break down along chromatid arms |
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During anaphase 1, where do the homologs move? |
Toward opposite poles, guided by the spindle apparatus |
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Why do chromatids move as a unit toward the same pole? |
Sister chromatid cohesion persists at the centromere. (Kinda looks like a jellyfish/spider) |
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At the beginning of telophase 1, each half of the cell has a complete... |
Haploid set of duplicated chromosomes {Each chromosome is composed of 2 sister chromatids; one or both chromatids include regions of nonsister chromatid DNA} |
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Cytokinesis usually occurs simultaneously with ... forming 2 ... |
Telophase 1; Haploid daughter cells |
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In what phase of meiosis 1 does a cleavage furrow form? A cell plate? |
Cytokinesis |
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During cytokinesis, chromosomes... and... form |
Decondense; Nuclear envelopes form |
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Does chromosome duplication occur between meiosis 1 and meiosis 2? |
No |
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When does a spindle apparatus form? |
Prophase 2 |
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At the end of prophase 2, chromosomes each still composed of two chromatids associated at the centromere, move towards what? |
The metaphase 2 plate |
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During metaphase 2, where are the chromosomes located? |
At the metaphase 2 plate |
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During metaphase 2, the two sister chromatids of each chromosome are not genetically identical. Why? |
Because of crossing over in meiosis 1 |
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During metaphase 2, the kinetochores of sister chromatids are attached to... |
Microtubules extending from opposite poles |
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During anaphase 2, what allows the chromatids to separate & move toward opposite poles as individual chromosomes. |
Breakdown of proteins holding the sister chromatids together |
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During telophase 2/cytokinesis, what forms? |
Nuclei |
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During telophase 2/cytokinesis, the chromosomes begin... |
Decondensing |
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During telophase 2/cytokinesis, the meiotic division of one parent cell produces how many daughter cells? |
4; each with a haploid set of chromosomes |
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At the end of meiosis, the 4 daughter cells are ... |
Genetically distinct from one another & from the parent cell |
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What three events unique to meiosis occur during meiosis 1? |
Synapsis and crossing over, homologous pairs at the metaphase plate, and the separation of homologs |
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Meiosis 1 is called the ... because it halve the number of chromosome sets per cell, from 2 sets (diploid state) to one set (haploid state) |
Reductional division |
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During meiosis 2 (sometimes called the equational division) the sister chromatids separate producing ... |
haploid daughter cells |
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What is the original source of all genetic diversity? |
Mutation |
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In species that reproduce sexually, what is responsible for most of the variation that arises in each generation? |
The behavior of chromosomes during meiosis and fertilization |
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At metaphase 1, the homologous pairs, each consisting of one maternal and one paternal chromosome, are situated at the metaphase plate. What is the chance that a given daughter cell of meiosis 1 will get the maternal chromosome? |
50% |
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Independent assortment |
Each pair of homologous chromoskmes is positioned independently of the other pairs at metaphase 1... the first meiotic division results in each pair sorting its maternal & paternal homologs into daughter cells independently of every other pair |
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How many combinations are possible for daughter cells formed by meiosis of a diploid cell (with n = 2)? |
4 |
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The number of possible combinations when chromosome assort independently during meiosis is... |
2^n where n = the haploid number of the organism |
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In humans (n=23), the number of possible combinations of maternal and paternal chromosomes in the resulting gametes is... |
2^23 =8.4 million |
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Crossing over produces... |
Recombinant chromosomes |
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Recombinant chromosome |
Chromosome created when crossing over combines DNA from 2 parents into a single chromosome |
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In meiosis in humans, about how many times does crossing over occur per chromosome pair? |
1-3 (Depending on the size of the chromosomes & the position of their centromeres) |
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Crossing over begins very early in prophase 1 when... |
Homologous chromosomes pair loosely along their lengths. Each gene on one homolog is aligned precisely w/ the corresponding gene on the other homolog |
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In a single crossover event, the DNA of two nonsister chromatids (one maternal, one paternal) is broken by... |
Specific proteins at precisely corresponding points, And the 2 segments beyond the crossover point are each joined to the other chromatid. |
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The fusion of a male gamete with a female gamete during fertilization will produce a zygote woth about ... diploid combinations |
70 trillion (2^23 × 2^23) |
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In spite of many disadvantages of sexual reproduction, it has stayed throughout evolution. WHY? |
The ability of sexual reproduction to generate genetic diversity |
