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| the scientific study of heredity and variation |
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| the transmission of traits from one generation to the next |
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| differences in appearance that offspring show from parents and siblings |
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| units of heredity, and are made up of segments of DNA |
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| Genes are passed to the next generation through reproductive cells called: |
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| Each gene has a certain locaontion called a _______on a certain chromosome |
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| Most DNA is packed into___________. |
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| One set of chromosomes is inherited from: |
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| One parent produces genetically identical offspring by mitosis |
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| A group of genetically identical individuals from the same parent |
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| Two parents give rise to offspring that have unique combinations of genes inherited from the two parents |
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| generation -to- generation sequance of stages in the reproductive history of an organism |
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| The sex chromosomes are called: |
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| Human females have a _____________ chromosomes. |
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| Homologous pair of X chromosomes. (XX) |
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| Human males have _____ and _____ chromosome |
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| The 22 pairs of chromosomes that do NOT determine sex are called: |
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| any cell other than a gamete |
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| Human somatic cells have ___ pairs of chromosomes |
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| An ordered display of the pairs of chromosomes from a cell |
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| The two chromosomes in each pair are called _________ ____________, or |
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| Homologous Chromosmes, or homologs |
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| each pair of homologous chromosomes includes ___ chromosomes from each parent |
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| The __ chromosomes in a human somatic cell are two sets of __: one from the mother and one from the father |
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| A diploid cell (2n) has ___ sets of chromosomes |
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| For humans the diploid number is ______ |
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| In a cell in which DNA synthesis has occurred each chromosome is_________. |
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| each replicated chromosome consit of two ____________ _________ ___________. |
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| identical sister chromatids |
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| a gamate contains a single set of chromosomes, and is ___________. |
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| for humans the haploid number is ___. |
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| each set of 23 consist of 22 autosomes and a single sex chromosomes |
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| in an unfertilized egg (ovum), the sex chromosomes is ___. |
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| in sperm cell, the sex chromosome may be either ___or___. |
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| the fertilized egg is call a _______ and has one set of chromosomes from each parent. |
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| the ______ produces somatic cells by mitosis and develops into an adult |
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| at sexual maturity, the ovaries and testes produce ____________. |
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| haploid gametes (gameteogenesis) |
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| Gametes are the only types of human cells produced by ___________, rather than mitosis. |
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| __________ results in one set of chromosomes in each gamete. |
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| the three main types of sexual life cycles differ in the timing of meiosis and ferilization. |
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| the only haploid cells in animals are _______. |
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| gametes fuse to form a ______ _______ that divides by mitosis to develop into a multicellular organisims. |
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| plants and some algae exhibit an: |
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| alternation of generations |
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| plants and some algaes life cycle includes both a ______ and _______ stage. |
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| diploid and haploid multicellular |
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| the diploid organisim, called the __________, makes haploid spores by meiosis |
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| each spore grows by mitosis into a haploid organism called a: |
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| makes haploid gametes by mitosis |
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| fertilization of gametes results in a : |
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| in most fungi and some protists, the only diploid stage is the : |
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| Single-celled zygote; there are no multicellular diploid stage |
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| the zygote produces _______ cells by meiosis |
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| each haploid cell grows by _______ into a ____________. |
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-Mitosis
-Haploid multicelllular organism
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| the haploid adult produces _____ by mitosis |
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| _______ reduces the number of chromosome sets from diploid to haploid |
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| Like mitosis, meiosis is preceded by: |
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| the replication of chromosomes |
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| Meiosis takes place in two sets of cell divisions, called: |
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| the two cell divisions in Meiosis result in ___ daughter cells, rather than the ___ daughter cells in Mitosis |
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-four daughter cells-meiosis
-two daughter cells-mitosis |
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| each daughter cell has only HALF as many ____ as the parent cell |
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| Only _______ cells can go under Meiosis |
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-homologous chromosomes seperate
-the first cell division
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| Meiosis l: Reducional division |
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| results in 2 haploid daughtere cells with replicated chromosomes |
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-Sister chromatids seperate
-second cell division |
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| Meiosis ll: Equational division |
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| results in 4 haploid daughter cells with UNreplicated chromosomes. |
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| Meiosis l is preceded by _________. |
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| chromosomes are replicated to form sister chromatids |
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| the sister chromatids are genetically ______ and joined at the ________. |
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| The single centrosome replicates, forming ___ centrosomes |
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| Division in meiosis l occurs in four phases: |
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-Prophase l
-Metaphase l
-Anaphase l
-Telophase l and Cytokinesis |
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| Prophase l typicallly occupies more than ___% of the time required by meiosis. |
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| Chromosomes begin to condense at what stage? |
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| homologous chromosomes loosely pair up, aligned gene by gene |
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| a group of four chromaids |
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| nonsister chromatids exchange DNA segments |
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| Each tetrad usually has one or more ________, X-shaped regions where |
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| tetrads line up at the metaphase plate, one chromosome facing each pole. |
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| pairs of chromosomes seperate and move toward each pole guided by the spindle apparatus |
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| In Anaphase l sister chromatids remain attached at the centromere |
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| each half of the cell has haploid set of chromosomes; consists of two sister chromatids |
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| forms two haploid daughter cells |
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| in telophase and cytokinesis phases in animal cells a ______ forms. |
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| in telophase and cytokinesis in plant cells a _____ forms. |
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| Division in Meiosis ll also occurs in four phases: |
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Definition
-Prophase ll
-Metaphase ll
-Anaphase ll
-Telophase ll and Cytokinesis
* meiosis ll is very similar to mitosis |
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| chromosomes move toward the metaphase plate |
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-Sister chromatids are arranged at the metaphase plate
-two sister chromatids are NO longer identical |
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Definition
-Sister chromatids seperate
-sister chromatids move as two new individual chromosomes toward opposite poles |
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-chromosomes arrive at opposite poles
-nuclei form, and chromosomes begin decondensing |
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Definition
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| at the end of meiosis there are four daughter cells, each with a haploid set of ___________ chromosomes |
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Definition
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Comparing Mitosis and Meiosis:
Mitosis- |
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Definition
| conserves number of chromosome sets, producing cells that are genetically IDENTICAL to the parent cell |
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Comparing Mitosis and Meiosis:
Meiosis |
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Definition
| Reduces the number of chromosomes sets from two(diploid) to one (haploid), producing cells that DIFFER genetically from eachother and parent |
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| the mechanism for separating sister chromatids is virtually identical in : |
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| in mitosis, cohesins are cleaved at the end of : |
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| in Meiosis, cohesins are cleaved along the chromosome arms in : |
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Definition
-changes in an organism's DNA
-are the original source of genetic diversity |
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| Mutations create different versions of genes called: |
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| Reshuffling of alleles during sexual reproduction produces |
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| Three mechanisms contribute to genetic variation: |
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-Independent assortment of chromsomes
-Crossing over
-Random fertiliztion |
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Definition
| each pair of chromosomes sorts maternal and paternal homologues into daughter cells |
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| Crossing over produces ___________, which combine genes inherited from each parent |
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| in crossing over, homologous portions of two nonsister chromatids ... |
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| crossing over contributes to genetic variation by combining |
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| DNA from two parents into a single chromosome |
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| Natural selection results in: |
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| the accumulation of genetic variations favored by the enviroment |
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| Sexual reproduction contributes to the : |
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| genetic variation in a population, which originates from mutations |
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