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28 Cards in this Set
- Front
- Back
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You get _____ your DNA from each parent |
Half |
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Meiosis: the process of making ____ _____ |
Sex cells (gametes) |
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What are gonads and why are they important in meiosis? |
Gonads= testes and ovaries Meiosis only occurs in the gonads |
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Gametes (___________) contain ___ the number of chromosomes of somatic (______) cells. |
Egg/sperm 1/2 Body |
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N represents |
One set of chromosomes |
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Differentiate between somatic cells and gametes |
Somatic cells: diploid (2N) Gametes: haploid (1N) |
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Diploid (2N)= ____ in humans Haploid (1N)=____ in humans |
46 23 |
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Homologous Chromosomes |
Same chromosomes from different parents - each one carries the same genes |
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Each locus (______) is in the _______ location on homologous chromosomes |
Gene location Same |
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Humans have______ pairs of homologous chromosomes |
23 |
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22 pairs of _______ (#1-22) 1 pair of ________ (X or Y) |
Autopsies Chromosomes |
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What happens during meiosis? |
Cells divide twice to create Haploid sex cells |
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Precursor cells |
Diploid, have homologous chromosomes - one copy from each parent |
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Chromosomes copied during interphase create _____________. |
Identical sister chromatid |
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Describe meiosis 1 |
First divisions: homologous chromosomes separate; creates Haploid cells (1N) with replicated chromosomes |
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Describe Meiosis 2 |
Second division: skips interphase; sister chromatids separate; Haploid (1N) |
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Meiosis 1: Interphase |
Same as in mitosis ( chromosomes replicate in S phase) |
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Meiosis 1: Prophase 1 |
Duplicated chromosomes condense Homologous Chromosomes pair up to form a tetrad |
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Prophase 1: Crossover |
= homologous DNA segments are exchanged between homologous chromosomes from each parent Result= genetic variation in offspring by mixing genes from both parents on each sister chromatid |
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Meiosis 1: Metaphase 1: |
Tetrad align in random orientation along equator Independent assortment Each cell gets 1 copy of each chromosomes Each chromosome is from either parent |
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Independent assortment |
Chromosomes from each parent will randomly go to different sides tho form each new gamete. Provides 2 possible chromosome combinations (2 to the nth power) |
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Meiosis 1: Anaphase 1: |
Homologous Chromosomes separate and move to opposite poles Sister chromatids ( now not identical) remain attached at their centromeres Daughter cells will have 2 copies of each chromosome in the Haploid set (1N) |
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Telophase 1 and cytokinesis |
Each pole now has a Haploid set of chromosomes (each from 1 parent) Each chromosome consists of 2 sister chromatids Cytokinesis occurs and two Haploid daughter cells are formed (each one only one complete set of chromosomes) |
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Describe Meiosis 2 |
Skips interphase Meiosis is identical tho mitosis |
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How does meiosis differ from Mitosis |
Meiosis- 2 rounds of cell division Meiosis- exchanges DNA between homologous chromosomes Meiosis- skips interphase in the second division cycle Meiosis- starts with 1 diploid precursor and ends with 4 unique Haploid sex cells |
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4 sources of genetic variation that occur during sexual reproduction (meiosis) |
1. Crossover ( Prophase 1) 2. Independent assortment of homologous chromosomes (Metaphase 1) 3. Fertilization is random 4. Any male mates with any female |
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What do mitosis and meiosis have in common? |
Chromosomes are only duplicated once Chromosomes are separated before cell division |
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When are diploid turned into Haploids? |
Meiosis 2 |
