e are two types of chromosomes found in cells: - autosomes - sex chromosomes r body cells have 23 pairs of omosomes - homologous pairs of chromosomes have the same structure - for each homologous pair, one chromosome comes from each parent romosome pairs 1-22 are autosomes. x chromosomes, X and Y , determine nder in mammals. XX = XY = female male Bio NOTES: Chromosomes and Meiosis
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There are two types of chromosomes found in cells: - autosomes - sex chromosomes Your body cells have 23 pairs of chromosomes - homologous pairs of chromosomes.
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There are two types of chromosomes found in cells:- autosomes- sex chromosomes
Your body cells have 23 pairs ofchromosomes
- homologous pairs of chromosomes have the same structure- for each homologous pair, one chromosome comes from each parent
Chromosome pairs 1-22 are autosomes.
Sex chromosomes, X and Y, determinegender in mammals.
XX =XY =
femalemale
Bio NOTES: Chromosomes and Meiosis
HOMOLOGOUS CHROMOSOMES
• SAME SIZE• SAME SHAPE• CARRY GENES for the SAME TRAITS
• BUT ______________! (Don’t have to have the SAME CHOICES)
to make cells with ½ the number of chromosomesfor sexual reproduction
http://waynesword.palomar.edu/lmexer2a.htm
Cells go through two rounds of division in meiosis:
Meiosis reduces the chromosome number and creates genetic diversity.
homologous chromosomes
sisterchromatids
sisterchromatids
• Meiosis I and meiosis II each have four phases, similar to those in mitosis• During meiosis I – pairs of homologous chromosomes separate
- homologous chromosomes are similar, but not identical• During meiosis II – sister chromatids divide
- sister chromatids are copies of the same chromosome
Meiosis I• Meiosis I occurs after DNA has been replicated in interphase• Meiosis I divides homologous chromosomes in four phases: prophase I metaphase I anaphase I telophase I• After cytokinesis, two cells are produced with one homologous chromosome each
Meiosis II
• Meiosis II divides sister chromatids in four phases: prophase II metaphase II anaphase II telophase II
• DNA is not replicated between meiois I and meiosis II
• After cytokinesis, four new cells are produced, each with half the chromosome number (haploid)
Stop here day 1
• Option 1• Work on Vocab List
• Option 2• Complete Web quest
MITOSIS vs MEIOSISINTERPHASE INTERPHASE I
• DNA is spread out as chromatin• Nuclear membrane/
nucleolus visible• DNA is copied during S phase• Makes stuff new cell needs in G2