Download Meiosis and mitosis

Meiosis
• Homologous chromosomes
Meiosis and mitosis
http://www.erin.utoronto.ca/~w3bio/bio207/index.htm
January 25
– Identical in size and shape
– Carry the same genes in the same linkage order
– Very similar in nucleotide sequence
• Homologs
– Two chromosomes of a homologous pair
– E.g. X and Y chromosomes act as homologous
chromosomes because a small part of the nucleotide
sequences match
Meiosis
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Meiosis
Meiosis
Meiosis
Meiosis
2
Meiosis
Meiosis
Meiosis
3
Meiosis
Meiosis
Meiosis
4
Meiosis
Meiosis
Chromosomes of tomatoes
• How many chromosomes
does a tomato have?
– 12
• Where are the
centromeres?
– Constrictions between the
dark regions
• What is the dark region
flanking the centromere
of each chromosome?
– heterochromatin
Text p. 130
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Chromosomes of tomatoes
• How many chromosomes
does a tomato have?
– 12
• Where are the
centromeres?
– Constrictions between the
dark regions
• What is the dark region
flanking the centromere
of each chromosome?
– heterochromatin
Text p. 130
Mitosis
Mitosis
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Meiosis and Mitosis
• Meiosis
• Mitosis
– Parent cell 2n
produces 4 gametes n
– Forms new
combinations of
chromosomes in
gametes
– New combinations of
chromosomes are
formed during
crossing-over
– Daughter cell is
identical to parent cell
– A 2n cell gives two
(2n) daughter cells
2n
2n
DNA
Replication
DNA
Replication
Meiosis
Meiosis
n
n
Diploid life cycle
• For example
Drosophila
melanogaster,
humans, mice…
Stages in the production of mature
male and female gametes
2n Oogonium
2n Spermatogonium
2n Primary Oocyte
2n Primary Spermatocyte
Meiosis I
2n
Secondary Spermatocytes
DNA
Replication
n
Mitosis
2n
Secondary Oocyte
First Polar body
Meiosis II
n n
n
Spermatids
Spermatozoa (sperm)
n
n
n
n
n
Ootid
n
n
n
Three polar bodies
Ovum (egg)
n
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Haploid life cycle
Haploid life cycle
• Neurospora crassa
Neurospora crassa
Alternation of haploid and diploid
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Genes and chromosomes
• What is a gene?
– Functional regions along the DNA molecule of
a chromosome that are transcribed into RNA
• Even before the structure of DNA was
elucidated it was thought that
chromosomes represented large numbers
of genes in a linear array
Genes and chromosomes
• What is a gene?
– Functional regions along the DNA molecule of
a chromosome that are transcribed into RNA
• Even before the structure of DNA was
elucidated it was thought that
chromosomes represented large numbers
of genes in a linear array
Introduction to genetic analysis
Griffiths, A., Wessler, S.R., Lewontin,R.C., Gelbart, W.M.,Suzuki, D.T.
and Miller, J.H.
Eighth Edition, W.H. Freeman and Company NY
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•
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Part I Transmission genetic analysis
Chapter 1: all questions p. 24-26
Chapter 2: all the questions p. 62-72
Chapter 3: questions #1-12,18,19, 22, 25-27, 29,
30, 32, 40-42.
• Test covers chapters 1 to 3, multiple choice
– You will need a calculator
• Chapter 15:
Text p. 130
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Tutorials
Evaluation
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end of each chapter covered
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doctor’s note to the instructor within 48h of
missing a quiz or a test
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• Tutorial Quizzes/Assignments worth a total
of 15%
• 4 Term Tests worth a total of 50%:
– January 30
– February 27
– March 15
– April 3
• Final Exam worth 35%
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