2.2.5 My, Oh, Meiosis
A DANGEROUS DIVIDE
IN 2.2.4, YOU VIEWED A NORMAL CHROMOSOME SPREAD WHICH WOULD BE USED BY A GENETICIST TO CREATE A KARYOTYPE NOT ALL KARYOTYPES ARE NORMAL MOST ABNORMALITIES OCCUR WHEN THE CELL DIVIDES
GETTING DOWN TO GAMETES
- WHAT IS A SOMATIC CELL?
- HOW MANY CHROMOSOMES SHOULD IT HAVE?
- HOW DO SOMATIC CELLS DIVIDE?
- WHAT IS A GAMETE?
- HOW MANY CHROMOSOMES SHOULD IT HAVE?
- HOW ARE GAMETES CREATED?
LET'S REVIEW MITOSIS
So, what's meiosis?
Formation of gametes Overall goal: 1 diploid cell (2n) -> 4 haploid gametes (n) Diploid cell replicates DNA
- each sister chromosome has 2 sister chromatids
Meiosis I (PMAT)
- crossing over occurs during Prophase I
- end with 2 daughter cells each with 46 chromosomes
Meiosis II (PMAT again)
- No crossing over
- creates 4 daughter cells each with 23 chromosomes
CLUES IN THE KARYOTYPE
Karyotypes allow us to observe major chromosomal errors. Errors in # of chromosomes is usually the result of nondisjunction
When sperm and egg meet -> should create a cell with 46 chromosomes Nondisjunction means they could have more or fewer chromosomes
Let's Compare/Contrast Mitosis and Meiosis
chromosome structure
Possible Changes that can Occur in Chromosomes
Reflection Question: Which do you think is easier to identify on a karyotype - changes in chromosome number or in chromosome structure? Explain your answer.
Disorder Detectives
You're waiting for Riley's results, but there's a backlog of samples to review. Complete the karyotype with your group Once complete, research the disorder and fill out the cytogenetics report. Turn in when finished.
- Use genome.gov to get info about the disorder
Making the Call
Riley's karyotype results are in!
- Observe the karyotype and fill in the cytogeneticist report.
- Research the chromosomal findings -> determine a diagnosis.
- Add notes about the diagnosis:
- what life will be like
- potential complications
- available treatments
- support services for the family
- Add this information to the Notes for Caregiver section of the report and keep with your notes
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Transcript
2.2.5 My, Oh, Meiosis
A DANGEROUS DIVIDE
IN 2.2.4, YOU VIEWED A NORMAL CHROMOSOME SPREAD WHICH WOULD BE USED BY A GENETICIST TO CREATE A KARYOTYPE NOT ALL KARYOTYPES ARE NORMAL MOST ABNORMALITIES OCCUR WHEN THE CELL DIVIDES
GETTING DOWN TO GAMETES
LET'S REVIEW MITOSIS
So, what's meiosis?
Formation of gametes Overall goal: 1 diploid cell (2n) -> 4 haploid gametes (n) Diploid cell replicates DNA
- each sister chromosome has 2 sister chromatids
Meiosis I (PMAT)- crossing over occurs during Prophase I
- end with 2 daughter cells each with 46 chromosomes
Meiosis II (PMAT again)CLUES IN THE KARYOTYPE
Karyotypes allow us to observe major chromosomal errors. Errors in # of chromosomes is usually the result of nondisjunction
When sperm and egg meet -> should create a cell with 46 chromosomes Nondisjunction means they could have more or fewer chromosomes
Let's Compare/Contrast Mitosis and Meiosis
chromosome structure
Possible Changes that can Occur in Chromosomes
Reflection Question: Which do you think is easier to identify on a karyotype - changes in chromosome number or in chromosome structure? Explain your answer.
Disorder Detectives
You're waiting for Riley's results, but there's a backlog of samples to review. Complete the karyotype with your group Once complete, research the disorder and fill out the cytogenetics report. Turn in when finished.
Making the Call
Riley's karyotype results are in!