Sources of Genetic Variation

How does Meiosis lead to genetic variation?

What is Crossing Over? Crossing over is when homologous chromosomes EXCHANGE genetic information to create genetic DIFFERENCES!

When does it happen? ONLY during MEIOSIS!

What does it mean? It means that one person can NEVER make the same EGG or SPERM cell!

What does it look like?

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What is Random (Independent) Assortment of Chromosomes? Random assortment of chromosomes means that it is completely RANDOM which CHROMOSOMES go into which gametes.

When does it happen? ONLY during MEIOSIS!

What does it mean? All gametes are genetically DIFFERENT!

What does it look like?

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What are Mutations? A Mutations is when there is a MISTAKE in the DNA sequence.

What can it be? Mutations can be BAD, GOOD or NEUTRAL!

What happens in a BODY cell? The mutations will ONLY affect that PERSON

What happens in a SEX cell? The mutation can be passed onto the offspring!

What does it look like?

What is Non-Disjunction of chromosomes? Non-Disjunction is when chromosomes FAIL to separate from each other

When does it happen? During MEIOSIS!

What does it result in? It results in the WRONG number of CHROMOSOMES in each cell.

What are two famous examples? 1.Down Syndrome – 3 chromosomes at # 21 2.Klinefelters Syndrome – an extra X chromosome (XXY instead of XY)

What does it look like?

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What is fertilization? Fertilization is when an EGG and SPERM come together.

What does it create? They create 100% UNIQUE combination of genes!

What does it look like?

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EOC Practice Question