Mitosis, Meiosis, and Ploidy: Understanding the Processes and Their Impact on Genetics, Notas de aula de Genética

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Mitosis, meiosis, and ploidy

Mitosis

• Produces two diploid daughter cells gene1cally iden1cal to single parent diploid cell. - Essen1al for growth & development
• Basically iden1cal to original fer1lized egg.
• What happens when have muta1on during mitosis?

Meiosis

• Produces haploid (1N) daughter cells with one copy

of genes from a parent diploid cell.

• Precursor to fer1liza1on

Fer=liza=on brings together gametes

from the two parents in an offspring

• 1N meio1c gametes come together to form a new 2N diploid cell (zygote)
• Half of gene1c material is from “mother”, half from “father”

Meiosis

• Produces haploid (1N) daughter cells with one copy

of genes from a parent diploid cell.

• Precursor to fer1liza1on
• What would happen if got two copies of a

chromosome from one parent (and a third copy from

the other)?

Down syndrome, Klinefelter syndrome, etc

Fic=onal Example:

Star=ng cell has a (homologous) pair of one chromosome Fig 2-­‐8 in Griffiths et al Chroma1ds are “iden1cal” This picture has 2 pairs of chroma1ds

Image Credits, Unit 3-­‐

• Chromosomes, (c) Alexandr Mi1uc, all rights reserved, www.photoxpress.com
• Soma1c muta1on, (c) 2009 Mar1n LaBar, CC by-­‐NC 2.0, www.flickr.com
• Microwave, (c) 2005 吉恩, CC by-­‐SA 3.0, en.wikipedia.org.
• Third eye, (c) Kheng Guan Toh, all rights reserved, www.photoxpress.com

Meiosis + fer=liza=on needed for

Mendelian inheritance

Gregor Mendel Austrian monk 1822-­‐

Iden=fied simple rules of inheritance Masking of yellow color by green color copy (Y) is called “ dominance ” of Y. Green (Y) is dominant, yellow (y) is recessive.

Mendel’s First Law:

Three Postulates

• Unit factor in pairs (diploid)
  • Get one “allele” from mom, one “allele” from dad
• Dominance/ recessivity
  • Don’t always see this-­‐ some1mes F 1 is intermediate.
• Equal segrega1on in gametes
  • Paired factors separate, and equally likely to transmit either one to offspring

Try this...

• You are a farmer working on corn.
• You have pure-­‐breeding TALL and short strains of corn, and you’ve heard the difference is caused by a single gene.
• You cross the TALL and short strains together, and you get strains that are Intermediate in height.
• You cross these Intermediate height corns together. What will you see?

Try this 2...

• You are a farmer working on corn.
• You have pure-­‐breeding TALL and short strains of corn, and you’ve heard the difference is caused by a single gene.
• You cross the TALL and short strains together, and you get strains that are Intermediate in height.
• You cross the Intermediate height corn to TALL corn. What will you see?