BIOS E-1a Lecture 09 101911 annotated

BIOS E-1a Lecture 09 101911 annotated - Lecture 8:...

Info iconThis preview shows pages 1–18. Sign up to view the full content.

View Full Document Right Arrow Icon
Lecture 8: Chromosome Theory, continued… Reading: Chapters 7, 9 (concepts 9.1 and 9.2) 1
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Crossing over occurs during Pachynema of Prophase I
Background image of page 2
3
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4
Background image of page 4
Meiosis vs. Mitosis • Mitosis produces two diploid daughter cells that are genetically identical – 6 chromosomes in 3 homologous pairs • Meiosis produces four haploid daughter cells – Each daughter has a random mix of 3 chromosomes 5
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
6 A comparison of mitosis, meiosis I, and meiosis II
Background image of page 6
Chromosomes • Geneticists have discovered that variations on chromosome structure and number can have major effects on organisms – Several human diseases – Important in evolution of new species • Chromosome variation – On rare occasions, structure or number of chromosomes changes so that individual is different from other members of same species – abnormal – Normal for structure and number of chromosomes to vary between species 7
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Variation in Chromosomes • Chromosome composition within a given species tends to remain relatively constant – Humans: 2 sets of 23 chromosomes (total of 46) – Dog: 78 chromosomes (39 per set) – Fruit fly: 8 chromosomes (4 per set) – Tomato: 24 chromosomes (12 per set) 8
Background image of page 8
• Chromosomes identified by –S ize – Location of centromere • Short arm is p , long arm is q , short arms on top • Metacentric: middle • Submetacentric: off center • Acrocentric: near end • Telocentric: at the end – Banding pattern • Giemsa stain gives G banding 9
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
10 Centromere location
Background image of page 10
Chromosomal mutations • Deletions – Segment missing • Duplications – Section occurs 2 or more times in a row • Inversions – Change in direction along a single chromosome • Translocations – One segment becomes attached to another chromosome – Simple or reciprocal 11
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
12 Chromosomal mutations
Background image of page 12
Changes in chromosome number • Euploid: chromosome number that is viewed as the normal number – In a diploid organism, 2 sets is normal • Polyploid: 3 or more sets of chromosomes – Diploid 2n – Triploid 3n – Tetraploid 4n 13
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
• Aneuploidy – Alteration number of particular chromosomes – Total number not an exact multiple of a set • Trisomic – Normal 2 copies of a chromosome plus a 3 rd – 2n+1 • Monosomic – Missing one of normal copies of a chromosome – 2n-1 14
Background image of page 14
15
Background image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Nondisjunction • Chromosomes do not sort properly during cell division • During meiosis can produce gametes with too many or too few chromosomes 16
Background image of page 16
Consequences • Animals do not tolerate deviations from diploidy well – usually lethal – However, male bees (drones) contain a single set of chromosomes while female bees are diploid – Diploid and polyploid species of amphibians and reptiles
Background image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 18
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/09/2012 for the course BIOLOGY 102 taught by Professor Anderson during the Spring '11 term at Harvard.

Page1 / 59

BIOS E-1a Lecture 09 101911 annotated - Lecture 8:...

This preview shows document pages 1 - 18. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online