Chapter 9.7 Flashcards
Two possible outcomes of error in meiosis
- extra chromosomes
2. missing chromosomes
POLYPLOID
“many sets”
one or more complete sets of chromosomes
human vs plant polyploid tolerance
human : cease as embryos or fetus
plant : 30% of flowering plants and many crop plants tolerate well ( e.g. durum wheat is tetraploid =4 sets)
NONDISJUNCTION
gametes have just ONE extra or missing chromosome
why does NONDISJUNCTION occur
When chromosomes fail to separate at either the first or the second meiotic division
the result an egg or sperm cell with 2 copies or non at all, rather than the normal one copy
When a gamete with Non disjunction fuses with another in fertilization the result in number of chromosomes
1 too little: 45
1 too many 47
too many is better than too few
TRISOMY
An example of 1 extra chromosome resulting from 1 extra
3 different types of autosomal trisomy
extra autosomes : 21, 18 13
Trisomy 21
the most common cause of Down syndrome that has 3 copies of 21 instead of 2
4 possibilities of sex chromosomes abnormalities
Resulting from aa gamete having 2X OR 2Y
XXX TRIPLO-X (FEMALE)
XXY KLINEFELTER (MALE)
XYY JACOBS (MALE)
Resulting from a gamete have no X nor Y
XO TURNER SYNDROME ( FEMALE)
Why hasn’t a OY been reported
since a x chromosome carries so much genetic information an embryo would not survive many cell divisions
XXX TRIPLO-X (FEMALE)
1.tallness
2. menstrual irregularities
3. normal range IQ
4.
XXY KLINEFELTER (MALE)
- sexually underveloped
- rudimentary testes
3 no pubic or facial hair - slow to learn
- large hands long limbs
XYY JACOBS (MALE)
- apparently normal
- very tall
- acne
4, problems with speech and reading
XO TURNER SYNDROME ( FEMALE)
- female with missing x chromosome has only one
- short
3 sexually underdeveloped - infertile