Lesson 4: Abnormalities in Sexual Reproduction Flashcards
what is our (humans) sex chromosomes like? how does each sex differ
- males have X and Y chromosome
- females have a pair of X chromosomes
what are non-sex chromosomes called
autosomes
what are some ways sex can be determined?
- xx/xy (mammals, some insects)
- zz/zw (birds)
- temperature (crocodiles, turtles; if the eggs are kept relatively warm, most or all eggs hatch as females- if the eggs are kept relatively cool, most or all eggs hatch as males
- age (some fish, some mollusks; all young are born as male- as they become older and larger, they change into females
- social structure (some fish; all young fish are females, when the dominant male fish dies, a large female changes into a male
- fertilization (haploid and diploid): bees, wasps, ants; fertilized eggs (2n) becomes females and unfertilized eggs (n) becomes males
- infection (some insects; variable- in one form, infected individuals develop into females)
- none (earthworms and other hermaphroditic organisms; all individuals have both female and male reproductive organs)
what are some factors that can impact meiosis and fertilization (sexual reproduction)
several, including:
- these factors would be random meiotic errors
- environmental factors
what are some ways meiosis can become abnormal?
chromosome seperation during anaphase 1 or 2 of meiosis 1 or 2
what does abnormal meiosis seperation do? what does it result in? what is the name of THIS
results in one daughter cell having an extra chromosome and one daughter cell having a missing chromosome; known as non-disjunction
example/explain non-disjunction in humans
results in gametes with 22 or 24 chromosomes, not the expected 23; this means that the resulting zygote would have 45 or 47 chromosomes, not the expected 46 (after fertilization)
karyotype (how does it work and what is it)
non-disjunction can be easily observed through the use of a karyotype- it is a picture of chromosomes that have been arranged according to number, size, shape, and other characteristics
- it takes a snapshot of the chromosomes in the cell and you can identify any errors
- during cell division, chromosomes can be stated and photographed so they can be counted and compared
types of non disjunction
- trisomy: a chromosomial abnormality in which there are 3 homologous chromosomes in place of a homologous pair (when theres an extra chromosome)
- monosomy: a chromosomal abnormality in which there is a single chromosome in place of a homologous pair (when theres a missing chromosome)
non-disjunction disorders (what is it and what is an example of it)
many human genetic conditions are a result of non-disjunction
- down syndrome is an example
down syndrome (whats it caused by, symptoms..)
caused by trisomy 21, or having 3 copies of the 21st chromosome
- the extra chromosome means theres an excess of genetic information
- symptoms: round full face, short statue, intellectual disabilities, poor immune function, etc.
turner syndrome
- one X and no Y sex chromosome
- approximately one in 2500 female births
- female in appearance but do not mature sexually and are sterile
- most turner syndrome fetuses are miscarried before the 20th week of pregnancy
Klinefelter syndrome
- two X and one Y sex chromosome
- approximately one in 500 male births
- males are usually sterile and exhibit some feminine body characteristics, but severity varies
patau syndrome
- trisomy of chromosome 13
- approximately one in 25000 live births
- many serious developmental problems including brain, kidney, and heart defects
- children rarely live more than a few months
edwards syndrome
- trisomy of chromosome 18
- approximately one in 6000 live births
- many organ system defects
- very low survival rate
- most fetuses die before birth
- average life expectancy of live-born infants is less than one month