Chapter 19 Pt. 4 Flashcards
What is crossing over?
corresponding pieces of chromatids of maternal and paternal homologues (nonsister chromatids) are exchanged during synapsis when the homologues are aligned side by side
What happens after crossing over?
the affected chromatids have a mixture of DNA from the two parents
________ _____ increases the genetic variability of gametes
crossing over
crossing over increases the _______ ________ of gametes
genetic variability
__________ ___________- a second way that meiosis provides for the shuffling of genes between generations
independent assortment
In independent assortment, the relative positioning of homologous maternal and paternal chromosomes with respect to the poles of the cell is _______
random
In ___________ __________, the relative positioning of homologous maternal and paternal chromosomes with respect to the poles of the cell is random
independent assortment
During ___________ _________, the members of each homologous pair orient independently of the other pairs
independent assortment
What is nondisjunction?
the failure of homologous chromosomes to separate during meiosis I or of sister chromatids to separate during meiosis II
What is the difference between trisomy and monosomy?
trisomy- the condition in which there are 3 representatives of 1 chromosomes
monosomy- the condition in which there is only one representative of a particular chromosome in a cell
Monosomy can be severe enough to cause the death of the _____, which will result in a _________
fetus
miscarriage
What is a syndrome?
a group of symptoms that generally occur together
What are the different types of syndromes?
Turner Syndrome Klinefelter Syndrome Triple-X Syndrome Jacob Syndrome Down Syndrome
Which syndrome is this: occurs in individuals who have only a single X chromosomes (XO)
Turner Syndrome
Which syndrome is this: is observed in males who are XXY
Klinefelter Syndrome
Which syndrome is this: a female with 3 X chromosomes
Triple-X Syndrome
Which syndrome is this: a male with 2 Y chromosomes
Jacob Syndrome
Which syndrome is this: born with 3 copies of chromosome 21
Down Syndrome
What are the symptoms of Turner Syndrome?
- has the external appearance of a female
- may have thick fold of skin on the neck
- noticeably short
- chest is wide and underdeveloped breast
- ovaries are poorly developed, leading to infertility
an extra X chromosome is twice as likely to come from the ____
egg
True or False: Klinefelter Syndrome is very rare
False; Klinefelter Syndrome is fairly common
What are the symptoms of XXY males (Klinefelter Syndrome)?
- testes remain small and don’t produce an adequate amount of the male sex hormone (testerone)
- taller than average (but less muscular)
- breasts may slightly develop
- testes may not produce sperm, which leads to sterile
What are the symptoms of Triple-X Syndrome?
- have abnormal sexual development and are able to conceive children
- some have learning disabilities and delayed language skills
What are the symptoms of Jacob Syndrome?
- produced when the chromatids of a replicated Y chromosomes fail to separate
- often taller than normal, and some have slightly lower than normal intelligence
Down Syndrome is also known as _______ ___.
trisomy 21
What are the symptoms of Down Syndrome?
- moderate to severe mental impairment
- short stature or shortened body parts (due to poor skeletal growth)
- typically have flattened nose
- a forward-protruding tongue that forces the mouth open
- upward-slanting eyes
- a fold of skin at the inner corner of each eye
True or False: the risk of having a baby with Down Syndrome increases with the mother’s age
True
