differentiation of sexes in animals is evident of this
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Heteromorphic chromosomes
dissimilar ; chromosome pair with some homology but differing in size, shape, or staining properties
ex: sex chromosomes X and Y
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Life cycles depend on ______ differentiation
sexual
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Primary sexual differentiation
* before birth
involves only gonads where gametes are produced
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Secondary sexual differentiation
* after birth
involves overall appearance of organism
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Unisexual, dioecious, gonochoric
have only male or female reproductive organs
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Bisexual, monoecious, hermaphroditic
have both male and female reproductive organs
* common in plants and animals * produce both egg and sperm
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Self Fertilization
* eggs fertilized by stored sperms
* majority produced are hermaphrodites ( both male and female reproductive organs) * less than 1% offspring are males * adults male mate w/ hermaphrodites * produce 1/2 male and 1/2 hermaphrodite offspring
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Human Karyotype :
* 22 pairs of autosomal chromosome * 1 pair of sex chromosome * 2 sex chromosomes * normal human have 46 chromosomes
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Klinefelter and Turner Syndromes
* 1940 * human abnormalities * aberrant sexual development * result from nondisjunction * X chromosome failed to segregate during meiosis
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Klinefelter Syndrome XXY
* 47, XXY * tall, long arms and legs * large hands and feet * internal ducts are male, rudimentary testes fail to produce sperm * feminine development not suppressed * enlarged breast, rounded hips * abnormal social development
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Turner Syndrome X
* 45, X * phenotypically female * male external genitalia and internal ducts * ovaries are rudimentary * undeveloped breast * short * cognitive impairment
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The human diploid number is
46 chromosomes
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The karyotype for a Klinefelter individual
XXY
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Which of the following human genetic conditions is missing a chromosome?
a. klinefelter syndrome
b. turner syndrome
c. down’s syndrome
b. turner syndrome
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What is the ratio of male to female conceptions in a population called?
primary sex ratio
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What is the ratio of male to female born in a population called?
secondary sex ratio
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How many Barr bodies would one expect to see in cells of Turner syndrome females and Klinefelter syndrome males?
zero and one
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Where is the general location of a barr body?
attached to the nuclear envelope
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Which is not the tenant of the Lyon hypothesis?
a. X inactivation occurs early in development
b. X inactivation is passed down during mitosis
c. X inactivation occurs on the maternal X chromosome
d. initial X inactivation is random
c. X inactivation occurs on the maternal X chromosome
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Female calico cats are an example of
Lyon hypothesis
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The Y chromosome is genetically blank, however it has a gene that encodes for the protein
TDF
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Members of diploid species normally contain ____ haploid sets
two
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Mutations or aberrations
* variation from 2 haploid sets * variation from the number of chromosomes * rearrangement of genetic material within or among chromosomes
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Aneuploidy
gain or loss of 1 or more chromosomes, but not a complete set
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Euploidy
gain or loss of a complete haploid set
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Polyploidy
* triploid - 3 sets * tetraploid - 4 sets
3 or more sets
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Monosomy
loss of 1 chromosome
2n - 1 ; 45
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Trisomy
gain of 1 chromosome
2n + 1 ; 47
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Tetrasomy
gain of 2 chromosome
2n + 2
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Pentasomy
gain of 3 chromosomes
2n + 3
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Autopolyploidy
multiples of the same genome
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Allopolyploidy
multiples of closely related genomes
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_______ resulting in monosomy and trisomy
nondisjunction
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Monosomy 2n - 1
What is haploinsufficiency?
when 1 copy is not sufficient for organism to survive
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Partial monosomy
part of a chromosome is lost
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Autosome loss is not easily tolerated.
True or False
True
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Cri-du-chat syndrome (cry of the cat
* 1/2 short arm of #5 is missing * 46 * 5p (p arm is missing)
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Trisomies for autosomes are often lethal
True or False
True
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Autosomal Additions
* severe effects * most lethal during development * Down syndrome * trisomy 21 * 47, 21+ * nondisjunction of chromosome 21 during meiosis resulting in n + 1 gametes * ovum most often is the source
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Down Syndrome or Trisomy 21
* extra chromosome at #21 * 12 to 14 characteristics * affected indicuduals express 6 to 8 on average
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DSCR - Down Syndrome Critical Region
* critical region of chromosome 21 * genes are dosage sensitive * responsible for many phenotypic associated syndromes
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Origin of Extra Chromosome 21
* nondisjunction of #21 during meiosis * homologs do not disjoin in anaphase I or II * lead to n+1 gametes * ovum is source of 95% of trisomy cases