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chapter 13 Flashcards

1
Q

chromosomal theory of inheritance

A

walter sutton (1902) - based on observations that similar chromosomes paired with one another during meiosis

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2
Q

carl correns

A

1900 - first suggested central role for chromosomes
- authored one of the scientific papers announcing rediscovery of Mendel’s work

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3
Q

inheritance of eye color in fruit flies

A

T.H. Morgan (1910) - working with fruit fly (Drosophila melanogaster)
- discovered a mutant male fly with white eyes instead of red
- crossed the mutant male to a normal red-eyed female
-> all F1 progeny were red eyed = dominant trait

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4
Q

inheritance of eye color in fruit flies (Morgan)

A
  • crossed F1 females and F1 males
  • F2 generation contained red and white-eyed flies
    *all white eyed flies were male
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5
Q

X-chromosome

A
  • test cross of a F1 female with a white eyed male showed the viability of white eyed females

conclusion: eye color gene resides on the female X chromosome

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6
Q

sex-chromosomes

A

a pair of dissimilar chromosomes that still that still pair during meiosis and mitosis

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7
Q

drosophila sex determination

A

based on number of x chromosomes
- 2 X chromosomes = female
- 1 X and 1 Y chromosome = male

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8
Q

birds sex determination

A

ZZ = male
ZW = female

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9
Q

insects (grasshoppers) sex determination

A

XX = female
XO = male (O indicates absence of chromosome)

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10
Q

honeybees sex determination

A

diploid = female
haploid = male

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11
Q

sex chromosomes in humans

A

46 total chromosomes
- 22 pairs are autosomes; 1 pair are chromosomes
- Y chromosomes = highly condensed (recessive alleles on male X’s have no active counterpart on Y)

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12
Q

autosomes

A

non-sex chromosomes

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13
Q

SRY gene

A

default sex is female; requires SRY gene on Y for maleness

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14
Q

sex-linkage

A
  • in XY sex-determination organisms, few genes from the Y chromosome are expressed
  • recessive alleles have no active partner on Y so a single recessive sex-linked gene can produce recessive phenotype

ex: hemophilia, red-green color blindness

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15
Q

dosage compensation

A
  • ensures equal expression of genes from sex chromosomes (even tho # of chromosomes is different between sexes)
  • in mammalian female cells, 1 X chromosome is randomly inactivated and condensed into a Barr body
  • females heterozygous for genes on the X chromosomes are genetic mosaics
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16
Q

female genetic mosaics

A

Calico cat
- allele for black fur is inactivated some places; allele for orange fur is inactivated in others; second gene causes patchy discrimination of pigment

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17
Q

chromosome theory exceptions

A

mitochondria + chloroplasts contain genes
- traits controlled by these genes do not follow the chromosomal theory of inheritance
- genes from mitochondria and chloroplasts are often passed to offspring by one parent

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18
Q

maternal inheritance

A

genes from mitochondria and chloroplasts are often passed to offspring by one parent, usually mother

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19
Q

plant maternal inheritance

A

in plants, chloroplasts are often inherited from the mother (species dependent)

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20
Q

genetic mapping

A

distance between genes on a chromosome could be estimated based on genetic recombination(crossing over) patterns between genes
- if crossover occurs, parental alleles are recombined producing recombinant gametes

21
Q

Creighton and McClintock experiment hypothesis

A

crossing over involves a physical exchange of genetic material

22
Q

Creighton and McClintock experiment prediction

A

recombination of visible differences in a chromosome should correlate with genetic recombination of alleles

23
Q

Creighton and McClintock experiment test

A

using two visible chromosome markers (yellow extension marker and green knob marker) combined with two genetic markers (kernel color and kernel texture)

24
Q

Creighton and McClintock experiment result

A

genetically recombinant progeny also have physically recombinant chromosomes

25
Creighton and McClintock experiment conclusion
a physical exchange of genetic material accompanied with genetic recombination
26
T.H. Morgan
observed that recombinant progeny reflected relevant location of genes
27
Alfred Sturtevant
put Morgan's observation in quantitative terms - as physical distance on chromosome increases, so does the probability of recombination (crossover) occurring between gene loci
28
constructing genetic maps
1% recombination = 1 map unit (m.u.) 1 map unit = 1 centiMorgan (cM) *the distance between genes is proportional to the frequency of recombination events
29
multiple crossovers
-if homologues undergo 2 crossovers between gene loci, the parental recombination is restored (leads to an underestimate of true genetic distance) - odd #'s of crossover events (1,3, etc) produce recombinant gametes - no crossover or even numbers produce parental gametes - relationship between true distance on a chromosome and recombination frequency is not linear
30
3 point testcross
- use 3 loci instead of 2 to construct maps - middle gene allows tracking of recombination events - in any 3 pt cross, the offspring with 2 crossovers is the least frequent class - geneticists use 3 pt crosses to determine the order of genes, then use data from closest two point crosses to determine distance
31
dominant/recessive inheritance
- some human traits are controlled by a single gene; some of which show dominant/recessive inheritance ex: dominant pedigree - juvenile glaucoma; recessive pedigree - albinism
32
hereditary juvenile glaucoma
- causes degeneration of optic nerve leading to blindness - dominant trait appears every generation
33
albinism
- when pigment melanin is not produced; due to nonfunctional allele of enzyme tyrosinase - males and females affected equally - most unaffected individuals have unaffected parents
34
sex-linked human genetic disorders
some affect males more than females
35
hemophilia
affect a protein in a cascade involved in formation of blood clots - caused by an X-linked recessive allele - heterozygous females are asymptomatic carriers
36
human genetic disorder causes
a single amino acid change in a single protein can result in clinical syndrome - sickle cell anemia: caused by defect in hemoglobin (oxygen carrier molecule) - leads to impaired oxygen delivery to tissues
37
sickle cell anemia
-homozygotes for sickle cell allele exhibit intermittent illness and reduced life span - heterozygotes appear normal but have hemoglobin with reduced ability - confers resistance to blood-borne parasite that causes malaria, explains higher proportion of allele
38
nondisjunction
failure of homologues or sister chromatids to separate properly during meiosis *changes chromosome number
39
aneuploidy
result of nondisjunction; gain/loss of a chromosome - in all but a few cases, they do not survive
40
monosomy
loss of a chromosome
41
trisomy
gain of a chromosome
42
nondisjunction of autosomes
embryos trisomic for 5 of the smallest autosome can survive birth 13,15,18 - severe defects, die within a few months 21,22 - can survive to adulthood
43
down syndrome
trisomy 21 - can be a full, third 21st chromosome - can be a translocation of a part of chromosome 21 - mother's age influences risk
44
nondisjunction of sex chromosomes
- do not generally experience severe developmental abnormalities - individuals have somewhat abnormal features, but often reach maturity and in some cases can be fertile
45
XXX
triple X syndrome
46
XXY
Klinefelter syndrome (males)
47
XO
Turner syndrome (females)
48
OY
nonviable zygotes
49
XYY
Jacob syndrome (XYY)

BIOL214 (4 decks)

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