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Bio > AP Bio Flashcards Chapters 14 and 15 - Sheet1 > Flashcards

AP Bio Flashcards Chapters 14 and 15 - Sheet1

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Biology 101 flashcards
2
Q

Who started the gene idea?

A

Gregor Mendel, with pea plants

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3
Q

Who discovered the basic principles of heredity?

A

Gregor Mendel, with pea plants

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4
Q

What makes peas conducive to genetic experiments?

A

The fact that they are available in many varieties, short generation time, large number of offspring, and that each trait can only be expressed one of two ways

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5
Q

What is a heritable features that varies among indivduals?

A

a character

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6
Q

What is a character?

A

a heritable feature that varies among indivudals

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7
Q

What is a trait?

A

a variant for a character, such as purple or white flowers

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8
Q

What is true-breeding?

A

plants that produce only the same variety as the parent plant

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9
Q

What is hybridization?

A

the mating/crossing of two true-breeding varieties

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10
Q

P generation

A

parental generation, the true-breeding parents

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11
Q

F1 generation

A

first filial generation, hybrid offspring of P generation

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12
Q

F2 generation

A

when F1 offspring self-pollinate or cross-pollinate with other F1s

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13
Q

What is Mendel’s model to explain 3:1 inheritance?

A

1) alternative versions of genes account for variations in inherited characters; 2) for each character, an organism inherits two copies of a gene, one from each parent; 3) if the two allelles at a locus differ, then the dominant allele determines the organism’s appearance, and the recessive allele has no noticeable phenotypic effect; 4) two alleles for a heritable character segregate during gamete formation and end up in different gametes

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14
Q

allele

A

alternative versions of a gene

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15
Q

law of segregation

A

that the two alleles for a heritable character segregate during gamete formation and end up in different gametes

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16
Q

testcross

A

breeding an organism of unknown genotype with a recessive homozygote

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17
Q

monohybrid

A

organisms that are heterozygous for one particular character being followed in the cross

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18
Q

dihybrid

A

organisms that are heterozygous for two characters being followed in the cross

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19
Q

law of independent assortment

A

each pair of alleles segregates independently of each other pair of alleles during gamete formation

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20
Q

What is the phenotype for a dihybrid cross?

A

AaBb x AaBb = 9:3:3:1

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21
Q

What is the genotype for a dihybrid cross?

A

AaBb x AaBb = 1:2:1:2:4:2:1:2:1

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22
Q

complete dominance

A

phenotypes of AA and Aa are indistinguishable

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23
Q

incomplete dominance

A

neither allele is completely dominant: red x white = pink

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24
Q

What is the genotype for incomplete dominant F1 hybrids?

A

1:2:1 (homoz dom, hetero, homoz rec)

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25
Q

What is the phenotype for incomplete dominant F1 hybrids?

A

1:2:1 (homoz dom, hetero, homoz rec)

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26
Q

codominance

A

two alleles each affect the phenotype in separate, distinguishable ways: ex: human MN blood

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27
Q

How is the human blood type MN phenotypically expressed?

A

Codominantely: with both M and N phenotypes appearing

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28
Q

What does Tay-Sachs disease show about genetics?

A

That the observed dominant/recessive relationship between alleles depends on the level of examination: Tay-Sachs allele is recessive at organismal level, but incompletely dominant at the biochemical level, and codominant at molecular level

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29
Q

What are multiple alleles?

A

Characters that exhibit more than two traits, such as blood: ABO

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30
Q

What are the four blood types humans can have?

A

A, B, AB, O

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31
Q

pleiotropy

A

when genes have more than one phenotypic effect

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32
Q

Give a human example of pleiotropy.

A

Multiple symptoms associated with cystic fibrosis and sickle-cell disease

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33
Q

epistasis

A

when the phenotypic expression of a gene at one locus alters that of a gene at a second locus

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34
Q

What is the phenotype for a cross of two dihybrid individuals with epistasis?

A

9:.3:.4

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35
Q

When homoz. Rec. ee is epistatis to Lab color, what happens to dogs that are homoz-dom or heteroz-dom for black?

A

They’re yellow anyway, since the homoz-rec ee turns the coat yellow regardless of B/b expression

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36
Q

quantitative characters

A

when characters vary in gradations rather than in the either-or behavior of pea plants

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37
Q

polygenic inheritance

A

an additive effect of two or more genes on a single phenotypic character

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38
Q

Polygenic inheritance is the opposite of what?

A

Pleiotropy

39
Q

Give a human example of polygenic inheritance/quantitative characters.

A

Skin color

40
Q

norm of reaction for a genotype

A

phenotypic range due to environmental influences: ex: hydrangea color

41
Q

Generally, norms of reaction are broadest for what kind of characters?

A

polygenic characters

42
Q

What does it mean when characters are multifactorial?

A

That many factors, both genetic and environmental, collectively influence phenotype

43
Q

pedigree

A

the family tree describing traits of parents and children across the generations

44
Q

carriers

A

individuals that are phenotypically normal for a disorder, but heterozygous, so that they MAY transmit the recessive allele to offspring

45
Q

What does consanguinuity contribute to?

A

recessive disorders

46
Q

What is the most common lethal genetic disease in the US?

A

cystic fibrosis

47
Q

Give four examples of recessive disorders.

A

Albinism, Tay-Sachs, cystic fibrosis, sickle-cell

48
Q

Give two examples of dominant disorders.

A

Dwarfism (achondroplasia) and Huntingdon’s disease

49
Q

Which is more likely to result in early death, lethal rec-disorders or lethal dom-disorders?

A

Dominant disorders, since heterozygous rec-disorder carriers don’t exhibit the disorder, whereas the only survivors of lethal dom-disorders are the homoz-rec.

50
Q

What allows lethal dom-disorders to be passed on?

A

If onset of death occurs at a later age

51
Q

amniocentesis

A

physicians insert a needle into the uterus and extract amniotic fluid for genetic testing

52
Q

CVA (chorionis villus sampling)

A

physicians insert narrow tube through cervix into uterus and suction out a sample of placenta tissue for genetic testing: faster results, can be done earlier than amniocentesis

53
Q

What is one common newborn screening for?

A

PKU

54
Q

chromosome theory of inheritance

A

developed by sutton and Boveri: Mendelian genes have specific loci/positions along chromosomes and these chromosomes undergo segregation and independent assortment, which accounts for those genetic properties

55
Q

Who gave the first evidence that chromosoems are the location of Mendel’s inheritable factors?

A

TH Morgan, with drosophila melanogaster

56
Q

wild type

A

the phenotype for a character most commonly obersved in natural populations

57
Q

mutant

A

phenotype opposite to what’s most commonly observed in natural populations

58
Q

How does Morgan’s notation differe from Mendel’s notation?

A

Morgan uses + for wildtype and nothing for mutant, whereas Mendel uses capital for dominant and lowercase for recessive

59
Q

What is one fly characteristic that is sex-linked?

A

Eye colors: red or white

60
Q

In embryos, the absence of what allows the development of ovaries?

A

the SRY gene

61
Q

sex-linked gene

A

a gene located on either sex-chromosome

62
Q

X-linked gene

A

~1,000 genes conatined in the human X chromosome

63
Q

Why are so few disorders Y-linked?

A

Because the Y chromsome has so few genes on it

64
Q

Most Y-linked genes determine ___, but many X-linked genes code for what?

A

Y-linked: sex; but X-linked: lots of things unrelated to sex

65
Q

hemizygous

A

term used for males to refer to the recessive x-linked allele, since they have only one X chromosome and tehrefore homoz or heteroz don’t really apply

66
Q

Give three examples of X-linked disorders.

A

color-blindness, Duchenne muscular dystrophy, hemophilia

67
Q

Why do males and females have the same effective “dose” or X-linked genes?

A

One of the X-chromosomes in female mammals becomes inactivated during early embryonic development: condeses into a Barr body

68
Q

What happenes to Barr bodies in cells that become gametes?

A

Reactivated so that each gamete has an X chromosome

69
Q

Why do females consist of a mosaic of two types of cells: active X from father vs. active X from mother?

A

The X-chromosome inactivated into a Barr body is selected randomly in each embryonic cell

70
Q

If a female is hereterozygous for a sex-linked trait, what percentage of her cells exhibit each trait?

A

50% each

71
Q

What is the XIST gene?

A

a gene that becomes active only on the chromosome that will become the Barr body to inactivate the chosen X chromosome

72
Q

linked genes

A

genes located near each other on the same chromosome that tend to be inherited together in genetic crosses

73
Q

genetic recombination

A

the production of offspring with combinations of traits that differ from those found in either parent

74
Q

parental types vs. recombinant types

A

look like parents vs. look like combination of parents

75
Q

When 50% of all offspring are recombinant, geneticists say that there is a ___ frequency of recombination.

A

50%

76
Q

What percent frequency of recombination in testcrosses is observed for any two genes that are not linked?

A

50%

77
Q

If two genes are recombined with 50% frequency, then the genes are what?

A

Not linked

78
Q

How do you calculate the recombination frequency?

A

total recombinants over total offspring times 100

79
Q

What accounts for the recombination of linked genes?

A

crossing over

80
Q

genetic map

A

an ordered list of the genetic loci along a particular chromosome

81
Q

What determines recombination frequency?

A

the distance between genes on a chromosome

82
Q

The farther apart two genes are, the ___ the probability that a crossover will occur between them and therefore the ___ the recombination frequency.

A

Higher, higher

83
Q

linkage map

A

genetic map based on recombination frequences

84
Q

How does one express distances between genes?

A

With map units

85
Q

T/F: genes that are physically connected are always genetically linked

A

False, they can be genetically unconnected if they’re far enough apart to be almost certainly separated during crossing-over

86
Q

T/F: map units correspond to actual physical distances between genes/

A

False, because the frequency of crossing over is not actually uniform over the length of the chromosome

87
Q

cytogenetic maps

A

locate genes with respect to chromosomal features, such as stained bands, that can be seen in the microscope

88
Q

nondisjunction

A

members of a pair of homologous chromosomes do not move apart properly during meiosis I, or sister chromatids fail to separate during meiosis II

89
Q

aneuploidy

A

when zygotes have an abnormal number of a particular chromosome

90
Q

monosomic

A

when a cell only has one of a chromosome instead of two (2n-1)

91
Q

trisomy

A

when a cell has an extra of a chromosome instead of two (2n+1)

92
Q

polyploidy

A

when organisms have more than two complete chromosome sets in all somatic cells

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