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Bio ch 9 genetics Flashcards

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Biology 101 flashcards
1
Q

what is the idea of pangenesis

A

particles called pangenes travel from each part of an organism’s body to the eggs or sperm and then are passed on to the next generation; changes that occur in the body during an organism’s life are also passed on in this way

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2
Q

what disproves pangenesis

A
  • reproductive cells are not composed of particles from somatic (body) cells
  • changes in somatic cells do not influence eggs or sperm
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3
Q

what is the blending hypothesis

A

the idea that the hereditary materials contributed by the male and female parents mix in forming the offspring and the original traits become lost

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4
Q

what disproves the blending hypothesis

A

it does not explain how traits that disappear in one generation can reappear in later ones

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5
Q

what is heredity

A

the transmission of traits from generation to the next

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6
Q

what is the field of genetics

A

the scientific study of heredity

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7
Q

who was Gregor Mendel

A

monk that bred garden peas

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8
Q

what did Mendel hypothesize

A

genes permanently retain their identities and do not blend

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9
Q

what is a character

A

a heritable feature that varies among individuals, such as flower color

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10
Q

what is a trait

A

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

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11
Q

what is self-fertilization

A

the fertilization of plants by their own pollen rather than that of another individual

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12
Q

what is cross fertilization

A

fertilization of one plant by pollen from a different plant

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13
Q

how did mendel ensure self-fertilization when he wanted it

A

covering the flower with a small bag so no pollen from another plant could reach the carpel

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14
Q

how did mendel ensure cross fertilization when he wanted it

A
  1. prevented self-fertilization by cutting off the immature stamens of a plant before they produced pollen
  2. to cross-fertilize the stamenless flower, he dusted its carpel with pollen from another plant
  3. after pollination, the carpel developed into another pod containing seeds that 4. he planted
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15
Q

what are true-breeding varieties

A

varieties for which self-fertilization produced offspring all identical to the parent

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16
Q

what are hybrids

A

the offspring of 2 different varieties

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17
Q

what is the p generation

A

true breeding parental plants

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18
Q

what is the F1 generation

A

their hybrid offspring

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19
Q

what is the F2 generation

A

offspring when F1 plants self-fertilize or fertilize each other

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20
Q

what is a monohybrid cross

A

when the parent plants differ in only one character

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21
Q

what are Mendel’s laws

A
  1. there are alternative versions of genes that account for variations in inherited characteristics
  2. for each character, an organism inherits two alleles, one from each parent
  3. if the 2 alleles of an inherited pair differ, then one determines the organism’s appearance and is called the dominant allele; the other has no noticeable effect on the organism’s appearance and is called the recessive allele
  4. a sperm or egg carries only one allele for each inherited character because allele pairs separate from each other during the production of gametes
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22
Q

what are alleles

A

alternative versions of a gene

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23
Q

what does homozygous mean

A

having 2 identical alleles for a gene

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24
Q

what does heterozygous mean

A

having 2 different alleles for a gene

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25
Q

what is a punnet square

A

shows possible combinations of alleles that could occur when gametes combine

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26
Q

what is phenotype

A

an organism’s physical traits

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27
Q

what is genotype

A

an organism’s genetic makeup

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28
Q

what is mendel’s law of segregation

A

pairs of alleles segregate during gamete formation

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29
Q

what is a dihybrid cross

A

a mating of parental varieties differing in 2 characters

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30
Q

what is dependent assortment

A

genes inherited as a set

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31
Q

what is independent assortment

A

genes inherited independently from each other

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32
Q

what is mendel’s law of independent assortment

A

the inheritance of one character has no effect on the inheritance of another

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33
Q

an event that is certain to occur has a probability of what

A

1

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34
Q

how can geneticists determine unknown genotypes

A

by performing a test cross with a homozygous recessive individual

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35
Q

an event that is certain to not occur has a probability of what

A

0

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36
Q

what is the rule of multiplication

A

The probability of two independent events is the product of the probabilities of each independent event. Ex. ½ x ½ = ¼

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37
Q

what is the rule of addition

A

the probability that an event can occur in 2 or more alternative ways is the sum of the separate probabilities of the different ways

38
Q

what are wild-type traits

A

those prevailing in nature

39
Q

what is a pedigree

A

a family tree based on a family’s history for the trait of interest

40
Q

what are carriers

A

heterozygotes who have the recessive allele but are phenotypically normal

41
Q

why are most genetic disorders not evenly distributed across all ethnic groups

A

possibly bc of prolonged geographic isolation of certain populations that led to inbreeding

42
Q

why is inbreeding more likely to produce offspring homozygous for recessive traits

A

bc people with recent common ancestry are more likely to carry the same recessive alleles than unrelated people

43
Q

why are dominant alleles that cause lethal diseases much less common than lethal recessives

A

bc the dominant allele cannot be carried without being expressed. Many lethal dominant alleles are fatal before the organism is even born, or before they are old enough to reproduce, thus the lethal allele is not passed on to future generations. In contrast, lethal recessive mutations are perpetuated from generation to generation by healthy carriers

44
Q

what is achondroplasia

A

a dominant disorder that is a type of dwarfism in which the head and toros develop normally but the arms and legs are short

45
Q

what is cystic fibrosis

A

a recessive genetic disorder characterized by an excessive secretion of very thick mucus from the lungs, pancreas, and other organs

46
Q

what is huntington’s disease

A

a dominant degenerative disorder of the nervous system that does not usually appear until middle age

47
Q

how can a lethal dominant allele escape elimination

A

if it does not cause death until a relatively advanced age

ex: huntington’s disease

48
Q

what are examples of recessive disorders

A

Cystic fibrosis, PKU, sickle cell

49
Q

what are examples of dominant disorders

A

Huntingtons disease

dwarfism

50
Q

what is amniocentesis

A

a form of genetic testing before birth, performed between 14 and 20 weeks of pregnancy; a physician inserts a needle through the abdomen into the mother’s uterus to extract some amniotic fluid, which they then test for genetic disorders

51
Q

what is chorionic villus sampling

A

a form of genetic testing before birth; a physician extracts a tiny sample of chorionic villus tissue from the placenta using a narrow, flexible tube inserted through the mothers vagina and cervix into the uterus. Results are available faster than amniocentesis and tests can be done earlier; however both cause risks so theyre reserved for situations where theres a higher possibility of genetic disease

52
Q

what are some ethical considerations about genetic/fetal testing

A
  • if confidentiality is breached, will carriers be stigmatized?
  • who should pay for it?
  • parents can choose between terminating the pregnancy or preparing themselves for a baby with severe problems
53
Q

what is complete dominance

A

when the dominant allele has the same phenotypic effect whether present in one or two copies

54
Q

what is incomplete dominance

A

Hybrids that have a phenotype in between the two parental varieties; the phenotypes of heterozygotes differ from the 2 homogenous varieties

55
Q

why does incomplete dominance not support the blending hypothesis

A

bc the blending hypothesis predicts that the red and white traits could never be retrieved from the pink hybrids. however, these traits reappear in the f2 generation bc the red and white alleles segregate during gamete formation in the pink f1 hybrids

56
Q

what antibodies are present in type a blood

A

anti-b

57
Q

what types of blood does type a clot with

A

type b and type AB

58
Q

what antibodies are present in type b blood

A

anti a

59
Q

what types of blood does type b clot with

A

type a and type ab

60
Q

what antibodies are present in type ab blood

A

none

61
Q

what type of blood does type ab clot with

A

none

62
Q

what type of antibodies are present in type O blood

A

anti a and anti b

63
Q

what type of blood does type O clot with

A

a, ab, and b

64
Q

which blood type is a universal donor

A

type O bc when donated it doesnt cause any clumping because it doesnt have any carbohydrates so nothing will be foreign to the recipient

65
Q

which blood type is a universal recipient

A

type AB bc they can receive blood from anyone without risk of clumping because they have both carbohydrates so nothing introduced will be foreign to them

66
Q

what are the 3 alleles responsible for blood type

A

IA, IB, and i; each person gets one of these alleles from each parent

67
Q

what is codominance

A

when both alleles are expressed in heterozygous individuals (ex: IA AB (AB) blood)

68
Q

when does blood clump with regard to blood transfusions

A

if the donor’s blood cels have a carbohydrate (a or b) that is foreign to the recipient

69
Q

what is pleiotropy

A

when one gene influences multiple characters

70
Q

what is an example of pleiotropy in humans

A

sickle-cell disease

71
Q

what is the direct effect of the sickle cell allele

A

to make red blood cells produce abnormal hemoglobin proteins

72
Q

how does sickle-cell disease exemplify the concept of pleiotropy

A

Homozygosity for the sickle-cell allele causes abnormal hemoglobin, and the impact of the abnormal hemoglobin on the shape of red blood cells leads to a cascade of symptoms in multiple organs of the body

73
Q

what are the secondary effects of sickle-cell disease

A

kidney failure, heart failure, spleen damage, brain damage, pain and fever, joint problems, physical weakness, anemia, pnuemonia

74
Q

why has sickle cell disease not gone extinct/why is is so common in african americans/africans

A

people with sickle cell are immune to malaria, so they live longer and have more offspring compared to noncarriers

75
Q

what is polygenic inheritance

A

when many genes contribute to a single characteristic

76
Q

what is an example of polygenic inheritance

A

skin color, eye color, hair color

77
Q

why will a purely genetic description of skin color always be incomplete

A

bc some intermediate shades of skin color result from the effects of environmental factors, such as exposure to the sun

78
Q

what are examples of how the environment affects phenotype

A
  • the leaves of a tree might all have the same genotype, but they may vary greatly in size, shape, and color depending on exposure to wind and sun and the tree’s nutritional state
  • in humans, nutrition alters height, exercise alters build
79
Q

are many human phenotypes influenced by both genes and environment?

A

yes

80
Q

what is one character that is not influenced at all by the environment

A

blood type

81
Q

what is the important difference between traits affected by a persons genes and the environment

A

only genetic influences are inherited; any effects of the environment are generally not passed down to the next generation

82
Q

what is the chromosome theory of inheritance

A

genes have loci on the chromosomes and it is the chromosomes that segregate during meiosis

83
Q

what is the chromosomal basis for the law of independent assortment

A

the non homologous chromosomes (and their genes) assort independently in metaphase 1 leading to 4 gamete genotypes

84
Q

what are linked genes

A

genes located close together on the same chromosome that tend to be inherited together; generally do not follow mendel’s law of independent assortment; meiosis will yield mostly two genotypes of gametes rather than equal numbers of the four types of gametes that would result otherwise

85
Q

what is the recombination frequency

A

the percent of recombinants; # recombinant/# offspringw

86
Q

what are recombinant gametes

A

ones that are created from crossing over - not the parental phenotype

87
Q

what is genetic mapping

A

where on the chromosome are specific genes located

88
Q

what is a linkage map

A

a diagram of relative gene locations

89
Q

what is the real beauty of the linkage mapping method

A

a wealth of information about genes can be learned simply by breeding and observing the organisms - no fancy equipment

90
Q

what is important about the SRY gene on the y chromosome

A

triggers testis development

91
Q

what is a sex-linked gene

A

a gene located on either sex chromosome

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