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Genetics Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what are biological characteristics and give examples.

A

heritable traits… height, skin color, eye colour, and developmental and control processes run by enzymes

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2
Q

what are acquired characteristics… give 2-3 examples

A

characteristics that cannot be inherited

e.g. learned skill or knowledge and muscular development

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3
Q

if the parent is a genius or a bodybuilder, what will the child inherit

A

brain cells but not the knowledge, muscles but not the developped muscles

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4
Q

on what organisms did Mendel do most of his work and what did he observe?… What results emerged from his work?

A

on pea plants. He chose seven characteristics that are easy to quantify and qualify. Mathematical analysis that gave the Mendel Laws.

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5
Q

Why did Mendel choose garden pea plants to do his work?… include the name of the specie

A

He chose to work on Pisum sativum because hybrids can be produced and have a short generation time. They can also be self-fertilized or fertilized

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6
Q

What didn’t Mendel know when elaborating the conclusions of his studies?

A

the existence of meiosis or genes and chromosomes

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7
Q

What 2 principles resulted from Mendel’s work

A

Principle of segregation and principle of assortment

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8
Q

what are reciprocal crosses

A

If A X B is the initial cross, then B X A is the reciprocall cross

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9
Q

what is a monohybrid cross

A

a cross that studies only two variations of a single trait

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10
Q

what is the modern explanation of what Mendel observed

A

characteristics are controlled by genes, which are located on the chromosomes. Each chromosome contains a large number of genes.

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11
Q

what is a gene and what is it made up of?

A

basic unit of heredity… made up of DNA and a unique group of nucleotides

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12
Q

what do genes do

A

they contain information to make proteins (enzymes), which work in an assembly line fashion and produce substances that affect reaction developments

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13
Q

what is the gene locus

A

the specific location of a gene on a chromosome (which is a predicatble location)

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14
Q

how many copies of a given gene exist for each characteristic

A

two, one on each member of a homologuous pair of chromosomes

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15
Q

what is the name of the alternative form of a gene

A

allele. If a gene occurs in two forms, it has two alleles

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16
Q

what is the dominant allele

A

the allele that masks the presence of another different allele

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17
Q

what is the recessive allele

A

the allele that is masked by a dominant allele

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18
Q

what is the genetic notation

A

dominant allele is shown by capital letter and the letter is associated with the trait of the DOMINANT allele. Recessive allele is designated by lower case letter (same letter than the dominant allele).

e.g. a heterozygous tall male would be Tt

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19
Q

what is the genotype

A

the short hand notation for the combination of alleles present in an organism

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20
Q

what is the phenotype

A

the appearance of the characteristics

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21
Q

what is the principle of segregation

A

the fact that two alleles for a gene are segregated during gamete formation and rejoined at random during fertilization (one from each parent)

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22
Q

what is the expressed phenotypic ratio when crossing two heterozygous individuals

A

a 3:1 ratio dominant to recessive

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23
Q

what is the modern explanation for the principle of segragation

A

with meiosis, there are 4 resultant daughter cells that each have one set of chromosomes (gametes)

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24
Q

what is the gamete ratio of a homozygous parent

A

100% of the gametes will carry the same allele

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25
Q

what is the gamete ratio of a heterozygous parent

A

50% will carry one allele and the other 50% will carry the other allele

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26
Q

how can we determine if a dominant individual is heterozygous or homozygous… how is this procedure called

A

by crossing it with a recessive individual and observing the results. If homozygous, there will be no recessive children. This is called a test cross.

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27
Q

what does the principle of independent assortment state

A

that in a dihybrid cross, the segregation of the two allele pairs is independent

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28
Q

why is the segragation of the allele pairs for a dihybrid cross independent

A

because there is an independent alignment of the chromosomes pairs during metaphase 1

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29
Q

what is the expected phenotypic ratio when crossing two heterozygous individuals in a dihybrid cross (heterozygous for both traits)

A

a 9:3:3:1 ratio

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30
Q

how many pairs of autosomal chromosomes are there for humans and what type of genes do these carry

A

there are 22 pairs, which carry genes that are necessary for normal development

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31
Q

how many pairs of sex chromosomes do humans have and what do they carry/control

A

1 pair, which carries the genes that determine the sex and control the development of most of secondary sexual characteristics

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32
Q

how many types of sex chromosomes are there in mammals

A

two types

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33
Q

what genes do the X chromosomes carry

A

the genes responsible for femaleness and other genes that have no counterpart on the Y chromosomes

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34
Q

what genes do the Y chromosomes carry

A

genes responsible for maleness and other genes that have no counterpart on the X chromosomes

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35
Q

what is the sex determination pattern for humans, drosophila, birds, grasshoppers/other insects and honeybees

A

humans/drosophila: XY for males and XX for females

birds: ZZ for the males and ZW for the females
grasshoppers: XO for males and XX for females
honeybes: males are haploid and develop unfertilized eggs (have no father), and females are diploid and develop fertilized eggs

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36
Q

in what cells is there X inactivation and what is it

A

in female somatic cells… one of the two X chromosomes is randomely inactivated during embryonic development

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37
Q

what do the inactive X chromosomes condense into

A

in compact objects called Barr bodies

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38
Q

why is X inactivation important

A

because it ensures an equal level of expression fron the sex chromosomes despite a differing number of chromosomes in males and females

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39
Q

what is a sex-linked gene

A

a gene that is located on either sex chromosome

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40
Q

where are most sex-linked genes found in humans

A

on the X chromosome

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41
Q

what is a hemizygous individual

A

an individual that only has one allele due to the presence of only one sex chromosome

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42
Q

give 2 examples of sex-linked genes for humans

A

red-green colorblindness and hemophilia

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43
Q

how can the location of a particular gene be seen

A

by tagging isolated chromosomes with a fluorescent dye that highlights the gene

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44
Q

what does the chromosomal theory of inheritance state (2)

A

genes have a specific position (loci) on the chromosomes

it is the chromosomes that undergo segregation and independant assortment

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45
Q

from who came the first solid evidence associating a specific gene to a specific chromosome

A

Thomas Hunt Morgan

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46
Q

why did Mendel study fruit flies (4) and what are their complete name

A

he chose to study Drosophila melanogaster because they are easy to breed in the lab, they breed at a high rate, they have a short lift cycle (2 weeks) and have only 4 chromosomes pairs

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47
Q

what are some differences between male and female fruit flies

A

males are smaller, they have a black cap encircling their abdomen, they have a rounded caudal tip, they have a sex comb and their abdomen has five segments

females are larger, they have stripes that extend across the dorsal abdomen, have a pointed caudal tip, do not have a sex comb and their abdomen has seven segments

48
Q

what are wild type drosophila

A

the most natural populations of Drosophila. Have a special notation for fruit flies ++

49
Q

what are mutant type drosophila

A

natural variants. Mutant alleles often designated by abbreviations of the mutant name

50
Q

what is the chi^2 test used for?

A

to determine if the data corresponds to a given distribution

51
Q

can a hypothesis be proven true? what else can be done

A

no… instead prove that the alternatives are false

52
Q

what is the null hypothesis and what is its symbol

A

it is the hypothesis that there is no difference between 2 given data sets (theoretical and experimental). Symbol H_0

53
Q

what conclusion can be reached about the null hypothesis

A

that we reject it or that we fail to reject it

54
Q

what is the alternate hypothesis (and symbol)?

A

hypothesis of difference. Generally generated first. CAN NEVER BE ACCEPTED

55
Q

what is the test statistic?

A

a numerical quantity used in reaching a decision on whether to reject or fail to reject H_0.

56
Q

based on the value obtained for X^2, what conclusion can be reached

A

if X^2 calc ≥ X^2 crit (theo.), reject H_0

if X^2 calc < X^2 crit (theo.), fail to reject H_0

57
Q

what conclusion can be reached with the value of p (probability… look in table)

A

if p ≤ 0.05 reject H_0

if p > 0.05 fail to reject H_0

58
Q

how is the degree of freedom (d.f.) calculated

A

d.f.=(#factors (rows)-1)

59
Q

what does each symbol represent in a pedigree

A

females are circles, males are squares, and matings are lines. Affected individuals are often black.

60
Q

how are individuals and generations labelled in the pedigree

A

generations are labelled with roman numerals and individuals with arabic numerals

61
Q

what conclusion can be reached if the trait is expressed more frequently in males or females (males for humans)

A

the trait is sex-linked

62
Q

what conclusion can be reached if the trait is expressed equally for males and females

A

that the trait is autosomal

63
Q

what conclusion can be reached if all person that have the trait gave a parent that has also the trait

A

the trait is dominant

64
Q

what conclusion can be reached if some individuals that have the trait have parents that do not possess the trait themselves

A

the trait is recessive (be careful if it is sex-linked… more complicated)

65
Q

approximately how many genes are there per chromosome

A

100-1000

66
Q

what are linked genes

A

genes that are located on the same chromosome but tend to be inherited together

67
Q

how is distance between genes linked to recombination frequency

A

the farther 2 genes are, higher probability of crossover and higher recombination frequency

68
Q

what are the 6 factors that can cause Mendel’s laws to not be observed?

A

1: polygenic inheritance
2: pleiotropy
3: epistasis
4: degree of dominance
5: multiple alleles for one gene
6: environmental factors

69
Q

what is polygenic inheritance

A

many traits controlled by the interaction of MULTIPLE GENES and their alleles.

70
Q

how can polygenic inheritance be recognized

A

continuous nature of the traits, referred to as quantitative traits

71
Q

give 2 examples of polygenic inheritance in humans

A

human height, skin color

72
Q

what is pleiotropy

A

single gene can affect more than one trait (single allele has more than one effect on phenotype and can be dominant to one and recessive to other).

73
Q

yellow fur in mice is an example of ____?

A

pleiotropy

74
Q

what is epistasis

A

a gene at one locus alters the phenotypic expression of another gene at another locus

75
Q

give 2 epistasis examples

A

mice: black coat dominant to white but another gene determines if there is pigmentation or not. If the second gene is recessive/albino, the first one will not be noticeable.

corn and the fact that some have a purple pigment.

76
Q

what is degree of dominance and what are the 2 types

A

neither allele is dominant. 2 types are incomplete dominance and codominance.

77
Q

what incomplete dominance

A

failure to completely mask the recessive allele. intermediate phenotype like mixture for heterozygotes. e.g. pink flowers

78
Q

what is codominance

A

for heterozygotes, both alleles can be seen. not a mixture. e.g. roan cattle, blue andalusian fowl, A-type and B-type blood cell coatings.

79
Q

how many alleles can an individual have (no matter of how many exist)

A

2

80
Q

what is a polymorphic trait

A

a trait for which MORE than two distinct phenotypes are present in a population due to multiple allelism

81
Q

what is the notation for blood type problems and how to solve them

A

I^A: type A
I^B: type B
i: type O
both A and B dominant to O but they are codominant to each other

82
Q

what are antigens

A

substances that stimulate the body to make antibodies. Most are foreign proteins.

83
Q

what are antibodies

A

substances that react with the antigen that formed them. Most of the time clumping.

84
Q

what is the Rh antigen

A

another antigen found in red blood cells. People that have it are positive and those that do not are negative.

85
Q

what is erythroblastosis fetalis

A

the fact that if the dad is RH+ and the mother is RH-, for the first baby, the mom will produce antibodies. With the second babies, the antibodies could destroy the placenta.

86
Q

give an example of environmental factors that break Mendel’s laws

A

in hymalayan rabbits and siamese cats, allele produces enzyme for color only above 30 celsius.

87
Q

what is multiple allele hierarchical dominance

A

three alleles and phenotypes. if X, Y, Z, then X dominant to Y/Z, Y dominant to Z. Does not occur in nature.

88
Q

what is multiple allele circular dominance

A

three alleles and phenotypes. if X, Y, Z, then X dominant to Y, Y dominant to Z and Z dominant to X. Does not happen in nature.

89
Q

what are most human genetic disorders commonly caused by

A

inherited alleles (mostly recessive)

90
Q

what are the two types of alterations of chromosome structure

A

deletion of parts of DNA

mutation of DNA

91
Q

what causes disease in terms of genotype and phenotype

A

the dominant phenotype and the recessive genotype

92
Q

what is Huntington’s disease

A

progressive brain deterioration with effects seen after age of 30. Dominant allele disorder.

93
Q

what is progeria

A

dominant genetic disorder. Mutation during meiosis. Dwarfism and rapid aging and early death.

94
Q

give 6 examples of diseases caused by dominant alleles

A 
Marfan's syndrome (tall/eye effects)
Polydactyly (extra fingers/toes)
Achondroplasia (dwarfism)
Hypercholesterolemia (high cholesterol)
Progeria
Huntington's disease
95
Q

what increases the chance of a mating of two carriers of the same rare recessive allele

A

matings in the same family

96
Q

what is albinism

A

recessive allele disease. Lack of pigmentation in skin and hair.

97
Q

what is cystic fibrosis

A

most common lethal genetic disease (recessive). Defective or absent chloride transport channels in plasma membranes causing buildup of chloride outside the cell.

98
Q

what is sickle cell anemia

A

recessive allele disease. Defect in hemoglobin, the oxygen carrier molecule.

99
Q

what are multifactorial diseases and give examples

A

diseases that have both genetic and environmental components. e.g. heart disease, diabetes, alcoholism, mental ilnesses and cancer.

100
Q

what is aneuploidy and what is it caused by

A

condition in which there is an abnormal number of chromosomes. Often caused by nondisjunction.

101
Q

what is nondisjunction and how do the consequences differ for autosomal and sex chromosomes

A

failure of homologues or sister chromatids to separate properly during meiosis. Severe developmental abnormalities for autosomal chromosomes but not for sex chromosome.

102
Q

what are monosomics

A

individuals that lose one autosome chromosome (2n-1). Do not survive development.

103
Q

what are trisomics

A

individuals that have an extra chromosome (2n+1). Usually do not survive development.

104
Q

what are the pairs of chromosomes that allow for the survival of trisomic individuals

A

13, 15, 18: severe developmental defects. Death within a few months
21, 22: Maturation of skeletal system is delayed and mental development affected. Individuals survive to adulthood

105
Q

what is down syndrome and what is it caused by

A

trisomy 21. caused by nondisjunction of chromosome 21 during egg formation. Risk increases with age and these children have greater risk of cancer.

106
Q

what is the consequence of nondisjunction of the X chromosomes

A

one gamete has XX and the other has nothing

107
Q

what happens if an XX gamete combines with a X

A

XXX individual (triple X syndromome). Zygote develops into a female with 1 functional X and 2 Barr Bodies. Fertility problems but could be fertile

108
Q

what happens if an XX gamete combines with a Y

A

Klinefelter syndrome. Sterile male with female characteristics and diminished mental capacity. Large hands and feet and long arms and legs

109
Q

what happens if an O gamete combines with a Y

A

OY individual does not develop and dies. X chromosome needed to survive.

110
Q

what happens if an O gamete combines with an X

A

Turner’s syndrome. Short stature and webbed neck. Sterile females.

111
Q

what happens if there is nondisjunction of the Y chromosome

A

gametes are YY

112
Q

what happens if an X gamete combines with a YY

A

Jacob’s syndrome. Normal appearance, more testo., taller, persistent acne. Speech and reading problems.

113
Q

what is genetic counselling

A

process of identifying parents at risk of having children with genetic defects. Assessment of genetic state of early embryos. Predictions

114
Q

give 2 examples of techniques used to diagnose genetic disorders during pregnancy

A

amniocentesis and chorionic villi sampling

also ultrasound, fetoscopy

115
Q

what is amniocentesis

A

procedure to diagnose genetic disorders… needle into the uterus to take sample of amniotic fluid. Done during the 4th month. 1 out of 200 can result in fetal death

116
Q

what is chronic villi sampling

A

removal of cells from the chorion to diagnose genetid disease. Week 8 of pregnancy. Risks of fetal death.

117
Q

how are the results from tests done to diagnose genetic diseases analysed

A

analysis of the karyotype for chromosomes abnormalities
test for proper functioning of the enzymes
test for specific alleles by sequencing

Biology 1 (13 decks)

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