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Bio Final (Lec 20-27) > Lec 20-23 > Flashcards

Lec 20-23 Flashcards

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Biology 101 flashcards
1
Q

What is a gene?

A

a discrete unit of hereditary information consisting of a specific sequence of DNA

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2
Q

What is genetics?

A

the study of heredity and hereditary variation

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3
Q

What is inheritance?

A

the process by which genetic information is passed from parent to offspring

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4
Q

Modern genetics began with _______ _______’s quantitative experiments with _______ _______.

A

Gregor Mendel
pea plants

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5
Q

What are some model organisms?

A

yeast, drosophila, mouse, rhesus, aplysia, rat

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6
Q

What is a character?

A

an observable heritable feature

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7
Q

What is a trait?

A

any detectable variation in a genetic character

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8
Q

Why was studying pea plants the best choice?

A

pea plant characteristics (purple/white pigment) is dependent on one gene

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9
Q

What are the two different hypotheses for the pattern of inheritance? Describe each one.

A

blending: genes blend, creating a medium between the two genes (e.g. purple + white pigment = light purple)

particulate: discrete “particle” is passed from parents to offspring

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10
Q

What was Mendel’s hypothesis in his experiment?

A

Inheritance of certain traits depends on parents passing down discrete heritable units.

*testing the particulate theory

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11
Q

In Mendel’s experiment, the parental generation (P) consisted of…?

A

purple and white flowers of pea plants

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12
Q

In Mendel’s experiment, what happened to the flowers in the first generation offspring (F1)?

A

all purple flowers

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13
Q

In Mendel’s experiment, what happened to the flowers in the second offspring generation (F2)?

A

reappearance of white flowers

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14
Q

In Mendel’s experiment, what was the ratio of purple to white pea plant flowers?

A

3/4 purple, 1/4 white

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15
Q

What hypothesis did Mendel’s experiment support?

A

particulate theory/hypothesis

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16
Q

The gene for flower color (in pea plants) comes in two versions, called ______.

A

alleles

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17
Q

Offspring inherit _____ _____ from each parent.

A

one allele

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18
Q

The ___________ ______ determines the pea plant flower’s appearance.

A

dominant allele

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19
Q

What are alleles?

A

alternative forms of a gene

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20
Q

Where are alleles at?

A

at the same locus on homologous chromosomes

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21
Q

What are the two laws that Mendel discovered?

A

the law of segregation and the law of independent assortment

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22
Q

What is the law of segregation?

A

2 alleles for each character segregate into different gametes

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23
Q

Different alleles do NOT ________ with each other.

A

interact

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24
Q

What phase does the law of segregation occur in?

A

Anaphase I

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25
Q

What does the test cross determine?

A

whether or not a dominant phenotype is homozygous dominant or heterozygous

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26
Q

What do you do in the test cross? Explain the results

A

cross the dominant phenotype (with an unknown genotype) with a recessive phenotype (known genotype)

all purple: homozygous
1/2 purple, 1/2 white: heterozygous

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27
Q

What was Mendel’s seed experiment trying to determine?

A

whether or not two characters (color and smoothness) were inherited dependently or independently

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28
Q

What is the law of independent assortment?

A

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

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29
Q

What is the ratio for independent assortment?

A

9 : 3 : 3 : 1

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30
Q

What phase does the law of independent assortment occur in?

A

metaphase I

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31
Q

When does independent assortment NOT hold true?

What is the exception to this?

A

NOT true when 2 characters are on the same chromosome

if 2 characters are far enough apart, a crossing over event occurs

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32
Q

What is the multiplication rule?

A

when trying the calculate the probability of a single genetic event

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33
Q

What is the addition rule?

A

when trying to calculate probability of MORE than 1 mutually exclusive genetic event

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34
Q

Some inheritance patterns are more ________ than predicted by simple __________ genetics.

A

complex

Mendelian

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35
Q

What are the examples of inheritance patterns that are more complex?

A

incomplete dominance
co-dominance
pleiotropy
epistasis
polygenic inheritance
environmental impact

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36
Q

What is incomplete dominance?

A

2 dominant alleles, one is NOT dominant over the other

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37
Q

What is an example of incomplete dominance in plants? What is the ratio that was produced?

A

flower color of snapdragons

Crossing between red x white –>
F1 produced: 25% white, 25% red, and 50% pink offspring

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38
Q

What is an example of incomplete dominance in humans?

A

hypercholesterolemia

HH: ability to make LDL receptors
Hh: an intermediate
hh: inability to make LDL receptors

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39
Q

What is co-dominance?

A

multiple alleles (normally two) affect the phenotype in separate, distinguishable ways

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40
Q

What is an example of co-dominance?

A

blood type

IA and IB are co-dominant, both are dominant over i

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41
Q

What is pleiotropy?

A

when a gene affects more than one phenotypic character

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42
Q

What is example of pleiotropy?

A

the wide-ranging symptoms of sickle-cell disease due to a single gene (change in 1 base)

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43
Q

What are the inheritance patterns associated with a SINGLE GENE?

A

dominance relationships, multiple alleles, pleiotropy

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44
Q

What are the inheritance patterns associated with TWO OR MORE genes determining a phenotype?

A

epistasis, polygenic inheritances

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45
Q

What is epistasis?

A

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

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46
Q

What is an example of epistasis? What is the ratio?

A

(in dogs) coat color depends on two genes
E (dom): determines whether or not pigment will be deposited
B (dom): the color of the pigment

***E/e is epistatic to gene that codes for pigment (B/b)

9 : 3 : 4
*****NOT 9 : 3 : 3 : 1

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47
Q

What is polygenic inheritance?

A

when a character is influenced by two or more genes

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48
Q

What is an example of polygenic inheritance? What is the result?

A

skin color

produce offspring covering a wide range of shades

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49
Q

(In polygenic inheritance) The range of phenotypes forms a _______ _______.

A

normal distribution

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50
Q

What is the norm of reaction?

A

a range of phenotypic possibilities

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51
Q

What is the norm of reaction determined/influenced by?

A

environmental factors

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52
Q

Norms of reactions are broadest for _________ _________.

A

polygenic characters

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53
Q

Changing chromatin structure to turn _____ _________ on or off is considered an ________________ mechanism.

A

gene expression

epigenetic

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54
Q

What phrase is associated with epigenetics?

A

“beyond your genes”

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55
Q

What is epigenetics?

A

a change in gene expression that is not due to a change in the DNA sequence

56
Q

What is the epigenome?

A

collection of epigenetic tags

57
Q

Epigenetic “tags” change with _________ , _________ _________ , and even our _______!

A

experiences, environmental interaction, diet

58
Q

What are two examples of epigenetics, specifically about the impact of diet?

A

royal jelly (turning a worker bee into a queen bee)
–> royal jelly turned on the “queen genes”

feed pregnant yellow mice folic acid: normal
feed pregnant yellow mice BPA: abnormal

59
Q

In epigenetics, what happens when there are and there aren’t “tags”?

A

normal (with tags): no gene expression

abnormal (without tags): gene expression

60
Q

Genetic traits in humans can be tracked through ______ _______.

A

family pedigrees

61
Q

What are two examples of a dominant trait? (HINT: one of them is a disorder)

A

polydactyly, Huntington’s disease

62
Q

Why is there such a difference in the incidence of colorblindness between males and females?

A

colorblindness has X-chromosome linkage

males only have 1 X, females have 2 X’s
–> only 1 defective X chromosome is enough to cause color blindness

63
Q

What was Thomas Morgan’s experiment? (HINT: flies)

A

cross between red-eyed (dom) female with white-eyed (recess) male

64
Q

What were the results of Thomas Morgan’s experiment? Give the ratio. What did he conclude of this?

A

white-eye trait showed up only in males
3 red : 1 white

concluded that fly’s eye color is linked to its sex

65
Q

Morgan hypothesized that the eye color gene is located on the ___ __________.

A

X chromosome

66
Q

What was the overall conclusion from Thomas Morgan’s experiment?

A

provided evidence that a specific gene is carried on a specific chromosome

67
Q

Genes located on a ____ __________ exhibit unique inheritance patterns.

A

sex chromosome

68
Q

What are linked genes? What is the exception?

A

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

exception: sex- or X-linked genes

69
Q

What is the significance of Thomas Morgan’s experiment concerning fly body color and wing size?

A

small number of NONPARENTAL phenotypes indicated that some mechanism occasionally breaks the linkage between genes on the same chromosome

70
Q

What mechanism breaks the linkage between genes on the same chromosome?

A

crossing over

71
Q

The percentage of recombinant offspring (the _______ _______) is related to the ________ between linked genes.

A

recombinant frequency

distance

72
Q

The occasional production of recombinant gametes during __________ ___ accounts fr the occurrence of reccombinant phenotypes in Morgan’s testcross.

A

prophase I

73
Q

What is a linkage map?

A

shows the relative locations of genes along a chromosome

74
Q

Genes located far apart on a chromosome are mapped by adding the _________ _________ between the ________ genes and the _________ genes.

A

recombination frequencies

distant, intervening

75
Q

The true recombination frequency of distant genes is less than the added frequencies of the intervening genes (closer). Why is this the case?

A

**check lec. 22, slide 15
further the distance could mean two crossing over events occuring (flip once and back again) –> decrease in frequency

76
Q

What was Strurtevant and his colleagues able to do? What was the result of this?

A

map linear positions of genes in Drosphila into four groups (one for each chromosome)

result: supported the chromosome theory of inheritance

77
Q

The sex of an offspring depends on what?

A

whether the sperm cell contains an X chromosome or a Y

78
Q

What is an example of the transmission of X-linked recessive traits?

A

color blindess

79
Q

Is the male or female usually the carrier of X-linked recessive traits?

A

females

80
Q

Because females have 2 X chromosomes, each gene on the X could be expressed at twice the level of as in males.

How are genes on the X expressed at equal levels in males and females?

A

by shutting off one X-chromosome (Barr body)

81
Q

During female development, one X chromosome per cell condenses into a compact object called a _______ _____.

A

Barr body

82
Q

Where is the condensed Barr body reactivated?

A

in ovarian cells that produce ova

83
Q

What happens to a female who is heterozygous for a sex-linked trait? What is an example of this?

A

half of her cells will express one allele and the other half will express the other allele

hypohidrotic ectodermal dysplasia (patches of normal and sweat gland lacking skin)

84
Q

What’s an example in cats of Barr body dependent inheritance patterns?

A

tortoiseshell cats
cell 1: orange allele expressed in one (black is Barr body)
cell 2: black allele is expressed (orange is Barr body)

85
Q

How do you get a male calico cat? (What are the sex chromosomes)?

A

XXY

86
Q

Changing ______ _______ to turn _____ _________ on or off is considered an epigenetic mechanism.

A

chromatin structure

gene expression

87
Q

What is genomic imprinting? What is this considered?

A

silencing of one allele of certain genes

considered as an epigenetic mechanism

88
Q

When does genomic imprinting occur?

A

during the formation of the gametes

89
Q

IMPORTANT: Genomic imprinting is NOT associated with _____ _______.

A

sex linkage

90
Q

What are four alterations of chromosome structure?

A

deletion, duplication, inversion, translocation

91
Q

What is deletion?

A

removes a chromosomal segmet

92
Q

What is duplication?

A

repeats a chromosomal segment

93
Q

What is inversion?

A

reverses a segment WITHIN a chromosome

94
Q

What is translocation?

A

moves a segment from one chromosome to a nonhomologous chromosome

95
Q

Translocation generations novel fusion proteins:

(HINT: 2 of them)

A

BCR:ABL
kinase that controls cell-cycle

96
Q

What causes cells to become different from one another (e.g. liver cell v.s. brain cell)?

A

differential gene expression

***most cells are composed of the same genes/DNA content

97
Q

How does differential gene expression occur?

A

each stage is a potential control point for gene expression and ultimately protein function

98
Q

What is chromatin? Where is it found?

A

a complex of DNA and protein

found in the nucleus of eukaryotic cells

99
Q

What are histones?

A

proteins that are responsible for the first level of DNA packing in chromatin

100
Q

What is heterochromatin?

A

densely arranged/condensed chromatin (10nm fiber)

101
Q

What is euchromatin?

A

loosely arranged chromatin (10nm fiber)

102
Q

DNA wraps around ____ histones. This complex is called a ______________.

A

8, nucleosome

103
Q

Most chromatin is ________ packed in the nucleus during interphase. Which type of chromatin is this?

A

loosely, euchromatin

104
Q

During interphase, what regions of chromatin are condensed? This type of chromatin is called…?

A

centromeres and telomeres

called heterochromatin

105
Q

What are the effects of the dense packing of heterochromatin?

A

difficult for the cell to express genetic information coded in these regions

106
Q

What phase does heterochromatin form?

A

metaphase of mitosis

107
Q

What charge are histone tails? Why?

What component of the tail causes this?

A

positive charge, attracts DNA (negatively charged)

lysines

108
Q

What is histone acetylation?

A

the addition of acetyl groups to be positively charged lysines in histone tails

109
Q

What are subject to histone acetylation?

A

histone tails, specifically the lysines

110
Q

What does histone acetylation do?

A

loosens chromatin structure –> promoting initiation of transcription

111
Q

What is the underlying mechanism for genomic imprinting?

A

DNA methylation

112
Q

What is DNA methylation? What does this process do?

A

CH3 is attached to the promotor region of the DNA molecule

inactivates DNA long-term

113
Q

How does DNA methylation inactivate DNA?

A

prevents RNA polymerase II and transcription factors from transcribing/attaching by adding CH3 to the promoter region of the DNA

114
Q

Control elements are ________ (or _________) of the promotor region.

A

before, upstream

115
Q

What is a distal control element? What’s the other name?

A

region of DNA that is far from the promoter region that allows for the regulation of gene expression by the binding of transcription factors

other name: enhancers

116
Q

What is a proximal control element?

A

region of DNA that is close to the promoter region that allows for the regulation of gene expression by the binding of transcription factors

117
Q

What are general transcription factors?

A

transcription factors that are essential to ALL trasncription

118
Q

What are specific transcription factors?

A

activators, repressors

119
Q

What is an activator?

A

a protein (transcription factor) that binds to an enhancer and stimulates transcription

120
Q

What are the two domains of an activator?

A

1 binds to DNA and 2nd activates transcription

121
Q

Bound activators facilitate a sequence of ________ - ________ _________________ that result in transcription of a given gene.

A

protein-protein interactions

122
Q

What are repressors?

A

transcription factors that block transcription of a gene

123
Q

What are the steps of the formation of an active transcription initiation complex? (HINT: activator)

A
  1. activator proteins bind to enhancer
  2. DNA-bending protein binds and transcription factors bind to promoter
  3. formation of active transcription initiation complex
124
Q

What allows for cell-type specific transcription? (HINT: 2)

A
  1. particular combination of control elements in an enhancer region associated with a gene
  2. available activators (specific to the cell) to interact with the enhancer regions
125
Q

Each gene has different _____________ ______________ ______________, which activates the transcription that gene.

A

required transcription factors

126
Q

What does post-transcriptional regulation allow the cell to do?

A

allows the cell to fine-tune gene expression rapidly in response to environmental changes

127
Q

What is the relationship between the size of the genome and the complexity of the organism?

A

no relationship

128
Q

What is alternative RNA splicing? What are the results of this process?

A

cell regulates what exons are and are not spliced

creates proteins that are similar but functionally different/distinct proteins
increases complexity in organisms

129
Q

What is mRNA degradation initiated by?

A

shortening of the poly-A tail and the removal of 5’ cap

130
Q

What is mRNA degradation? What facilitates this process?

A

degrade mRNA that is no longer required in the cell

nuclease enzymes chew up mRNA

131
Q

Why does bacteria have shorter mRNA half lives than eukaryotes?

A

single celled, short half life allows for adaption to changes in environment quickly

eukaryotes are multicellular, carry our environments with us

132
Q

Regulator PROTEINS bind to what part of the DNA? What do these proteins do?

A

5’ UTR (untranslated region)

prevents attachment of ribosomes

133
Q

What aspects of protein processing are subject to control/regulation?

A

cleavage and addition of chemical groups

134
Q

What are proteasomes?

A

giant protein complexes that bind protein protein molecules and degrade them

135
Q

How are proteins recognized by proteasomes?

A

tagged with ubiquitin

136
Q

What is an example of protein degradation?

A

Cdk regulation in the cell cycle

137
Q

What does hemizygous mean?

A

expression of a gene that is only present on one chromosome

Bio Final (Lec 20-27) (1 decks)

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