Lec 20-23 Flashcards
1
Q
What is a gene?
A
a discrete unit of hereditary information consisting of a specific sequence of DNA
2
Q
What is genetics?
A
the study of heredity and hereditary variation
3
Q
What is inheritance?
A
the process by which genetic information is passed from parent to offspring
4
Q
Modern genetics began with _______ _______’s quantitative experiments with _______ _______.
A
Gregor Mendel
pea plants
5
Q
What are some model organisms?
A
yeast, drosophila, mouse, rhesus, aplysia, rat
6
Q
What is a character?
A
an observable heritable feature
7
Q
What is a trait?
A
any detectable variation in a genetic character
8
Q
Why was studying pea plants the best choice?
A
pea plant characteristics (purple/white pigment) is dependent on one gene
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
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
11
Q
In Mendel’s experiment, the parental generation (P) consisted of…?
A
purple and white flowers of pea plants
12
Q
In Mendel’s experiment, what happened to the flowers in the first generation offspring (F1)?
A
all purple flowers
13
Q
In Mendel’s experiment, what happened to the flowers in the second offspring generation (F2)?
A
reappearance of white flowers
14
Q
In Mendel’s experiment, what was the ratio of purple to white pea plant flowers?
A
3/4 purple, 1/4 white
15
Q
What hypothesis did Mendel’s experiment support?
A
particulate theory/hypothesis
16
Q
The gene for flower color (in pea plants) comes in two versions, called ______.
A
alleles
17
Q
Offspring inherit _____ _____ from each parent.
A
one allele
18
Q
The ___________ ______ determines the pea plant flower’s appearance.
A
dominant allele
19
Q
What are alleles?
A
alternative forms of a gene
20
Q
Where are alleles at?
A
at the same locus on homologous chromosomes
21
Q
What are the two laws that Mendel discovered?
A
the law of segregation and the law of independent assortment
22
Q
What is the law of segregation?
A
2 alleles for each character segregate into different gametes
23
Q
Different alleles do NOT ________ with each other.
A
interact
24
Q
What phase does the law of segregation occur in?
A
Anaphase I
25
What does the test cross determine?
whether or not a dominant phenotype is homozygous dominant or heterozygous
26
What do you do in the test cross? Explain the results
cross the dominant phenotype (with an unknown genotype) with a recessive phenotype (known genotype)
all purple: homozygous
1/2 purple, 1/2 white: heterozygous
27
What was Mendel's seed experiment trying to determine?
whether or not two characters (color and smoothness) were inherited dependently or independently
28
What is the law of independent assortment?
each pair of alleles segregates independently of other pairs during gamete formation
29
What is the ratio for independent assortment?
9 : 3 : 3 : 1
30
What phase does the law of independent assortment occur in?
metaphase I
31
When does independent assortment NOT hold true?
What is the exception to this?
NOT true when 2 characters are on the same chromosome
if 2 characters are far enough apart, a crossing over event occurs
32
What is the multiplication rule?
when trying the calculate the probability of a single genetic event
33
What is the addition rule?
when trying to calculate probability of MORE than 1 mutually exclusive genetic event
34
Some inheritance patterns are more ________ than predicted by simple __________ genetics.
complex
Mendelian
35
What are the examples of inheritance patterns that are more complex?
incomplete dominance
co-dominance
pleiotropy
epistasis
polygenic inheritance
environmental impact
36
What is incomplete dominance?
2 dominant alleles, one is NOT dominant over the other
37
What is an example of incomplete dominance in plants? What is the ratio that was produced?
flower color of snapdragons
Crossing between red x white -->
F1 produced: 25% white, 25% red, and 50% pink offspring
38
What is an example of incomplete dominance in humans?
hypercholesterolemia
HH: ability to make LDL receptors
Hh: an intermediate
hh: inability to make LDL receptors
39
What is co-dominance?
multiple alleles (normally two) affect the phenotype in separate, distinguishable ways
40
What is an example of co-dominance?
blood type
IA and IB are co-dominant, both are dominant over i
41
What is pleiotropy?
when a gene affects more than one phenotypic character
42
What is example of pleiotropy?
the wide-ranging symptoms of sickle-cell disease due to a single gene (change in 1 base)
43
What are the inheritance patterns associated with a SINGLE GENE?
dominance relationships, multiple alleles, pleiotropy
44
What are the inheritance patterns associated with TWO OR MORE genes determining a phenotype?
epistasis, polygenic inheritances
45
What is epistasis?
when a gene at one locus alters the phenotypic expression of a gene at a second locus
46
What is an example of epistasis? What is the ratio?
(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
47
What is polygenic inheritance?
when a character is influenced by two or more genes
48
What is an example of polygenic inheritance? What is the result?
skin color
produce offspring covering a wide range of shades
49
(In polygenic inheritance) The range of phenotypes forms a _______ _______.
normal distribution
50
What is the norm of reaction?
a range of phenotypic possibilities
51
What is the norm of reaction determined/influenced by?
environmental factors
52
Norms of reactions are broadest for _________ _________.
polygenic characters
53
Changing chromatin structure to turn _____ _________ on or off is considered an ________________ mechanism.
gene expression
epigenetic
54
What phrase is associated with epigenetics?
"beyond your genes"
55
What is epigenetics?
a change in gene expression that is not due to a change in the DNA sequence
56
What is the epigenome?
collection of epigenetic tags
57
Epigenetic "tags" change with _________ , _________ _________ , and even our _______!
experiences, environmental interaction, diet
58
What are two examples of epigenetics, specifically about the impact of diet?
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
In epigenetics, what happens when there are and there aren't "tags"?
normal (with tags): no gene expression
abnormal (without tags): gene expression
60
Genetic traits in humans can be tracked through ______ _______.
family pedigrees
61
What are two examples of a dominant trait? (HINT: one of them is a disorder)
polydactyly, Huntington's disease
62
Why is there such a difference in the incidence of colorblindness between males and females?
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
What was Thomas Morgan's experiment? (HINT: flies)
cross between red-eyed (dom) female with white-eyed (recess) male
64
What were the results of Thomas Morgan's experiment? Give the ratio. What did he conclude of this?
white-eye trait showed up only in males
3 red : 1 white
concluded that fly's eye color is linked to its sex
65
Morgan hypothesized that the eye color gene is located on the ___ __________.
X chromosome
66
What was the overall conclusion from Thomas Morgan's experiment?
provided evidence that a specific gene is carried on a specific chromosome
67
Genes located on a ____ __________ exhibit unique inheritance patterns.
sex chromosome
68
What are linked genes? What is the exception?
genes located on the same chromosome that tend to be inherited together in genetic crosses
exception: sex- or X-linked genes
69
What is the significance of Thomas Morgan's experiment concerning fly body color and wing size?
small number of NONPARENTAL phenotypes indicated that some mechanism occasionally breaks the linkage between genes on the same chromosome
70
What mechanism breaks the linkage between genes on the same chromosome?
crossing over
71
The percentage of recombinant offspring (the _______ _______) is related to the ________ between linked genes.
recombinant frequency
distance
72
The occasional production of recombinant gametes during __________ ___ accounts fr the occurrence of reccombinant phenotypes in Morgan's testcross.
prophase I
73
What is a linkage map?
shows the relative locations of genes along a chromosome
74
Genes located far apart on a chromosome are mapped by adding the _________ _________ between the ________ genes and the _________ genes.
recombination frequencies
distant, intervening
75
The true recombination frequency of distant genes is less than the added frequencies of the intervening genes (closer). Why is this the case?
**check lec. 22, slide 15
further the distance could mean two crossing over events occuring (flip once and back again) --> decrease in frequency
76
What was Strurtevant and his colleagues able to do? What was the result of this?
map linear positions of genes in Drosphila into four groups (one for each chromosome)
result: supported the chromosome theory of inheritance
77
The sex of an offspring depends on what?
whether the sperm cell contains an X chromosome or a Y
78
What is an example of the transmission of X-linked recessive traits?
color blindess
79
Is the male or female usually the carrier of X-linked recessive traits?
females
80
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?
by shutting off one X-chromosome (Barr body)
81
During female development, one X chromosome per cell condenses into a compact object called a _______ _____.
Barr body
82
Where is the condensed Barr body reactivated?
in ovarian cells that produce ova
83
What happens to a female who is heterozygous for a sex-linked trait? What is an example of this?
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
What's an example in cats of Barr body dependent inheritance patterns?
tortoiseshell cats
cell 1: orange allele expressed in one (black is Barr body)
cell 2: black allele is expressed (orange is Barr body)
85
How do you get a male calico cat? (What are the sex chromosomes)?
XXY
86
Changing ______ _______ to turn _____ _________ on or off is considered an epigenetic mechanism.
chromatin structure
gene expression
87
What is genomic imprinting? What is this considered?
silencing of one allele of certain genes
considered as an epigenetic mechanism
88
When does genomic imprinting occur?
during the formation of the gametes
89
IMPORTANT: Genomic imprinting is NOT associated with _____ _______.
sex linkage
90
What are four alterations of chromosome structure?
deletion, duplication, inversion, translocation
91
What is deletion?
removes a chromosomal segmet
92
What is duplication?
repeats a chromosomal segment
93
What is inversion?
reverses a segment WITHIN a chromosome
94
What is translocation?
moves a segment from one chromosome to a nonhomologous chromosome
95
Translocation generations novel fusion proteins:
(HINT: 2 of them)
BCR:ABL
kinase that controls cell-cycle
96
What causes cells to become different from one another (e.g. liver cell v.s. brain cell)?
differential gene expression
***most cells are composed of the same genes/DNA content
97
How does differential gene expression occur?
each stage is a potential control point for gene expression and ultimately protein function
98
What is chromatin? Where is it found?
a complex of DNA and protein
found in the nucleus of eukaryotic cells
99
What are histones?
proteins that are responsible for the first level of DNA packing in chromatin
100
What is heterochromatin?
densely arranged/condensed chromatin (10nm fiber)
101
What is euchromatin?
loosely arranged chromatin (10nm fiber)
102
DNA wraps around ____ histones. This complex is called a ______________.
8, nucleosome
103
Most chromatin is ________ packed in the nucleus during interphase. Which type of chromatin is this?
loosely, euchromatin
104
During interphase, what regions of chromatin are condensed? This type of chromatin is called...?
centromeres and telomeres
called heterochromatin
105
What are the effects of the dense packing of heterochromatin?
difficult for the cell to express genetic information coded in these regions
106
What phase does heterochromatin form?
metaphase of mitosis
107
What charge are histone tails? Why?
What component of the tail causes this?
positive charge, attracts DNA (negatively charged)
lysines
108
What is histone acetylation?
the addition of acetyl groups to be positively charged lysines in histone tails
109
What are subject to histone acetylation?
histone tails, specifically the lysines
110
What does histone acetylation do?
loosens chromatin structure --> promoting initiation of transcription
111
What is the underlying mechanism for genomic imprinting?
DNA methylation
112
What is DNA methylation? What does this process do?
CH3 is attached to the promotor region of the DNA molecule
inactivates DNA long-term
113
How does DNA methylation inactivate DNA?
prevents RNA polymerase II and transcription factors from transcribing/attaching by adding CH3 to the promoter region of the DNA
114
Control elements are ________ (or _________) of the promotor region.
before, upstream
115
What is a distal control element? What's the other name?
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
What is a proximal control element?
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
What are general transcription factors?
transcription factors that are essential to ALL trasncription
118
What are specific transcription factors?
activators, repressors
119
What is an activator?
a protein (transcription factor) that binds to an enhancer and stimulates transcription
120
What are the two domains of an activator?
1 binds to DNA and 2nd activates transcription
121
Bound activators facilitate a sequence of ________ - ________ _________________ that result in transcription of a given gene.
protein-protein interactions
122
What are repressors?
transcription factors that block transcription of a gene
123
What are the steps of the formation of an active transcription initiation complex? (HINT: activator)
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
What allows for cell-type specific transcription? (HINT: 2)
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
Each gene has different _____________ ______________ ______________, which activates the transcription that gene.
required transcription factors
126
What does post-transcriptional regulation allow the cell to do?
allows the cell to fine-tune gene expression rapidly in response to environmental changes
127
What is the relationship between the size of the genome and the complexity of the organism?
no relationship
128
What is alternative RNA splicing? What are the results of this process?
cell regulates what exons are and are not spliced
creates proteins that are similar but functionally different/distinct proteins
increases complexity in organisms
129
What is mRNA degradation initiated by?
shortening of the poly-A tail and the removal of 5' cap
130
What is mRNA degradation? What facilitates this process?
degrade mRNA that is no longer required in the cell
nuclease enzymes chew up mRNA
131
Why does bacteria have shorter mRNA half lives than eukaryotes?
single celled, short half life allows for adaption to changes in environment quickly
eukaryotes are multicellular, carry our environments with us
132
Regulator PROTEINS bind to what part of the DNA? What do these proteins do?
5' UTR (untranslated region)
prevents attachment of ribosomes
133
What aspects of protein processing are subject to control/regulation?
cleavage and addition of chemical groups
134
What are proteasomes?
giant protein complexes that bind protein protein molecules and degrade them
135
How are proteins recognized by proteasomes?
tagged with ubiquitin
136
What is an example of protein degradation?
Cdk regulation in the cell cycle
137
What does hemizygous mean?
expression of a gene that is only present on one chromosome
