Chapter 3 - Genetics Flashcards
1
Q
genetics
study of..
A
how traits are inhereted from one generation to the next
2
Q
basic unit of heredity
A
gene
3
Q
genes composed of
A
4
Q
genes are located on the
A
5
Q
alleles
A
genes existing in more than one form
6
Q
genotype
A
genetic makeup of an individual
7
Q
phenotype
A
physical manifestation of genotype
8
Q
phenotypes can correspond to a single or several of these
A
genotypes
9
Q
Gregor Mendel
A
1860s
basic principles of genetics
garden pea experiments
10
Q
garden pea experiment
A
inheritance of individual pea traits by performing genetic crosses
11
Q
genetic crosses
mendel’s pea experiments
A
true-breeding individuals with different traits
mated them
statistically analyzed inheretance of traits in progeny
12
Q
mendel’s first law
A
law of segregation
13
Q
mendel’s four postulates of inheritance
(law of segregation)
A
- genes exist in alternative forms (alleles)
- organism has two alleles for each inherited trait, one from each parent
- two alleles segregate during meiosis —> gametes carry one allele for any given trait
- two alleles in individual are different - only one expressed, other is silent
14
Q
dominant allele
A
allele which is expressed
15
Q
recessive allele
A
allele which is silent in presence of dominant allele
16
Q
homozygous
A
organisms that contain two copies of same allele
homozygous for that trait
17
Q
heterozygous
A
organisms that carry two different alleles
18
Q
Mendel’s law of dominance
A
dominant allele appears in phenotype
19
Q
monohybrid cross
(mendel’s first law - law of segregation)
A
only one trait studied in particular mating
(i.e. color)
20
Q
Parental or P Generation
(mendelian genetics)
A
individuals being crossed
21
Q
filial / F generation
A
progeny generations
22
Q
Punnett Square Diagram
(Mendel’s First Law - Law of Segregation)
A
used to predict genotypes expected from a cross
23
Q
Testcross
Reasoning
(Mendel’s First Law - Law of Segregation)
A
genotype can only be predicted from recessive phenotype
dominant phenotype - homozygous or heterozygous
24
Q
testcross
used to
A
determine unknown genotype of org with dominant phenotype
25
test cross
(aka back cross)
definition
organism with dominant phenotype of unknown genotype (Ax) crossed with phenotypically recessive organism (genotype aa)
26
results of test cross
P: AA x aa
F1: 100% Aa; 100% dominant phenotype
P: Aa x aa
F1: 50% Aa; 50% dominant phenotype
50% aa; 50% recessive phenotype
27
Mendel's Second Law
Law of independent assortment
28
law of independent assortment
(principle)
law of segregation applies as long as genes are on separate chromosomes and assort independently
genes on same chromosomes stay together unless crossing over occurs
29
law of independent assortment
dihybrid cross
P generation:
purple flower tall pea plant (TTPP)
x
white flowered dwarf pea plant (ttpp)
F1 progeny - TtPp genotype
dominant phenotype
30
crossing over
(application to law of independent assortment)
crossing over may break linkage of certain pattern
i.e. redheads + freckles; sometimes blondes have freckles
31
Dihybrid Cross
F1 Generation
F1 Generation self crossed
TtPp x TtPp
4 phenotypes
9:3:3:1
(sorts as it would in monohybrid:
3:1 ratio favor dominant)
32
Non-Mendelian Inheritance
Complications with Mendelian
Genotype doesn't translate into phenotype 100%
not 100% of recessive phenotype have 100% recessive genotype
33
Incomplete Dominance
(complications with mendelian genetics)
phenotype of heterozygote is intermediate of phenotypes of homozygotes
34
incomplete dominance
example:
snapdragon flowers
P: RR x rr
(red x white)
F1 genotypic ratio: 100% Rr
F1 phenotypic ratio: Rr = pink
F1: Rr x Rr
(pink x pink)
F2 genotypic ratio: 1 RR: 2 Rr: 1 rr
F2 phenotypic ratio: 1 red: 2 pink: 1 white
35
Codominance
| (non-mendelian inheritance)
multiple alleles exist for given gene
more than one is dominant
each dominant allele fully dominant when combined with recessive
two dominant alleles:
phenotype is result of expression by both dominant alleles simultaneously
36
Codominance
example:
ABO blood groups
Blood type determined by three alleles:
IA, IB, i
only 2/3 allele present in individuals
all alleles present in human population
IA, IB - dominant
i - recessive
IAIA or IAi - blood type A
IBIB or IBi - blood type B
ii - blood type O
IAIB - blood type AB
37
Sex Determination
| (Mendelian genetics)
for every mating event, 50% chance boy, 50% girl
38
autosomes
non sex chromosomes
22/23 chromosome pairs
39
sex chromosomes
1/23 pairs
determine sex of organism
females - XX
males XY
40
gender determination
females produce only X chromosome
male determine gender of zygote - produce X or Y
41
sex linked chromosomes
genes located on X or Y chromosomes
42
most sex linked chromosomes carried on the ___ chromosome
X chromosome
43
Sex Linkage
(Mendelian Genetics)
recessive genes carried on X chromosome will produce recessive phenotype in males
(only one X)
no dominant allele present to mask
recessive phenotype much more common in males
44
examples of sex linked recessives
hemophilia
color-blindness
45
sex-linkage inheritance
affected males pass on trait to all daughters (X), no sons (Y)
can be passed from father to grandson via carrier daughter
46
Drosophila melanogaster
helped provide explanations for mendelian genetic patterns
advantages for genetic research
47
Advantages of Drosophila melanogaster for genetic research
(5)
* reproduce often (short life cycle)
* reproduce large numbers
* large chromosomes
* few chromosomes (4 pairs; 2n=8
* frequent mutations
48
analyses of D. melanogaster led to discoveries
(2)
pattners of embryological dev.
how genes expressed in early dev affect adult organism
49
Environmental Factors
| (Mendelian Genetics)
interaction between environment and genotype produces phenotype
50
Enviornmental factors in genetics and Drosophila
with given set of wings:
crooked wings at low T
straight wings at high T
51
environmental factors in mendelian genetics in Himalayan hare
same color genes
white on warmer parts of body
black on colder parts of body
(if naturally warm parts cooled with ice, hair will grow black)
52
Genetic Problems
chromosome number and structure maybe altered by abnornal cell division
* during meiosis
* by mutagenic agents
53
Nondisjunction
| (genetic problems)
failure of homologous chromosomes to sep. properly during
meiosis I
failure of sister chromatids to separate properly during
meiosis II
54
result of nondisjunction
| (genetic problems)
3 copies of a chromosome - trisomy
(somatic cells - 2N + 1)
1 copy of chromosome - monosomy
(somatic cells - 2N - 1)
55
most monosomies and trisomies result in
spontaneous abortion of embryo early in term
56
nondisjunction may also occur in sex chromosomes, resulting in
extra or missing copies of X and/or Y
57
Chromosomal Breakage
| (genetic problems)
occur spontaneously
or induced by environmental factors
58
environmental factors causing chromosomal breakage
X-rays, mutagenic agents
59
deficiency
(chromosomal breakage - genetic problems)
chromosome that loses fragment
60
Mutations
definition
(genetic problems)
changes in genetic information of a cell
coded in DNA
61
Mutations in somatic cells
can lead to tumors
62
mutations in gametes (sex cells)
transmitted to offspring
63
most mutations occur in regions of DNA that
do not code for proteins
are silent
64
silent regions of DNA
not expressed in phenotype
65
mutations that change the sequence of the amino acids in proteins are most often
recessive
deleterious
66
Mutagenic Agents
| (mutations)
mutagenic agents induce mutations
e.g. cosmic rays
X-rays
UV rays
radioactivity
chemical compounds - colchicine, mustard gas
67
mutagenic agents are generally
| (mutations - genetic problems)
carcinogenic
68
colchicine
(chemical compound - mutagenic agent)
inhibits spindle formation
causes polyploidy
69
polyploidy
cells and organisms containing more than two paired (homologous) sets of chromosomes
70
carcinogenic
any substance directly involved in causing cancer
71
mutation types
| (mutations - genetic problems)
gene
protein
72
gene mutation
nitrogen bases
added
deleted
subsituted
thus creating different genes
73
protein mutations
incorrect amino acid inserted in polypeptide chain
mutated protein produced
74
mutation
definition
genetic error with wrong/no base on DNA at particular position
75
examples of genetic disorders
phenylketonuria (PKU)
sickle-cell anemia
76
phenylketonuria (PKU)
definition
autosomal recessive
genetic disorder
molecular disease
77
PKU caused by
inability to produce proper enzyme for metabolism of phenylanine
78
result of PKU
degradation product (phenypyruvic acid) accumulates
can affect mental development
79
Sickle-cell anemia
definition
red blood cells become crescent-shaped because contain defective hemoglobin
80
sickle cell hemoglobin characteristic
carries less oxygen
81
sickle cell anemia caused by
substitution of valine (GUA or GUG)
for glutamic acid (GAA or GAG)
due to single base pair substitution in gene coding for hemoglobin
82
Molecular Genetics
DNA is basis for heredity
self-replication ensures that coded sequence will be passed on to successive generations
83
genes composed of
DNA
84
DNA contains
information coded in sequence of base pairs
85
DNA provides
blueprint for protein synthesis
86
DNA reproduces via
self replication
87
DNA's ability to self-replicate is crucial for
cell division ---\> reproduction
88
mutable
DNA is mutable and can be altered
89
Changes in DNA and evolution
changes in DNA are stable and can be passed on from gen to gen ---\> evolution
90
CUT PIE
cytosine, uracil, thymine
are
PYrimidines
91
PURe As Gold (Ag)
Adenine and Guanine are Purines
92
basic unit of DNA
| (structure of DNA)
nucleotide
93
composition of nucleotide
deoxyribose (sugar)
bonded to:
phosphate group
nitrogenous base
94
two types of nitrogen bases
purines
pyrimidines
95
purines in DNA
adenine
guanine
96
pyrimidines in DNA
Cytosine
Thymine
Uracil
97
backbone of nucleotide
phosphate group and sugar (deoxyribose)
98
bases arranged as (on chain)
side groups
99
physicality of DNA
double-stranded helix
100
composition of double-stranded helix
sugar phosphate on outside
base pairs on inside
101
hydrogen bonding in double-stranded helix
base pairs are attracted by hydrogen bonds
2 hydrogen bonds between A = T
3 hydrogen bonds between C = G
the more C=G pairs, the tighter the two strands are bound
102
base pairing forms
"rungs" on interior of double helix
links two polynucleotide chains together
103
Watson-Crick DNA Model
double-standed helix
sugar phosphate backgone
nucleotide base pairs inside
A-T; C-G
base pairs bonded via hydrogen bonding
holds together polynucleotide chains
104
DNA replication
| (function of DNA)
double-stranded DNA unwinds
separates into two single strands
each strand template for complementary base-pairing
synthesis of two new daughter helices proceeds
105
each new daughter helix contains
| (DNA replication)
strand from parent helix
newly synthesized complementary strand
106
semiconservative
| (DNA replication)
in reference to new daughter helices complementary to parent helices
107
daughter helices are identical to
each other
parent helix
108
Language of DNA
Genetic Code
(fxn of DNA)
A,T,C,G
109
language of proteins
genetic code
20 amino acids
110
to form amino acids, DNA translated by
mRNA
111
triplet code
amino acid codons
64 different codons coding 20 amino acids
112
base sequence of mRNA translated to
codons
series of triplets
113
composition of codons
sequence of three consecutive bases
codes for particular amino acids
e.g. GGC - glycine
GUG - valine
114
genetic code is universal!
genetic code is universal!
for all organisms
115
codon possibilities
64 codons based on triplet code
20 amino acids to code for
redundancy
116
redundant codons
64 codons
20 amino acids
codon synonyms
multiple codons code for the same amino acid
each codon codes for only one amino acid
117
degeneracy
or
redundancy
of the genetic code
property of 64 codons coding for 20 amino acids
118
AUG
start codon
Met (Methionine)
119
stop codons
UAA
UGA
120
RNA
| (molecular genetics)
ribonucleic acid
polynucleotide structurally similar to DNA
121
RNA structure
similiar to DNA
sugar = ribose
contains uracil (U) instead of thymine (T)
usually single stranded
122
RNA found in
nucleus
cytoplasm
123
main types of RNA
mRNA
tRNA
rRNA
124
all types of RNA are involved in some aspect of
protein synthesis
125
mRNA
messenger RNA
fxn
carries complement of a DNA sequence and transports it from nucleus to ribosomes
(ribosomes = sight of protein synthesis)
126
mRNA structure
composed of ribonucleotides complimentary to "sense" strand of DNA
"inverted" complmenentary of original master DNA
e.g.
DNA - AAC (valine)
mRNA - UUG
127
monocistronic
one mRNA strand codes for one polypeptide
128
tRNA
transfer RNA
found in
cytopolasm
129
tRNA
fxn
aids in translation of mRNA's nucleotide code into sequence of amino acids
brings amino acids to ribosomes during protein synthesis
130
tRNA quantity
40 known types
at least one type of tRNA for each amino acid
131
rRNA
ribosomoal RNA
structural component of ribosomes
132
most abundant RNA
rRNA
133
site of rRNA synthesis
nucleolus
134
Protein Synthesis
2 events
Transcription
Translation
135
Transcription
information coded in base sequence of DNA transcribed into strand of mRNA
136
DNA is transcribted into mRNA in the \_\_\_\_
then mRNA \_\_\_\_
nucleus
leaves nucleus through nuclear pores
137
Translation
site
(protein synthesis)
cytoplasm
138
translation process
mRNA codons translated into sequence of amino acids
involves tRNA, ribosomes, mRNA, amino acids, enzymes, other proteins
139
tRNA function
| (translation)
brings amino acids to ribosomes in correct sequence for polypeptide synthesis
140
in translation, tRNA recognizes
both amino acid and mRNA codon
dual function
141
tRNA structure
reflects function
one end:
contains anticodon - 3 nucleotide sequence
complimentary to one of the mRNA codons
other end:
site of amino acid attachment
142
aminoacyl-tRNA synthetase
has active site that binds to amino acid and corresponding tRNA
forms aminoacyl-tRNA
143
ribosomes
structure
two subunits - one large, one small
consits of proteins and rRNA
subunits bind together only during protein synthesis
144
ribosome binding sites
| (3)
1. mRNA
2. P site - tRNA
3. A site - tRNA
145
p site
tRNA ribosome binding site
peptidyl-tRNA binding site
binds to tRNA attached to growing polypeptide chain
146
A site
tRNA
ribosome binding site
aminoacyl-tRNA complex binding site
binds to incoming aminoacyl-tRNA complex
147
polypeptide synthesis
stages
initiation
elongation
termination
148
initiation
| (translation)
1. ribosome binds to mRNA near 5' end
ribosome scans mRNA until binds to start codon (AUG)
2. initiator aminoacyl-tRNA complex, methionin-tRNA (anticodon 3'-UAC-5') base pairs with start codon
149
elongation
| (translation)
1. hydrogen bonds form between mRNA codon in A site and its complementary anti-codon on incoming aminoacyl-tRNA complex
2. peptide bond formed between amino acid attached to tRNA in A site and met attached to tRNA in P site
3. ribosome carries uncharged tRNA in P site and peptidyl-tRNA in A site
4. translocation - ribsoome advances 3 nucleotides along mRNA in 5'--\>3'
5. uncharged tRNA in P site expelled and peptidyl-tRNA from A site moves onto P site
6. ribosome has empty A site ready for entry of aminoacyl-tRNA corresponding to next codon
150
translocation
(translation - elongation)
ribsome advances 3 nucleotides along mRNA in 5'--\>3'
151
termination
| (translation)
1. stop codon arrives in A site
2. signal ribsoome to terminate translation
3. DO NOT CODE FOR AMINO ACIDS
4. frequently, polyribosome formed
152
polyribosome formation
(translation - termination)
many ribosomes simultaneously translate a single mRNA molecule forming a polyribosome
occurs during termination
153
protein primary formation following termination
upon release from ribosome, protein immediately assumes conformation
conformation determined by primary sequence of amino acids
154
Cytoplasmic Inheritance
| (molecular genetics)
heredity systems exist outside nucleus
DNA found in chloroplasts, mitochondria etc
cytoplasmic genes interact with nuclear genes ---\> determine characteristics of organelles
155
plasmids
| (cytoplasmic inheritance)
cytoplasmic DNA
contain 1+ genes
regulate drug resistance in micro-organisms
156
Bacterial genome
structure and location
(Bacterial genetics)
single circular chromosome located in nucleoid
may also contain plasmids
157
plasmids
| (bacteria)
small circular rings of DNA
contain accessory genes
158
episomes
plasmids
capable of intergraiton into bacterial genome
159
replication
| (bacterial genetics)
begins at unique origin
proceeds in both directions simultaneously
160
Genetic Variance
3 mechanisms
(bacterial genetics)
transformation
conjugation
transduction
161
method of bacterial replication
binary fission
162
binary fission
method of bacteria cells replication
asexual process
163
transformation
(genetic variance - bacterial genetics)
foreign chromosome fragment (plasmid) incorporated into bacterial chromosome
via recombination
164
conjugation
genetic variance - bacterial genetics
"sexual mating" in bacteria
transfer of genetic material between two bacteria that are temporarily joined
165
conjugation
mechanism
genetic variance
bacterial genetics
cytoplasmic conjugation bridge formed between two cells
genetic material transferred from donor male (+) to recipient female (-)
bacteria must contain plasmids - sex factors
166
Sex Factor
F factor
Conjugation
Genetic Variation
Bacterial Genetics
present in E. coli
bacteria possessing it - F+
bacteria void - F-
during conjugation bw F+/F-
F+ replicates F factor, donates copy to recipient --\> converts to F+
167
Sex Factor and transfer
Conjugation
Genetic Variance
Bacterial Genetics
genes that code for various characteristics
e.g. antibody resistance
may be found on plasmids and transferred to recipient cells along with sex factors (i.e. F+)
168
Consequences of Conjugation + Sex factors
sex factor may become integrated into bacterial genome
during - entire bacterial chromosome replicates and begins to move from donor cell to recipient cell
conjugation bridge breaks before entire chromosome transferred
bacterial genes may recombine with bacteria genes already present to form novel genetic combinations
169
170
Hfr cells
bacterium with a conjugative plasmid (often the F-factor) integrated into its genomic DNA
171
Transduction
(genetic variation - bacterial genetics)
fragments of bacterial chromosome accidentally become packaged into viral progeny produced during viral infection
virions may infect other bacteria
introduce new genetic arrangements through recombination with the new host cell's DNA
the closer two genes are to one another on a chromosome the mroe likely they will be to transduce together
172
Recombination
genetic variation - bacterial genetics
occurs when linked genes are separated
via breakage and rearrangements of adjacent regions of DNA
when organisms carrying different genes or alleles for the same traits are crossed
173
regulation of gene expression allows prokaryotes to control their
metabolism
174
regulation of transcription is based on accessiblity of
RNA polymerase
175
RNA polymerase
enzyme
3' ---\>
necessary for constructing RNA chains using DNA genes as templates (transcription)
176
gene regulation enables...
| (bacterial genetics)
prokaryotes to control metabolism
177
another word for gene expression
| (bacterial genetics)
transcription
178
regulation of transcription based on..
(bacterial genetics)
accessbility of RNA polymerase to the genes being transcribed
179
regulation of transcription directed by..
(bacterial genetics)
operon
180
operon
| (bacterial genetics)
consists of
structural genes
operator gene
promoter gene
181
structural genes
sequences of DNA that code for proteins
182
operator gene
sequence of nontranscribable DNA
repressor binding site
183
repressor
DNA-binding protein
regulates the expression of one or more genes
binds to the operator and blocks the attachment of RNA polymerase to the promoter
preventing transcription of the genes
184
promoter
noncoding sequence
intial binding site for RNA polymerase
185
regulator gene
codes for synthesis of a repressor molecule
186
in order to transcribe structural genes, RNA polymerase must
move past operator
187
regulatory systems function
prevent or permit RNA polymerase to pass on to structural genes
188
modes of regulation
inducible systems
repressible systems
189
inducible system
basic
(transcription - bacterial genetics)
require presence of inducer
190
repressible system
basic
(transcription - bacterial genetics)
in constant state of transcription
unless corepressor inhibits
191
inducible systems
mechanism
repressor binds to operator
forms barrier that prevents RNA polymerase from transcribing structural genes
