Chapter 9- Genetics Flashcards
1
Q
Genetics
A
The study of how traits are inherited from one generation to the next
2
Q
Where are genes located?
A
Chromosomes
3
Q
Alleles
A
An alternative form of a gene
4
Q
Genotype
A
Genetic makeup of an individual
5
Q
Phenotype
A
Physical manifestation of the genetic makeup
6
Q
What is Mendel’s first law?
A
Law of segregation
7
Q
Mendel’s 4 principles of inheritance
A
- Genes exist in alternative forms
- Gene= 2 alleles, one from each parents
- Two alleles segregate through meiosis- gametes only carry one allele for one given trait
- Dominant and recessive alleles
8
Q
What does true breeding mean in terms of Mendelian genetics?
A
organism must be homozygous for every trait for which it is considered true breeding.
9
Q
How many traits can be tested by a monohybrid cross at a time?
A
One at a time
10
Q
P generation
A
Parental generation- the individual being crossed
11
Q
F generation
A
Filial generation- Progeny of the parental generation
12
Q
Crossing one homozygous dominant and one homozygous recessive results in a f2 generation of
A
1:2:1
1 Homozygous dominant
2 Heterozygous dominant
1 homozygous recessive
13
Q
Testcross
A
Diagnostic tool to determine genotype of an organism- also known as a backcross
14
Q
When can a genotype be determined with 100% accuracy?
A
When a recessive phenotype is being tested
15
Q
If a dominant phenotype is expressed, the genotype can be either:
A
Homozygous dominant or hetozygous
16
Q
In a testcross, the appearance of the recessive phenotype in the progeny indicates that the phenotypically dominant parent is genotypically ________
A
Heterozygous
17
Q
What is Mendel’s Second law?
A
Law of independent assortment
18
Q
What does the law of independent assortment say?
A
Genes assort independently during the formation of gametes (meiosis)– as long as genes are on separate chromosomes
19
Q
Typical pattern for Mendelian inheritance in a dihybrid cross between heterozygotes with independently assorting traits
A
9:3:3:1
20
Q
Incomplete dominance
A
Blend. White+red= pink
Intermediates of the phenotypes of the homozygotes
21
Q
Codominance occurs when…?
A
Multiple alleles exist for a given gene and more than one allele is dominant. Each dominant allele is fully dominant when combined with a recessive allele but when combined with another dominant allele, they both show through.
22
Q
Classic dominance of codominance
A
Individuals with IA and IB blood are group AB because both IA and IB are dominant
23
Q
Three alleles of ABO blood group
A
IA
IB
i
24
Q
True or false: the two members of each of the chromosome are the exact same shape
A
FALSE. All the autosomal ones are but not the sex chromosomes
25
Central dogma
```
DNA-RNA= transcription
RNA-Proteins= translation
```
26
Nucleotide
The basic structure of DNA- composed of deoxyribose bonded to a phosphate group and a nitrogenous base.
27
Two types of bases
Purines and pyrimidines
28
Purines
Adenine, Guanine
29
Pyrimidines
Cyrosine and thymine
30
The phosphate and sugar form a chain with the bases and are arranged as: ________
side groups off the chain
31
Double stranded helix is arranged with ____
The sugar-phosphate chains on the outside of the helix and the bases on the inside.
32
Nucleotides are bonded by
Hydrogen bonds
33
T always forms __hydrogen bonds with __
G always forms __ hydrogen bonds with __
2 A
3 C
34
Each strand of a double helix acts as a template for ____
complementary base-pairing in the synthesis of two new daughter helices.
35
Semiconservative replication
Each new DNA helix is one old strand and one new
36
Leading strand
Continually synthesized by the DNA polymerase in a 5'-3' direction
37
Lagging strand
Synthesized discontinuously in the 5'-3' direction as okazaki pragments
38
DNA polymerase only synthesized new strands in the ___ direction
5'-3'
39
Codons
The base sequence of mRNA in translation is a series of triplets called codons
40
True or false: the genetic code is universal for almost all organisms?
True
41
How many different codons are possible?
64 but there are only 20 amino acids- hence some codons code for the same amino acids- called degenerate or redundacy of the genetic code
42
How is RNA different the DNA?
- Sugar is ribose
- Contains Uracil instead of thymine
- Single stranded
43
RNA can be found in both___
the nucleus and cytoplasm
44
Types of RNA
mTNA, tRNA, rRNA
45
mRNA
Messenger RNA -Messenger RNA (mRNA) is synthesized from a gene segment of DNA.The messenger RNA carries the code into the cytoplasm where protein synthesis occurs.
46
mRNA is assembled from_____
ribonucleotides that are complementary to strand of DNA
47
One mRNA codes for __ polypedtide
one. This is called monocistronic
48
Is DNA code for amino acid is AAC, the mRNA is ___
UUG
49
tRNA
Transfer RNA- small RNA found in the cytoplasm that aids in the translation of mRNAs nucleotide code into a sequence of amino acids. Brings amino acids to the ribosomes during protein synthesis.
50
There is atleast ___ type of tRNA for each amino acid
1
51
rRNA
Ribosomal RNA is a structure component of ribosomes and is the most abundant type of RNA. Carries the enzymes necessary for protein synthesis
52
Where is rRNA synthesized
Nucleolus
53
Transcription
Process whereby information coded in the base sequence of DNA is transcribed into a strand of mRNA that leaves the nucleus through nuclear pores
54
After transcription, the remaining events of protein synthesis occur in the
cytoplasm
55
Translation
Process whereby mRNA codons are translated into a sequence of amino acids.
56
Translation occurs in the ___ and involves ___, ___, ____, _____________, and ______
tRNA, ribosomes, mRNA, amino acids, and enzymes
57
tRNA recongized both the ___
amino acid and mRNA codon.
58
Anticodon
in the tRNA-- is complementary to one of the mRNA codons
59
Structure of tRNA
one end- anticodon
| Other end- site of amino acid attachment
60
Aminoacyl-tRNA synthetase
On each amino acid. Has an active site that binds to both amino acid and its corresponding tRNA
Catalyzes formation of aminoacyl-rTNA complex
61
Ribosomes are composed of...
two subunits, one large and one small
62
When do the two subunits of a ribosome bind together?
During protein synthesis
63
How many binding sites do Ribosomes have and what are they?
A total of three binding sites
One for mRNA
two for tRNA
64
The two binding sites for tRNA on a ribosome are called what? What are they?
P site- peptidyl-tRNA bdining site
| A site- aminoacyl-tRNA complex binding site
65
P site
binds to the tRNA attached to the growing polypeptide chains
66
A site
Binds to the incoming aminoacyl-tRNA complex
67
E site
where uncharged tRNA leaves
68
3 stages of polypeptide synthesis
1. Initiation
2. Elongation
3. Termination
69
When does synthesis begin?
When the ribosome binds to the mRNA near its 5' end-
70
During initiation, what base pairs with the start codon?
Methionine tRNA
71
What happens during elongation?
Peptide bond is formed between the amino acid attached to the tRNA in the A site and the amino acid attached to the tRNA in the P site
After peptide bond formation, a ribosome carried uncharged tRNA in the P site and peptidyl-tRNA in the A site
Cycle is completed by translocation
72
Translocation
Ribosome advances 3 nucleotides along the mRNA in the 5'-3' direction
The uncharged tRNA from P site is expelled and the peptidyl tRNA from the A site moves into the P side.
Ribosome then has an empty A site ready for entry
73
Nondisjunction
Failure of homologous chromosomes to separate properly during meiosis II
can lead to trisomy or monosomy
74
Trisomy
2N+1
| 3 copies of chromosome
75
monosomy
2N-1
| single copy of chromosome
76
Downs Syndrome is caused by
Trisomy of chromosome 21
77
True or false: nondisjunction of sex chromosomes can also occur
True
78
Chromosomal breakage
occur spontaneously or can be induced by environmental factors such as mutagenics and X rays
79
Mutations
Changes in the genetic information of a cell coded in the DNA
80
Mutations in the somatic cells can lead to
tumors in the individual
81
Mutations that occur in the sex cells/ gametes can be
transmitted to the offspring
82
Most mutations occur in regions of DNA that..
do not code for proteins and are silent, hence not expressed in the phenotype
83
Mutations that do change the sequence of amino acids in proteins are most often ____ and ______
recessive and deleterious
84
Mutagenic agents
induce mutations. Also called carcinogenic
85
Types of mutagenic agents
Cosmic rays, x rays, UV rays, and radtioactivity and colchicine, mustard gas
86
In gene mutation, nitrogen caes are _____, _____, or ______. This alters the__________________
added, deleted or substituted. This alters the amino acid sequence, may produce mutation
87
Point mutation
a nucleic acid is replaced by another nucleic acid- usually involved 1-3 nucleotides. Length of the genome does not change
88
Three possible results on a codon as a consequence of a point mutation
1. The new codon may code for the same amino acid (silent mutation)
2. The new codon may code for a different amino acid (missense mutation)
3. The new codon may be a stop codon (nonsense mutation)
89
Frameshift mutation
Nucleic acids are deleted or inserted int o the genome sequence.
Freq. Lethal
Throws off the entire sequence of codons from that point
Length of genome changes
90
PKU
phenylketonuria- a molecular disease caused by the inability to produce the proper enzyme for the metabolism of phenylalanite
Is a type of hyperphenylaninemia
A degradation product accumulates
Individuals cannot consume food with aspartame
91
Sickle-cell anemia
Red blood cells become cresent-shaped because they contain defective hemoglobin-- which carries less oxygen
92
How is sickle-cell anemia caused?
Substitution of valine for glutamic acid because of a single base-pair substitution in the gene coding for hemoglobin
93
T/F: heredity systems exist outside the nucleus
True. Example: cytoplasmic inheritance
| DNA is found in chloroplasts, mitochondria and other cytoplasmic bodies
94
Plasmids
Cytoplasmic DNA that regulates drug resistance.
contain one or more genes
95
Bacterial genome
Consists of single circular chromosome located in the nucleoid region of the cell
96
True or false: Many bacteria contain plasmids
True
97
What are plasmids in bacteria?
Circular rings of DNA that contain accessory genes
98
Episomes
plasmids that are capable of integration into the bacterial genome
99
Replication of bacterial chromosome begins at a..
Unique origin of replication and proceeds in both directions simultaneously
100
DNA is synthesized in bacteria in the ___' - ___' direction
5' to 3'
101
Binary fission
How bacterial cells reproduce
asexual process
102
Three mechanisms by which bacteria increase genetic variance of a population:
transformation, conjugation, and transduction
103
Transformation
Process by which a foreign chromosome fragment (plasmid) is incorporated into the bacterial chromosome via recombination, creating new inheritable genetic combinations
104
Conjugation
sexual mating in bacteria- transfer of genetic material between two bacteria that are temporarily joined
105
How is genetic material transferred during conjugation?
Conjugation bridge is formed and genetic material is passed between the donor male (+) and recipient female (-)
106
What kind of bacteria are capable of conjugating?
bacteria containing plasmids called sex factors
107
F Factor
in E. Coli bacteria
F+ = bacteria containing this factor
F- = bacteria not containing this factor
During conjugation F+ cell replicated F factor and donates it to F- cells
108
Antibody resistance may be found on the...
plasmids and transferred into recipient cells along with sex factors
109
Hfr cells
Cells that have a high frequency of recombination
Sometimes, the sex factors become a part of the genome and the whole chromosome replicated. Before it can be transferred to the recipient, it breaks. The part that's transferred makes novel combination with parts that are already there,
110
What is transduction?
Occurs when fragments of the bacterial chromosome accidentally become packaged into viral progeny during a viral replication-- called virions
111
What do virions do?
May infect other bacteria and introduce new genetic arrangements through recomb. with new host cell's DNA.
112
The closer two genes are to one another on a chromosome, the more likely they are to _____ as a result of virions
Transduce
113
Recombination
When linked genes are separated--- ocurs by breakage and rearrangements of adjacent regions of DNA when organisms carrying different genes or alleles for the same traits are crossed.
114
Regulation of gene expression
transcription
115
Regulation of transcription is based on the accessibility of ____________ _________
RNA polymerase to the genes being transcribed
116
Regulation of transcription is directed by an ___
operon
117
What does an operon consist of?
Structural genes, an operator region and a promoter region on the DNA before the protein coding genes
118
What contains the sequences of DNA that code for proteins?
Structural genes
119
Operator
Sequence of nontranscribable DNA that is the repressor binding site
120
Promoter
Noncoding sequence of the DNA that serces as the initial binding site for RNA polymerase
121
Regulator gene
codes for the synthesis of a repressor molecule that binds to the operator and blocks RNA polymerase from transcribing the structural genes
122
Inducible systems
Require an inducer for transciption to occur
123
Repressible systems
Are in a constant state of transcription unless a corepressor is present to inhibit transcription
124
What happens in an inducible system?
The repressor binds to the operator- acts as a barrier for RNA polymerase
125
What must happen for transcription to occur in an inducible system?
An inducer must bind to the repressor, forming an inducer-repressor complex
126
Can the inducer-repepressor complex bind too the operator?
No, hence this promotes transcription
127
What typically codes for an enzyme?
The structural genes
128
The inducer is usually the:
substrate or substrate derivative on with the enzyme acts upton
129
When the inducer is present
enzyme is synthesized if not then enzyme not synthesized
130
Repressible system- the repressor is inactive until
combined with corepressor
131
The repressor can bind to the operator and prevent transcription only when it has ___
Formed a repressor-corepressor complex
132
Corepressor are often the end-products of the
biosynthetic pathway that they control
133
Proteins produced are said to be ____ because ________________________
repressible because they are normally bring synthesized, transcription and translation only stop when corepressor is synthesized
134
Constitutive enzyme
Always being synthesized-- operons containing mutations such as deletions or whose regulator genes code for defective repressors
incapable of being turned off
135
Bacteriophase
virus that infects its host bacterium by attaching to it- makes a hole through cell wall and injects its own DNA
136
A bacteriophase's protein coat remains
attached to the cell wall
137
Once a bacteriophage is inside of tis host, it
enter the lytic or a lysogenic cycle
138
Lytic cycle
Phase DNA takes control of bacterial DNA machinary
Bacterial cell wall lyses and releases new virions- which can infect other bacteria
139
Virulent
bacteriaphages that replicate using lytic cycle and kill their host cells
140
Lysogenic cycle
If bacteriophage does not lyse host cell, it becomes integrated into the bacterial genome
harmless (provirus) dormant
141
As a result of env. circumstances or spontaneously, a provirus can
enter lytic cycle
142
True or false: bacteria containing proviruses are normally resistant to further infection (super infection) by similar phages
TRUE
