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Old Classes > Chapter 9- Genetics > Flashcards

Chapter 9- Genetics Flashcards

1
Q

Genetics

A

The study of how traits are inherited from one generation to the next

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2
Q

Where are genes located?

A

Chromosomes

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3
Q

Alleles

A

An alternative form of a gene

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4
Q

Genotype

A

Genetic makeup of an individual

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5
Q

Phenotype

A

Physical manifestation of the genetic makeup

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6
Q

What is Mendel’s first law?

A

Law of segregation

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7
Q

Mendel’s 4 principles of inheritance

A
  1. Genes exist in alternative forms
  2. Gene= 2 alleles, one from each parents
  3. Two alleles segregate through meiosis- gametes only carry one allele for one given trait
  4. Dominant and recessive alleles
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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.

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9
Q

How many traits can be tested by a monohybrid cross at a time?

A

One at a time

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10
Q

P generation

A

Parental generation- the individual being crossed

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11
Q

F generation

A

Filial generation- Progeny of the parental generation

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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

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13
Q

Testcross

A

Diagnostic tool to determine genotype of an organism- also known as a backcross

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14
Q

When can a genotype be determined with 100% accuracy?

A

When a recessive phenotype is being tested

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15
Q

If a dominant phenotype is expressed, the genotype can be either:

A

Homozygous dominant or hetozygous

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16
Q

In a testcross, the appearance of the recessive phenotype in the progeny indicates that the phenotypically dominant parent is genotypically ________

A

Heterozygous

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17
Q

What is Mendel’s Second law?

A

Law of independent assortment

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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

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19
Q

Typical pattern for Mendelian inheritance in a dihybrid cross between heterozygotes with independently assorting traits

A

9:3:3:1

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20
Q

Incomplete dominance

A

Blend. White+red= pink

Intermediates of the phenotypes of the homozygotes

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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.

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22
Q

Classic dominance of codominance

A

Individuals with IA and IB blood are group AB because both IA and IB are dominant

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23
Q

Three alleles of ABO blood group

A

IA
IB
i

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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

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25
Q

Central dogma

A 
DNA-RNA= transcription
RNA-Proteins= translation
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26
Q

Nucleotide

A

The basic structure of DNA- composed of deoxyribose bonded to a phosphate group and a nitrogenous base.

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27
Q

Two types of bases

A

Purines and pyrimidines

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28
Q

Purines

A

Adenine, Guanine

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29
Q

Pyrimidines

A

Cyrosine and thymine

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30
Q

The phosphate and sugar form a chain with the bases and are arranged as: ________

A

side groups off the chain

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31
Q

Double stranded helix is arranged with ____

A

The sugar-phosphate chains on the outside of the helix and the bases on the inside.

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32
Q

Nucleotides are bonded by

A

Hydrogen bonds

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33
Q

T always forms __hydrogen bonds with __

G always forms __ hydrogen bonds with __

A

2 A

3 C

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34
Q

Each strand of a double helix acts as a template for ____

A

complementary base-pairing in the synthesis of two new daughter helices.

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35
Q

Semiconservative replication

A

Each new DNA helix is one old strand and one new

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36
Q

Leading strand

A

Continually synthesized by the DNA polymerase in a 5’-3’ direction

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37
Q

Lagging strand

A

Synthesized discontinuously in the 5’-3’ direction as okazaki pragments

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38
Q

DNA polymerase only synthesized new strands in the ___ direction

A

5’-3’

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39
Q

Codons

A

The base sequence of mRNA in translation is a series of triplets called codons

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40
Q

True or false: the genetic code is universal for almost all organisms?

A

True

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41
Q

How many different codons are possible?

A

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

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42
Q

How is RNA different the DNA?

A
  • Sugar is ribose
  • Contains Uracil instead of thymine
  • Single stranded
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43
Q

RNA can be found in both___

A

the nucleus and cytoplasm

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44
Q

Types of RNA

A

mTNA, tRNA, rRNA

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45
Q

mRNA

A

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.

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46
Q

mRNA is assembled from_____

A

ribonucleotides that are complementary to strand of DNA

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47
Q

One mRNA codes for __ polypedtide

A

one. This is called monocistronic

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48
Q

Is DNA code for amino acid is AAC, the mRNA is ___

A

UUG

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49
Q

tRNA

A

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.

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50
Q

There is atleast ___ type of tRNA for each amino acid

A

1

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51
Q

rRNA

A

Ribosomal RNA is a structure component of ribosomes and is the most abundant type of RNA. Carries the enzymes necessary for protein synthesis

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52
Q

Where is rRNA synthesized

A

Nucleolus

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53
Q

Transcription

A

Process whereby information coded in the base sequence of DNA is transcribed into a strand of mRNA that leaves the nucleus through nuclear pores

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54
Q

After transcription, the remaining events of protein synthesis occur in the

A

cytoplasm

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55
Q

Translation

A

Process whereby mRNA codons are translated into a sequence of amino acids.

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56
Q

Translation occurs in the ___ and involves ___, ___, ____, _____________, and ______

A

tRNA, ribosomes, mRNA, amino acids, and enzymes

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57
Q

tRNA recongized both the ___

A

amino acid and mRNA codon.

58
Q

Anticodon

A

in the tRNA– is complementary to one of the mRNA codons

59
Q

Structure of tRNA

A

one end- anticodon

Other end- site of amino acid attachment

60
Q

Aminoacyl-tRNA synthetase

A

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
Q

Ribosomes are composed of…

A

two subunits, one large and one small

62
Q

When do the two subunits of a ribosome bind together?

A

During protein synthesis

63
Q

How many binding sites do Ribosomes have and what are they?

A

A total of three binding sites
One for mRNA
two for tRNA

64
Q

The two binding sites for tRNA on a ribosome are called what? What are they?

A

P site- peptidyl-tRNA bdining site

A site- aminoacyl-tRNA complex binding site

65
Q

P site

A

binds to the tRNA attached to the growing polypeptide chains

66
Q

A site

A

Binds to the incoming aminoacyl-tRNA complex

67
Q

E site

A

where uncharged tRNA leaves

68
Q

3 stages of polypeptide synthesis

A
  1. Initiation
  2. Elongation
  3. Termination
69
Q

When does synthesis begin?

A

When the ribosome binds to the mRNA near its 5’ end-

70
Q

During initiation, what base pairs with the start codon?

A

Methionine tRNA

71
Q

What happens during elongation?

A

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
Q

Translocation

A

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
Q

Nondisjunction

A

Failure of homologous chromosomes to separate properly during meiosis II

can lead to trisomy or monosomy

74
Q

Trisomy

A

2N+1

3 copies of chromosome

75
Q

monosomy

A

2N-1

single copy of chromosome

76
Q

Downs Syndrome is caused by

A

Trisomy of chromosome 21

77
Q

True or false: nondisjunction of sex chromosomes can also occur

A

True

78
Q

Chromosomal breakage

A

occur spontaneously or can be induced by environmental factors such as mutagenics and X rays

79
Q

Mutations

A

Changes in the genetic information of a cell coded in the DNA

80
Q

Mutations in the somatic cells can lead to

A

tumors in the individual

81
Q

Mutations that occur in the sex cells/ gametes can be

A

transmitted to the offspring

82
Q

Most mutations occur in regions of DNA that..

A

do not code for proteins and are silent, hence not expressed in the phenotype

83
Q

Mutations that do change the sequence of amino acids in proteins are most often ____ and ______

A

recessive and deleterious

84
Q

Mutagenic agents

A

induce mutations. Also called carcinogenic

85
Q

Types of mutagenic agents

A

Cosmic rays, x rays, UV rays, and radtioactivity and colchicine, mustard gas

86
Q

In gene mutation, nitrogen caes are _____, _____, or ______. This alters the__________________

A

added, deleted or substituted. This alters the amino acid sequence, may produce mutation

87
Q

Point mutation

A

a nucleic acid is replaced by another nucleic acid- usually involved 1-3 nucleotides. Length of the genome does not change

88
Q

Three possible results on a codon as a consequence of a point mutation

A
  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
Q

Frameshift mutation

A

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
Q

PKU

A

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
Q

Sickle-cell anemia

A

Red blood cells become cresent-shaped because they contain defective hemoglobin– which carries less oxygen

92
Q

How is sickle-cell anemia caused?

A

Substitution of valine for glutamic acid because of a single base-pair substitution in the gene coding for hemoglobin

93
Q

T/F: heredity systems exist outside the nucleus

A

True. Example: cytoplasmic inheritance

DNA is found in chloroplasts, mitochondria and other cytoplasmic bodies

94
Q

Plasmids

A

Cytoplasmic DNA that regulates drug resistance.

contain one or more genes

95
Q

Bacterial genome

A

Consists of single circular chromosome located in the nucleoid region of the cell

96
Q

True or false: Many bacteria contain plasmids

A

True

97
Q

What are plasmids in bacteria?

A

Circular rings of DNA that contain accessory genes

98
Q

Episomes

A

plasmids that are capable of integration into the bacterial genome

99
Q

Replication of bacterial chromosome begins at a..

A

Unique origin of replication and proceeds in both directions simultaneously

100
Q

DNA is synthesized in bacteria in the ___’ - ___’ direction

A

5’ to 3’

101
Q

Binary fission

A

How bacterial cells reproduce

asexual process

102
Q

Three mechanisms by which bacteria increase genetic variance of a population:

A

transformation, conjugation, and transduction

103
Q

Transformation

A

Process by which a foreign chromosome fragment (plasmid) is incorporated into the bacterial chromosome via recombination, creating new inheritable genetic combinations

104
Q

Conjugation

A

sexual mating in bacteria- transfer of genetic material between two bacteria that are temporarily joined

105
Q

How is genetic material transferred during conjugation?

A

Conjugation bridge is formed and genetic material is passed between the donor male (+) and recipient female (-)

106
Q

What kind of bacteria are capable of conjugating?

A

bacteria containing plasmids called sex factors

107
Q

F Factor

A

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
Q

Antibody resistance may be found on the…

A

plasmids and transferred into recipient cells along with sex factors

109
Q

Hfr cells

A

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
Q

What is transduction?

A

Occurs when fragments of the bacterial chromosome accidentally become packaged into viral progeny during a viral replication– called virions

111
Q

What do virions do?

A

May infect other bacteria and introduce new genetic arrangements through recomb. with new host cell’s DNA.

112
Q

The closer two genes are to one another on a chromosome, the more likely they are to _____ as a result of virions

A

Transduce

113
Q

Recombination

A

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
Q

Regulation of gene expression

A

transcription

115
Q

Regulation of transcription is based on the accessibility of ____________ _________

A

RNA polymerase to the genes being transcribed

116
Q

Regulation of transcription is directed by an ___

A

operon

117
Q

What does an operon consist of?

A

Structural genes, an operator region and a promoter region on the DNA before the protein coding genes

118
Q

What contains the sequences of DNA that code for proteins?

A

Structural genes

119
Q

Operator

A

Sequence of nontranscribable DNA that is the repressor binding site

120
Q

Promoter

A

Noncoding sequence of the DNA that serces as the initial binding site for RNA polymerase

121
Q

Regulator gene

A

codes for the synthesis of a repressor molecule that binds to the operator and blocks RNA polymerase from transcribing the structural genes

122
Q

Inducible systems

A

Require an inducer for transciption to occur

123
Q

Repressible systems

A

Are in a constant state of transcription unless a corepressor is present to inhibit transcription

124
Q

What happens in an inducible system?

A

The repressor binds to the operator- acts as a barrier for RNA polymerase

125
Q

What must happen for transcription to occur in an inducible system?

A

An inducer must bind to the repressor, forming an inducer-repressor complex

126
Q

Can the inducer-repepressor complex bind too the operator?

A

No, hence this promotes transcription

127
Q

What typically codes for an enzyme?

A

The structural genes

128
Q

The inducer is usually the:

A

substrate or substrate derivative on with the enzyme acts upton

129
Q

When the inducer is present

A

enzyme is synthesized if not then enzyme not synthesized

130
Q

Repressible system- the repressor is inactive until

A

combined with corepressor

131
Q

The repressor can bind to the operator and prevent transcription only when it has ___

A

Formed a repressor-corepressor complex

132
Q

Corepressor are often the end-products of the

A

biosynthetic pathway that they control

133
Q

Proteins produced are said to be ____ because ________________________

A

repressible because they are normally bring synthesized, transcription and translation only stop when corepressor is synthesized

134
Q

Constitutive enzyme

A

Always being synthesized– operons containing mutations such as deletions or whose regulator genes code for defective repressors

incapable of being turned off

135
Q

Bacteriophase

A

virus that infects its host bacterium by attaching to it- makes a hole through cell wall and injects its own DNA

136
Q

A bacteriophase’s protein coat remains

A

attached to the cell wall

137
Q

Once a bacteriophage is inside of tis host, it

A

enter the lytic or a lysogenic cycle

138
Q

Lytic cycle

A

Phase DNA takes control of bacterial DNA machinary

Bacterial cell wall lyses and releases new virions- which can infect other bacteria

139
Q

Virulent

A

bacteriaphages that replicate using lytic cycle and kill their host cells

140
Q

Lysogenic cycle

A

If bacteriophage does not lyse host cell, it becomes integrated into the bacterial genome

harmless (provirus) dormant

141
Q

As a result of env. circumstances or spontaneously, a provirus can

A

enter lytic cycle

142
Q

True or false: bacteria containing proviruses are normally resistant to further infection (super infection) by similar phages

A

TRUE

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