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Biology > Genetics > Flashcards

Genetics Flashcards

1
Q

DNA Structure Overview

A

Polymer composed of nucleotides

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2
Q

3 Components of DNA

A

Phosphate group, ribose sugar, nitrogenous base

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3
Q

The bond between sugar molecule and the phosphate group

A

Phosphodiester bond

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4
Q

Formation of the Phosphodiester Bond

A

A condensation reaction in which a ribose sugar loses a hydroxide molecule and a phosphate group loses a hydrogen atom. An excess water molecule forms.

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5
Q

Ribonucleotide vs deoxyribonucleotide

A

Ribonucleotides have one more oxygen atom than deoxyribonucleotides on the pentose sugar

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6
Q

Types of Nitrogenous Bases

A

Purines: adenine and guanine, have two smaller rings
Pyrimidines: thymine and cytosine, haev lone, larger rings

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7
Q

Uracil

A

Replaces thymine in RNA

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8
Q

Nucleoside

A

Single pentose sugar

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9
Q

Nucleoside mono/di/…phosphate

A

Pentose sugar + one/two/…phosphate groups

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10
Q

Chargaff’s Rule

A

Adenine pairs with thymine; guanine pairs with cytosine

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11
Q

Explanation for Chargaff’s Rule

A

The location of hydrogen bonds create an energetically stable arrangement: purine to pyrimidine

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12
Q

Structure of DNA strands

A

Double helical. Double stranded and antiparallel: one 5’ to 3’, other 3’ to 5’.

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13
Q

Rosalind Franklin and DNA

A

Used X ray crystallography; shot X rays at DNA, scattering and creating a pattern on a plate, creating an image. Discovered that DNA forms a helix, is double stranded, with phosphate molecules stick out.

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14
Q

Watson and Crick

A

Used Franklin’s work to discover the double helix structure, suggesting possible mechanisms for replication

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15
Q

Nucleic Acids

A

Categorized as nucleotides, compoased of C, H2, O2, N2 and P, can be DNA, RNA, ATP, coenzymes, responsible for forming genetic materials, energy carriers and enzyme assistants.

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16
Q

DNA Replication

A
  1. Helicase disrupts hydrogen bonds long enough to unzip the strands, creating the replication fork. It moves along the strand until complete separation
  2. Single strand binding proteins prevent reannealation. and come off once they’re no longer needed
  3. The toposiomerase/gyrase releases torsional tension ahead of the replication fork to release torsional tension
  4. DNA polymerase builds the new strand of DNA by catalyzing the production of phosphodiester bonds
  5. A nucleoside triphosphate comes in; the bond between 2 phosphates broken, releasing energy, gets transferred to make the bond between a P group and a carbon from another nucleotide -> monophosphate
  6. DNA Pol III links the nucleotides in the leading strand with phosphodiester bonds
  7. As more is built, more is unzipped
  8. For the lagging strand, DNA Pol III cannot build from 3’ to 5’, so it moves away from the fork, builds, then leaps back to strart with a new segment
  9. The primse builds RNA 10 nucleotides long, becoming the foundation (primer), needed by both the leading and lagging strand
  10. DNA Pol I recognizes where the RNA is and replaces it with DNA
  11. Ligase binds the Okazaki fragments together, creating phosphodiester bonds, creating one continuous strand
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17
Q

Goal of Meiosis

A

Create haploid cells (gametes) that can be used for sexual reproduction

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18
Q

Fertilization

A

Two gametes, a sperm and an ovum, each contain the haploid number of chromosomes, fuse together to form a diploid cell

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19
Q

Loci

A

Location (on a chromosome). A particular spot where protein codes for specific trait: type of info at the same spot.

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20
Q

Tetrads (Bivalents)

A

Two pairs of homologous chromosomes. Sister chromatids of homologous chromosomes that line up next to each other and temporarily attach, exchanging different segments of their genetic material to form unique recombinant chromosomes

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21
Q

Chiasma

A

Location of crossing over

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22
Q

Allele

A

Alternate version of a gene

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23
Q

Maternal and paternal chromosomes in a homologous pair have the same x at the same y but not necessarily the same z

A

X: genes
Y: loci
Z: alleles

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24
Q

Meiosis I

A

Prophase I: chromosomes condense, the nuclear envelope dissolve, crossing over takes place

Metaphase I: tetrads move to the equator of the cell

Anaphase I: homologous chromosomes are pulled to the opposite poles of the cell

Telophase I: chromosomes gather at the poles, the cytoplasm divides

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25
Q

Meiosis II

A

Prophase II: a new spindle forms around the chromosomes

Metaphase II: chromosomes line up vertically

Anaphase II: centromeres divide, chromatids move to opposite poles

Telophase II: a nuclear envelope forms around each set of chromosomes, the cytoplasm divides

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26
Q

Is the cell diploid or haploid during meiosis?

A

Diploid until telophase I, haploid afterwards.

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27
Q

Human Karyotype

A

Image of a person’s complete set of chromosomes, can reveal abnormalities

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28
Q

Non - disjunction

A

The failure of homologous chromosome pairs to separate properly during meiosis or mitosis, resulting in an imbalance of chromosomes

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29
Q

Is non - disjunction more destructive during anaphase I or II?

A

Anaphase I, because four daughter cells are affected instead of two

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30
Q

Monosomy

A

Daughter cell missing single chromosome

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31
Q

Trisomy

A

Daughter cell has one extra chromosome

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32
Q

Down Syndrome

A

Trisomy 21

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33
Q

Transcription Summary

A

DNA to RNA synthesis. DNA is copied into single stranded RNA, which is transported into the cytoplasm

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34
Q

4 Stages of Transcription

A
  1. Initiation
  2. Elongation
  3. Termination
  4. Post - Transcriptional Modifications
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35
Q

Nontemplate Strand

A

Coding, sense

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36
Q

Template

A

Noncodng, transcribed, antisense

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37
Q

The promoter

A

Example of non - coding DNA with a function, located upstream of the gene coding region. “A”s and “T”s in the promoter region serve as a recognition site for RNA polymerase

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38
Q

Enhancers and Repressors

A

Upstream from the gene, help determine transcription rate

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39
Q

The RNA transcript is complementary to the template/nontemplate strand?

A

Template

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40
Q

The promoter is upstream/downstream from RNA - coding region?

A

Upstream

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41
Q

Transcription Initiation (2 Steps)

A
  1. Enzyme RNA polymerase binds to a strand of DNA to form an initiation complex and opens the doublie helix to form the transcription bubble
  2. The binding occurs at a promoter, with a characteristic base pair patter, the TATA box
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42
Q

Transcription Elongation (3 Steps)

A
  1. RNA polymerase builds RNA from 5’ to 3’ using nucleoside triphosphates
  2. Results in a primary transcript
  3. DNA strands reform a helix afterwards
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43
Q

First Step in Transcription Termination

A

RNA Pol recognizes the end when it comes across a terminator sequence.

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44
Q

Eukaryotic Transcription Termination

A

Terminator sequence is a string of adenines: AAAAAAA
The precursor mRNA, the primary transcript, isn’t the full gene yet, as it’s vulnerable to enzymes and conditions outside the nucleus and contains non - coding regions

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45
Q

Prokaryotic Transcription Termination

A

Two types of terminators: protein binding and stopping transcription or mRNA binding to itself, the complementary bases attracting each other. Then, the mRNA is immediately ready to be translated.

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46
Q

Post - Transcriptional Modifications

A

The spliceosome cleaves the intron

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47
Q

Poly(A) tail

A

A chain of adenine nucleotides to protect the chain from enzymes in the cytosol

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48
Q

5’ cap

A

7 sequences of Gs recognized by ribosomes

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49
Q

Exon

A

Sequence that codes for part of a gene

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50
Q

Intron

A

Non - coding sequence

51
Q

Spliceosome

A

Enzyme - protein complex that removes introns

52
Q

Small Nuclear Ribonucleoproteins (snRNO)

A

Remove the intron without cutting any nucleotides from the exon

53
Q

Alternative Splicing

A

Allows for one gene to code for more than one protein. How the RNA is edited determines the type fo protein created. Introns allow for one gene to code for multiple proteins.

54
Q

Translation Function

A

RNA to protein synthesis

55
Q

The Anticodon

A

A sequence of three bases complementary to the mRNA codon

56
Q

The Acceptor Site

A

On the opposite arm of the anticodon, binds to and carries the corresponding amino acid, has the nucleotide sequence CCA

57
Q

Four Stages of Translation

A

Initiation, elongation, translocation and termination

58
Q

A site (Amino acid site)

A

Position where the new tRNA codon - anticodon binds making sure that the correct AA is in position

59
Q

P site (polypeptide site)

A

Position in which the AA on the tRNA adds to the polypeptide

60
Q

Exit site

A

Position the tRNA, without the AA, locates and is released from the ribosome to become re - activated

61
Q

Translation Initiation (5 Steps)

A
  1. Ribosomes bind to the mRNA, recognizing the 5’ cap in eukaryotes
  2. The tRNA charged with AA methionine has the anti - codon UAC, complementray to the start codon of mRNA, AUG
  3. The small subunit associates with the methionine tRNA, moves over start codon
  4. The large subunit of the ribosome moves over the mRNA
  5. The sart codon occupies the P site, while the A site is free for the complementary tRNA to bind
62
Q

Translation Elongation (3 Steps)

A
  1. tRNA enters the A site using the matching of the codon to the anticodon to ensure the correct AA is added
  2. Bond between the tRNA and methionine is broken
  3. Free energy is released, used to form the peptide bond between methionine and the new AA
63
Q

Translation Translocation (3 Steps)

A
  1. The large subunit moves 3 bases towards the 3’ end of the mRNA
  2. The tRNA for methionine, called methione, enters the E site to exit and become recharged with another mehtionine
  3. The elongation process is repeated until termination
64
Q

Translation Termination (2 Steps)

A
  1. Stop codons (UAG, UAA, UGA) recognized by the release factor and aids the release of the polypeptide chain from the ribosome
  2. 2 subunits of the ribosome fall off the mRNA and separate
65
Q

Nucleosome

A

A molecule of DNA wrapped around a core of eight histone proteins, an octamer

66
Q

Octamer

A

Contain 2 copies of 4 different types of histones

67
Q

The … charged DNA associates with … charged AA on the surface of the histones

A

Negatively, positively

68
Q

Chromosomal Condensation

A

Tails that extrude outwards from adjacent octamers link up and draw the nucleosomes together

69
Q

Purpose of Nucleosomes

A

Supercoil DNA for more efficient storage and to protect it from damage and allow chromosomes to be mobile during mitosis and meiosis

70
Q

Tightness of Nucleosomes and Transcription Rate

A

Loosening the nucleosomes increases transcription rate

71
Q

Methylation

A

Addition of methyl groups to DNA: causes nucleosomes to pack tightly together. Transcription factors cannot bind to the DNA and genes are not expressed

72
Q

Acetylation

A

Addition of acetyl groups; results in loose packing, allowing transcription factors to bind.

73
Q

Heterochromatin

A

Tightly packed chromatin

74
Q

Euchromatin

A

Loosely packed chromatin

75
Q

Epigenetic Tag

A

Markers from methylation and acetylation on the DNA that affect transcription

76
Q

For a new organism to grow it needs … DNA that can develop into lots of different specialized cell types

A

Unmarked

77
Q

Factors affecting methylation and acetylation

A

Changes in the environment, e.g. mother’s diet, exercise, which affect the cell metabolism

78
Q

Operator

A

Region of DNA that can regulate transcription, typically inhhibiting transcription

79
Q

Enhancer

A

Non - coding DNA region that increasese transcription rate when an activator protein is bound to it

80
Q

Silencer

A

Non - coding DNA region that inhibit transcription when a repressor protein is bound to it

81
Q

Point Mutation

A

One nucleotide substituted for another

82
Q

Sickle Cell Anemia

A

Example of point mutation: caused by a single substitution error. Adenine substituted by thymine; originally codes for glutamine instead of valine. The cell becomes sickled, crescent shaped, which form clumped hemoglobin that obstruct blood vessels. However, this is beneficial in malaria ridden areas, as paraites are killed by this type of blood.

83
Q

Gene Mutation

A

Change in the nucleotide sequence of a section of DNA

84
Q

Mutagen

A

Agents that cause gene mutations, result in the creation of new alleles

85
Q

Examples of Mutagens

A

Environmental factors like UV and X rays, chemicals like benzene

86
Q

Consequences of Radiation

A

High energy radiation causes mutation in the form of waves or particles that disrupt the backbone of DNA molecules

87
Q

Nature of the Impact of Radiation

A

Duration and intensity

88
Q

Non ionizing vs ionizing radiation

A

Non ionizing radiation has low energy while ionizing radiation has higher energy. Capable of breaking bonds between atoms, anything above UV< alpha and beta particle radiation.

89
Q

Gregor Mendel

A

First documented scientist to conduct a controlled experiment, father of genetics, discovered the principle of dominance

90
Q

Principle of Dominance

A

When organisms with contrasting traits are crossed, the offspring will only display the dominant trait

91
Q

Genotype

A

Specific allelic combination

92
Q

Phenotype

A

Physical appearance of a trait

93
Q

Dominance

A

The allele that’s expressed under all circumstances

94
Q

Recessiveness

A

The allele that’s masked in the presence of a dominant trait and only expressed in their absence

95
Q

Homozygous

A

The alleles are both dominant or recessive

96
Q

Heterozygous

A

One dominant allele, one recessive

97
Q

F1

A

First filial, first generation of offspring

98
Q

F2

A

Second filial, second generation of offspring

99
Q

Monohybdrid Cross

A

Crossing two organisms with homozygous (pure breeding) genotypes

100
Q

Dihybrid Cross

A

Crossing two heterozygous organisms: two separate monohybrid crosses

101
Q

Law of Segregation

A

Because homologous chromosomes are oriented randomly during metaphase I, the alleles for each gene segregate from each other so that each gamete carries only one allele for each gene.

102
Q

Law of Independent Assortment

A

The alleles of two or more different genes get sorted into gametes independently of one another

103
Q

An Exception to Mendel Genetics

A

Blood type

104
Q

Type O Blood

A

Genotype: ii
Both A and B antibodies present, no antigens
Can only receive from O

105
Q

Type A Blood

A

Genotype: IAIA or IAi
Only antibody B present, only antigen A present
Can receive from O and A

106
Q

Type B Blood

A

Genotype: IBIB or IBi
Only antibody A present, only antigen B present
Can receive from O and B

107
Q

Type AB Blood

A

Genotype: IAIB
No antibodies present, both antigens A and B
Can receive from any blood type

108
Q

2 Types of Non - Mendelian Genetics

A

Incomplete dominance and codominance

109
Q

Incomplete Dominance

A

Two different alleles both partially expressed, blended. No dominance or recessiveness but heterozygous

110
Q

Codominance

A

Two different alleles both fully expressed.

111
Q

Sex Linked Traits

A

Located on chromosome 23

112
Q

Y Linked Traits

A

Only males carry the trait. Rarer than X linked as the Y chromosome is smaller. Leads to male infertility and not passed on, but there are some exceptions. No dominance or recessiveness since there is only one Y chromosome. When drawing a punnett square, signal Y’ for having the trait.

113
Q

X Linked Traits

A

Recessive. Female may be carrier but 0% chance get sick. X comes from mother, Y comes from father. For the female offspring to get sick, the motehr has to be a carrier and the father has it.

114
Q

Size of X and Y chromosomes

A

X is larger than Y

115
Q

Examples of Sex Linked Syndromes

A

Hemophilia (X recessive), hairy ears (Y linked)

116
Q

Autosomal Traits

A

On chromosome 1 - 22; not sex linked

117
Q

Examples of Autosomal Syndromes

A

Cystic fibrosis: recessive, excessive mucus production, difficulty breathing and increases infection possibility.

Huntington’s Disease: dominant, loss of muscle coordination and cognitive decline

118
Q

Pedigree Legend

A
  • Circle for female, square for male
  • Horizontal line indicates mating
  • Vertical line indicates offspring
  • Roman numerals indicate generations
  • Shaded has the trait
  • Triangle: identical twins
  • Cherry shape: fraternal twins
119
Q

Continuous vs Discontinuous Variation

A

Continuous variation occurs when an array of possible phenotypes can be produced. Discontinuous variation cocurs when only a small number of phenotypes can be produced.

120
Q

Polygenic Traits

A

Two or more genes influence the expression of one trait

121
Q

Assumptions of Polygenic Traits

A
  1. Each contributing gene has a small and relatively equal effect
  2. The effects of each allele are cumulative
  3. The value of the trait depends solely on genetics, ignoring environmental influences
122
Q

Linked Genes

A

The tendency of certain genes to be inherited together

123
Q

Linked Genes Process

A

Loci on the samm chromosome that are physically close to one anotehr tend to stay together during meiosis and become linked, resulting in crossing over. No longer independently sorted, not segregated, creates recombinant genotypes.

Biology (7 decks)

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