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BIOL243 DNA, Inheritance and Evolution > Theme 2D > Flashcards

Theme 2D Flashcards

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1
Q

What are mutations?

A

Changes to the nucleic acid sequence (DNA and RNA)

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2
Q

How do mutations appear?

A

Inherited (germline) or not inherited (somatic)

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3
Q

What are the degrees of change from mutations?

A

Small (gene-level) or large (chromosomal)

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4
Q

What does an altered gene sequence change?

A

The amino acid sequence of a polypeptide resulting in variation of phenotype

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5
Q

What is the effect on the phenotype?

A

Harmless/neutral, harmful/deleterious, or beneficial/advantageous

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6
Q

Specifics of germline mutations

A

Sex influenced trait: an autosomal dominant trait that is dependent on sex
Only occurs in gametes

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7
Q

Specifics of somatic mutations

A

The mutation occurs in a progenitor cell and all other daughter cells will express the mutation (occurs in all cell types except gametes). Are expressed as sectors (size depends on time of mutation), i.e cancer

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8
Q

What is a base substitution?

A

A single nucleotide change as a result of point mutations

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9
Q

What is an insertion mutation?

A

One or more base pairs added in sequence during DNA replication usually resulting in a frameshift mutation

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10
Q

What is a deletion mutation?

A

One or more base pairs skipped during DNA replication usually resulting in frameshift mutations

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11
Q

What is a transition mutation?

A

Purine-to-purine or pyrimidine-to-pyrimidine changes

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12
Q

What is a transversion mutation?

A

Purine-to-pyrimidine or pyrimidine-to-purine changes

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13
Q

What is a missense/nonsynonymous mutation?

A

When a codon change causes a change in amino acid

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14
Q

What is a nonsense mutation?

A

Premature stop, sense codon changes into a stop codon

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15
Q

What is a silent/synonymous mutation?

A

When the codon does not change the amino acid due to the degeneracy of the genetic code

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16
Q

What is a frameshift mutation?

A

Insertion or deletion of a small number of base pairs that alter the reading frame

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17
Q

Which type(s) of mutation would have the most effect on the function of the polypeptide?

A

Nonsense or frameshift depending on location

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18
Q

What are the large-scale chromosomal mutations?

A

Deletion, Duplication/amplification, translocation, and inversion

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19
Q

What is a deletion (large-scale) mutation?

A

Loss of genes

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20
Q

What is a duplication/amplification mutation?

A

Increasing dosage of genes

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21
Q

What is a translocation mutation?

A

Interchange of genetic parts from non-homologous chromosomes

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22
Q

What is an inversion mutation?

A

Reversing the orientation of a segment of a chromosome

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23
Q

What is a spontaneous mutation?

A

Naturally occurring mutations caused by replication errors and spontaneous lesions (depurination and deamination of bases)

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24
Q

What is an induced mutation?

A

Natural/environmental or artificial agent or mutagen that causes mutations at a rate much higher than spontaneous mutations.

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25
Q

What do mutagens do?

A

Induce mutations by replacing a base, alter a base so it mispairs with another base, or damage a base where it can no longer pair with any base.

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26
Q

What do base analogs do?

A

Mimic bases and get incorporated into DNA, which can cause mispairing during DNA replication

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27
Q

What do some chemicals do?

A

Alter base structure to cause mispairing

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28
Q

What is an allele?

A

One of the different forms of a gene (sequence variation) which can cause different phenotypes

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29
Q

What is a wild-type allele?

A

The normal form of the gene found in nature or the standard laboratory strain of a model organism

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30
Q

What are loss-of-function alleles?

A

Mutations that reduce/eliminate gene function/expression

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31
Q

What are gain-of-function alleles?

A

Mutations that enhance gene function/expression

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32
Q

What is the eukaryotic cell cycle?

A

An ordered set of processes by which one cell grows and divides into two daughter cells.
Needs to fully replicate DNA and organelles and properly separate them into daughter cells.

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33
Q

What are the G1 and G2 phases?

A

Gap phases for the synthesis of proteins, RNA, metabolizes, other than DNA

34
Q

What is the S phase?

A

DNA replication

35
Q

What is the M phase?

A

Mitosis phase, nuclear division

36
Q

What is cytokinesis?

A

Cell division

37
Q

What is the G0 phase?

A

Resting phase (most adult humans are in this phase permanently or semi-permanently (liver))

38
Q

What is the G1/S checkpoint?

A

DNA damage checkpoint -> is DNA okay for replication?

39
Q

What is the G2/M checkpoint?

A

DNA replication checkpoint -> is DNA fully replicated before mitosis?

40
Q

How does a cell get past the checkpoints?

A

Progresses when the activation of cyclin-dependent kinase (CDK) bound to its regulatory cyclin subunit in each phase of the cell cycle occurs.

41
Q

When are cyclins active?

A

When they are expressed in specific phases of the cell cycle which determines when CDK is active

42
Q

What is cancer?

A

A malignant growth caused by uncontrolled cell division and is caused by altered expression of multiple genes as a result of mutations (polygenic disease).

43
Q

Which mutated genes are implicated in cancers?

A
  1. Oncogenes
  2. Tumor suppressor genes
  3. Inactivated p53 gene
  4. Different mutated genes
44
Q

What are oncogenes?

A

Positive regulators of the cell cycle (gain-of-function) including cyclin D/E (gene amplification), cdk4 alleles (insensitive to inhibition)

45
Q

What are tumor suppressor genes?

A

Negative regulators of the cell cycle (loss of function) including checkpoint genes p53 and RB

46
Q

What are inactivated p53 genes?

A

About 50% of tumors have an inactivated p53 gene and cyclin D and E are often highly expressed in breast cancer carcinomas.

47
Q

Why is cancer hard to find a cure for?

A

Each cancer is caused by different gene mutations

48
Q

What are n and 2n?

A

n: haploid number of chromosomes
2n: diploid number of chromosomes

49
Q

What are homologous chromosomes?

A

Maternal and paternal pair of chromosomes

50
Q

What is the same and difference between homologous chromosomes?

A

The number and order of genes are the same between homologous chromosomes but alleles could be different.

51
Q

G1 to G2

A

4 chromosomes, 1 chromatid per chromosome
DNA replicates, centriole duplication
4 chromosomes, 2 chromatids per chromosomes

52
Q

G2 to Prophase

A

4 chromosomes, 2 chromatids per chromosomes throughout phases
Duplicated chromosomes condense and become visible with sister chromatids. Duplicated centrioles (centrosomes) move further apart and form mitotic spindles. The nuclear envelope breaks down.

53
Q

Why should all the genes on sister chromatids be the same allele?

A

DNA replication, the sequence must be exactly the same

54
Q

Why should some genes on non-sister chromatids or homologous chromosomes have different alleles?

A

One is from the mother, one from the father

55
Q

Events of Mitotic Cell Cycle I?

A

G1 -> G2 -> Prophase

56
Q

Event of Mitotic Cell Cycle II?

A

Prometaphase -> Metaphase -> Anaphase

57
Q

Prophase to Prometaphase

A

Each kinetochore of the sister chromatid is attached to spindle microtubules.
Chromosomes move to the equator of the cell.
Still 4 chromosomes, 2 chromatids per chromosome.

58
Q

Prometaphase to Metaphase

A

All chromosomes are aligned at the equator (metaphase plate).
Chromosomes are attached to opposite poles and are under tension.
Still 4 chromosomes, 2 chromatids per chromosome.

59
Q

Metaphase to Anaphase

A

Cohesins are degraded
Sister chromatids and centromere separate to the poles
(spindle microtubules shortened).
Centrosomes move further apart in anaphase B (polar microtubules lengthened).
Now 8 chromosomes, 1 chromatid per chromosome.

60
Q

Events of Mitotic Cell Cycle III?

A

-> Telophase -> G1

61
Q

Anaphase to Telophase

A

Chromosomes are clustered at opposite poles and decondensing
Nuclear envelope reforms around chromosomes
Cytoplasm is beginning to divide by furrowing (cytokinesis)
Still 8 chromosomes, 1 chromatid per chromosome

62
Q

Telophase to G1

A

Two daughter cells are genetic duplicates of the parental cell.
4 chromosomes in each cell, 1 chromatid per chromosome.

63
Q

What are the steps of binary fission? (prokaryotes)

A
  1. Replication begins at the origin
  2. Bacterial chromosome (template and daughter) is attached to the inner membrane
  3. Cell elongates and bacterial chromosomes separate
  4. Inward growth of plasma membrane and partition assembly of the new cell wall, dividing replicated DNA.
64
Q

Why is binary fission effective?

A

Only 1 chromosome to replicate

65
Q

How many daughter cells does binary fission produce?

A

2 daughter cells

66
Q

What process did mitosis evolve from?

A

binary fission

67
Q

What are the steps of Meiosis I?

A

Pre-meiotic DNA replication -> condensation of chromosomes -> synapsis (homologous chromosomes come together and pair) -> recombination -> prometaphase I -> metaphase I -> anaphase I -> telophase I

68
Q

What is recombination in eukaryotes?

A
  • Homologous chromosomes align with each other during prophase I and exchange of sections of non-sister chromatids occur by crossing over
  • precise breakage of each strand
  • equal exchange of non-sister chromatids
  • repair of breakage after genetic exchange
69
Q

Why is it important for the perfect exchange of genetic material between non-sister chromatids during recombination?

A

Missing/extra DNA = mutations (fucked up kids)

70
Q

What is different in Meiosis I?

A
  • The number of homologous pairs of chromosomes is reduced from two in the parental cell to one in the daughter cell.
  • Therefore, after meiosis I, the chromosome number is haploid, but two chromatids/chromosome
  • The sister chromatids and centromeres do not split unlike mitosis and meiosis II.
  • The sister chromatids are no longer identical due to crossing over.
71
Q

What is different in Meiosis II?

A
  • No DNA replication happens between meiosis I and meiosis II.
  • The process between meiosis II and mitosis is similar except there is no DNA replication.
  • Centromeres and sister chromatids separate during anaphase II.
  • At the end of meiosis II, four cells are produced with haploid number of chromosomes (one chromatid/chromosome) that are not identical due to crossing over and a random assortment
72
Q

Steps of Meiosis II?

A

Prophase II -> Prometaphase II -> Metaphase II -> Anaphase II -> Telophase II

73
Q

Metaphase I

A

Movements of the spindle microtubules align the tetrads on the equator between the two spindle poles

74
Q

Anaphase I

A

Two out of four of the chromosomes are pulled to each pole

75
Q

Telophase I

A

Undergo little to no change except for limited condensation. Cells are almost two separate ones but still one massive cell u know?

76
Q

Prophase II

A

Chromosomes condense and a spindle forms.

77
Q

Prometaphase II

A

Nuclear envelope breaks down, spindles attach

78
Q

Metaphase II

A

Chromosomes are aligned along the equator by spindles tug-of-war

79
Q

Anaphase II

A

Chromosomes are pulled apart into single chromatids and go to opposite poles

80
Q

Telophase II

A

Chromosomes begin decondensing, spindles disassemble, and a new nuclear envelope develops

BIOL243 DNA, Inheritance and Evolution (9 decks)

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