Theme 2D Flashcards by Daddy Longlegs

Q

What does germine mean

A

inherited

mutation

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Q

What does somatic mean?

A

not inherited

mutation

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Q

What are mutations

A

changes to nucleic acid sequence (DNA & RNA)
can be germine or somatic
changes can be small (gene level) or large (chromosomal)
altered gene sequence can change the amino acid sequence of polypeptide resulting in variation of phenotype
effect on phenotype can be harmful, neutral, or beneficial
primary force in evolution (beneficial mutations are favored)

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Q

Germline mutations

A

mutation originally occured in gametes and become heritable

example: sex-influenced trait - autosomal dominant trait that is dependant on sex

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Q

Somatic Mutations

A

can occur in all other cell types except gametes and are not heritable

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Q

Where does a somatic mutation occur? What are they expressed as?

A

occurs in a progenitor cell and all other daughter cells will express mutations; they are expressed as sectors (size depends on time of mutation)

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Q

Small Scale Mutations

Base Substituation

A

single nucleotide change as a result of point nutations

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Q

Small Scale Mutations

Insertion

A

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

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Q

Small Scale Mutations

Deletion

A

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

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Q

Small Scale Mutations

Transition

A

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

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Q

Small Scale Mutations

Transversions

A

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

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Q

Effect of point mutations on amino acid sequence

Missense mutation (nonsynonymous)

A

codon change causes change in amino acid

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Q

Effect of point mutations on amino acid sequence

Nonsense mutation (premature stop)

A

sense codon change into a stop codon (truncated polypeptide)

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Q

Effect of point mutations on amino acid sequence

Silent mutation (synonymous)

A

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

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Q

Effect of point mutations on amino acid sequence

Frameshift Mutation

A

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

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Q

Effect of point mutations on amino acid sequence

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

A

frameshift but depends where
or early premature stop

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Q

Sickle Cell Anemia (missense mutation)

A

single missense mutation in the entire genome and a resulting single amino acid change can have effect on phenotype

missense mutation in the beta hemoglobin gene causes 6th amino acid to change from glutamic acid to valine
Red blood cells: defficient in oxygen exchange, clogged arteries, circulatory problems, higher risk of heart attack and stroke

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Q

Large scale chromosomal mutations

Deletion

A

loss of genes

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Q

Large scale chromosomal mutations

Duplication/amplification

A

increasing dosage of genes

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Q

Large scale chromosomal mutations

Translocation

A

interchange of genetic parts from nonhomologous chromosomes

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Q

Large scale chromosomal mutations

Inversion

A

reversing orientation of a segment of the chromosome

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Q

Spontaneous Mutation

A

naturally occuring mutations mainly caused by replication errors and spontaneous lesions

a low rate (freuquency) of mutation - usually during replication

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Q

Induced Mutation

A

natural/environmental or artificial agent or mutagen that causes mutation at a rate much higher than spontaneous mutagens
mutagens induce mutations by replacing base, alter a base so it mispairs with another base, or damage base so it can no longer pair up
base analogs mimic bases and incorporates into DNA
chemicals that alter base structure to cause mispairing
damage to bases

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Q

Allele

A

one or different forms of a gene (sequence variation) which can cause different phenotypes

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Wild-type allele

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

Loss-of-function alleles

mutations that reduce/eliminate gene function/expression

Gain-of-function alleles

mutations that enhance gene function/expression

The eukaryotic cell cycle

* cell cycle is ordered set of processes by which one cell grows and divides into two daughter cells * need to fully replicate DNA and organelles and properly segregate them to daughter cells * G1 & G2 (gap phases)' * S phase * M phase * Cytokinesis * G0 (most adult human cells are here)

# Eukaryotic Cell Cycle G1 & G2 (gap phases)

synthesis of proteins, RNA, metabolites, and other DNA

# Eukaryotic Cell Cycle S phase

DNA replication

# Eukaryotic Cell Cycle M phase (mitosis)

nuclear division

# Eukaryotic Cell Cycle Cytokinesis

cell division

# Eukaryotic Cell Cycle G0

resting phase or quiescence

# Regulation of the eukaryotic cell cycle Progression of the cell cylce depends upon activities of a __________________________ bound to its regulatory _________ subunit in each phase of the cell cycle

cyclind-dependant kinase (CDK); cyclin

# Regulation of the eukaryotic cell cycle Cyclin-dependant kinase (CDK)

protein/enzyme that phosphorylates other proteins

# Regulation of the eukaryotic cell cycle 3 checkpoints

1. DNA Damage (G1/S) Checkpoint (is DNA ok for replication?) 2. DNA Replication (G2/M) Checkpoint (is DNA fully replicated before mitosis?) 3. Mitotic Spindle Checkpoint (Are chromosomes aligned properly in metaphase?) | checkpoints will not stop cycle permenantly ## Footnote important b/c cells will die if they proceed w/ incomplete steps

What happens when cell cycle regulation goes wrong?

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

Which mutated genes are implicated in cancers?

1. Oncogenes 2. Tumor Supressor Genes 3. Inactivated p53 gene (in 50% of tumors) & cyclin D and E are often highly expressed in breast cancer carcinomas

Why is it difficult to find universal cure for cancer?

each cancer is caused by different gene mutations

Oncogenes

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

Tumor Suppressor Genes

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

# Homologous Chromosomes n

haploid number of chromosomes

# Homologous chromosomes 2n

diploid number of chromosomes

Homologous chromosomes have _________________ and _______________ pair of chromosomes

maternal and paternal

# Homologous Chromosomes the ___________ & ___________ of genes are the same between homologous chromosomes but alleles could be different

number and order

# Events of the mitotic cell cycle I Events in order

G1 G2 Prophase

Review diagram on slide 4

G1

(2n) 4 chromosomes 1 chromatid/chromosome

G2

2n 4 chromosomes 2 chromatic/chromosome

Prophase

2n 4 chromosomes 2 chromatids/chromosome

A human is diploid with 2n = 46. A cell in G2 would contain:

46 chromosomes 23 homologous pairs 92 chromatids

Why should all genes on sister chromatids be the same allele

DNA replication; multiple forms of gene

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

b/c one comes from mom and one from dad

Events of the mitotic cell cycle II

prometaphase metaphase anaphase

# Events of the mitotic cell cycle II prometaphase

2n 4 chromosomes 2 chromatids/chromosome

# Events of the mitotic cell cycle II metaphase

2n 4 chromosomes 2 chromatids/chromosome

# Events of the mitotic cell cycle II anaphase

4n 8 chromosomes 1 chromatid/chromosome

Evenets of the mitotic cell cycle III

telophase G1

# Events of the mitotic cell cycle III telophase

4n 8 chromosomes 1 chromatid/chromosome

# Events of the mitotic cell cycle III G1

2n 4 chromosome 1 chromatid/chromosome

Cell cylcle in prokaryotes

binary fission

binary fission

* replication begins at origin * bacterial chromosome is attached to the inner membrane * cell elongates and chromosomes seperate * inward growth of plasma membrane and partition assembly of new cell wall, dividing replicated DNA * two daughter cells produced * effective bc only 1 chromosome * mitosis evolved from this

Meiosis I

* creation of gametes * germ cell (2n, 4 chromosomes 1 chromatid/chromosome) --> germ cell (2n, 4 chromosomes, 2 chromatid/chromosome) * non-sister chromatids from 2 homologous chromosomes are attached by protein structure called synaptonemal complex * pieces of non-sister chromatids are exchanged by recombination

# Recombination in Eukaryotes 1. _______________ align with each other during prophase I and exchange of sections of non-sister chromatids occur by crossing over

homologous chromosomes

# Recombination in Eukaryotes 2. _________________________ occurs of each strand

precise breakage

# Recombination in Eukaryotes 3. __________- of non-sister chromatids

equal exchange

# Recombination in Eukaryotes 4. ______________ after genetic exchange

repair of breakage

# Recombination in Eukaryotes 5. genetic exchange can involve large sections of homologous chromosomes creating __________________ with various combinations of 100s of genes/alleles

new chromatids

# Recombination in Eukaryotes Why is it important for perfect exchange of genetic material between non-sister chromatids during recombination?

because if it wasn't perfect, there would be loss or gain of genetic mutation

Meiosis I (reductional division) | Diploid - haploid

* the number of homologous pair of chromosomes is reduced from 2 in parental to 1 in daughter cell * chromosome number is haploid, but there are still 2 chromatids/chromosome * sister chromatids no longer identical due to crossing over

Meiosis II

* process between MI & MII is similar but no DNA replication * centromeres & sister chromatids separate during anaphase II * at the end: 4 cells are produced with haploid number of chromosomes (1 chromatid/chromosome) that are not identical due to crossing over and random assortment

If a human is diploid with 2n=46. A cell after meiosis I would contain:

46 chromosomes 23 homologous pairs 46 chromatids

If a human is diploid with 2n=46. A cell after mitosis II would contain:

23 chromosomes 0 homologous pairs 23 chromatids